WO2007051252A1

WO2007051252A1 - Porous polymeric materials and polymer particles for preparation thereof

Info

Publication number: WO2007051252A1
Application number: PCT/AU2006/001645
Authority: WO
Inventors: Greg Guanghua Qiao; Luke Andrew Connal; James Thomas Wiltshire
Original assignee: The University Of Melbourne
Priority date: 2005-11-03
Filing date: 2006-11-03
Publication date: 2007-05-10

Abstract

The present invention relates to porous honeycomb polymeric materials, to polymer particles useful in the preparation of honeycomb polymeric materials and to systems comprising honeycomb polymeric materials.

Description

POROUS POLYMERIC MATERIALS AND POLYMER PARTICLES FOR PREPARATION THEREOF

FIELD OF THE INVENTION

The present invention relates to porous honeycomb polymeric materials, systems comprising honeycomb polymeric materials and to polymer particles useful in the preparation of honeycomb polymeric compositions.

BACKGROUND

The formation of porous polymers having a self-organised honeycomb structure was first described by Bernard Francois in Nature (1994), volume 369, page 387. These porous polymeric materials, also known as honeycomb polymeric materials, have a highly ordered three-dimensional architecture, which is characterized by a pore structure having a high degree of uniformity in size and shape.

Honeycomb polymeric materials are typically formed as a film by casting a solution containing a polymer and a volatile solvent onto planar substrates such as glass or mica. Upon exposure of the polymer solution to a stream of humid air, evaporation of the solvent occurs. The evaporation of the solvent causes the condensation of water from the humid air and the formation of an ordered hexagonal array of water droplets on the surface of the polymer solution. The water droplets act as a template for the pores due to nucleation of the polymer around the water. The polymer in turn, stabilizes the water droplets against coalescence and maintains the ordered three-dimensional pore structure. Further evaporation of the volatile solvent and water then results in a polymeric material having a honeycomb appearance. The relative ease of preparation of honeycomb polymeric materials, coupled with the ability to obtain a narrow pore size distribution make these materials attractive for many applications such as in catalysis, sensors, adsorbents, scaffolds, photonic band gaps and optical stop-bands.

Honeycomb polymeric materials incorporating different organic polymer materials including for example, rod-coil copolymers, block copolymers and amphiphilic polymers, as well as branched polymers have been described in the prior art. The physical properties and potential applications of the honeycomb polymeric materials however are limited. For example, the present inventors have found that it is not generally possible to prepare useful honeycomb polymeric materials on other than a completely flat surface using prior art compositions. This places a significant limitation on the applications in which the desirable properties of honeycomb polymeric materials can be utilised.

There exists a need to provide porous honeycomb polymeric materials that are able to be used in a wide variety applications, such as photonic, optoelectronic, chemical and biotechnological applications.

The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Throughout the description and the claims of this specification the word "comprise" and variations of the word, such as "comprising" and "comprises" is not intended to exclude other additives, components, integers or steps.

SUMMARY It has been found that the regularity and pore structure of porous polymeric materials can be more readily controlled on three-dimensional surfaces by using star polymers having a low glass transition temperature (low Tg).

Accordingly, in one aspect, the present invention provides a honeycomb polymeric material formed of a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the star polymer has a low glass transition temperature.

Generally, the star polymers have a glass transition temperature of less than about 80^°C, preferably less than about 50^°C, preferably less than about 30^°C, more preferably less than about 25^°C, even more preferably less than about 0^°C, still more preferably less than about -50^°C, yet more preferably, a glass transition temperature of less than about -100^°C.

Preferably, the pendant arms of the star polymer comprise a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof.

In a preferred embodiment, the pendant arms comprise a polymer chain of formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of Ci to Cs alkylene optionally substituted with one or more substituents selected from hydroxy, halo and alkoxy, and SiR¹R² where R¹ and

R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl, alkoxy and aryl,

Y may be the same or different at each occurrence and is selected from a carbonyl or a covalent bond, n is the number of repeating units and is preferably at least 10, more preferably at least 15 and most preferably at least 20. Preferably, the pendant arms of the star polymer have a number average molecular weight of at least 2,000, more preferably a number average molecular weight of at least 5,000.

It is preferred that the core of the star polymer is a crossl inked network or a polyvalent molecule.

In one embodiment, the star polymer of the invention has a polydispersity of between about 1 and 10, preferably between 1 and 4, more preferably between 1 and 2, even preferably between 1 and 1.5 and most preferably between 1 and 1.3.

In another aspect, the present invention provides a process for the preparation of a honeycomb polymer comprising:

(a) providing a star polymer composition comprising star polymer units in a volatile solvent, wherein the star polymer has a core and a plurality of pendant arms and a low glass transition temperature;

(b) forming a layer of the composition; (c) subjecting the layer of the composition to a humid atmosphere; and

(d) evaporating the solvent to form a honeycomb polymer from the polymer composition.

In a preferred embodiment, the glass transition temperature of the star polymer is less than about 80^°C. More preferably, the glass transition temperature of the star polymer is less than about 50^°C, preferably less than about 3O⁰C, more preferably less than about 25⁰C, even more preferably less than about 0^°C, still more preferably less than about -50^°C, yet more preferably, a glass transition temperature of less than about -100^°C. The pendant arms of the star polymer preferably have a number average molecular weight of at least 2,000, more preferably a number average molecular weight of at least 5,000, even more preferably a number average molecular weight of at least 10,000.

In a preferred embodiment of the process of the present invention, the honeycomb polymeric material is formed as a layer on a surface, preferably a non-planar surface such as a curved surface or a patterned surface. Preferably, the non-planar surface comprises variations of more than 5 microns and more preferably, more than 10 microns from planar.

In another embodiment of the process of the present invention, the surface is provided by a support matrix having a plurality of interstitial spaces arranged therein and the honeycomb polymeric material is formed as a layer that extends across at least one and preferably, a multiplicity, of the interstitial spaces.

In one embodiment, the process of the invention preferably comprises the step of dipping the support matrix into the star polymer composition to form the layer of composition in step (b).

In a further aspect, the present invention provides a star polymer comprising:

(a) a core; and

(b) pendant arms attached to the core, wherein the pendant arms have a number average molecular weight of at least 2,000 and wherein the star polymer has a low glass transition temperature.

The star polymer of the invention is useful in the preparation of honeycomb polymeric materials. Preferably, the glass transition temperature of the star polymer is less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C.

In one preferred aspect, the pendant arms of the star polymer comprise a polymer chain comprising a polyoxyalkylene, polyester, polyoxysilane or mixtures thereof.

Preferably, the pendant arms comprise a polymer chain of formula:

-(OYX)_n- wherein

Y may be the same or different at each occurrence and is selected from a carbonyl or a covalent bond, n is the number of repeating unit and is preferably at least 10, more preferably at least 15 and most preferably at least 20.

The core of the star polymer may be a crossl inked network or a polyvalent molecule. Preferably, the core is a crosslinked network.

The star polymer formed with polyester arms are in many instances fully biodegradable. Accordingly star polymers of this embodiment of the invention may be used in the preparation of honeycomb or other polymer architectures to provide templates or scaffolds for casting or forming materials for applications such as electrical, biomedical or other applications and can be subsequently degraded. In this way the template or scaffold formed of the polyester may be selectively removed to leave the shaped materials for which the polymers provide a template or scaffold.

In this embodiment the core may and preferably is formed of a polyester cross linker.

The most preferred star polymers in this embodiment comprise polyester arms and polyester cross linked core components wherein said core and arms are formed by ring opening polymerization of lactones such as caprolactones. In a preferred embodiment, the pendant arms comprise a polyester comprising one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone.

It is preferred that the pendant arms of the star polymers of the present invention have a number average molecular weight of at least 5,000.

In one embodiment, the star polymers of the invention have a polydispersity of between about 1 and 10, preferably between 1 and 4, more preferably between 1 and 2, even preferably between 1 and 1.5 and most preferably between 1 and 1.3.

The honeycomb polymeric materials of the present invention can be advantageously formed into a variety of patterns and shapes without losing the substantially uniform pore size and structure that characterises the materials. The honeycomb polymeric materials prepared in accordance with the invention may also incorporated into a system with a support matrix and used in a number of different applications.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a gel permeation chromatography (GPC) trace showing the elution volumes of linear polydimethylsiloxane (PDMS) arms and a PDMS star microgel polymer particle prepared in accordance with one aspect of the invention.

Figure 2 is a differential scanning calorimetry (DSC) trace showing the glass transition temperature (Tg) of a PDMS star microgel polymer particle prepared in accordance with one aspect of the invention.

Figure 3 is a gel permeation chromatography (GPC) trace showing the elution volumes of linear poly(ε-caprolactone) arms and a poly(ε-caprolactone) star microgel polymer particle prepared in accordance with one aspect of the invention.

Figures 4A and 4B show a scanning electron micrograph of a planar honeycomb polymer prepared from a PDMS star microgel polymer in accordance with one aspect of the invention. Scale bar: Figure 4A: 5 μm; Figure 4B: 10 μm.

Figure 4C shows a scanning electron micrograph of a sandblasted aluminum plate having a rough surface. Scale bar: Figure 4C: 5 μm.

Figure 4D shows a scanning electron micrograph of the sandblasted aluminium plate of Figure 4C coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 4D: 5 μm.

Figures 4E and 4F show a scanning electron micrograph of magnified areas of the coated sandblasted aluminium plate of Figure 4D. Scale bar: Figures 4E and 4F: 10 μm; Insert of Figure 4E: 5 μm.

Figures 5A shows a scanning electron micrograph of kaolin particles. Scale bar: Figure 5A: 10 μm. Figure 5B shows a scanning electron micrograph of the kaolin particles of Figure 5A coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 5B: 10 μm.

Figure 5C shows a scanning electron micrograph of a doughnut shaped kaolin particle. Scale bar: Figure 5C: 10 μm.

Figure 5D shows a scanning electron micrograph of the kaolin particle of Figure 5C coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 5D: 10 μm.

Figure 5E shows a scanning electron micrograph of silica particles. Scale bar: Figure 5E: 100 μm.

Figure 5F shows a scanning electron micrograph of the silica particles of Figure 5E coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 5F: 20 μm.

Figure 5G shows a scanning electron micrograph of glass microbeads. Scale bar: Figure 5G: 20 μm.

Figure 5H shows a scanning electron micrograph of the glass microbeads of Figure 5G coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 5H: 5 μm.

Figure 6A shows a scanning electron micrograph of a sodium chloride crystal coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 6A: 20 μm. Figure 6B shows a scanning electron micrograph of the honeycomb polymer material of Figure 6A after treatment of the coated sodium chloride crystal with water to remove the sodium chloride crystal. Scale bar: Figure 6B: 20 μm.

Figure 6C shows a scanning electron micrograph of a copper sulphate crystal coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 6C: 20 μm.

Figure 6D shows a scanning electron micrograph of the honeycomb polymer material of Figure 6C after treatment of the coated copper sulphate crystal with water to remove the copper sulphate crystal. Scale bar: Figure 6D: 20 μm.

Figure 6E shows a scanning electron micrograph of a sugar crystal coated with a honeycomb polymer prepared from a PDMS star microgel polymer. Scale bar: Figure 6E: 20 μm; Insert of Figure 6E: 5 μm.

Figure 6F shows a scanning electron micrograph of the honeycomb polymer material of Figure 6E after treatment of the coated sugar crystal with water to remove the sugar crystal. Scale bar: Figure 6F: 20 μm.

Figure 7 shows a scanning electron micrograph of a honeycomb polymer formed in comparative example 1 from a poly(methyl methacrylate) / ethylene glycol dimethacryate (PMMA/EGDMA) star microgel on a kaolin particle.

Figure 8 is a schematic illustration showing the formation of hollow honeycomb polymer structure in accordance with an aspect of the present invention.

Figure 9 is a DSC trace showing the glass transition temperature (Tg) of PMMA, poly(f-butyl acrylate) (PfBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(dimethyl siloxane ) (PDMS) based star microgel polymers. Figure 10 shows scanning electron micrographs of honeycomb polymeric materials prepared from (a) PMMA, (b) PfBA, (c) PMA, (d) PEA and (e) PDMS star microgel polymers on a planar substrate.

Figure 11 shows scanning electron micrographs of a honeycomb polymeric material in accordance with one embodiment of the invention prepared from a PfBA star microgel on a transmission electron microscope (TEM) grid support matrix having hexagonal interstitial spaces.

Figure 12 shows scanning electron micrographs of a honeycomb polymeric material in accordance with one embodiment of the invention prepared from a PMA star microgel on a TEM grid support matrix having hexagonal interstitial spaces.

Figure 13 shows scanning electron micrographs of a honeycomb polymeric material in accordance with one embodiment of the invention prepared from a PEA star microgel on a TEM grid support matrix having hexagonal interstitial spaces.

Figure 14 shows scanning electron micrographs of a honeycomb polymeric material in accordance with one embodiment of the invention prepared from a PDMS star microgel on a TEM grid support matrix having hexagonal interstitial spaces.

Figure 15 shows scanning electron micrographs of a comparative example of a honeycomb polymeric material prepared from a PMMA star microgel on a TEM grid support matrix having hexagonal interstitial spaces. Figure 16 is a schematic illustration showing the formation of a honeycomb polymer material on a support matrix in accordance with one aspect of the present invention.

Figure 17A shows a scanning electron micrograph of a 600 mesh TEM grid support matrix having hexagonal interstitial spaces.

Figure 17B shows a scanning electron micrograph of a honeycomb polymeric material prepared from a PDMS star microgel polymer on the surface of the support matrix of Figure 17A.

Figure 17C shows a scanning electron micrograph of a negative image made by replica molding using the honeycomb polymeric material of Figure 17B as a master template.

Figure 17D shows a scanning electron micrograph of the honeycomb polymeric material of Figure 17B in higher magnification.

Figure 17E shows a scanning electron micrograph of the negative image of Figure 17C in higher magnification.

Figure 17F shows a scanning electron micrograph of a 1000 mesh TEM grid support matrix having square interstitial spaces.

Figure 17G shows a scanning electron micrograph of a honeycomb polymeric material prepared from a PDMS star microgel polymer on the surface of the support matrix of Figure 17F.

Figure 17H shows a scanning electron micrograph of a negative image made by replica molding using the honeycomb polymeric material of Figure 17G as a master template. Figure 171 shows a scanning electron micrograph of a 2000 mesh TEM grid support matrix having square interstitial spaces.

Figure 17J shows a scanning electron micrograph of a honeycomb polymeric material prepared from a PDMS star microgel polymer on the surface of the support matrix of Figure 171.

Figure 17K shows a scanning electron micrograph of a negative image made by replica molding using the honeycomb polymeric material of Figure 17J as a master template.

Figure 18 is a schematic illustration showing a dip coating technique used to form a honeycomb polymer structure in at least one interstitial space of a support matrix in accordance with an aspect of the present invention.

Figure 19A shows a scanning electron micrograph of a honeycomb polymeric material prepared from a PDMS star microgel polymer spanning the hexagonal interstitial spaces of a 600 mesh TEM grid support matrix.

Figure 19B shows a scanning electron micrograph of a negative image formed by replica molding using the honeycomb polymeric material of Figure 19A as a master template, with a higher magnification shown in the inset.

Figure 20 shows a scanning electron micrograph of a honeycomb polymeric material prepared from a PMA star microgel polymer spanning a square interstitial space of a 60 mesh TEM grid support matrix, with a higher magnification of the support matrix / honeycomb polymeric material interface shown in the inset. Figure 21 shows a scanning electron micrograph of a honeycomb polymeric material prepared from a PMA star microgel polymer crossl inked with anthracene spanning the hexagonal interstitial spaces of a TEM grid support matrix.

Figure 22 is a schematic representation of pattern transfer onto a honeycomb polymeric material using photo-lithography.

Figure 23 shows a series of scanning electron micrographs of (a) a patterned material prepared by uncrosslinking selective areas of honeycomb polymeric material prepared from a PMA star microgel polymer crossl inked with anthracene, (b) the region indicated as (b) in micrograph (a) in higher magnification, (c) the region indicated as (c) in micrograph (b) showing the crosslinked honeycomb morphology and (d) the region indicated as (d) in micrograph (b) of the honeycomb polymeric material showing the uncrosslinked region where the honeycomb morphology has been lost.

Figure 24 shows a range of fluorescence microscope images of patterned honeycomb polymeric materials prepared from a PMA star microgel polymer crosslinked with anthracene in which selective regions of the honeycomb polymeric material have been uncrosslinked following masking the honeycomb material with (a) a TEM grid having a striped mesh, (b) a TEM grid with reference cells, (c) a TEM grid having hexagonal interstitial spaces of 600 mesh and (d) a TEM grid having hexagonal interstitial spaces of 600 mesh at higher magnification.

Figure 25 shows a graph comparing the fluorescence intensity (at 490 nm) of an anthracene amine coupled NPC functional film with honeycomb morphology with that obtained from a featureless film.

DETAILED DESCRIPTION Various terms that will be used throughout the specification have meanings that will be well understood by a skilled addressee. However, for ease of reference some of these terms will now be defined.

As used herein reference to a percentage of a component in a reaction mixture or composition refers to the percentage by weight unless otherwise specified.

As used herein reference to molecular weight for a polymer refers to number average molecular weight unless otherwise specified.

As used herein reference to a unit of a star polymer refers to a discrete molecule of the star polymer.

Glass transition temperature (Tg) - this is the temperature at which the material characteristics of a polymer changes from hard and brittle to soft and pliable. This property may be measured using standard techniques such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) or dynamic mechanical thermal analysis (DMTA).

Low Tg - where used herein, the term low Tg includes a Tg of generally less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C. Some polymers, such as block copolymers, contain discrete polymeric components which give rise to two or more glass transition temperatures. In such cases the polymer is considered to be of low Tg where a significant glass transition is observed at a temperature of no more than about 80^°C, preferably no more than about 5O⁰C, more preferably no more than about 30^°C, even more preferably no more than about 25^°C, still more preferably no more than about 0^°C, yet more preferably no more than about - 50^°C, and most preferably no more than about -100^°C. Polydispersity - this is the ratio of weight average molecular weight (M_w) and number average molecular weight (M_n) for a given polymer. It may be expressed by the equation PD = M_w/M_n. The weight average molecular weight and number average molecular weight may be calculated using standard techniques such as gel permeation chromatography (GPC).

Star Microgel - this is a polymer having a central core comprising a highly crosslinked network and three or more radiating polymeric arms attached to the network core. Star microgels are also known as core-crossl inked star (CCS) polymers.

Star polymer - this is a polymer having a central core (either crosslinked or polyvalent) and three or more radiating polymeric arms covalently attached to the core.

As used herein the terms "uniform pore size", "regular pore size", "regular pore structure" and "pores of substantially regular size" and the like mean that the porous polymer has a region or regions within which there is little variation of the pore diameters. This can be assessed by scanning electron microscopy (SEM) and other techniques known in the art for measuring pore size.

