EP2391657A1

EP2391657A1 - Method for producing metal-containing nanoparticles enveloped with polymers and particles that can be obtained therefrom

Info

Publication number: EP2391657A1
Application number: EP10711530A
Authority: EP
Inventors: Andreas Greiner; Seema Agarwal; Julia Getze; Stefan Bokern
Original assignee: Philipps Universitaet Marburg
Current assignee: Philipps Universitaet Marburg
Priority date: 2009-01-30
Filing date: 2010-02-01
Publication date: 2011-12-07
Also published as: US20120302703A1; WO2010085945A1

Abstract

The present invention discloses a method for producing metal-containing nanoparticles enveloped with polymers and to particles that can be obtained therefrom. In the method according to the invention, at least one anionic polymerizable monomer is polymerized at room temperature in the presence of an anionic macroinitiator. Then, first an aliphatic or aromatic sulfide is added, thereafter a solution of at least one organosoluble metal salt in an aprotic organic solvent, and finally a homogeneous reducing agent. Metal-containing nanoparticles are created, which are covalently bound to the growing anionic polymerides. The metal salts are preferably salts of silver, copper, gold, tin, lead, chromium or zinc, or mixtures thereof. Anionic polymerizable monomers are, for example, styrene (St), butadiene, isoprene, ethylene oxide, propylene oxide, caprolactone, lactide, glycolide, acrylates, methacrylates, bisacrylates, cyanoacrylates, amides, siloxanes, vinyl pyridines or acrylonitrile. The particles according to the invention can be used to provide polymers in textiles and materials with an antibacterial finish. Furthermore, they are suited for producing inks. If the underlying metals are such which exhibit plasmon resonance, the particles can also be used in sensors utilizing the plasmon resonance effect. The metal-containing nanoparticles which are enveloped with polymers and accessible by using the method according to the invention do not aggregate or agglomerate, and the physical and chemical properties thereof remain unchanged for extended periods.

Description

Process for the preparation of metal-containing nanoparticles coated with polymers and particles obtainable therefrom

The present invention relates to the fields of polymer chemistry, metalworking and materials science. It provides a method of making polymer-coated metal-containing nanoparticles and particles obtainable therefrom.

State of the art

Metal-containing nanoparticles coated with polymers have numerous technical properties

Applications. They serve, for example, the antibacterial finishing of polymers in textiles and materials. Furthermore, the plasmon resonance effect of some metals in sensors and thermally switchable windows is used. Also inks such metal-containing nanoparticles are used.

There are therefore already some possibilities of antibacterial finishing of polymers known. A technically well established method of finishing polymers is the incorporation of silver salts or silver manure particles into these polymers. Due to the silver ions that are released, the membranes are destroyed by bacteria.

However, the incompatibility of the polymers with the silver salts or silver particles is often problematic, which is why mechanical defects, severe discoloration or clouding of the polymers often occur. Remedy here is the wrapping of silver particles with polymers, for which there are different methods.

DE-A1-10 2006 058 202 describes a process for preparing an aqueous dispersion comprising at least one polymer and / or oligomer and inorganic surface-modified particles. The inorganic particles may be metal oxides and they may be surface-modified with anionic polymers. DE-A1-103 46 387 describes a germicidal silver-containing agent for antimicrobial finishing of surfaces. The germicide may optionally contain one or more film-forming polymers selected from the group comprising polyacrylates, polyvinyl alcohols, polyvinyl acetals. The silver used is preferably nanosilver.

DE-A1-102 61 806 describes polymer-stabilized nanoparticles or nanostructured composite materials. The nanoparticles can be metals. However, only those metal-containing nanoparticles which are prepared from barium salts are disclosed.

The metals silver, copper and gold not only have antibacterial properties. They also show plasmon resonance, which can be excited by IR or UV-VIS radiation. The interaction between the plasons is higher for Ag than for other metals, as described in David D. Evanoff, Jr., George Chumanov, "Synthesis and Optical Properties of Silver Nanoparticles and Arrays" ChemPhysChem 2005, 6, 1221-1231 Plasmon resonance is a collective vibration of all the electrons of a nanoparticle, and in the case of spherical particles it is independent of the angle of incidence and the direction of the electric field vector (E vector), ie the direction of polarization Wavelength range of 400 to 800 nm cover, where the geometry of the particle (shape and size) play a crucial role.

The article cited above by Evanoff et al. describes a process for the preparation of polymer-coated silver nanoparticles wherein silver nanoparticles are charged; Subsequently, in the presence of polystyrene or PMMA is polymerized by emulsion polymerization. However, the method is useful only for a limited number of monomers and solvents as well as for relatively large silver particles (around 100 nm in diameter). The generated particles aggregrieren also fast.