The highly ordered and regular pore structure of honeycomb polymeric materials makes these materials attractive for many applications. Honeycomb polymeric materials however, are generally formed as planar layers cast on flat, planar surfaces. This is because of the tendency of the honeycomb polymeric materials to shear or break if cast on surfaces other than planar. Without wishing to be bound by theory, the brittleness of the honeycomb polymeric materials and their tendency to break may be reduced or avoided by using polymers of low glass transition temperature (low Tg). It is conventionally thought that a high Tg material is required in order to effectively precipitate the polymer around water droplets to stabilize the droplets against coalescence and to impart sufficient rigidity to the honeycomb polymeric material to enable a defined pore structure to be formed. As a result, the ability to use the honeycomb polymeric materials in a wide range of applications has been limited by the physical properties of the materials.

The glass transition temperature (T₉) may be defined as the temperature (or temperature range) at which a polymer losses its glass-like properties and behaves more like a rubber. The glass transition is accompanied by greater rotational freedom and consequently greater segmental motion of individual chains. The T₉ of polymers is a very important property, it is one of the fundamental characteristics which relates to properties and processing.

The Tg of polymers is generally affected by three factors: (1 ) the inherent flexibilities/backbone bond rotation barriers of their individual chains, (2) the size or steric bulk of their side chains, and (3) the interactions (steric dipolar, hydrogen bonding, etc.) between chains. In general, variables that restrict the rotation of polymers should increase T₉.

The present inventors have found that honeycomb polymeric materials may be formed from a star polymer composition comprising star polymer units which have either a low glass transition temperature or a specific chemical structure. The honeycomb polymeric materials of the present invention do not exhibit the brittle characteristics typical of those materials described in the prior art, and may be formed into a variety of shapes or patterns without loss of the regular pore size and structure that characterizes honeycomb polymeric materials.

Honeycomb polymeric materials

In one aspect, the present invention provides a honeycomb polymeric material formed from a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the star polymer has a low glass transition temperature.

Star polymers typically comprise a core moiety and a plurality of pendant arms, preferably three or more arms, extending from the core. The core moiety of a star polymer may be a polyvalent molecule or it may be a crosslinked network. The pendant arms are preferably linear polymeric arms. Examples of star polymers include non core-crossl inked star polymers and star microgels (also known as core-crosslinked star (CCS) polymers. Representations of non core- crossl inked star polymers and star microgel polymers are shown below.

non core-crosslinked core-crosslinked star polymer star (CCS) polymer (star microgel)

A key difference between the non core-crosslinked star polymers and star microgels is that non core-crosslinked star polymers comprise a polyvalent core, which is typically a polyvalent compound, whereas the core of a star microgel polymer consists of a crosslinked network. In both instances, the arms are covalently attached to the core and extend from the core. The number of functional groups and hence branching points in the polyvalent core of a non core-crosslinked star polymer however may dictate the number of arms that may be attached to the core. In comparison, a larger number of arms may extend from the crosslinked core of a star microgel polymer as the attachment of the arms is not limited by the functionality of the core. As a result, a high number of arms, for example, ten or more arms may extend from the core of a star microgel polymer.

The low glass transition temperature of the star polymers advantageously enables the honeycomb polymeric material of the invention to exhibit rubber- like or plasticized characteristics. Generally, the star polymers have a glass transition temperature of less than about 80^°C, preferably than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C. The glass transition temperature of the star polymers may be ascertained using techniques known to those skilled in the art. A suitable technique is differential scanning calorimetry (DSC), which determines the thermal transitions experienced by polymers as a sample of polymer is heated and cooled. Other conventional techniques such as thermogravimethc analysis (TGA) and dynamic mechanical thermal analysis (DMTA) can also be used to measure Tg using methodology known in the art. For the purpose of the present invention, when glass transition temperature is to be determined, only the Tg of the star polymer needs to be measured.

The star polymers used to form the honeycomb polymeric materials may comprise any monomer component, provided that the star polymer possesses the property of low Tg. The polymer may comprise a homopolymer or a copolymer. A person skilled in the art will have no difficulty in selecting monomers suitable for low Tg polymers in accordance with the invention. The Tg of polymers is widely reported and lists of Tg for homopolymers are included for example in the Sigma-Aldrich catalogue 2004. A copolymer may comprise two or more different repeating monomer units arranged randomly or in blocks. Where blocks of distinct monomer units are present, the resulting polymer may exhibit a number of glass transitions. When a significant glass transition occurs at the low Tg range referred to above, the polymer is considered useful in the present invention. Preferably, at least 25% of the glass transition is at a temperature in the defined low Tg range.

Examples of monomers useful in preparing low Tg polymers include: (i) substituted acrylates such as n-butyl acrylate, /so-butyl acrylate, tert- butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, ethyl acrylate and methyl acrylate

(ii) substituted methacrylates such as dodecyl methacrylate, 2-ethylhexyl methacrylate and octadecyl methacrylate (iii) vinyls such as 1 -butene, isobutylene and vinylidene fluoride

(iv) alkylenes such as high density polyethylene

(v) cyclic siloxanes such as octamethylcyclotetrasiloxane (D4)

(vi) alcohols such as ethylene glycol, propylene glycol and dihydroxy perfluoropolyalkanes (Z-DoIs) (vii) esters such as caprolactone, glycolide, lactide and dioxanone, and

(viii) acids such as tetramethylene adipic acid and ethylene adipic acid.

Generally, the Tg of the polymer is a result of the monomer component and its relative proportion in a given polymer. Accordingly, depending on the type and proportion of monomers present, monomers which in a homopolymer will give rise to a polymer having a high Tg, may be present in the polymer having the required low Tg. The presence of monomer repeating units such as those described above in a sufficient proportion provides the resultant polymer with a low Tg.

In a preferred embodiment of the invention, the star polymers used in the formation of the honeycomb polymeric material comprise a polymer chain comprising a polyoxyalkylene, a polyester or a polyoxysilane.

Preferably, the polymer chain is of a formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of optionally substituted Ci to C₈ alkylene, and SiR¹R² wherein the optionally substituted Ci to Cs alkylene may comprise one or more substituents selected from hydroxy, halo (preferably fluoro) and alkoxy (preferably Ci to C₆ alkoxy),

R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl (preferably Ci to Cβ alkyl), alkoxy (preferably Ci to Ce alkoxy) and aryl (preferably C₅ to Cio aryl), Y may be the same or different at each occurrence and is selected from a carbonyl or a covalent bond, n is the number of repeating unit and is preferably at least 10, more preferably at least 15 and most preferably at least 20.

In one preferred embodiment, the polymer chain comprises poly(dimethyl siloxane) (PDMS), which has a Tg of -127^°C. The bond angle and bond length of Si-O (130° and 1.63 A) are greater than that of C-C bonds (112° and 1.54 A). Therefore, polymer chains based on Si-O bonds give rise to polymers with backbones that are extremely flexible and hence poly(dimethyl siloxane) (PDMS) polymers have an extremely low T₉.

In another preferred embodiment, the polymer chain comprises a polyester. Preferred polyesters comprise one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone. A particularly preferred polyester is poly(ε-caprolactone) which has a Tg of -60^°C. Other useful polyesters may include acid monomers such as lactic acid, glycolic acid and mixtures thereof. It would be appreciated by the person skilled in the art that depending on the choice of monomer component, a polymer chain comprising a copolymer may also possess the property of low Tg. The preparation of suitable copolymers would be apparent to the skilled person. In a further preferred embodiment, the polymer chain comprises poly(acrylates) having pendant substituent groups, such as alkyl substituent groups. Suitable alkyl pendant groups may be Ci to Ci₈ alkyl, preferably Ci to C₈ alkyl, more preferably Ci to C₄ alkyl. The alkyl group may be linear or branched. Changing the nature of the pendant group of poly(acrylates) is another way to tune the T₉. Without wishing to be limited by theory, it is believed that by increasing the length of the alkyl pendant group a decrease in T₉ may occur until a threshold point, at which, with a further chain increase the T₉ then begins to rise. This can be explained by a plasticizing effect at low carbon number substituents which is offset with higher-carbon-chain pendant groups which undergo increased entanglements and side chain crystallization. In one embodiment, the honeycomb polymeric materials of the invention may be prepared from a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the pendant arms comprise a polymer chain comprising a poly(alkyl acrylate). Preferred poly(alkyl acrylates) comprise one or more monomers selected from the group consisting of tert- butyl acrylate, ethyl acrylate and methyl acrylate. In one preferred embodiment, at least a percentage of the pendant arms of the star polymer comprises a poly(alkyl acrylate).

In addition to the low Tg, the star polymers used in the honeycomb polymeric materials of the invention may also exhibit other desirable properties. For example, star polymers including polysiloxanes may also exhibit other properties such as high thermal and oxidative stability, hydrophobicity, low surface tension, good dielectric properties and biocompatibility. Furthermore, polymers including polyesters comprising ester monomers such as ε- caprolactone may advantageously exhibit the properties of biocompatibility and biodegradation in the physiological environment. Such properties can impart favourable characteristics to the honeycomb polymeric materials of the invention and therefore can allow the honeycomb materials to be used in a variety of applications. The honeycomb polymeric materials of the present invention are preferably formed from star polymers having a number average molecular weight of at least about 2,000. It would be appreciated by the person skilled in the art that in addition to the chemical composition of the polymer, the molecular weight of the polymer may have an influence on the glass transition temperature. It is an advantage of the present invention that honeycomb polymeric materials may be prepared using low Tg polymers of high molecular weight. In a preferred embodiment, the star polymers have a number average molecular weight of at least about 5,000 and more preferably, at least about 10,000.

In another aspect, the present invention provides a honeycomb polymer formed of a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the pendant arms comprise a polyoxyalkylene, a polyester, a polyoxysilane or mixtures thereof.

Preferably, the pendant arms comprise a polymer of formula:

-(OYX)_n- wherein X may be the same or different at each occurrence and is selected from the group consisting of optionally substituted Ci to C₈ alkylene, and SiR¹R² wherein the optionally substituted Ci to C₈ alkylene may comprise one or more substituents selected from hydroxy, halo (preferably fluoro) and alkoxy

(preferably Ci to C₆ alkoxy), R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl (preferably Ci to C₆ alkyl), alkoxy (preferably Ci to C₆ alkoxy) and aryl (preferably C₅ to Cio aryl),

Y may be the same or different at each occurrence and is selected from a carbonyl or a covalent bond, n is the number of repeating unit and is preferably at least 10, more preferably at least 15 and most preferably at least 20. In one embodiment, the star polymers in the honeycomb polymeric materials of the invention have polydispersity of between about 1 to 10, preferably between 1 and 4, more preferably, between 1 and 3, even more preferably between 1 and 2, still more preferably, between 1 and 1.5 and most preferably between 1 and 1.3.

In another aspect, the honeycomb polymeric materials of the invention may be supported by a substrate. The substrate may be made from any suitable material. It is preferred that the substrate is an inert substrate that comprises a material does not react with the honeycomb polymeric material. The substrate may include for example, glass, silicon wafer, metal or metal coated substrate and plastic substrates such as polyolefins.

In one preferred embodiment, the honeycomb polymeric material of the invention is supported on a substrate that has a planar surface. A planar surface is a substantially flat surface having variations of less than about 10 microns, more preferably less than about 5 microns from planar. The honeycomb polymeric material supported on a planar surface is therefore a flat, planar layer of material that coats the surface of the substrate.

In another preferred embodiment, the substrate has a non-planar surface. As used herein, "non-planar" refers to a surface that is not smooth, but has topographical features such as roughness, curvature or patterning. Preferably, the non-planar surface is a curved or patterned surface. A patterned surface may include variations of at least 5 microns, more preferably at least 10 microns and even more preferably at least 20 microns from planar. Typically, the variations will be no more than 1 mm. The honeycomb polymeric materials of the invention are able to conform to the shape and/or topography of the underlying substrate. The honeycomb polymeric materials may therefore replicate a number of complex, non-planar shapes and surface topographies. When the honeycomb polymer is supported on a curved non-planar surface of a substrate, it is preferred that the surface comprises variations of more than 5 microns, preferably more than 10 microns from planar.

In another embodiment of the present invention, the substrate may be a particle such that a non-planar surface may be provided by the particle surface. Any suitable particle which is capable of supporting the honeycomb polymeric materials of the present invention may be used. Preferably, the particle is selected from mineral particles, salt particles, sugar particles and beads. In a preferred embodiment, the particle is soluble in a solvent so that the particle may be removed from the honeycomb polymeric material. Preferably, the particle is soluble in water. Preferably, the non-planar surface is a surface of a particle of no more than 1 mm in diameter.

In a further embodiment, the substrate may be a porous support matrix. Generally, the support matrix would comprise an open frame structure having a plurality of interstitial spaces arranged therein. The support matrix may be of any suitable size, shape and configuration and the person skilled in the art would understand that the exact dimensions and configuration of the support matrix is not critical to the invention, as these parameters will usually be determined by the intended application in which the system is to be employed. An advantage of the support matrix is that it provides reinforcement to the honeycomb polymeric material. Thus, the honeycomb material is not reliant upon its own inherent strength characteristics to maintain structure and integrity.

The support matrix may be made of any suitable material. Preferably, the support matrix is formed from a material that is relatively inert. This helps to ensure that the matrix does not participate in any unwanted reactions in applications that use the honeycomb polymeric materials of the invention. In a preferred embodiment, the support matrix is provided by a rigid material, for example, such as metal, ceramic or glass or hard plastics. The support matrix may also be provided by a flexible material, such woven or non-woven fibrous materials or soft plastics. The support matrix may also be planar or non-planar. The thickness of such support matrices may be in the range of from 500 nm to 1 mm.

The support matrix generally comprises a plurality of interstitial spaces that typically extend through the entire thickness of the support matrix and are dispersed throughout the area of the matrix. The interstitial spaces may be of any size and shape, such as for example, square, circular or hexagonal shapes, or slots. In a preferred embodiment, the interstitial spaces are provided as a regular array in the support matrix. Preferably, the interstitial spaces are of a substantially uniform size. The support matrix may be in the form of a grid, mesh, net or other porous structure which will typically comprise a regular array of interstices. The commercially available transmission electron microscope (TEM) grids supplied by ProSciTech are examples of substrates having a regular array of interstitial spaces, which are suitable for use as a support matrix. Such TEM grids typically have interstitial spaces ranging in size from about 1.0 μm to centimeters in diameter. In one embodiment, the average size of the interstitial spaces of the support matrix is in the range of from 1 μm to 1 cm.

The honeycomb polymeric materials of the invention extend across at least one interstitial space of the support matrix and preferably extends across a multiplicity of interstitial spaces. In this regard, the honeycomb polymeric material would typically traverse at least one interstitial space of the support matrix in a continuous manner so that it is suspended within the interstitial space. The honeycomb material may also be supported on the surface of the support matrix itself. The surface of the support matrix is generally regarded as a non-planar surface. In one embodiment, the substrate may be modified to render the substrate more compatible with the honeycomb polymeric material. Such modification may involve coating the substrate with a suitable material. Suitable coatings may be formed by techniques known to the art, such as by grafting polymers to the surface of the substrate. Surface modification techniques such as chemical treatment or plasma treatment may also be used to alter the characteristics of the substrate. The substrate may also possess a surface charge, such as a negative or positive surface charge, which may be provided by introducing appropriate functional groups in the substrate. Such surface charges do not interfere with the properties of the honeycomb polymer.

Star polymers

In accordance with another aspect, the present invention provides a star polymer comprising:

(a) a core; and

(b) pendant arms attached to the core, wherein the star polymer has a low glass transition temperature.

The glass transition temperature of the star polymer is preferably less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C.

It is preferred that at least one of the arms, and preferably each arm, of the star polymer comprises a low glass transition temperature polymer chain. It would be appreciated by the person skilled in the art however, that a number of different polymer chains comprising different monomeric components may possess a low Tg. As a result, when more than one arm of a star polymer comprises a polymer chain having a low Tg, the composition of the polymer chain may be the same or different for each arm. The Tg of the pendant arms may be determined prior to synthesis of the star polymer or by excising the arms from a given star polymer. The Tg of the polymer chains is preferably less than about 80^°C, preferably less than about 5O⁰C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C.

Examples of monomers useful in preparing the polymer chain of the pendant arms include:

(i) substituted acrylates such as n-butyl acrylate, /so-butyl acrylate, tert- butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, ethyl acrylate and methyl acrylate

(ii) substituted methacrylates such as dodecyl methacrylate, 2-ethylhexyl methacrylate and octadecyl methacrylate

(iii) vinyls such as 1 -butene, isobutylene and vinylidene fluoride

(iv) alkylenes such as high density polyethylene

(v) cyclic siloxanes such as octamethylcyclotetrasiloxane (D4)

(vi) alcohols such as ethylene glycol, propylene glycol and dihydroxy perfluoropolyalkanes (Z-DoIs)

(vii) esters such as caprolactone, glycolide, lactide and dioxanone, and (viii) acids such as tetramethylene adipic acid and ethylene adipic acid.

Preferably, the pendant arms of the star polymer of the invention comprise a polymer chain comprising a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof. The polyester, polyoxyalkylene and polyoxysilane polymer chains may be optionally substituted with any group.

More preferably, the pendant arms of the star polymer may comprise a polymer chain of formula:

-(OYX)_n- wherein

Preferred alkyl are Ci to Cβ alkyl, more preferably Ci to C₄ alkyl, still more preferably methyl or ethyl and most preferably methyl.

Preferred alkoxy are Ci to C₆ alkoxy, more preferably Ci to C₄ alkoxy, still more preferably methoxy or ethoxy and most preferably methoxy.

Preferred aryl is phenyl.

Preferred halo is fluoro.

In one embodiment, the pendant arms of the star polymer comprises poly(dimethyl siloxane) (PDMS), which has a Tg of -127⁰C. In another embodiment, the pendant arms of the star polymer comprise a polyester. Preferred polyesters comprise one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone. A particularly preferred polyester is poly(ε-caprolactone) which has a Tg of -60^°C. Other useful polyesters may include acid monomers such as lactic acid, glycolic acid and mixtures thereof.

In a further embodiment, the pendant arms of the star polymer of the invention may comprise a polymer chain comprising a poly(alkyl acrylate). The alkyl subsituent group of the poly(alkyl acrylate) may be Ci to Ci₈ alkyl, preferably Ci to Cs alkyl, more preferably Ci to C₄ alkyl. The alkyl group may be linear or branched. Preferred poly(alkyl acrylates) comprise one or more monomers selected from the group consisting of terf-butyl acrylate, ethyl acrylate and methyl acrylate.

The present invention also provides a star polymer comprising:

(a) a core; and

(b) pendant arms attached to the core, wherein the pendant arms comprise a polyoxyalkylene, polyester, polyoxysilane or mixtures thereof.

The polyoxyalkylene, polyester and polyoxysilane polymer chains may be optionally substituted with any group. Preferably, the core is a crosslinked core.

In a preferred embodiment, the pendant arms of the star polymer particle comprise a polymer chain of formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of optionally substituted Ci to C₈ alkylene and SiR¹R², wherein the optionally substituted may comprise one or more substituents selected from hydroxy, halo and alkoxy (preferably Ci to C₆ alkoxy), R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl (preferably Ci to C₆ alkyl), alkoxy (preferably Ci to C₆ alkoxy) and aryl (preferably C₅ to Cio aryl),

Preferred alkyl are Ci to C₆ alkyl, more preferably Ci to C₄ alkyl, still more preferably methyl or ethyl and most preferably methyl.

Preferred aryl is phenyl.

Preferred halo is fluoro.

In this embodiment, the pendant arms of the star polymers of the present invention may advantageously exhibit a low glass transition temperature. The glass transition temperature is often influenced by the chemical composition of the pendant arm as well as its molecular weight. Preferably, the pendant arms exhibit a glass transition temperature of less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about O⁰C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C.

The pendant arms of the star polymers of the invention may be of any appropriate molecular weight. Preferably, the pendant arms of the star polymers have a number average molecular weight of at least 2,000, more preferably at least 5,000, even more preferably at least 10,000. The pendant arms of the star polymers of the invention extend from the core and may be directly attached to the core by a covalent bond or indirectly attached via an appropriate linking group. The star polymers of the invention comprise at least three, and preferably at least ten, pendant arms.

Preferably, the star polymer is a non core-crossl inked star polymer or a star microgel. Consequently, it is preferred that each pendant arm comprises a linear polymer chain. The pendant arms may be a homopolymer or a copolymer. The core of the star polymer may be a polyvalent molecule or a crosslinked network prepared from a divinyl crosslinking agent optionally together with a monovinyl monomer. Preferably the core is a crosslinked network.

When the star polymer is a star microgel polymer, the crosslinked core of the star microgel may comprise a polymer that is prepared from the same monomers or different monomers used to prepare the polymer chains forming the arms. For the low Tg star polymers, the crosslinked core may or may not be formed of a low Tg material provided that the Tg of the whole star polymer is in the Tg range referred to above.

The crosslinked core may be formed from the reaction of a monovinyl monomer with a divinyl monomer or crosslinking agent. Suitable monovinyl monomers include but are not limited to methyl methacrylate, methyl acrylate, styrene and ε-caprolactone, while examples of suitable crosslinking agents include ethylene glycol dimethacrylate, ethylene glycol diacrylate, divinyl benzene and bis(ε- caprolactone-4-yl). Suitable monovinyl and divinyl monomer combinations for the preparation of the crosslinked core will be apparent to the person skilled in the art. The divinyl monomer may also be used on its own without a monovinyl monomer in the preparation of the crosslinked core. The star polymers preferably have a number average molecular weight of at least about 2,000, more preferably at least about 5,000 and still more preferably, at least about 10,000.

The star polymers of the invention may be prepared by any method known to the art, and the choice of method may depend on the monomeric components of the polymer and the nature of the reactive functional group (if any) present on core and the pendant arms. Suitable methods include for example, condensation polymerization, ionic polymerization, ring opening polymerization (ROP) and free radical polymerization, including living free radical polymerization. A preferred method for the preparation of star polymers involves free radical polymerization, and more preferably, living free radical polymerization. Living free radical polymerization is distinguished from other free radical polymerization processes in that the propagating free radical is not extinguished, and the polymer is able to continue to grow from the radical centre whenever additional monomer is supplied. An advantage of living free radical polymerization conditions is that control over the construction of the polymer fragment, including its molecular weight, functionality and polydispersity, may be achieved. Examples of living free radical polymerization techniques include nitroxide mediated radical polymerization (NMP), atom radical transfer polymerization (ATRP) and reversible-addition fragmentation chain transfer (RAFT) polymerization.

In one embodiment, monomers and compounds used to prepare the pendant arms and the core of a star polymer are reacted together in the presence of a suitable catalyst or initiator. Alternatively, the pendant arms of the star polymer may be pre-formed then reacted with the monomers or compounds that form the core of the star polymer.

In one preferred embodiment, the pendant arms of the star polymers may be prepared from the ring opening polymerization of a suitable cyclic monomer. For example, pendant arms comprising poly(dimethylsiloxane) may be prepared from the acid catalysed ring opening polymerization of octamethylcyclotetrasiloxane (D4), while pendant arms comprising a polyester such as poly(ε-caprolactone) may be prepared from the ring opening polymerization of ε-caprolactone.

The star polymers of the invention may also be optionally modified with an appropriate reactive functional group to enable it to be used in the preparation of functional ised honeycomb polymeric materials. Examples of suitable reactive functional groups include hydroxyl, amino, ester, carboxyl, halogen and vinyl groups. Functional groups used in click chemistry can also be included and examples of these functional groups include azides and acetylenes. When such star polymers are used to prepare honeycomb polymeric materials, the functional groups may impart functionality to honeycomb materials and therefore assist to enhance certain properties, for example biocompatibility, of the honeycomb materials, or to allow the honeycomb material to react with other materials or substrates.

The present invention also provides a layer comprising a honeycomb polymer in accordance with the present invention as described herein. In the preparation of the honeycomb polymer the layer may be cast on any suitable substrate and may be planar or non-planar. Preferably, the layer is non-planar.

Preparation of Star polymers The star polymers of the invention may be prepared using any suitable technique known in the art. Exemplary techniques include but are not limited to synthetic organic chemical techniques, ionic polymerization, ring opening polymerization and free radical polymerization. Some suitable methods for preparing star polymers have been described in WO1998/031739, W01999/058588, WO2004/048428 and WO2004/048429, the disclosures of which are incorporated herein by reference. It is preferred that the star polymers be prepared using free radical polymerization, more preferably living free radical polymerization. The use of living free radical polymerization may enable the star polymers to exhibit a low polydispersity (PD). The low polydispersity value signifies that a high degree of uniformity in molecular size between polymer particles is obtained. The low polydispersity may contribute to the formation of uniform pore sizes in the honeycomb polymeric materials.

In one embodiment of the invention, the preparation of the star polymers involves the formation of the pendant arms followed by reaction of the pendant arms with appropriate monomers or compounds to generate the star polymers.

In accordance with one aspect of the invention, the pendant arms of the star polymer particle may comprise a low Tg polymer chain. Preferably, the Tg of the pendant arms is less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about

25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C. The low Tg polymer chain may also have a number average molecular weight of at least 2,000, more preferably a number average molecular weight of at least 5000, even more preferably a number average molecular weight of at least 10,000.

In accordance with another aspect of the invention, the pendant arms may comprise a polymer selected from at least one of a polyoxyalkylene, a polyester and a polyoxysilane. Preferably, the pendant arms comprise a polymer chain of formula:

-(OYX)_n- wherein X may be the same or different at each occurrence and is selected from the group consisting of optionally substituted Ci to C₈ alkylene and SiR¹R², wherein the optionally substituted may comprise one or more substituents selected from hydroxy, halo (preferably fluoro) and alkoxy (preferably Ci to C₆ alkoxy),

R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl (preferably Ci to C₆ alkyl), alkoxy (preferably Ci to C₆ alkoxy) and aryl (preferably C₅ to Ci_O aryl),

In accordance with a further embodiment of the invention, the pendant arms of the star polymer of the invention may comprise a polymer chain comprising a poly(alkyl acrylate). The alkyl subsituent group of the poly(alkyl acrylate) may be Ci to Ci8 alkyl, preferably Ci to Cs alkyl, more preferably Ci to C₄ alkyl. The alkyl group may be linear or branched. Preferred poly(alkyl acrylates) comprise one or more monomers selected from the group consisting of te/t-butyl acrylate, ethyl acrylate and methyl acrylate.

The pendant arms referred to above may be prepared using any method known in the art and the choice of method would depend on the nature of the monomeric components of the polymer chain. Preferably, the pendant arms are prepared by condensation polymerization or ring opening polymerization. For example, in one embodiment, the pendant arms may comprise a polyoxysilane. In this embodiment, the pendant arm may be prepared from the acid catalysed ring opening polymerization of a cyclic siloxane such as octamethylcyclotetrasiloxane (D4). In another embodiment, the pendant arms comprise a polyester. The preparation of the polyester may involve the ring opening polymerization of a lactone such as caprolactone, glycolide, lactide or dioxanone. The pendant arms may be optionally modified with an appropriate reactive functional group to enable it to be attached to the core of the star polymer particle. Examples of suitable reactive functional groups include hydroxyl, amino, ester, carboxyl, halogen and vinyl groups. Depending on the choice of functional group, the pendant arm may in itself, be capable of acting as a macromonomer or a macroinitiator in the formation of the star polymer particle.

To generate star polymers, the pendant arms may be reacted with a polyvalent compound, such as that used in the preparation of non core-crosslinked star polymers, or with a monomeric or macromolecular compound, such as those used in the preparation of star microgels.

Exemplary polyvalent compounds for the preparation of non core-crosslinked star polymers include, but are not limited to, 2,3,6,7,10,11-hexa(10'-hydroxy decanoxyl) thphenylene, glucose, phloroglucinol, 2,4,6 trihydroxytoluene and cyclodextrin hydrates. The pendant arms may be reacted with, and attached to, the polyvalent compound using any conventional technique known to the art. The choice of technique may be dictated by the nature of the functional groups on the pendant arms and the polyvalent compound. The pendant arms may also be directly attached to the polyvalent core or be indirectly attached to the core via a linking group.

In the preparation of star microgels, the pendant arms may be added to a mixture comprising one or more monomers. In one embodiment, the pendant arms are added to a monomer mixture that comprises at least one divinyl monomer. Preferably, the monomer mixture also includes a monovinyl monomer. The divinyl monomer may react on its own or together with the monovinyl monomer under appropriate conditions to form the crosslinked network core of the star microgel. When the formation of the network occurs in the presence of the polymer chain that is used to prepare the pendant arms, the arms may also become covalently bonded to the network core. The molar ratio of arms to crosslinker is preferably at least 5, more preferably at least 10, still more preferably at least 15 and most preferably in the range of from 15 to 100.

In a preferred embodiment, the pendant arms are functionalized with a reactive group that readily cleaves under free radical conditions to enable the pendant arms to act as a macroinitiator when it is added to a mixture of monomers, for example, a mixture of monovinyl and divinyl monomers, to initiate the formation of the star microgel under free radical polymerization conditions. Living free radical polymerization conditions are preferred. The reactive group may be a dithio compound, such as that employed in RAFT polymerizations, an alkoxyamine group, such as that used in nitroxide mediated polymerization (NMP) or the alkyl-halo group, which may be employed for ATRP. The relative quantities of monomer and the conditions required for living free radical polymerization may be readily ascertained by the person skilled in the art.

The functionalized pendant arms may act as a macromonomer in the formation of a microgel star polymer. For example, where the reactive functional group is a vinyl group, a macromonomer that may participate in free radical polymerization reactions is formed. Similar to above, the functionalised pendant arms may be added to a mixture of monomers. In this embodiment however, a separate initiator molecule may be required to initiate the free radical polymerization reaction used to form the star microgel polymer. Once again, living free radical polymerization conditions are preferred for the formation for the star microgels.

The use of living free radical polymerization conditions in the preparation of star microgel polymer advantageously enables the polymer to be generated in a controlled manner with controlled molecular weight and particle size and with low polydispersity. The star polymers in accordance with the present invention may have polydispersity of between about 1 and 10, preferably between 1 and 4, more preferably, between 1 and 3, even more preferably between 1 and 2, still more preferably, between 1 and 1.5 and most preferably between 1 and 1.3.

The star polymers of the present invention may also be prepared by growing the pendant arms as a branch from a reactive functional group on a polyvalent compound, a monomeric compound or macromolecular compound. In this embodiment, a single monomer unit of the pendant arms may react with and be attached to the polyvalent compound, monomeric compound or macromolecular compound. Further reaction of this monomer unit with subsequent monomer units then allows the arm to grow in molecular weight. The pendant arm may be grown using any suitable technique known in the art and the person skilled in the art would understand that the choice of technique will depend on the monomer composition of the pendant arms and its desired properties.

Without being limited by theory, it is believed that star polymers, which exhibit a spherical shape in solution advantageously facilitates the formation of the regular hexagonal array of pores in the honeycomb polymeric materials of the present invention. This may be due to the ability of the spherical-shaped polymers to precipitate around the water droplets during the preparation of the honeycomb materials and therefore support the highly ordered honeycomb pore structure of the material.

An example of the preparation of a star polymer in accordance aspect of the invention is shown in following scheme 1 : i *(

Scheme 1 : Preparation of PDMS-co-divinyl benzene star microgel

Star microgels have shown potential for application as templates for silicate materials with low dielectric constants. As a result of several potential areas of application, particularly in electronic materials or drug delivery, a need has arisen for star microgels that can be degraded under mild conditions.

The star polymers of the aspect of the invention comprising polyester arms (and preferably also polyester cross linked core) are the first example of a fully degradable star microgel.

Traditionally, star microgels synthesized via the 'arms first approach' make use of controlled free radical polymerization techniques such as Nitroxide Mediated Radical Polymerization (NMRP), Atom Transfer Radical Polymerization (ATRP) or Reverse Addition Fragmentation Transfer (RAFT) Polymerization, whereby previously synthesized living linear arms are reacted with a crossl inker to form star microgels. The fully degradable star microgel described here is synthesized via ring opening polymerization (ROP), also a controlled polymerization, of lactone based monomers.

The ROP method allows for the synthesis of star microgels with polyester based structures (both arm and core moieties) that can degrade under controlled conditions' via hydrolysis of the ester linkages in the polymer. The invention enables the practitioner to take advantage of the well established methods for controlled degradation of ester linkages to selectively remove a scaffold or template formed of the polyester microgel. Examples of controlled degradation conditions are for example discussed in CG. Pitt, Biodegradable Polymers as Drug Delivery Systems, M. Chasin, R. Langer, Eds., Dekker, New York, 1990, p71 ; M. Vert, M. Li, G. Splenlehauer, P. Guerin, J. Mater. Med., 1992, 3, 432; and Y. Doi, M. Kunioka, Y. Nakamura, K. Soga, Macromolecules, 1988, 81, 2722.

One advantage of a polyester based star microgel is that the degradation products can be absorbed by the body with minimal tissue reaction making them suitable for a wide variety of medical applications, particularly as tissue scaffolds or potential drug delivery agents.

In a preferred aspect of the present invention, there is provided a star polymer particle comprising:

(a) a core; and

(b) a multiplicity of pendant arms attached to the core, wherein at least one, and preferably a multiplicity, of the pendant arms comprise a polymer chain of formula: -(OYX)_n- wherein X may be the same or different at each occurrence and is selected from the group consisting of C₂ to C₈ alkylene (preferably C₄ to C₈ alkylene) optionally substituted with one or more substituents selected from hydroxy, halo and alkoxy, Y is carbonyl, n is the number of repeating unit and is preferably at least 10, more preferably at least 15 and most preferably at least 20.

The core may comprise any suitable material. The core may be formed of a polyester or it may be formed from a material other than a polyester. Depending on the monomers or compounds used to prepare the core, the core may not be degradable, or may be degradable under conditions that a different to those used to degrade the polyester pendant arms. Preferably, the core is a crossl inked network formed of a polyester cross linker.

In a preferred embodiment, the star polymers comprise polyester arms and a polyester crossl inked core. Preferably, said core and arms are formed by ring opening polymerization of lactones such as caprolactones. In a preferred embodiment, the pendant arms comprise a polyester comprising one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone. Such star polymers are fully degradable under hydrolysis conditions.

One advantage of the polymer particles formed with polyester arms is that they are biocompatible and fully biodegradable. In addition, the biodegradation products are non-toxic and can be digested or absorbed in the physiological environment with minimal adverse tissue reaction. Accordingly the star polymers of this embodiment of the invention may be used in the preparation of polymer architectures, including honeycomb polymers, to provide templates or scaffolds in the formation of materials suitable for use in electrical, biomedical, drug delivery or other applications. The resultant scaffold can then be subsequently degraded under appropriate conditions. In this way, the template or scaffold formed of the polyester star polymer may be selectively removed to leave the shaped materials for which the star polymers provide a template or scaffold.

In one preferred embodiment, the polyester star polymer particle can be used as a scaffolding or templating material to prepare composites of high temperature polymers such as polyimides. The polyester star polymers then can be degraded and removed under appropriate conditions to leave a porous composite organic material that has a low dielectric constant for electronics applications. The porous composite materials can be used in electronic chips and other devices.

An example of a fully degradable polyester star microgel polymer in accordance with one aspect of the invention is shown in following scheme 2:

Living Arms Star Microgel

Scheme 2: Preparation of degradable polyester star microgel via ring opening polymerization

The star polymers of the invention may also be formed from a combination of degradable and non-degradable monomeric components. By way of example, a range of star polymer structures may be obtained, as shown in scheme 3:

Scheme 3: Generalized schematic of selectively degradable core cross-linked star (CCS) polymer formation and subsequent hydrolysis to remove the labile component.

In one embodiment of the invention, the star polymers may comprise pendant arms comprising a polyester that is degradable under hydrolysis conditions and a core that does not degrade under hydrolysis conditions. Each pendant arm may comprise the polyester. Alternatively, only a proportion of the pendant arms may comprise the polyester with the remaining pendant arms being formed from one or more monomers that do not degrade under the hydrolysis conditions. By combining the use of degradable and non-degradable monomers it is possible to obtain a range of star polymers having different domains that can be selectively degraded. This provides avenues to a range of star polymers which can be structurally modified by hydrolysis of the degradable component to thereby result in star polymers that can be tailored to suit specific applications.

The person skilled in the art would understand that the relative proportions of the monomers and polymers used in the preparation of the star polymers of the invention will have an influence on glass transition temperature. Thus, it is still possible for star polymers comprising mixtures and blends of different polymeric components, including mixtures and blends of different types of pendant arms, to exhibit the property of low Tg.

The polyester star microgels of the invention may be synthesized via a 2-step process (which may in many instances be conducted in a "one pot" process) involving the synthesis of living linear arms followed by a crosslinking step to generate star microgels. In a preferred embodiment of the invention, in the first step, ring opening polymerization of a lactone such as ε-caprolactone (CL), with a suitable ring opening initiators (such as n-butanol) and catalysts (such as stannous octanoate) may occur in a suitable inert solvent such as toluene to form the linear arms. The arms may comprise a reactive functional group that cleaves under living polymerization conditions. A crosslinking agent, for example, a bislactone such as bis(ε-caprolactone-4-yl) (BCY) synthesized according to literature (Palmgren, R., Karlsson, S., Albertsson, A., J. Polym. Sci. Polym. Chem., 1997, 35, 1635) may then be added to the reaction solution containing the linear arms. The bislactone will typically be used in excess of the polycaprolactone arms (for example BCY/PCL = 10) and acts as a crosslinking component under ROP conditions.

Preparation of Honeycomb Polymeric Material

In another aspect, the present invention provides a process for the preparation of a honeycomb polymeric material comprising: (a) providing a star polymer composition comprising star polymer units in a volatile solvent, wherein the star polymer have a core and a plurality of pendant arms and a low glass transition temperature;

The present invention also provides a process for the preparation of a honeycomb polymer comprising:

(a) providing a star polymer composition comprising star polymer units in a volatile solvent, wherein the star polymers have a core and a plurality of pendant arms and wherein the pendant arms comprise a polyoxyalkylene, polyester, polyoxysilane or mixtures thereof; (b) forming a layer of the composition;

(c) subjecting the layer of the composition to a humid atmosphere; and

The layer of polymer solution is preferably formed on a surface.