The prior art also knows silver particles coated with a polymer or incorporated therein as an additive. For example, L Quaroni and G Chumanov in "Preparation of Polymer-Coated Functionalized Silver Nanoparticles", J Am Chem Soc 1999, 121, 10642-10643, describe silver nanoparticles coated with polystyrene or polymethacrylate coated with polystyrene or polymethacrylate Emulsion polymerization achieved, resulting particles with sizes between 2 and 10 nm.

In Zimmerman Evanoff Jr, P Zimmerman, G Chumanov: Teflon-coated silver nanoparticles are described as "Synthesis of Metal-Teflon AF Nanocomposites by Solution-Phase Methods," Adv Mater 2005, 17, 1905-1908, a very expensive fluorine-containing metal salt and Teflon dissolved in a perfluorinated solvent, then reduced and then precipitated.

Muriel K. Corbierre, Neil S. Cameron, and R. Bruce Lennox, "Polymer-Stabilized Gold Nanoparticles with High Grafting Densities" Langmuir, 2004, 20, 2867-2873 describes polystyrene-stabilized gold nanoparticles. The particles described are not antibacterial, have very large polydispersities, are relatively large and have many deformations.

Object of the invention

The object of the invention is to overcome these and other disadvantages of the prior art and to provide a novel process for the preparation of polymer-containing metal-containing nanoparticles. The aim is also metal-containing, polymer-coated nanoparticles, which are obtainable by such a method.

Solution of the task

The present invention overcomes the disadvantages of the prior art by providing a method by which metal-containing nanoparticles can be quickly and inexpensively coated with polymers without the addition of stabilizers. In this way polymer-coated nanoparticles coated with polymers are obtainable which have the antibacterial properties of the underlying metals or the plasmon resonance (in the case of silver, copper and gold), without the previously known disadvantages of such particles as discoloration, clouding and mechanical defects of Polymers or uncontrollable particle sizes and the undesirable tendency to aggregate. The object of providing a process for the production of polymer-containing metal-containing nanoparticles is thus achieved by a process comprising the steps: a) preparing a solution of an anionic macroinitiator in an aprotic organic solvent, b) adding at least one anionically polymerizable monomer to this solution c) anionic polymerization at room temperature, d) addition of an aliphatic or aromatic sulfide, e) addition of a solution of at least one organosoluble metal salt in an aprotic organic solvent, f) addition of a homogeneous reducing agent, if the redox potential of the at least one organosoluble metal salt is insufficient, g. precipitating the particles formed with an organic solvent, h) separating and drying the particles.

Surprisingly, it has been found that metal-containing nanoparticles can be covalently attached to growing anionic polymers if an aliphatic or aromatic sulfide is attached to the growing anionic chain end and then organosoluble metal salts are added. In this case, metal-containing nanoparticles coated with polymers are formed.

The process according to the invention for producing metal-containing nanoparticles coated with polymers and the metal-containing, polymer-coated nanoparticles obtainable therefrom are explained below, the invention encompassing all the preferred embodiments listed below individually and in combination with one another.

By "organosoluble metal salts" is meant those salts which dissolve in organic solvents, especially in aprotic organic solvents, such as, but not limited to, metal salts whose anion is selected from the group of acetates, trifluoroacetates, acetylacetonates, benzoates, iodide and / or a mixture thereof, with the associated metal cations For example, but not limited to, cations of silver, copper, gold, tin, lead, chromium, zinc, and / or a mixture thereof.

When more than one organosoluble metal salt is used, two or more of these metal salts may have a common anion or a common cation.

In a preferred embodiment, it is organosoluble salts of antibacterial metals, for example, salts of silver, copper, gold, tin, lead, chromium or zinc. Alternatively, these may also be metal alloys, e.g. silver / gold, silver / copper or copper / gold alloys, or nanoparticles coated with an antibacterial metal, e.g. Ag-coated Cu nanoparticles, Cu-coated Fe nanoparticles, Ag-coated magnetite nanoparticles, Ag-coated titanium dioxide nanoparticles.

The person skilled in the art knows how to prepare alloy nanoparticles. For this purpose, for example, mixtures of salts of two different metals can be reduced simultaneously. It is also known to those skilled in the art how to make a second metal-coated nanoparticles of a first metal. He can apply this knowledge without departing from the scope of the claims.

In a further preferred embodiment, it is organosoluble salts of metals that show plasmon resonance, for example, organosoluble silver, copper and gold salts.

By "macroinitiator" or in short "initiator" are meant according to the invention substances which initiate anionic polymerization. These include, for example, but not limited to, alkali metal alcoholates, metal alkyls, amines, Grignard compounds (alkaline earth alkyls), Lewis bases, and one electron transfer agents (e.g., naphthyl sodium).

Especially preferred are metal alkyls such as e.g. secondary butyl lithium (s-BuLi).