The present invention further provides a process for the preparation of a honeycomb polymeric material comprising:

(b) forming a layer of the composition on a surface;

(c) subjecting the layer of the composition to a humid atmosphere; and

(d) evaporating the solvent to form a honeycomb polymeric material from the composition on the surface. The present invention also provides a process for the preparation of a honeycomb polymeric material comprising:

(a) providing a star polymer composition comprising star polymer units in a volatile solvent, wherein the star polymer has a core and a plurality of pendant arms and wherein the pendant arms comprise a polyoxyalkylene, polyester, polyoxysilane or mixtures thereof;

(b) forming a layer of the composition on a surface;

(c) subjecting the layer of the composition to a humid atmosphere; and

(d) evaporating the solvent to form a honeycomb polymeric material from the composition on the surface.

The process of the present invention may use the general procedure developed by Bernard Francois in Nature (1994), volume 369, page 387 to prepare honeycomb polymeric materials. The resulting honeycomb polymeric materials are typically layers having a thickness of about 0.1 to 1 mm, however structures having larger thickness can also be prepared by forming thick layers in a single application or by building up a thick layer by multiple applications on a substrate. In addition, thin layers or films may also be prepared. Generally, the thickness will be from 0.1 to 10mm. The general methodology used to prepare honeycomb polymeric materials and the conditions used to vary the pore size of such materials has been reported in the prior art.

The star polymer composition used in the preparation of the honeycomb polymeric materials of the invention comprises star polymer units which either have (i) a low Tg as described herein or (ii) a specific chemical structure as described herein. The star polymers are mixed with, and preferably dissolved in, a volatile solvent. The star polymer composition may therefore be in the form of a polymer solution. The volatile solvent may be any suitable solvent that readily evaporates under the conditions employed to generate the honeycomb polymeric material. The evaporation of the solvent assists in the condensation of water droplets, which subsequently self-assemble on the surface of the star polymer composition to give rise to the honeycomb pore morphology. The selection of volatile solvent will depend on the particular results desired. Examples of suitable solvents include carbon disulfide, chloroform, benzene and toluene. Such solvents have different physical properties that can affect the morphology of the resultant honeycomb material. For example, carbon disulfide has a greater density than water. The higher density carbon disulfide inhibits the migration of water droplets throughout the cross-section of the honeycomb polymeric layer. As a result, the pores of the honeycomb polymer may only form near the surface of the layer. In comparison, the use of a solvent that is less dense than water provides a honeycomb layer having pores that extend throughout the entire cross-section of the layer.

In the star polymer composition, the star polymer units may be mixed in the volatile solvent at any concentration that achieves the advantages of the present invention. Preferably, the star polymers are present in a concentration in the range of between about 0.5 to 20%, more preferably about 10% in the polymer composition. The star polymers are generally soluble in the solvent.

In accordance with the present invention, a layer is formed from the star polymer composition. In one embodiment, the layer may be formed by applying the polymer solution containing the star polymers onto a surface, such as by roller coating or brush coating, so that the solution is spread onto the surface. The surface is preferably provided by a substrate. In another embodiment, the layer may be formed by dipping the substrate into the polymer solution or by spraying the solution onto the substrate. The layer of star polymer composition need not be supported by a surface and may also be suspended within a space.

The substrate may be made from any suitable material. It is preferred that the substrate is an inert substrate that comprises a material does not react with the polymer or the volatile solvent in the polymer composition. The substrate may also possess a surface charge, such as a negative or positive surface charge, which may be provided by appropriate functional groups in the substrate. Such surface charges do not interfere with the formation of the honeycomb polymer. The substrate may include for example, glass, silicon wafer, metal or metal coated substrate and plastic substrates such as polyolefins.

In one preferred embodiment, the honeycomb polymeric material of the invention is formed on a substrate that has a planar surface. A planar surface is a substantially flat surface having variations of less than about 10 microns, more preferably less than about 5 microns from planar. The honeycomb polymeric material formed on a planar surface is therefore a flat, planar layer coating the surface of the substrate.

In another preferred embodiment, the substrate has a non-planar surface. As used herein, "non-planar" refers to a surface that is not smooth, but has topographical features such as roughness, curvature or patterning. Preferably, the non-planar surface is a curved or patterned surface. A patterned surface may include variations of at least 5 microns, more preferably at least 10 microns and even more preferably at least 20 microns from planar. Typically, the variations will be no more than 1 mm. The application of the star polymer composition on a non-planar surface provides a honeycomb polymeric material as a layer that conforms to the shape and/or topography of the underlying substrate. It is believed that the advantages of the present invention described herein enable the honeycomb polymeric material to form around and replicate a number of complex, non-planar shapes and surface topographies.

When the honeycomb polymer is formed on a curved non-planar surface, it is preferred that the surface comprises variations of more than 5 microns, preferably more than 10 microns from planar. Preferably, the non-planar surface is a particle surface. Even more preferably, the non-planar surface is a surface of a particle of no more than 1 mm in diameter.

In a further embodiment, a porous support matrix may provide a substrate for the polymer solution. Generally, the support matrix would comprise an open frame structure having a plurality of interstitial spaces arranged therein. The support matrix may be of any suitable size, shape and configuration and the person skilled in the art would understand that the exact dimensions and configuration of the support matrix is not critical to the invention, as these parameters will usually be determined by the intended application in which the system is to be employed. An advantage of the support matrix is that it provides reinforcement to the honeycomb polymeric material. Thus, the honeycomb material is not reliant upon its own inherent strength characteristics to maintain structure and integrity.

The support matrix may be made of any suitable material. Preferably, the support matrix is formed from a material that is relatively inert. This helps to ensure that the matrix does not participate in any unwanted reactions during use of the system. In a preferred embodiment, the support matrix is provided by a rigid material, for example, such as metal, ceramic or glass or hard plastics. The support matrix may also be provided by a flexible material, such woven or non-woven fibrous materials or soft plastics. The support matrix may also be planar or non-planar. The thickness of such support matrices may be in the range of from 500 nm to 1 mm.

The support matrix generally comprises a plurality of interstitial spaces that typically extend through the entire thickness of the support matrix and are dispersed throughout the area of the matrix. The interstitial spaces may be of any size and shape, such as for example, square, circular or hexagonal shapes, or slots. In a preferred embodiment, the interstitial spaces are provided as a regular array in the support matrix. Preferably, the interstitial spaces are of a substantially uniform size. The support matrix may be in the form of a grid, mesh, net or other porous structure which will typically comprise a regular array of interstices. The commercially available transmission electron microscope (TEM) grids supplied by ProSciTech are examples of substrates having a regular array of interstitial spaces, which are suitable for use as a support matrix. Such TEM grids typically have interstitial spaces ranging in size from about 1.0 μm to centimeters in diameter. In a preferred embodiment, the average size of the interstitial spaces of the support matrix is in the range of from 1 μm to 1 cm.

Upon coating the support matrix with a star polymer composition, a layer of the polymer composition would extend across at least one interstitial space of the support matrix. A layer of polymer composition may also be formed on the surface of the support matrix itself. The surface of the support matrix is generally regarded as a non-planar surface. Upon evaporation of the solvent from the star polymer composition and formation of the honeycomb polymeric material, the honeycomb polymer therefore extends across at least one interstitial space of the support matrix and preferably extends across a multiplicity of interstitial spaces. In this regard, polymer composition and the honeycomb polymeric material would typically traverse at least one interstitial space of the support matrix in a continuous manner so that it is suspended within the space. The honeycomb polymeric material may also form on the surface of the support matrix if a layer of the star polymer composition has also been applied to the matrix surface.

In one embodiment, the support matrix may be modified to render the matrix more compatible with the honeycomb polymeric material. Such modification may involve coating the support matrix with a suitable material. Suitable coatings may be formed by techniques known to the art, such as by grafting polymers to the surface of the support matrix. Surface modification techniques such as chemical treatment or plasma treatment may also be used to alter the characteristics of the support matrix. The support matrix may also possess a surface charge, such as a negative or positive surface charge, which may be provided by introducing appropriate functional groups in the support matrix. Such surface charges do not interfere with the formation of the honeycomb polymer.

In another embodiment of the present invention, the non-planar surface may be provided by a particle surface. In this embodiment, the particles may be mixed into the star polymer composition comprising the volatile solvent and the star polymer used to prepare the honeycomb polymer prior to application of the star polymer composition. The particles that are mixed in the star polymer composition may therefore be a template for the formation of the honeycomb polymer. Because the template particles are typically insoluble in the solvent of the star polymer composition, a suspension may be formed.

In a further aspect, the present invention provides a process for the preparation of a honeycomb polymer comprising:

(a) providing star polymer composition comprising star polymer units and a template particle in a volatile solvent, wherein the star polymer has a low glass transition temperature;

(b) forming a layer of the composition on a surface

(c) subjecting the layer of the composition to a humid atmosphere; and

(d) evaporating the solvent to form a honeycomb polymer from the polymer composition on the surface.

(a) providing star polymer composition comprising star polymer units and a template particle in a volatile solvent, wherein the star polymer has a core and a plurality of pendant arms and wherein the pendant arms comprise a polyoxyalkylene, polyester, polyoxysilane or mixtures thereof; (b) forming a layer of the composition on a surface

(c) subjecting the layer of the composition to a humid atmosphere; and

The template particle may be any suitable particle which is capable of supporting the star polymer composition during the preparation of honeycomb polymers. Preferably, the template particle is selected from mineral particles, salt particles, sugar particles and beads.

In a preferred embodiment, the template particle is water soluble.

The present invention further provides a process for the preparation of a honeycomb polymer comprising: (a) providing star polymer composition comprising star polymer units and a template particle in a volatile solvent, wherein the star polymer has a low glass transition temperature;

(b) forming a layer of the composition on a surface

(c) subjecting the layer of the composition to a humid atmosphere; (d) evaporating the solvent to form a honeycomb polymer from the polymer composition on the surface; and

(e) contacting the honeycomb polymer with a solvent to remove the template particle from the honeycomb polymer.

Even further, the present invention provides a process for the preparation of a honeycomb polymer comprising:

(a) providing star polymer composition comprising star polymer units and a template particle in a volatile solvent, wherein the star polymer has a core and a plurality of pendant arms and wherein the pendant arms comprise a polyoxyalkylene, polyester, polyoxysilane or mixtures thereof;

(b) forming a layer of the composition on a surface (c) subjecting the layer of the composition to a humid atmosphere;

(d) evaporating the solvent to form a honeycomb polymer from the polymer composition on the surface; and

The solvent used to remove the template particle may be any liquid that is compatible with the template particle. Preferably, the template particle is soluble in the solvent. In a preferred embodiment, the solvent is water. In this embodiment, it is preferable that the template particle be water soluble.

The star polymer composition may be applied onto the substrate using a wide variety of techniques known to the art, including by dispersing the polymer composition onto the substrate or by using printing techniques such as ink jet printing, piezoelectric printing and stamping. For non-planar substrates, a layer of the polymer composition may be formed by using dip coating methodology or by spraying. It may also be possible to apply the polymer composition onto the surface of a liquid.

It has been found that the presence of some long chain polymers in the star polymer composition, for example linear polymers with a number average molecular weight of at least about 5000, may have a beneficial effect on the honeycomb morphology of the porous polymeric material, both in assisting in the formation of uniform pores as well as improving the mechanical properties of the porous polymeric material. Such linear polymers may engage in entanglements with the star polymers to provide resilience and adhesion and thereby enhance the properties of the honeycomb polymeric material. As a result, it may not be necessary to purify the synthesized star polymers in order to remove such linear polymers, which may be a by-product of the synthetic procedure, prior to preparation of the honeycomb material and its application onto a substrate. When linear polymers are present in the star polymer composition used to prepare the honeycomb polymeric materials of the invention, the linear polymers are preferably present in a concentration of between about 1-50%, more preferably between about 1-30% and even more preferably between about 1 -10% by weight of the total polymer content of the star polymer composition.

In accordance with the process of the present invention, the applied layer of the star polymer composition is subjected to a humid atmosphere. The humid atmosphere is used to generate water droplets, which are instrumental in the formation of the regular array of pores observed in honeycomb polymeric materials. The humid atmosphere may be generated by any means known in the art. Preferably, the humid atmosphere is generated by a stream of humid air that passes over the polymer composition layer. As would be appreciated by the person skilled in the art, the conditions employed in the generation of the humid atmosphere, including the relative humidity of the air and the rate of air flow may be varied in order to produce honeycomb polymeric materials having different pore sizes. Preferably, the humid atmosphere has a relative humidity of 10-90%, even more preferably 60-80%.

In accordance with the process of the invention, upon exposure of the polymer composition layer comprising the star polymer and volatile solvent to a humid atmosphere, evaporation of the volatile solvent then ensues. The evaporation of the solvent causes cooling of the humid atmosphere and assists in promoting the condensation of water droplets from the humid air. Without wishing to be limited by theory, it is believed that the units of star polymer in the casting solvent are able to assemble around the water droplets to prevent coalescence of the water. As a result, once the water and the solvent have evaporated completely, a porous honeycomb polymeric material having an array of regular and substantially uniform pores is formed. The pore size of the resultant honeycomb material is typically in the range of 50 nm to 30 microns, preferably in the range of 0.1 to 10 microns and most preferably in the range of 0.2 to 2 microns, although as discussed above, the pore size may be varied by adjusting the concentration of star polymers in the solution and the humidity of the air during application of the star polymer composition onto a substrate.

In one embodiment, the substrate used in the preparation of the honeycomb polymeric materials of the invention may be suspended in a stream of gas or liquid, such as that provided by a fluidized bed. In this embodiment, the substrate is preferably a spherical substrate. In one preferred embodiment, the preparation of the honeycomb polymeric materials may performed by applying the star polymer composition (optionally together with a template particle) onto a substrate on the fluidized bed and then subjecting the polymer composition to the conditions for forming the honeycomb material described above. The subsequent suspension of the substrate on the fluidized bed enables the polymer composition to coat the entire surface of the substrate. In a preferred embodiment, when the substrate is a spherical shaped substrate, the resultant honeycomb polymeric material is therefore in the shape of a sphere.

In another embodiment of the present invention, the substrate onto which the polymer composition layer is applied may be a removable substrate that can be removed after formation of the honeycomb material. When the substrate is removed, a hollow porous polymeric material structure may thereby result. The substrate may be removed by any suitable technique, and the technique employed would depend on the nature of the substrate. In one embodiment, the substrate is soluble in a solvent. A preferred solvent is water. As a result, the substrate may therefore be removed by contacting the honeycomb polymeric material and substrate on which it has been formed with a quantity of water for a time sufficient to dissolve the substrate. Suitable water-soluble substrates include water soluble crystals, such as crystals of a salt or sugar. In another embodiment, the substrate may be a chemical entity or a drug, including a drug composition. The porous honeycomb polymeric material may be used to encapsulate the drug for controlled release applications. In this embodiment, the drug composition is therefore released under appropriate conditions through the pores of the honeycomb material. Other substrates and methods of removing those substrates are contemplated in accordance with the present invention. The person skilled in the art would be able to determine suitable substrates and removal conditions.

A representation of the formation of a honeycomb polymeric material on a non- planar substrate is shown in Figure 8. With reference to Figure 8, an illustration of a method for the preparation of a honeycomb polymer in accordance with the present invention is shown. As seen in part 1 of Figure 8, a star polymer of the present invention, such as a star microgel, may be dissolved in a volatile solvent such as benzene to provide a star polymer composition in the form of a solution containing the star polymer. The polymer composition may also be mixed with a template particle such as water soluble crystal. The polymer composition, containing the star polymer and the template particle, is applied onto a flat, planar surface. A flow of humid air is directed towards the polymer composition. The evaporation of benzene from the polymer composition causes a cooled benzene layer to form on top of the composition. As seen in part 2 of Figure 8, following commencement of the evaporation of the benzene, water droplets from the humid air condense and form an array of water microspheres on the surface of the benzene solution. The star polymers present in the polymer composition precipitate around the surfaces of the condensed water droplets to stabilize the micro-spheres. Upon further evaporation of the benzene, this array of water micro-spheres begins to form a honeycomb polymer. The honeycomb polymer then move towards the planar substrate under continued evaporation of the benzene. As seen in part 3 of Figure 8, as the initially formed honeycomb polymer layer travels towards the substrate, the layer eventually reaches an area in which it contacts the surface of a template particle that was also present in the polymer composition. Capillary forces acting on the layer then causes the honeycomb polymer to conform to the shape of the template particle surface. As seen in part 4 of Figure 8, contacting the honeycomb polymer with water can result in the removal of template particle and the formation of a hollow honeycomb polymer structure.

It would be appreciated by the person skilled in the art that the honeycomb polymeric materials of the present invention are able to be readily formed under a variety of conditions and moulded into a variety of shapes and morphologies by casting on a number of different substrates without detrimental effects on the regular and uniform pore structure of the polymeric material.

System Comprising Honeycomb Polymeric Materials

In a further aspect, the present invention provides a system comprising:

(a) a support matrix having a plurality of interstitial spaces therein; and

(b) a honeycomb polymeric material formed of a star polymer composition comprising star polymer units having a low glass transition temperature, wherein the honeycomb polymeric material extends across at least one interstitial space of the support matrix.

The system of the invention comprises a support matrix, which may be provided by any suitable solid and porous substrate. Generally, the support matrix would comprise an open frame structure having a plurality of interstitial spaces arranged therein. The support matrix may be of any suitable size, shape and configuration and the person skilled in the art would understand that the exact dimensions and configuration of the support matrix is not critical to the invention, as these parameters will usually be determined by the intended application in which the system is to be employed. An advantage of the support matrix is that it provides reinforcement to the honeycomb polymeric material. Thus, the honeycomb material is not reliant upon its own inherent strength characteristics to maintain structure and integrity.

The support matrix may be made of any suitable material. Preferably, the support matrix is formed from a material that is relatively inert. This helps to ensure that the matrix does not participate in any unwanted reactions during use of the system. In a preferred embodiment, the support matrix is provided by a rigid material, for example, such as metal, ceramic, glass or hard plastics. The support matrix may also be provided by a flexible material, such woven or non-woven fibrous materials or soft plastics. The support matrix may also be planar or non-planar. The thickness of such support matrices may be in the range of from 500 nm to 1 mm.

The support matrix comprises a plurality of interstitial spaces. The interstitial spaces typically extend through the entire thickness of the support matrix and are dispersed throughout the area of the matrix. The interstitial spaces may be of any size and shape, such as for example, square, circular or hexagonal shapes, or slots. In a preferred embodiment, the interstitial spaces are provided as a regular array in the support matrix. Preferably, the interstitial spaces are of a substantially uniform size. The support matrix may be in the form of a grid, mesh, net or other porous structure which will typically comprise a regular array of interstices. The commercially available transmission electron microscope (TEM) grids supplied by ProSciTech are examples of substrates having a regular array of interstitial spaces, which are suitable for use as a support matrix. Such TEM grids typically have interstitial spaces ranging in size from about 1.0 μm to centimeters in diameter. In a preferred embodiment, the average size of the interstitial spaces of the support matrix is in the range of from about 1 μm to 1 cm.

In accordance with the present invention, a honeycomb polymeric material extends across at least one interstitial space of the support matrix. In this regard, the honeycomb polymeric material traverses at least one interstitial space of the support matrix in a continuous manner so that it is suspended within the space. Preferably, the honeycomb polymeric material extends across a multiplicity of interstitial spaces of the support matrix.

In accordance with one aspect, the honeycomb polymeric material used in the systems of the invention is formed of a star polymer composition comprising star polymer units having a low glass transition temperature and a number average molecular weight of at least about 2,000. Without being limited by theory, it is believed that favourable interactions which support the honeycomb polymer in the interstitial spaces of the support matrix arise when a star polymer composition comprising star polymer units contacts the support matrix. These interactions may be a capillary forces or favorable surface tension effects. The interactions maintain the honeycomb polymeric material within the interstitial spaces of the support matrix. As noted above, the support matrix may be modified in order to enhance the interactions.

In a preferred embodiment, the honeycomb polymeric material is formed from a star polymer composition comprising star polymer units, wherein the a glass transition temperature of the star polymer is less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about 0^°C, yet more preferably less than about -50^°C, and most preferably less than about - 100^°C. Without being limited by theory, it is believed that the low glass transition temperature of the star polymer imparts a degree of flexibility to the honeycomb polymeric material. This flexibility allows the honeycomb polymeric material to span at least one interstitial space, and preferably to span a plurality of interstitial spaces, of the support matrix without significant risk of breakage or shear.

Preferably, the star polymers having a low glass transition temperature is a star microgel as described herein. A suitable star polymer may comprise any monomer component, provided that the resultant star polymer possesses the property of low Tg. The star polymer may comprise be a homopolymer or a copolymer. When the star polymer comprises a copolymer, provided that significant glass transition occurs at the low Tg range referred to above, the polymer is considered useful in the present invention. Preferably, at least 25% of the glass transition is at a temperature in the defined low Tg range.

Examples of monomers useful in preparing low Tg star polymers include: (i) substituted acrylates such as n-butyl acrylate, /so-butyl acrylate, tert- butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, ethyl acrylate and methyl acrylate (ii) substituted methacrylates such as dodecyl methacrylate, 2-ethylhexyl methacrylate and octadecyl methacrylate (iii) vinyls such as 1 -butene, isobutylene and vinylidene fluoride (iv) alkylenes such as high density polyethylene (v) cyclic siloxanes such as octamethylcyclotetrasiloxane (D4) (vi) alcohols such as ethylene glycol, propylene glycol and dihydroxy perfluoropolyalkanes (Z-DoIs)

(vii) esters such as caprolactone, glycolide, lactide and dioxanone, and (viii) acids such as tetramethylene adipic acid and ethylene adipic acid. In a preferred embodiment, the star polymers comprise a polymer chain comprising a polyoxyalkylene, a polyester or a polyoxysilane. Preferably, the star polymers comprise a polymer chain of formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of optionally substituted Ci to Cs alkylene, and SiR¹R² wherein the optionally substituted Ci to Cs alkylene may comprise one or more substituents selected from hydroxy, halo (preferably fluoro) and alkoxy (preferably Ci to C₆ alkoxy),

R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl (preferably Ci to C₆ alkyl), alkoxy (preferably Ci to C₆ alkoxy) and aryl (preferably C₅ to Cio aryl), Y may be the same or different at each occurrence and is selected from a carbonyl or a covalent bond, n is the number of repeating unit and is preferably at least 10, more preferably at least 15 and most preferably at least 20.

In one preferred embodiment, the star polymer comprises poly(dimethyl siloxane) (PDMS), which has a Tg of -127^°C. In another preferred embodiment, the star polymer comprises a polyester. Preferred polyesters comprise one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone. A particularly preferred polyester is poly(ε-caprolactone) which has a Tg of -60^°C. Other useful polyesters may include acid monomers such as lactic acid, glycolic acid and mixtures thereof. The person skilled in the art would understand that depending on the choice of monomer component, a copolymer may also possess the property of low Tg. The preparation of suitable copolymers would be apparent to the skilled person. In a further embodiment, the star polymers comprise a polymer chain comprising poly(alkyl acrylate). The alkyl subsituent group of the poly(alkyl acrylate) may be Ci to Ci₈ alkyl, preferably Ci to C₈ alkyl, more preferably Ci to C₄ alkyl. The alkyl group may be linear or branched. Preferred poly(alkyl acrylates) comprise one or more monomers selected from the group consisting of te/f-butyl acrylate, ethyl acrylate and methyl acrylate.

The star polymers in the honeycomb polymeric material used in the systems of the present invention also preferably have a number average molecular weight of at least about 2,000, more preferably at least about 5,000 and most preferably, at least about 10,000. The relatively high molecular weight of the low Tg star polymers may advantageously assist to impart dimensional stability to the honeycomb polymeric material when the honeycomb polymer extends across an interstitial space of the support matrix. The low Tg star polymers may be prepared using any method known in the art and suitable methods of preparation have been described herein.

In yet another aspect, the present invention provides a system comprising: (a) a support matrix having a plurality of interstitial spaces therein; and (b) a honeycomb polymeric material formed of a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the pendant arms comprise a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof, and wherein the honeycomb polymeric material extends across at least one interstitial space of the support matrix.

It is preferred that the honeycomb polymeric material extends across a plurality of the interstitial spaces of the support matrix.

The pendant arms may comprise a homopolymer or copolymer that comprises the polyester, polyoxyalkylene or polyoxysilane. In a preferred embodiment, the pendant arms of the star polymer particle comprise a polymer chain of formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of Ci to Cs alkylene optionally substituted with one or more substituents selected from hydroxy, halo and alkoxy, and SiR¹R² where R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl, alkoxy and aryl,

In a preferred embodiment of the invention, the pendant arms of the star polymer may comprise a polymer chain comprising one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone.

The pendant arms of the star polymer preferably comprise linear polymer chains, which may be of any appropriate molecular weight. Preferably, the pendant arms of the star polymer has a number average molecular weight of at least 2,000, more preferably at least 5,000, even more preferably at least 10,000.

In one embodiment, the star polymer is a non core-crossl inked star polymer or a star microgel. The core of the star polymer may be a polyvalent molecule or a crosslinked network prepared from a divinyl crosslinking agent optionally together with a monovinyl monomer. Where a monovinyl and divinyl monomer combination is used for the preparation of the crosslinked core, such combinations will be apparent to the person skilled in the art. The crosslinked core of a star polymer such as a star microgel may be comprised of a polymer that is the same or different to that of the arms.

The pendant arms of the star polymer used in the system of the present invention preferably exhibit a low glass transition temperature. The glass transition temperature is often influenced by the chemical composition of the pendant arm as well as its molecular weight. Preferably, the pendant arms exhibit a glass transition temperature of less than about 80^°C, preferably less than about 50^°C, more preferably less than about 30^°C, even more preferably less than about 25^°C, still more preferably less than about O⁰C, yet more preferably less than about -50^°C, and most preferably less than about -100^°C.

Preferably, the honeycomb polymeric material in the system of the invention is prepared from a star polymer composition comprising star polymer units having a low polydispersity. In one embodiment, the star polymer has a polydispersity of between about 1 and 10, preferably between 1 and 4, more preferably, between 1 and 3, even more preferably between 1 and 2, still more preferably, between 1 and 1.5 and most preferably between 1 and 1.3.

The star polymers of the invention may be optionally modified with an appropriate reactive functional group to enable it to be used in the preparation of functional ised honeycomb polymeric materials. Examples of suitable reactive functional groups include hydroxyl, amino, ester, carboxyl, halogen and vinyl groups. Functional groups used in click chemistry may also be included and examples of these functional groups include azides and acetylenes. Such functional groups may assist to enhance certain properties of the resultant honeycomb polymeric material, for example biocompatibility or resistance to dissolution, or to allow the honeycomb polymeric material to react with other materials or substrates. For example, such functional groups may allow the honeycomb polymeric material to be crosslinked, which may enhance the strength or other physical properties of the material. Examples of functional groups for crosslinking include epoxy-amines, isocyanates and photo- crosslinkable conjugated moieties such as anthracene. Such crosslinking reactions may be reversible, depending on the nature of the crosslinking moiety. For example, photocrosslinking of a honeycomb polymeric material may achieved by exposing a honeycomb material prepared from star polymers functional ized with anthracene to wavelengths of light of greater than 300 nm. Upon exposure of the honeycomb polymeric material to wavelengths of light of less than 300 nm, the crosslinking may be subsequently reversed. In a preferred embodiment, the pendant arms of the star polymers are functionalized to provide the functional groups.

An example of an approach to prepare a photocrossl inked honeycomb polymeric material in accordance with one aspect of the invention is shown in scheme 4:

nm> >300 nm

Scheme 4: Preparation of crosslinked honeycomb polymeric material using anthracene as crosslinking moiety between star microgel polymers. The ability to reversibly crosslink the honeycomb polymeric materials allows unique patterned materials to be formed. Such patterning may be achieved by crosslinking the functionalized honeycomb materials, for example, by exposing an anthracene functionalized honeycomb material to a wavelength of light greater than 300nm, then masking selected areas of the crosslinked honeycomb polymeric material using a template, such as a TEM grid. Appropriate treatment of the masked and crosslinked honeycomb polymeric material to uncrosslink selective regions of the honeycomb polymer that has not been covered by the template then results in the formation of a patterned honeycomb material comprising both crosslinked and uncrosslinked areas. For anthracene crosslinked honeycomb polymeric materials, an appropriate treatment would involve exposing the masked material to a wavelength of light of less than 300nm as described above, to reverse the crosslinking. A photo- lithographic process to form a patterned honeycomb polymeric material is shown in the schematic illustration of Figure 22.

Other appropriate treatments to crosslink and selective uncrosslink the honeycomb polymers to give patterned materials of various properties of topographies would be apparent to the person skilled in the art.

The star polymers of the invention may also incorporate functional groups that allow the resultant honeycomb polymeric material to react with biological molecules or other compounds for use as biosensors and in assays in diagnostic and analytical applications. For example, 4-nitrophenyl chloroformate (NPC) can be used to selectively couple hydroxyl functional polymer to a primary amine in a biological molecule such as a protein or peptide. It would be appreciated by the person skilled in the art that other suitable functional groups may be incorporated, depending on the desired use and the required interaction. The functional groups may also be optionally incorporated into polymers having crosslinkable moieties or be otherwise capable of undergoing crosslinking reactions.

An example of an approach to prepare an amine functionalised honeycomb polymeric material in accordance with one aspect of the invention using amine anthracene as a model compound is shown in scheme 5. Amine anthracene is used in the example as the reaction can be conveniently monitored by fluorescence spectrometry.

FLAT SURFACE FLAT SURFACE

HONEYCOMB SURFACE HONEYCOMB SURFACE

Scheme 5: Preparation of functional ized honeycomb polymeric material using 4-nitrophenyl chloroformate (NPC) coupled to anthracene amine. The honeycomb polymeric materials and the systems of the invention may further comprise nanoparticles. Nanoparticles are typically solid particles of a size in the range of 1 nm to 100nm. The nanoparticles are preferably dispersed through the honeycomb polymeric material and more preferably, line the surface of the pores of the honeycomb polymeric material. The nanoparticles may advantageously provide functional micro-environments within the porous honeycomb material. In accordance with one aspect of the invention, the systems may therefore comprise a tiered structural hierarchy having different surface patterning and/or functionality based on (i) nanoparticles within the pores of a honeycomb polymeric material, (ii) a honeycomb polymeric material on a support matrix and (iii) the porous support matrix. Any suitable nanoparticle may be used and such nanoparticles will generally be selected on the basis of functionality and the desired application. Examples of suitable nanoparticles include silver, gold or silica nanoparticles, cadmium sulfide (CdS) or cadmium selenide (CdSe) quantum dots and nanoparticles prepared from polymers such as polystyrene.

In one embodiment, the nanoparticles may be covalently bound to the honeycomb polymeric material and the attachment of the nanoparticles may be facilitated by the use of appropriately functionalised honeycomb polymeric materials. The nature of the functional group will depend on the type of nanoparticle and the desired application. For example, the polymer particles used to prepare a honeycomb polymeric material may be functionalized with an acetylene group prior to formation of a honeycomb polymeric material. A complementary functional nanoparticle (e.g azide functional gold nanoparticle) may then react with the acetylene functionalized honeycomb material under appropriate conditions to covalently attach the nanoparticle to the surface of the material. In another example, a honeycomb polymeric material functionalized with 4-nitrophenyl chloroformate may be used to couple with amine functional nanoparticles. In still a further example, nanoparticles having magnetic properties (eg. FeO₃ nanoparticles) may be covalently bonded to the honeycomb layers. The resultant layers could be deformed by using a magnetic field to attract the nanoparticles and thereby induce a rearrangement of the honeycomb material. However, because of flexible nature of the honeycomb polymeric materials of the invention, such deformation will not lead to substantial cracking of the honeycomb polymer.

It is envisaged that hybrid assemblies comprising nanoparticles and honeycomb polymeric materials may be useful in variety of applications, including pharmaceutical, biotechnological, photonic and optical applications.

Preparation of System Comprising Honeycomb Polymeric Material The system of the invention is generally prepared by applying the polymer solution onto the support matrix to form a layer, then exposing the layer to a humid atmosphere to form the honeycomb polymeric material in accordance with the methodology described herein.

Thus in one aspect, the present invention provides a process for the preparation of a system comprising a honeycomb polymer system comprising the steps of: (a) providing a support matrix having a plurality of interstitial spaces;

(b) providing star polymer composition comprising star polymer units having a low glass transition temperature in a volatile solvent, to form a layer of the composition on the support matrix extending across at least one interstitial space of the matrix; (c) subjecting the layer of the composition to a humid atmosphere; and

(d) evaporating the solvent from the layer to form a honeycomb polymeric material from the polymer composition.

The present invention also provides a process for the preparation of a system comprising a honeycomb polymeric material comprising the steps of: (a) providing a support matrix having a plurality of interstitial spaces; (b) providing a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the pendant arms comprise a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof, in a volatile solvent to form a layer of the composition on the support matrix extending across at least one interstitial space of the matrix;

(c) subjecting the layer of the composition to a humid atmosphere; and

In the preparation of the honeycomb polymeric material, the general procedure as described herein and based on the methodology of Bernard Francois in Nature (1994), volume 369, page 387 may be used. Generally, the star polymers used to prepare the honeycomb polymeric material, which either (i) has a low Tg or (ii) has a specific chemical structure, is mixed with and is preferably dissolved in a volatile solvent in order to provide a star polymer composition. The volatile solvent may be any suitable solvent that readily evaporates under the conditions employed to generate the honeycomb polymeric material. Examples of suitable solvents include carbon disulfide, chloroform, benzene and toluene, and the person skilled in the art would understand solvent may be selected to achieve a desired result. As noted above, such solvents have different physical properties that can affect the morphology of the resultant honeycomb material.

The star polymers may be mixed in the volatile solvent at any concentration that achieves the advantages of the present invention. Preferably, the star polymers are present in the star polymer composition in a concentration in the range of between about 0.5 to 20%, more preferably about 10%. It is preferred that the star polymers be soluble in the volatile solvent.

In accordance with the present invention, a layer is formed from the star polymer composition. In one embodiment, the layer may be formed by coating the polymer composition containing the star polymer onto a substrate. The polymer composition may be applied onto the support matrix using any suitable technique, including by dispersing the polymer composition onto the support matrix, by roller coating or brush coating, by printing techniques or by spraying the star polymer composition on to the support matrix. These techniques generally result in the formation of a layer of the polymer composition which covers the entire area of the support matrix, including the interstitial spaces of the support matrix.

In another embodiment, the layer may be formed by dip coating. In this regard, dip coating involves the immersion of the support matrix into a star polymer composition. This technique may result in a layer of the polymer composition being formed in the interstitial spaces of the support matrix only. Without being limited by theory, it is believed that a layer of the polymer composition is maintained in an interstitial space of the support matrix by the action of capillary forces or favourable surface tension effects arising between the polymer composition and the portions of the open frame of the support matrix that lies adjacent the interstitial space.

In accordance with the present invention, the layer of polymer composition is subjected to a humid atmosphere. The humid atmosphere generates water droplets, which are instrumental in the formation of the regular array of pores observed in honeycomb polymeric materials. The conditions employed in the generation of the humid atmosphere, including the relative humidity of the air and the rate of air flow may be varied in order to produce honeycomb polymeric materials having different pore sizes. Preferably, the humid atmosphere has a relative humidity of 10-90%, even more preferably 60-80%.

In accordance with the invention, upon exposure of the polymer composition layer to a humid atmosphere, evaporation of the volatile solvent occurs. The evaporation of the solvent causes cooling of the humid atmosphere and assists in promoting the condensation of water droplets from the humid air. It is believed that the star polymers in the casting solvent are able to assemble around the water droplets to prevent coalescence of the water. As a result, once the water and the solvent have evaporated completely, a porous honeycomb polymeric material having an array of regular and substantially uniform pores is formed. The pore size of the resultant honeycomb material is typically in the range of 0.05 to 30 microns, preferably in the range of from 0.1 to 10 microns and more preferably in the range of 0.2 to 2 microns, although as discussed above, the pore size may be varied by adjusting the concentration of polymer in the solution and the humidity of the air during application of the polymer composition. The honeycomb polymeric materials typically have a thickness of about 0.1 to 1 mm, although larger thicknesses of between about 0.1 to 10mm may be formed.

A layer of the star polymer composition may be applied to the support matrix by any suitable means having regard to the need to form a coating extending across one and preferably more than one interstitial space. Examples of possible techniques include dip coating, roller coating, brush coating and other methods known in the art. Dip coating is particularly preferred as a convenient and effective method of applying a suitable layer of polymer composition to the matrix.

When the star polymer composition is spread onto a support matrix, the composition will typically form as a layer over the surface area of the support matrix and will also form in at least one, and preferably a plurality, of the interstitial spaces of the support matrix. Upon exposure to the humid air, the honeycomb polymeric material will thus form over the area of the support matrix and in addition, also be suspended within at least one, and preferably more than one, interstitial space of the matrix, in concordance with the areas on which the polymer composition has been applied. This is shown in the schematic illustration of Figure 9. The flexibility of the resultant honeycomb polymeric material enables it to readily conform to the structural features of the support matrix. For example, as shown in Figure 10, the properties of the honeycomb polymeric material formed from a PDMS star polymer allow it to conform to the contours of TEM grids of various morphologies. Thus a sheet of a porous honeycomb polymeric material may be obtained having different patterns and textures, as dictated by the shape and morphology of the underlying support matrix. Because of the flexible structure, a portion of the honeycomb polymeric material is able span across an interstitial space of the support matrix and may be supported in this position by the remainder of the material that lies on the surface of the support matrix.

When the layer of the polymer composition is applied to the matrix by dip coating, such as by using the technique shown in the schematic illustration of Figure 11 , the solution may span across at least one, and preferably a plurality, of the interstitial spaces of the support matrix. Using this coating technique, it has been found that a polymer layer will typically only form in the interstitial space and generally does not form on the remaining surfaces of the support matrix. Thus, upon exposure to a humid atmosphere and formation of the honeycomb polymeric material, the honeycomb polymer material is generated only within the interstitial space of the open framework of the support matrix, as shown in Figures 12 and 13. The interactions between the polymer and the portions of the support matrix that lie adjacent the interstitial space maintain the honeycomb polymeric material in the interstitial space, and the flexible characteristics of the honeycomb polymeric material advantageously allow it to remain suspended within the interstitial space without breakage. The honeycomb polymeric material is capable of spanning an interstitial space of varying size and diameter and preferably, the honeycomb polymeric material is able to span an interstitial space having an average diameter of from about 1 μm to 1 cm. In order to enhance the interactions of the honeycomb polymeric material with the support matrix, the process of the invention may further comprise the step of modifying the support matrix to enhance the binding of the honeycomb polymeric material with the support matrix. Such modification may involve coating or treating the surface of the support matrix. Suitable modification techniques do not interfere with the formation of the honeycomb polymer from the polymer solution and have been described herein.

In accordance with one aspect of the invention, where the honeycomb polymeric materials and systems of the invention include nanoparticles, the star polymer composition used to form the honeycomb polymer layer may be provided with nanoparticles dispersed therein.

In a comparative system in which the honeycomb polymeric material is formed from a star polymer composition containing a poly(methyl methacrylate) star microgel polymer having at high glass transition temperature as shown in Figure 9, was not able to conform to the contours of an underlying TEM grid, as seen in Figure 15.

It is believed that the compatibility of the honeycomb materials of the invention with support matrices and the ability to reinforce and control the morphology of the honeycomb materials by use of an underlying support template provides greater flexibility and advantageously allows systems of variable size and properties to be generated for different applications. Consequently, it may be appreciated that the systems of the present invention enables honeycomb materials to be used in a more diverse range of applications than previously thought to be possible with the conventional polymer systems of the prior art. Applications

The honeycomb polymeric materials of the present invention may be used in a number of different applications, including electrical, optical, biotechnological and pharmaceutical applications. In particular, the ability to prepare honeycomb polymeric materials on non-planar substrates enables the shapes and topographies of the materials to be varied. This may have particular advantages in biomaterial applications, such as in the formation of artificial corneas, as the honeycomb material may be shaped into a variety of different forms. The ability to vary the topography of the honeycomb polymeric material may also have advantages for developing materials that promote cell growth. At the same time, the porous nature of the honeycomb polymeric materials may ensure that sufficient levels of nutrients are able to be supplied to the cells.

The porous structure of the honeycomb material enables chemical entities, drugs and the like to be taken up by the material for use in applications such in catalysis, as micro-reactors and in drug delivery. Once taken up by the honeycomb material, the entity may be conveniently delivered or added to the desired reaction vessel or site of action.

The ability to remove the substrate also enables the honeycomb polymeric materials of the invention to form hollow porous structures in which drugs and chemical entities can be encapsulated. In one embodiment, the encapsulation may occur as a result of migration of the entity through the pores and into the hollow structure. The encapsulation may also occur if a chemical entity or drug is used as the substrate for the formation of the honeycomb material. This hollow porous structure having the encapsulated entity may then be delivered to the required site of action.

The honeycomb polymeric materials of the present invention may also be used in opto-electronic and photonic applications. As the pore size of the polymeric material may be adjusted to approximate that of a photon of light, the honeycomb pore structure may be used to diffract or adjust the path of light in such applications.

The honeycomb polymeric materials of the invention may also be readily modified by appropriate functional groups to give rise to functional ized materials that may be used in biosensor applications and in diagnostic and analytical assays. For example, the ability of the honeycomb polymeric materials to conform to non-planar substrates means that the materials of the invention may be used to coat the surface of wells in plates such as tissue culture plates. Thus, star polymers functionalized with groups such as 4- nitrophenyl chloroformate may be applied onto the surface of a planar or non- planar well and therefore used to form a honeycomb polymeric material in the well. Such layers will possess a high surface area from the porous honeycomb structure and the well substrate. The layers can subsequently be used as a biosensor whereby a solution containing a biological molecule is placed in contact with the functionalized honeycomb polymeric material. The biological molecule may react with the functional group and thereby be selectively bonded to the honeycomb polymer. The high surface area of the honeycomb polymeric materials will produce a much greater signal to noise ratio that current techniques can offer.

The ability to tune the pore size, properties, shape, functionality and topography of honeycomb polymeric materials using the methods and star polymers described herein enables a variety of new materials to be prepared for a number of different applications.

For the systems of the present invention, the structure of the system is such that they may be used in membrane systems. The ordered structure provided by both the nanoporous honeycomb polymeric material and the porous support matrix makes the systems of the invention suitable for use as ultrafiltration membranes for water purification and other applications. Thus in a further aspect, the present invention also provides a membrane system comprising a support matrix having a plurality of interstitial spaces therein and a honeycomb polymeric material as described herein, wherein the honeycomb polymeric material extends across at least one interstitial space of the support matrix and preferably extends across a plurality of interstitial spaces of the support matrix.

The systems of the present invention may also act as templates useful for the preparation of negative images in soft lithography for the preparation of complex patterns on a micro-scale, as shown in Figures 17 and 19. Such images possess unique surface properties and may be useful as stamps to pattern other soft surfaces.

EXAMPLES

The present invention is described with reference to the following examples. It is to be understood that the examples are illustrative of and not limiting to the invention described herein.

Materials

Methyl acrylate, (MA), ethyl acrylate (EA), tert-butyl acrylate (f-BA) and methyl methacrylate (MMA) were passed over aluminium hydroxide (basic) immediately prior to use. Divinyl benzene (DVB) and ethylene glycol dimethacrylate (EGDMA) monomers were washed 3 times with 5% sodium hydroxide solution and once with distilled water. The solutions were dried over

MgSO₄, filtered and distilled from calcium hydride. N, N, N', N', N- pentamethyldiethylenetriamine (PMDETA) was distilled from calcium hydride.

Tetrahydrofuran (THF) (HPLC grade), methanol (AR grade), dichloromethane

(AR grade), 2-bromoisobutyryl bromide (98%), p-xylene (anhydrous, 99+%), anisole (anhydrous, 99+%) and copper (I) bromide were used without further purification. Water was purified by a Millipore system (Milli-Q-Millipore). Kaolin particles were supplied from Comalco (Rio Tinto) with the following composition: 95.7% Kaolin (3 Mole% Fe substituted for Al), 2% Mica (lllite), 1.3% Anatase (TiO₂), 0.15% Na₂O, 0.24% P₂O₅, <0.1 % quartz and 0.6% moisture. Monocarbinol terminated poly(dimethyl siloxane) was purchased from Gelest and used without purification. Gold TEM grids were supplied by ProSciTech with the following properties: mesh size 1000 or 2000 and having a hexagonal or square array of interstitial spaces. Slygard 184 was obtained from Dow Corning. 2-Bromoisobutyrylbromide (98%), anisole (anhydrous, 99.7%), copper (I) bromide (CuBr, 98%), 2,2'-bipyhdine (bpy, 99%), ethylene glycol (>99%), stannous 2-ethylhexanoate (Sn(OCt)₂, 95%) and urea hydrogen peroxide adduct (98%) were purchased from Aldrich and used as received. Formic acid (99%, Ajax Finechem), 4,4'-bicyclohexanone (Lomb Scientific), and 2,2-bis(4-oxocyclohexyl)propane (Lomb Scientific) were also used as received. Tetrahydrofuran (THF) and toluene were distilled from sodium benzophenone ketyl and sodium metal under argon and stored over 4A molecular sieves. Butanol (Merck) and ε-caprolactone (CL, 99+%) (Aldrich) were dried over CaH₂ for 24 hours and distilled under high vacuum prior to use. p-Toluenesulfonyl chloride (TsCI, 99+%) (Aldrich) was dissolved in minimum chloroform, diluted with petroleum ether (bp 40-60⁰C), clarified with charcoal, filtered, concentrated and collected by filtration.

Methods

Generation of Humid Air

The humidifier involved mixing of wet and dry air with humidity control being achieved through variation of the mixing ratio. Industrial compressed air (BOC Gases) was separated into two streams. The first stream was bubbled through water which was kept at 3O⁰C by a water bath. This 'wet' stream was then passed through a 500 mL flask to condense any excess water. The second stream bypassed the water bath and was mixed with the wet stream induced by inline mixers. The rates of both flow streams were controlled by rota-meters. Humidity was measured by a Cole Parma resistive humidity recorder. Humidity rangers obtainable were 10-90% (± 1 %) relative humidity (RH). Polymer Characterization

Size Exclusion Chromatography (SEC) was performed on a Shimadzu system with a Wyatt DAWN DSP multiangle laser light scattering (MALLS) detector (683 nm) and a Wyatt OPTILAB EOS interferomethc refractometer. THF was used as the eluent with three Phenomenex phenogel columns (500, 10⁴ and 10⁶ A) operated at 1 mL/min with column temperature set at 30 ⁰C.

Differential Scanning Calorimetry (DSC) measurements were conducted by initially curing a sample of the polymer at 150 ⁰C for 30 minutes. The temperature was ramped down to -150⁰C at a rate of 1 °C/min.

Honeycomb Polymeric Material Analysis

The honeycomb polymeric materials prepared in accordance with the invention were analysed by optical microscopy (Nikon Microflex AFX II) and scanning electron microscopy (SEM) (XL 30 Philips Head SEM). The sample was tilted to maximum 70° to image cross-sections.

Example 1 - Synthesis of Polysiloxane Star Microgel Polymer (a) Preparation of PDMS Arms

Monohydroxy terminated poly(dimethylsiloxane) (M_n = 10.5K, PD=1.6, 2Og, 2mmol) was dissolved in 40OmL of dry THF and triethylamine (2.787 mL, 20mmol) was added to the mixture followed by 2-bromoisobutyryl bromide (1.2360 mL, lOmmol). The reaction mixture was kept at O⁰C for 3 hours; then left overnight. The volatiles were taken off by rotary evaporation and the resultant yellow oil was re-dissolved in dichloromethane and washed with saturated hydrogen carbonate solution. The organic layer was dried over MgSO_4, filtered and solvent removed, to afford colourless oil. ¹H NMR: (CDCI₃, 400MHz) δ: 0.00 (m, 6H), 0.52 (m, 4H), 1.28 (m, 4H), 1.58 (m, 2H), 1.92 (s, 6H), 3.42 (t, 2H), 3.72 (t, 2H). (b) Preparation of PDMS-co-divinyl benzene star microgel polymer

A mixture of the PDMS macroinitiator prepared in part (a) (M_n = 10.5K, 2 g, 0.19 mmol), DVB (0.312 ml_, 2.4 mmol), CuBr (28.6 mg, 0.2 mmol) and PMDETA (0.125 ml_, 0.6 mmol) in anisole (5 ml.) was added to a Schlenk flask equipped with a magnetic stirrer. The mixture was degassed by three freeze- pump-thaw cycles and then heated at 100⁰C at atmospheric pressure. After 4Oh a sample was taken from the reaction mixture and analyzed directly by GC to check DVB conversion. The mixture was then diluted with THF (5 ml_), precipitated into methanol (500 ml.) twice and collected by filtration to afford a off white solid, which was analyzed by Gel Permeation Chromatography (GPC) (M_n = 255K, PD=1.3). The GPC results are shown in Figure 1.

According to the GPC measurements, the PDMS-co-divinyl benzene star- microgel polymer comprised an average of 19 arms extending from the divinyl benzene core and the final product formed had about 10% unconverted linear PDMS. As seen in Figure 2, the DSC results show that this microgel polymer displayed a low Tg at -125 ⁰C that is characteristic of the PDMS chains and a melting point at about -50 ⁰C.

The prepared PDMS-co-divinyl benzene star microgels were used in the formation of the porous honeycomb polymeric materials without removal of the unconverted linear PDMS arms.

Example 2 - One-step Synthesis of Polyester Star Microgel (a) Preparation of Bis(ε-caprolactone-4-yl) (BCY)

A solution of 10.0g of urea hydrogen peroxide (CO(NH₂^ H₂O₂) in 50 ml of formic acid (99%) was stirred at 23^°C for 90 minutes. Then 5 g of bis(4- cyclohexanone) was slowly added over 5-10 minutes with stirring. After 4 hours, 200 ml of water was added to the mixture and it was then extracted 4 times with chloroform after which the organic layer was washed with a saturated sodium bicarbonate solution and dried overnight with sodium sulphate. The chloroform was evaporated off and the resulting white powder dried under vacuum.

(b) Preparation of Poly(ε-caprolactone) Star Microgel 2 g of ε-caprolactone (CL) was added to a solution of toluene ([CL] = 2M) in a round bottom flask. To this mixture 30.8 μl of butanol (BtOH) and 55 μl of tin(ll) 2-ethylhexanoate (Sn(OCt)₂) was added ([BtOH]/[Sn(Oct)₂] = 2). A condenser and a drying tube (CaCI) was attached to the round bottom flask which was then heated at 100^°C for 24h with stirring.

A solution of 0.547g BCY in 3 ml chloroform was then injected into the 100^°C reaction mixture and left to react for a further 18 hours after which time the reaction mixture was cooled down and any solvents removed by evaporation. The remaining polymer mixture was then made up in tetrahydrofuran (THF) and precipitated into cold (O⁰C) methanol. Precipitate was collected via vacuum filtration and dried overnight in a desiccator.

Example 3 - Two-step Synthesis of Polyester Star Microgel

(a) Preparation of Poly(ε-caprolactone) Arms ε-caprolactone (CL) was subjected to ring opening polymerization in toluene in the presence of stannous octanoate and n-butanol ([CL]=2M, 105^°C) to provide living linear poly(caprolactone) arms. After 24 hours reaction time, the conversion of CL was determined to be >99%. The poly(caprolactone) arms were analyzed by Gel Permeation Chromatography (GPC) (M_n = 842K, PD=1.1 ).

(b) Preparation of Poly(ε-caprolactone) Star Microgel

Bis(ε-caprolactone-4-yl) (BCY) prepared in accordance with Example 2 was added to the reaction solution of Example 3(a) above. The reaction was monitored by gas chromatography mass spectrometery (GC-MS). After 18 hours reaction time, 87% of the BCY monomer had been consumed. Gel permeation chromatography (GPC) analysis revealed that 80% of the linear poly(caprolactone) arms had been converted to yield the poly(ε-caprolactone) star microgel. It was calculated that the star microgel had an average of 33 linear arms. The resulting star microgel was analyzed by GPC showed M_n = 344K, PD=1.23. The GPC results are shown in Figure 3.

Example 4 - Formation honeycomb polymeric material on planar surface

A 10g/L solution of the PDMS-co-divinyl benzene star-microgel polymers of Example 1 in benzene was prepared. A drop (20 μl_) of the star-microgel solution was cast onto glass cover slide. A humidified flow (80% R.H. at 25°C) of air was directed onto this droplet at a rate of 3L/min. The solution formed an opaque surface within seconds and solvent was evaporated within 45 seconds.

The layer was then allowed to dry at 20⁰C. The resultant porous polymer was analyzed by Scanning Electron Microscopy. As shown in Figure 4A and 4B, the porous polymer formed from the PDMS-co-divinyl benzene star-microgel polymer has highly ordered honeycomb morphology.

Example 5 - Formation of honeycomb polymeric material on sandblasted aluminium

A 10g/L solution of the PDMS-co-divinyl benzene star-microgel polymers of Example 1 in benzene was prepared. A drop (20 μl_) of the star-microgel solution was cast onto a sand-blasted aluminium plate having a non-planar surface. A humidified flow (80% R.H. at 25°C) of air was directed onto this droplet at a rate of 3L/min. The solution formed an opaque surface within seconds and solvent was evaporated within 45 seconds. The layer was then allowed to dry at 20⁰C and 30% R.H. overnight. The resultant porous polymer was analyzed by Scanning Electron Microscopy.

Figure 4C shows the rough, non-planar surface of the sandblasted aluminium plate. Figures 4D to 4F show that the honeycomb polymeric material cast onto the sandblasted aluminium plate retained a highly ordered pore structure and honeycomb morphology, despite the non-planar surface of the aluminium. The honeycomb polymeric material did not exhibit any breakages or shearing but rather, conformed to the shapes appearing in the non-planar surface of the aluminium plate.

The ability of the honeycomb material to conform to the non-planar surface sandblasted aluminium was not affected by the roughness of the surface, as shown in Figures 4E and 4F, in which craters of approximately 20 microns and 40 microns in the aluminium plate were covered by a layer of the porous polymer. In the bottom sections of the craters pore structure of the honeycomb material was enlarged, but still maintained a regular array. Along the side of the craters, the pores of the honeycomb material appeared to be stretched. This stretching may be caused by the formation of the pore structure before the material is able to conform to the non-planar surface of the substrate.

Example 6a - Formation of honeycomb polymeric material on kaolin particles

To investigate the ability of the star microgel of Example 1 to form honeycomb materials on non-planar surfaces, the star microgel was prepared in a solution of benzene (10g/L) and cast onto kaolin particles. The kaolin particles possessed a variety of shapes and sizes ranging from 2 to 50 microns. The kaolin particles were placed onto the glass slide and the microgel solution cast onto the glass slide carrying the kaolin particles. The honeycomb preparation and application was performed in accordance with the procedure of Example 4.

The resultant honeycomb polymeric material was analyzed by Scanning

Electron Microscopy.

As seen in Figures 5A and 5C, the mixture of kaolin particles used as the substrate in the preparation of the honeycomb polymeric material included particles that had a spherical or doughnut-like shape. After application onto the surface of these particles with the star microgel solution, a highly ordered porous polymeric layer with honeycomb morphology was formed on the surface of the kaolin particle and conformed to the shape of the particle as shown in Figures 5B and 5D respectively. This result demonstrates that not only can the honeycomb polymeric material cover rough surfaces with a low curvature but also surfaces with high curvature.

Example 6b - Formation of honeycomb polymeric material on kaolin particles To investigate the ability of the star microgel of Example 1 to form honeycomb materials on non-planar surfaces, the star microgel was prepared in a solution of benzene (10g/L). To this star microgel solution was added kaolin particles to form a suspension. The kaolin particles possessed a variety of shapes and sizes ranging from 2 to 50 microns. The suspension containing the star microgel polymer and the kaolin particles was then cast onto the glass slide. The honeycomb preparation and application was performed in accordance with the procedure of Example 4. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

Example 7 - Formation of honeycomb polymeric material on silica

The star microgel of Example 1 was prepared in a solution of benzene (10g/L) and cast onto chromatography silica particles and glass microbeads. The silica particles, which ranged in size from 80-150 microns, while the glass microbeads ranged in size from 90-150 microns. The honeycomb polymer preparation and application was performed in accordance with the procedure of Example 6a. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

As seen in Figure 5E, the silica particles are irregularly shaped and have sharp edges. As seen in Figure 5F, after application onto the surface of these particles, the PDMS-co-divinyl benzene star microgel solution was still able to provide a highly ordered porous polymeric layer with honeycomb morphology on the surface of the silica particle, despite the presence of sharp edges in the particle.

The microbeads possessed a more regular shape than the silica particles. As seen in Figures 5G and 5H, the polymeric honeycomb layer was also able to effectively coat these glass microbead surfaces without significantly affecting the regular porous structure and honeycomb morphology.

Example 8 - Formation of honeycomb polymeric materials on polar surfaces

The star microgel of Example 1 was prepared in a solution of benzene (10g/L) and cast onto sodium chloride and copper sulfate crystals. These crystals provide charged surfaces when exposed to the moisture in the humid air used to prepare the porous polymer. The honeycomb polymer preparation and application was performed in accordance with the procedure of Example 6a. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

Figures 6A and 6C show the effective coating of the honeycomb polymeric material on the sodium chloride and copper sulfate crystals, respectively. These figures show that the PDMS-co-divinyl benzene polymeric material can be formed on particles with a charged surface.

Example 9 - Formation of honeycomb polymeric material on sugar crystals

The star microgel of Example 1 was prepared in a solution of benzene (10g/L) and cast onto sugar crystals. The honeycomb polymer preparation and application was performed in accordance with the procedure of Example 6a. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy. Figure 6E shows that porous polymeric material successfully formed on the surface of sugar crystals. An interesting observation of this system was observed whereby the coating force that the layer experiences relative to the pore network has caused the discrete pores present in the polymer to be transformed into a square morphology.

Example 10 - Removal of salt and sugar crystal templates from honeycomb polymeric material The honeycomb polymeric materials of Examples 7 and 8, which were formed on salt or sugar crystals, were added to water and allowed to float on the surface of the water for 4 to 8 hours in order to dissolve the salt and sugar crystals and remove the templates from the honeycomb material. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

Figures 6B, 6D and 6F show the resultant structures after dissolving sodium chloride, copper sulfate and sugar crystal templates, respectively. They clearly demonstrated that hollow microporous structures are formed after the removal of the water soluble templates, resulting in collapse of the polymeric material.

Comparative Example 1 - Formation of honeycomb polymeric material on kaolin particle using PMMA-co-MMA /EGDMA star microgels.

The PMMA-co-MMA/EGDMA star microgels were prepared according to the method described by L.A. Connal et al in J. Mater. Chem., 2005, 15, 1286- 1292. The Tg of this star microgel polymer is approximately 125⁰C.

The star microgel polymer was cast onto kaolin particles in accordance with the method described in Example 6a. The resultant polymer was analyzed by Scanning Electron Microscopy. As seen in Figure 7, the pore sizes and pore structure of the honeycomb polymeric material is varies significantly across the material, and the regular pore morphology that generally characterizes the honeycomb material is lost.

Example 11 - Synthesis of Poly(ferf-Butyl Acrylate) Star Microgel Polymer

(a) Preparation of poly(ferf-butyl acrylate) macroiniator

A mixture of f-BA (15mL, 113.6 mmol), CuBr (0.2716 g, 1.8 mmol), PMDETA (396 μl_, 1.8 mmol), 2-methylbromo propionate (2-MPB) (211 μl_, 1.8 mmol) was added to a Schlenk flask and degassed by three freeze-pump-thaw cycles. The flask was then immersed in an oil bath at 60° and heated for 1 h. A sample of reaction mixture was taken for GC analysis. The reaction mixture was diluted with THF (100 ml_), passed through a column of basic alumina and celite (4:1 ), concentrated and precipitated into 50% Methanol/water (2 L) at - 15⁰C. The precipitate was collected by vacuum filtration and the precipitation repeated to afford PfBA macroinitiator as a white solid (70% yield, M_n =10.0 K

SEC _{=Q 5 κ} NM_R)_

(b) Preparation of Pf-BA-co-divinyl benzene Star Microgel Polymer

A mixture of PfBA macroinitiator (M_n = 10.0 K, 2 g, 0.2 mmol), DVB (252 μl_, 1.8 mmol), CuBr (29 mg, 0.2 mmol), PMDETA (125 μl_, 0.6 mmol) in p-xylene (13 ml_) was added to a Schlenk flask and degassed by three freeze-pump-thaw cycles. After 4Oh a sample was taken from the reaction mixture and analyzed directly by GC. The mixture was diluted with THF (100 ml_), passed through a column of basic alumina and celoite (4:1 ), concentrated and precipitated into 50% Methanol/water (1 L) at -15⁰C and collected by filtration to afford a colourless solid, which was analyzed by SEC-MALLS.

Example 12 - Synthesis of Poly(Ethyl Acrylate) Star Microgel Polymer (a) Preparation of poly(ethyl acrylate) macroinitiator A mixture of ethyl acrylate (16.3 mL, 0.15 mol), CuBr (0.143 g, 1.0 mmol), PMDETA (0.417 mL, 2.0 mmol) and 2-(2-bromo-2-methylpropanoyloxy)ethyl 2,2,5-trimethyl-1 ,3-dioxane-carboxylate (0.37 g, 1.0 mmol) was added to a Schlenk flask and degassed by three freeze-pump-thaw cycles. The flask was then immersed in an oil bath at 8O⁰C and heated for 4h. The reaction mixture was diluted with THF (100 ml_), passed through a column of basic alumina and celite (4:1 ) and precipitated into cold methanol. The precipitate was collected by vacuum filtration to give the PEA macroinitiator.

(b) Preparation of PEA-co-divinyl benzene Star Microgel Polymer

A mixture of PEA macroinitiator (M_n = 7.0 K, 0.3 g, 0.04 mmol), DVB (91.5 μl_, 0.6 mmol), CuBr (6 mg, 0.04 mmol), PMDETA (20 μl_, 0.08 mmol) in anisole (2.14 ml.) was added to a Schlenk flask and degassed by three freeze-pump- thaw cycles. After 4Oh a sample was taken from the reaction mixture and analyzed directly by GC. The mixture was diluted with THF (100 ml_), passed through a column of basic alumina and celite (4:1 ), concentrated and precipitated into cold methanol (250 ml_) and collected by filtration to afford a colourless solid, which was analyzed by SEC-MALLS.

Example 13 - Synthesis of Poly(Methyl Acrylate) Star Microgel Polymer (a) Synthesis of 2-hydroxyethyl 2-bromo-2-methlyproponoate 2-Bromoisobutyryl bromide (30.0 mL, 0.251 mol) was added dropwise to a cold solution of ethylene glycol (315.5 mL, 5.66 mol) and triethyl amine (34.8 mL, 0.251 mol) at 0 ⁰C. The reaction was held at 0 ⁰C for a further 4 h and then heated to 40 ⁰C for 6 h. The reaction mixture was cooled, added to 1 L of water, and extracted with chloroform three times. The combined chloroform layers were washed successively with diluted HCI, saturated NaHCO3, and water. The organic layer was dries over magnesium sulfate and evaporated to dryness to provide product. The product was vacuum distilled (yield 74%) and characterized by ¹H NMR spectroscopy (CDCI₃): δ 1.90 (s, 6H, CH₃), 3.85 (t, 2H, CH₂), 4.32 (t, 2H, CH₂). ¹³C NMR 530.65, 55.88, 60.50, 67.33, 171.92. (b) Synthesis of 2-(2-bromo-2-methylpropanoyloxy)ethyl 2,2,5-trimethyl- 1 ,3-dioxane-carboxylate

2-hydroxyethyl 2-bromo-2-methlyproponoate, (1) (1.0 g, 4.74 mmol) and DMAP (234 mg, 1.92 mmol) were dissolved in pyridine (4 ml_). Acetonide-2,2- bis(methoxy)propanoic anhydride (2.34 g, 7.11 mmol, 1.5 equiv) was dissolved in 5 ml_ of dichloromethane and then added to the reaction mixture. The reaction was left overnight at RT and checked with NMR. The residual anhydride was quenched by reaction with 10 mL of water under rigorous stirring for a couple of hours. The reaction mixture was then taken up into 100 mL of dichloromethane and extracted 3 times with 50 mL of NaHSO4 (10%), 3 times with 50 mL of NaHCO3 (10%), and finally with (50 mL) brine. The organic layer was dried with MgSO4, the solvent was evaporated, and the crude product was purified by MPLC using hexane gradually increasing to 20/80 EtOAc/hexane. The product was obtained as a white solid of 82% yield. ¹H NMR spectroscopy (CDCI₃): δ 1.20 (s, 3H, CH₃), 1.38 (s, 3H, CH₃) 1.41 (s, 3H, CH₃), 3.61 (d, 2H, CH₂O, J= 10.9 Hz), 4.27 (d, 2H, CH₂O, J= 10.9 Hz), 4.39 (s, 4H, CH₂). ¹³C NMR: δ 18.67, 22.90, 24.4,741.90, 55.45, 62.24, 63.18, 65.91 , 98.15, 171.45, 174.00.

(c) Preparation of poly(methyl acrylate) macroinitiator A mixture of methyl acrylate (15.69 mL, 0.15 mol), CuBr (0.166 g, 1.1 mmol), PMDETA (0.484 mL, 2.3 mmol) and 2-(2-bromo-2-methylpropanoyloxy)ethyl 2,2, 5-trimethyl-1 ,3-dioxane-carboxylate (0.43 g, 1.1 mmol) was added to a Schlenk flask and degassed by three freeze-pump-thaw cycles. The flask was then immersed in an oil bath at 8O⁰C and heated for 4h. The reaction mixture was diluted with THF (100 mL), passed through a column of basic alumina and celite (4:1 ) and precipitated into cold methanol. The precipitate was collected by vacuum filtration.

(d) Preparation of PMA-co-divinyl benzene Star Microgel Polymer A mixture of PMA macroinitiator (M_n = 7.0 K, 0.3 g, 0.04 mmol), DVB (91.5 μl_, 0.6 mmol), CuBr (6 mg, 0.04 mmol), PMDETA (20 μL, 0.08 mmol) in anisole (2.5 ml_) was added to a Schlenk flask and degassed by three freeze-pump- thaw cycles. After 4Oh a sample was taken from the reaction mixture and analyzed directly by GC. The mixture was diluted with THF (100 ml_), passed through a column of basic alumina and celoite (4:1 ), concentrated and precipitated into cold methanol (250 ml_) and collected by filtration to afford a colourless solid, which was analyzed by SEC-MALLS.

Comparative Example 2 - Synthesis of Poly(Methyl methacrylate) Star Microgel Polymer (a) Preparation of Poly(methyl methacrylate) macroinitiator

A mixture of methyl methacrylate (12.8 mL, 0.12 mol), CuBr (0.17 g, 1.2 mmol), PMDETA (0.25 mL, 1.2 mmol) and p-TsCI (0.51 g, 2.7 mmol) in p-xylene (17.2 mL) was added to a Schlenk flask and degassed by three freeze-pump-thaw cycles. The flask was then immersed in an oil bath at 8O⁰C and heated for 4Oh. The reaction mixture was diluted with THF (100 mL) and precipitated into MeOH (2 L). The precipitate was collected by vacuum filtration and the precipitation repeated to afford PMMA macroinitiator as a white solid (55% yield, M_n = 10.0K). ¹H NMR (CDCI₃, 400MHz): δ 7.74 (d, J= 8.2 Hz, 0.03H, ArH), 7.36 (d, J=8.0 Hz, 0.03H, ArH), 3.60 (s, 3H, OCH₃), 2.0-1.7 (m, 2H, CH₂), 1.02 (s, 0.45H, CH₃) 0.83 (s, 0.55H, CH₃). The Tg of this star microgel polymer is approximately 100⁰C, as seen in the DSC curve shown in Figure 9.

(b) Preparation of PMMA-co-EGDMA Star Microgel Polymer

A mixture of PMMA macroinitiator (M_n = 10K, 0.62 g, 0.062 mmol), EGDMA (0.18 mL, 0.93 mmol), CuCI (6.2 mg, 0.062 mmol) and bpy (29 mg, 0.19 mmol) in p-xylene (12.2 mL) was added to a Schlenk flask equipped with a magnetic stirrer. The mixture was degassed by three freeze-pump-thaw cycles and then heated at 100° at atmospheric pressure. After 9Oh a sample was taken from the reaction mixture and analyzed directly by GC. The mixture was diluted with THF (20 mL), precipitated into MeOH (1 L) and collected by filtration to afford a colourless solid, which was analyzed by Gel Permeation Chromatography (GPC) (0.68 g, 85% yield, M_n = 1 ,044K).

Example 14 - Formation of honeycomb polymeric materials from Star Microgel Polymers on planar surface

A 10g/L solution of each of the PDMS, PfBA, PEA, PMA star microgel polymers of Examples 1 , 11 , 12 and 13 in benzene was prepared. A 10g/L solution of the PMMA star microgel polymer of Comparative Example 2 in benzene was also prepared.

A drop (20 μl_) of each star microgel solution was cast onto a planar surface (glass cover slide) and honeycomb polymeric materials prepared in accordance with the general method described in Example 4.

The resultant porous polymers were analyzed by Scanning Electron Microscopy. As shown in Figure 10, the porous polymer formed from each star microgel polymer has highly ordered honeycomb morphology.

Example 15 - Formation of Honeycomb Polymeric Materials from Star Microgel Polymers on hexagonal TEM grid

A 10g/L solution of each of the PDMS, PfBA, PEA, PMA star microgel polymers of Examples 1 , 11 , 12 and 13 in benzene was prepared.

TEM grids having hexagonal interstitial spaces were then placed on a glass cover slip and a drop (20 μl_) of each star microgel solution was cast onto the grids. A humidified air flow (70% R. H. @ 25^°C) was directed onto these samples at a rate of 3L/min. The resultant porous polymers were analyzed by Scanning Electron Microscopy.

As shown in Figures 11 , 12, 13 and 14, the porous polymer formed from the PfBA, PEA, PMA and PDMS star microgel polymers respectively, are able to conform to morphology of the underlying TEM grid and moreover, are capable of spanning the interstitial spaces of the TEM support matrix without breakage.

Comparative Example 3 - Formation of honeycomb polymeric material on TEM grid using PMMA-co-MMA /EGDMA star microgels.

A 10g/L solution of the PMMA star microgel polymer of Comparative Example 2 in benzene was prepared and cast onto a TEM grid in accordance with the procedure described in Example 15. The polymer was analyzed by Scanning Electron Microscopy.

As shown in Figure 15, a large amount of cracking was observed to occur upon attempting to form a honeycomb polymeric material from the PMMA star microgel polymer. A homogenous layer was unobtainable and the polymeric material was not able to conform to the structure of the hexagonal TEM grid.

Example 16 - Formation of honeycomb polymeric material on hexagonal TEM grid with 600 mesh

The star microgel of Example 1 was prepared in a solution of benzene (10g/L) and a drop (20 μl_) of the solution was cast onto a gold TEM grid 600 mesh and a hexagonal array of interstitial spaces is placed on a glass cover slip. A humidified flow (70 % R. H. @ 25 ⁰C) of air was directed onto these samples at a rate of 3 L/min. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

Figure 17A shows the microporous open frame of the TEM grid with 600 mesh having an array of hexagonal interstitial spaces. Figures 17B and 17D show the resultant structures of the honeycomb polymeric material formed on the TEM grid of Figures 17A at different magnifications. The figures clearly demonstrate that the honeycomb polymeric material forms as a continuous sheet that conforms to the contours of the TEM grid. The result is the formation of a hierarchal ordered porous structure having one level of order originating from the contours of the TEM grid (the hexagonal pitch) and another level of order originating from the interstitial spaces in the TEM grid.

Example 17 - Formation of honeycomb polymeric material on square TEM grid with 1000 mesh

The star microgel of Example 1 was prepared in a solution of benzene (10g/L) and a drop (20 μl_) of the solution was cast onto a gold TEM grid of 1000 mesh and a square array of interstitial spaces is placed on a glass cover slip. A humidified flow (70 % R. H. @ 25 ⁰C) of air was directed onto these samples at a rate of 3 L/min. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

Figures 17F and 17G show the structures of the microporous open frame of the TEM grid with 1000 mesh having an array of square interstitial spaces and the honeycomb polymeric material formed on the TEM grid, respectively. Again, the honeycomb polymeric material appears as a continuous sheet conforming to the contours of the TEM grid. A number of the interstitial spaces of the TEM grid comprise the porous honeycomb polymeric material.

Example 18 - Formation of honeycomb polymeric material on square TEM grid with 2000 mesh

The PDMS star microgel of Example 1 was prepared in a solution of benzene (10g/L) and a drop (20 μl_) of the solution was cast onto a gold TEM grid of 2000 mesh and a square array of interstitial spaces is placed on a glass cover slip. A humidified flow (70 % R. H. @ 25 ⁰C) of air was directed onto these samples at a rate of 3 L/min. The resultant honeycomb polymeric material was analyzed by Scanning Electron Microscopy.

Figures 171 and 17J show the structures of the microporous open frame of the TEM grid with 2000 mesh having an array of square interstitial spaces and the honeycomb polymeric material formed on the TEM grid, respectively. Example 19 - Formation of honeycomb polymeric material in the interstitial spaces of a hexagonal TEM grid with 600 mesh

A gold TEM grid of 600 mesh and having a hexagonal array of interstitial spaces was dipped into a solution of the star microgel of Example 1 in benzene

(10g/L). The TEM grids were then suspended under a humidified flow (1 L/min;

70 % R. H. @ 25 ⁰C). The layers of the polymer solution formed in the interstitial spaces of the grid became opaque within seconds and solvent was evaporated within 20 seconds. The layer was then allowed to dry at 20 ⁰C. The resultant honeycomb polymeric material was analyzed by Scanning

Electron Microscopy.

Figure 19A shows the structure of the microporous open frame of the hexagonal TEM grid with 600 mesh in which the porous honeycomb polymeric material is located in the interstitial space of the TEM grid only. Using the dip coating method of application, the honeycomb polymeric material does not cover the surface of the grid and was observed to form only in the interstitial space of the grid.

Example 20 - Negative honeycomb structures by replica molding

A two part mixture of a crosslinkable PDMS prepolymer (Slygard 184, Dow corning) (A: B= 10:1 ) was mixed and placed under vacuum for 30min. The PDMS prepolymer was then poured over the pre-formed hierarchal honeycomb polymeric materials on TEM grids formed in Examples 16, 17, 18 and 19. The samples were placed under vacuum for a further 30min then cured at 80 °C for 3 hours. The TEM grid was then removed and the cured PDMS surface washed with THF to remove any remaining honeycomb material. The resultant PDMS polymers are again analyzed by Scanning Electron Microscopy. Figure 17C shows the negative image of the hierarchal hexagonal honeycomb polymeric material of Example 16 formed from the crosslinked PDMS polymer. A higher magnification of this negative image is shown in Figure 17E.

Figures 17H and 17K show the negative image of the hierarchal square honeycomb polymeric material of Examples 17 and 18 respectively, formed from the crosslinked PDMS polymer.

Figure 19B shows the negative image of the honeycomb polymeric material of Example 19. Discrete islands of 'bumps' that originate from the honeycomb polymeric material residing in the interstitial spaces of the TEM grid can be seen in the negative image, while relatively smooth channels are observed in between. The smooth channels result from replication of the portions of the TEM grid in which the honeycomb polymeric material has not formed.

Example 21 -Crosslinked Honeycomb Polymeric Material

(a) Preparation of 9-anthracene carbonyl chloride

A 10 ml. aliquot of SOCI₂ (0.21 mol) was placed in a N₂-purged flask followed by the addition of 1.0 g of 9-anthracenecarboxylic acid (4.5 mmol). One drop of anhydrous DMF was added to start the reaction. The reaction was refluxed at 60 ⁰C overnight. Upon reaction completion, excess SOCI₂ was evaporated under reduced pressure to give the final product (1.0 g, 93% yield). ¹H NMR spectroscopy (CDCI₃): δ 7.52 (m, 4H, CH), 7.59 (m, 2H, CH), 8.03 (d, 1 H, CH), 8.09 (d, 1 H, CH)₁ 8.56 (s, 1 H. CH)

(b) Preparation of hydroxyl end functional PMA Star Microgel Polymer The PMA star microgel polymer of Example 13 (Mn= 0.2 g) was dissolved in a solution of THF : Methanol 2:3 (50 ml_). Two teaspoons of Dowex, H⁺ resin was added, and the reaction mixture was stirred for 18 h at 50 ⁰C. When the reaction was complete the Dowex, H⁺ resin was filtered off in a glass filter and the solvents evaporated at reduced pressure. The polymer was re-dissolved in minimum THF and precipitated into methanol (150 ml_) and collected by filtration to afford a colourless solid, which was analyzed by SEC-MALLS.

(c) Preparation of anthracene end functionalised PMA star microgel polymer

9-anthracene carbonyl chloride (0.1 g, 0.4 mmol) and DMAP (10 mg) was dissolved in anhydrous THF (1 mL). Hydroxyl functional PMA star microgel polymer (0.15g) was dissolved in a mixture of dry pyridine (0.5 mL) and anhydrous THF (5 mL) and added drop wise to the reaction mixture. The reaction was stirred for 18 hours. The solution was filtered and the solvents evaporated under reduced pressure. The polymer was re-dissolved in minimum THF and precipitated into methanol (150 mL) and collected by filtration to afford a pale yellow solid, which was analyzed by SEC-MALLS.

(d) Preparation of crosslinked anthracene functional honeycomb polymeric material

The anthracene functionalized PMA star microgel polymer was cast onto a planar surface (glass cover slide) and a honeycomb polymeric material was formed from the star microgel polymer in accordance with the procedure of Example 4. The resultant honeycomb material was then placed in a vial, degassed with argon and placed under a UV lamp (365nm light at 5W) 3 cm from source for 30 minutes. The material was washed multiple times with THF. The honeycomb polymeric material remained resistant to dissolution in THF, which demonstrated that the material was effectively crosslinked.

Example 22 -Functionalised Honeycomb Polymeric Material

(a) Preparation of 4-nitrophenyl chloroformate end functional PMA star polymer

4-nitrophenyl chloroformate (0.1 g) and DMAP (10 mg) was dissolved in anhydrous THF (1 mL). Hydroxyl functional PMA star polymer (0.15g) prepared in accordance with Example 21 was dissolved in a mixture of dry pyridine (0.5 ml.) and anhydrous THF (5 ml_) and added drop wise to the reaction mixture. The reaction was stirred for 18 hours. The solution was filtered and the solvents evaporated under reduced pressure. The polymer was re-dissolved in minimum THF and precipitated into methanol (150 ml_) and collected by filtration to afford a white solid, which was analyzed by SEC- MALLS.

(b) Preparation of 4-nitrophenyl chloroformate functionalised honeycomb polymeric material The 4-nitrophenyl chloroformate functionalized PMA star microgel polymer was cast onto a planar surface (glass cover slide) and a honeycomb polymeric material was formed from the functionalized star microgel polymer in accordance with the procedure of Example 4.

Example 23 -Crosslinked and Functionalised Honeycomb Polymeric Material

(a) Preparation of 4-nitrophenyl chloroformate / 9-anthracene end functional PMA star polymer

A mixture of 4-nitrophenyl chloroformate (25 mg), 9-anthracene carbonyl chloride (25 mg) and DMAP (10 mg) was dissolved in anhydrous THF (1 mL).

Hydroxyl functional PMA star polymer (0.15g) prepared in accordance with

Example 21 was dissolved in a mixture of dry pyridine (0.5 mL) and anhydrous

THF (5 mL) and added drop wise to the reaction mixture. The reaction was stirred for 18 hours. The solution was filtered and the solvents evaporated under reduced pressure. The polymer was re-dissolved in minimum THF and precipitated into methanol (150 mL) and collected by filtration to afford a pale yellow solid, which was analyzed by SEC-MALLS.

(b) Preparation of honeycomb polymeric material The 4-nitrophenyl chloroformate / 9-anthracene functionalized PMA star microgel polymer was cast onto a planar surface (glass cover slide) and a honeycomb polymeric material was formed from the functionalized star microgel polymer in accordance with the procedure of Example 4.

(c) Preparation of crosslinked 4-nitrophenyl chloroformate functionalized honeycomb polymeric material

The 4-nitrophenyl chloroformate / anthracene functionalized PMA honeycomb material was then placed in a vial, degassed with argon and placed under a UV lamp (365nm light at 5W) 3 cm from source for 30 minutes. The material was washed multiple times with THF. The honeycomb polymeric material remained resistant to dissolution in THF, which demonstrated that the material was effectively crosslinked.

Example 24 - Patterned honeycomb polymeric material

A crosslinked 4-nitrophenyl chloroformate / anthracene functionalized PMA honeycomb material prepared in accordance with Example 23 was covered with a TEM grid to mask selected areas of the honeycomb polymeric material. The masked honeycomb polymer was then placed under a UV lamp (256 nm at 5W) 3 cm from source for 30 minutes to reverse the crosslinking. The TEM grid was then removed and the resultant material washed with THF.

As seen in Figure 23, the areas of the honeycomb polymeric material that had been covered by the TEM grid retained the morphology of the honeycomb polymer whereas those regions that had not been covered by the TEM grid and thus exposed to the UV light had lost the honeycomb morphology.

The methodology of Example 24 was employed to form a variety of patterns in the honeycomb polymeric materials as seen in Figure 24. The fluorescent microscope images of Figure 24 confirmed the presence of both crosslinked and uncrosslinked regions in the patterned honeycomb polymeric material, with the uncrosslinked areas displaying greater fluorescence. Example 25 - Preparation of 4-nitrophenyl chloroformate functionalized honeycomb polymeric material having amine functional surface

4-nitrophenyl chloroformate PMA star microgel polymer prepared in accordance with Example 22 was cast onto a planar surface (glass cover slide) and a honeycomb polymeric material was formed from the functionalized star microgel polymer in accordance with the procedure of Example 4. The same solution was used to cast a film under dry conditions to afford a flat featureless film.

To these films were added to a 0.01 mg /ml. solution of anthracene amine. The films were removed, washed, dried and analysed by fluorescent spectroscopy. A comparison of the fluorescence intensity (at 490 nm) of the anthracene amine coupled NPC functional films with honeycomb morphology and the featureless film is shown in Figure 25.

Example 26 - Preparation of Arm Degradable Polyester Star Microgel Polymer

(a) Synthesis of 2-hydroxyethyl 2'-methyl-2'-bromopropionate 2-Bromoisobutyryl bromide (5.45 g, 23.7 mmol) was added into a molar excess (25 times) of ethylene glycol (33 ml_, 593 mmol) and stirred for 16h at O⁰C. The mixture was then dissolved in water and extracted with dichloromethane. The organic phase was washed with a saturated aqueous sodium bicarbonate solution followed by water and dried with MgSO₄. The solvent was distilled off under reduced pressure to yield a colorless liquid (3.90 g, 78%). ¹H NMR (400 MHz, CDCI₃), δ (ppm): 1.95 (s, 6H, -C{CH₃)₂), 2.17 (s, 1 H, -OH), 3.87 (t, 2H, -CH₂OH), 4.31 (t, 2H, -COOCH₂-).

(b) Synthesis of Poly(ε-caprolactone)-Br Macroinitiator In a round bottom flask was charged with a mixture of ε-caprolactone (10 g, 87.6 mmol), Sn(OCt)₂ (2.366 g, 5.84 mmol), and 2-hydroxyethyl 2'-methyl-2'- bromopropionate (2.465 g, 11.7 mmol). A condenser and CaCb drying tube were attached to the flask which was heated at 13O⁰C. After 24h the reaction solution was diluted with THF and precipitated into cold methanol with the precipitate being collected by filtration and dried for 16h in a desiccator to yield poly(ε-caprolactone)-Br (PCL-Br) macroinitiator (yield: 8.73 g; M_n = 2700 g/mol, MJM_n = 1.12).

(c) Synthesis of arm degradable star microgel polymer

PCL-Br macroinitiator (0.3 g, 0.132 mmol; M_n = 2300 g/mol) was reacted with a mixture of CuBr (0.025 g, 0.172 mmol), N, N, N¹, N', N"- pentamethyldiethylenethamine (PMDETA) (36.0 μL, 0.172 mmol), ethylene glycol dimethacrylate (EGDMA) (0.622 mL, 3.30 mmol) and anisole (26 mL) in a Schlenk flask and degassed by three freeze-pump-thaw cycles. The flask was then backfilled with argon and immersed in an oil bath at 100⁰C. After 65h (93% EGDMA conversion) the reaction was stopped via exposure to air and diluted with THF before being passed through a column of basic alumina to remove the copper complex. The solution was then concentrated and precipitated into methanol with the precipitate being collected by filtration and dried under vacuum.

Example 27 - Preparation of Partially Arm-Degradable Polyester Star Microgel Polymer

(a) Synthesis of poly (methyl methacrylate)-CI (PMMA-CI) macroinitiator A mixture of MMA (1.95 mL, 18.2 mmol), CuBr (0.093 g, 0.650 mmol), bpy (0.305 g, 1.95 mmol), TsCI (0.124 g, 0.650 mmol) and anisole (2.60 mL) was added to a Schlenk flask and degassed by three freeze-pump-thaw cycles. The flask was then backfilled with argon and immersed in an oil bath at 100⁰C. After 48h (87% MMA conversion) the reaction was stopped via exposure to air and diluted with THF before being passed through a column of basic alumina to remove the copper complex. The solution was then concentrated and precipitated into cold methanol with the precipitate being collected by filtration and dried for 16h in a desiccator to yield PMMA-CI macroinitiator (yield: 1.51 g; M_n = 7500 g/mol, MJM_n = 1.08).

(b) Synthesis of partially arm degradable star microgel polymer A mixture of PCL-Br macroinitiator (0.250 g, 0.110 mmol; M_n = 2300 g/mol) prepared in accordance with Example 26 and PMMA-CI macroinitiator (0.825 g, 0.110 mmol; M_n = 7500 g/mol) was reacted with CuBr (0.025 g, 0.172 mmol), PMDETA (36.0 μl_, 0.172 mmol), EGDMA (0.374 ml_, 1.98 mmol) and anisole (17 ml.) in a Schlenk flask. The flask was degassed by three freeze-pump-thaw cycles and backfilled with argon before being immersed in an oil bath at 100⁰C. After 68h (80% EGDMA conversion) the reaction was stopped via exposure to air and diluted with THF before being passed through a column of basic alumina to remove the copper complex. The solution was then concentrated and precipitated into methanol with the precipitate being collected by filtration and dried under vacuum.

Example 28 - Preparation of Polyester Star Microgel (a) Synthesis of [4,4']-bioxepanyl-7,7'-dione (BOD)

A solution of urea hydrogen peroxide (CO(NH₂^-H₂O₂) (10.0 g, 106 mmol) in 50 mL of formic acid (99%) was stirred at 23⁰C for 90 minutes. 4,4'-

Bicyclohexanone (5.0 g, 25.7 mmol) was then slowly added over 5-10 minutes and stirred for a further 4h. 200 mL of water was added to the mixture followed by extraction with chloroform. The organic fractions were collected, washed with a saturated aqueous sodium bicarbonate solution and dried with Na₂SO₄. The organic fraction was concentrated and the solvent removed under reduced pressure to yield a white powder (3.50 g, 60%). ¹H NMR (400 MHz, CDCI₃), δ

(ppm): 4.34 (R, R) 4.17 (S, R) (t, 2H, -CH₂OOC-), 2.73 (R, R) 2.60 (S, R) (t,

2H, -CH₂COO-), 1 .93-1 .83 (m, 2H, -CH₂CH₂OOC-), 1 .70-1 .60 (m, 2H,

-CH₂CH₂COO-), 1 .49 (q, 1 H, -CHCH₂-). (b) Synthesis of polyester star microgel polymer

CL (2.0 g, 17.5 mmol) was added to a mixture of toluene (17.5 ml_), butaπol (30.8 μl_, 0.337 mmol) and Sn(OCt)₂ (54.5 μl_, 0.169 mmol). A condenser and CaCI₂ drying tube were attached to the flask which was then heated at 11O⁰C with stirring. After 24h (CL conversion >99%; M_n = 5300 g/mol) a solution of BOD (0.762 g, 3.37 mmol) in 3 mL chloroform was injected into the reaction mixture ([BOD]/[PCL] = 10) and left to react for a further 16h (86% BOD conversion). The reaction mixture was then cooled and the solvent removed under reduced pressure with the crude polymer being dissolved in THF and precipitated into methanol. The precipitate was collected by filtration and dried under vacuum.

(c) Hydrolysis of polyester star microgel

40 mg of a degradable polyester star microgel polymer was dissolved in 4 mL THF to which was added 0.3 mL H₂O and 0.1 mL 12 M HCI. Hydrolysis was carried out at 6O⁰C for 24h. For reactions where degradation was monitored using ¹H NMR, THF and H₂O were replaced with deuterated solvents (CD₃COCD₃ and D₂O respectively).

It is understood that various other modifications and/or alterations may be made without departing from the spirit of the present invention as outlined herein.

Claims

1. A honeycomb polymeric material formed of a star polymer composition comprising star polymer units having a core and a plurality of pendant arms, wherein the glass transition temperature of the star polymer is less than about 80^°C.

2. A honeycomb polymeric material according to claim 1 wherein the glass transition temperature of the star polymer is less than about 25^°C.

3. A honeycomb polymeric material according to claim 1 wherein the glass transition temperature of the star polymer is less than about 0^°C.

4. A honeycomb polymeric material according to any one of claims 1 to 3 wherein the core of the star polymer units is a crosslinked network.

5. A honeycomb polymeric material according to any one of claims 1 to 4 wherein the pendant arms have a number average molecular weight of at least about 2,000.

6. A honeycomb polymeric material according to any one of claims 1 to 5 wherein the pendant arms comprise a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof.

7. A honeycomb polymeric material according to claim 6 wherein the pendant arms comprise a polymer chain of formula: -(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of C₁ to C₈ alkylene optionally substituted with one or more substituents selected from hydroxy, halo and alkoxy, and SiR¹R² where R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl, alkoxy and aryl, Y may be the same or different at each occurrence and is selected from a carbonyl or a covalent bond, n is the number of repeating unit and is preferably at least 10, more preferably at least 15 and most preferably at least 20.

8. A honeycomb polymeric material according to claim 6 wherein the pendant arms comprise a polymer chain comprising one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone.

9. A honeycomb polymeric material according to any one of claims 1 to 8 wherein the pendant arms have a number average molecular weight of at least 5,000.

10. A honeycomb polymeric material according to any one of claims 1 to 9 wherein the star polymer composition further comprises linear polymers in an amount of between about 1 -50% by weight of the total polymer content of the star polymer composition.

11. A honeycomb polymeric material according to any one of claims 1 to 10 wherein the honeycomb polymeric material is supported by a substrate.

12. A honeycomb polymeric material according to claim 1 1 wherein the substrate is a support matrix having a plurality of interstitial spaces arranged therein and wherein the honeycomb polymeric material extends across at least one interstitial space of the support matrix.

13. A honeycomb polymeric material according to claim 12 wherein the average size of the interstitial spaces of the support matrix is in the range of from about 1 μm to 1 cm.

14. A honeycomb polymeric material according to claim 1 1 wherein the substrate has a non-planar surface.

15. A honeycomb polymeric material according to claim 14 wherein the non-planar surface comprises variations of more than 5 microns, preferably more than 10 microns from planar.

16. A honeycomb polymeric material according to claim 14 wherein the non-planar surface is a particle surface.

17. A honeycomb polymeric material according to any one of claims 1 to 16 further comprising nanoparticles dispersed in the honeycomb polymeric material.

18. A process for the preparation of a honeycomb polymeric material comprising: (a) providing a star polymer composition comprising star polymer units in a volatile solvent, wherein the star polymer has a core and a plurality of arms and a glass transition temperature of less than about 80^°C;

(b) forming a layer of the composition;

(c) subjecting the layer of the composition to a humid atmosphere; and (d) evaporating the solvent to form a honeycomb polymer from the polymer composition.

19. A process according to claim 18 wherein the glass transition temperature of the star polymer is less than about 25^°C.

20. A process according to claim 18 wherein the glass transition temperature of the star polymer is less than about 0^°C.

21. A process according to any one of claims 18 to 20 wherein the core of the star polymer units is a crosslinked network.

22. A process according to any one of claims 18 to 21 wherein the pendant arms have a number average molecular weight of at least about 2,000.

24. A process according to any one of claims 18 to 23 wherein the pendant arms comprise a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof.

25. A process according to claim 24 wherein the pendant arms comprise a polymer chain of formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of C₁ to C₈ alkylene optionally substituted with one or more substituents selected from hydroxy, halo and alkoxy, and SiR¹R² where R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl, alkoxy and aryl,

26. A process according to claim 24 wherein the pendant arms comprise a polymer chain comprising one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone.

27. A process according to any one of claims 18 to 26 wherein the pendant arms have a number average molecular weight of at least 5,000.

28. A process according to any one of claims 18 to 27 wherein the star polymer composition further comprises linear polymers in an amount of between about 1 -50% by weight of the composition.

29. A process according to any one of claims 18 to 28 wherein a layer of the composition is formed on a non-planar surface comprising variations of more than 5 microns, preferably more than 10 microns from planar.

30. A process according to claim 29 wherein the non-planar surface is a particle surface.

31. A process according to any one of claims 18 to 28 wherein the layer of the composition is formed on a support matrix having a plurality of the interstitial spaces arranged therein and wherein the layer of solution extends across at least one interstitial space of the support matrix.

32. A process according to claim 31 comprising the step of dipping the support matrix into the star polymer composition to form the layer of composition in step (b).

33. A star polymer comprising:

(a) a core; and

(b) pendant arms attached to the core, wherein the pendant arms have a number average molecular weight of at least about 2,000 and wherein the glass transition temperature of the star polymer is less than about 80^°C.

34. A star polymer according to claim 33 wherein the glass transition temperature of the star polymer is less than about 25^°C.

35. A star polymer according to claim 33 wherein the glass transition temperature of the star polymer is less than about 0^°C.

36. A star polymer according to any one of claims 33 to 35 wherein the pendant arms comprise a polymer chain comprising a polyester, polyoxyalkylene, polyoxysilane or mixtures thereof.

37. A star polymer according to claim 36 wherein the pendant arms comprise a polymer chain of formula:

-(OYX)_n- wherein

X may be the same or different at each occurrence and is selected from the group consisting of Ci to C₈ alkylene optionally substituted with one or more substituents selected from hydroxy, halo and alkoxy, and SiR¹R² where R¹ and R² are independently selected from the group consisting of hydrogen, hydroxy, alkyl, alkoxy and aryl,

38. A star polymer according to claim 36 wherein the pendant arms comprise a polymer chain comprising one or more monomers selected from the group consisting of caprolactone, glycolide, lactide and dioxanone.

39. A star polymer according to any one of claims 33 to 38 wherein the pendant arms have a number average molecular weight of at least 5,000.

40. A star polymer according to any one of claims 33 to 39 wherein the core is a crosslinked network.

41. A star polymer according to claim 40 wherein the pendant arms and crosslinked core components comprise polyester formed by ring opening polymerization of lactones such as caprolactone.

42. A star polymer according to any one of claims 33 to 41 , which has a polydispersity of between 1 and 2.