The aprotic organic solvents are selected, for example, but not exhaustively, from ethers (for example, tetrahydrofuran (THF), diethyl ether), toluene, benzene, hexane, cyclohexane, heptane, octane, DMSO, and mixtures thereof. In principle, any aprotic solvent which is anionic is suitable polymerizable monomer, the aliphatic or aromatic sulfide, which dissolves at least one organosoluble metal salt and the living polymer and does not chemically react with the monomer or the living polymer. For the purposes of the present invention, "dissolving" means that monomer, sulfide, metal salt or polymer are each at least 0.1% by weight soluble in the solvent or solvent mixture.

By a "living polymer" is meant a polymer chain which has not yet been quenched and therefore can continue to react.For example, it is known to polymerize styrene anionically and to attach other monomers or further styrene to this "living" polystyrene until the reaction stops.

Preferably, the same solvent or solvent mixture is used for the solution of the anionic macroinitiator according to step a) as for the solution of the at least one organosoluble metal salt according to step e).

Anionically polymerizable monomers include, but are not limited to, styrene (St), butadiene, isoprene, ethylene oxide, propylene oxide, caprolactone, lactide, glycolide, acrylates, methacrylates, bisacrylates, cyanoacrylates, amides, siloxanes, vinylpyridines, acrylonitrile. The anionic polymers obtainable therefrom are polystyrene, polybutadiene, polyisoprene, polyethylene oxide, polypropylene oxide, polycaprolactone, polylactide, polyglycolide, polyacrylates, polymethacrylates, polybisacrylates, polycyanoacrylates, polyamides, polysiloxanes,

Polyvinylpyridines, polyacrylonitrile. The anionic polymers may be linear, branched, highly branched, star-shaped, dendritic; it may also be random copolymers and block and graft copolymers.

"At least one anionically polymerizable monomer" according to step b) of the process according to the invention means that one or more anionically polymerizable monomers can be used according to the list above If at least two of these anionically polymerizable monomers are used, statistical copolymers or block or Copolymers are obtained, for example, by simultaneously introducing two similarly reactive monomers, which are then incorporated simultaneously into the forming nanoparticles Block copolymers are obtained by first adding one of the monomers, then adding the second and successively possibly further monomers. In a preferred embodiment, the anionically polymerizable monomer is selected from styrene and methacrylate. Through the use of sulfur-containing polymers, an envelope of the nanoparticles can likewise be produced. As polymers, for example, but not exhaustively, polyamides such as polyamide 66, polyvinylamides, polyvinylamine, polyvinyl acetate, polyvinyl alcohols, polyisoprene, polybutadiene and copolymers with, for example, styrene or acrylonitrile, polychloroprene, ethylene-propylene-diene rubber, crosslinkable polyurethanes, silicones with thiol - or sulfide groups, polyalkylsulfides, polyalkylsulfonic acids, polyalkylsulfonates, rubbers or combinations of these polymers are used as copolymers and block and graft copolymers or polymer blends. If the polymers have no sulfur groups, sulfur groups are introduced into these polymers, for example but not exhaustively by sulfur, sulfuric acid, disulfur dichloride, ethylene thiourea, mercaptans, polyarylene sulfides or xanthogen sulfide and derivatives, for example alkylxanthogen sulfides, xanthogen polysulfides or alkylxanthogen polysulfides. Vulcanization crosslinks the polymers. On the one hand, the sulfur groups lead to crosslinking of the polymers, on the other hand they bring about stabilization of the metal-containing nanoparticles.

This has the advantage that one engages only slightly in the production process of the crosslinked polymers, since only an addition of metal salts is necessary.

With the subsequent reduction of the metal salts polymers or rubbers can be produced with metal insert, which have antistatic properties.

The aliphatic or aromatic sulfide is, for example, an alkyl sulfide such as ethylene sulfide or propylene sulfide or an aromatic sulfide such as styrenesulfide. Preference is given to ethylene sulfide.

The homogeneous reducing agent is, for example but not limited to, superhydride (lithium triethyl borohydride) or hydrazine.

The aliphatic or aromatic sulfide according to step d) of the process according to the invention acts as a reducing agent for the metal salt, since it can transfer electrons to the metal cation. It is known to the person skilled in the art that such a reduction is dependent on the redox potential of the metal in question. The so-called standard potentials of metal / metal salt redox pairs can be found in the electrochemical series. Standard potentials are by definition based on

Standard conditions, ie to a temperature of 25 ° C, a pressure of 101, 3 kPa, a pH of 0 and an ionic activity of 1. If in step e) of the process according to the invention a metal salt is used whose corresponding metal according to the electrochemical series is less noble than hydrogen, a homogeneous reducing agent according to step f) must be added so that the reduction expires.

In the case of metal salts whose corresponding metal according to the electrochemical series of voltages is more noble than hydrogen, the reduction force of the sulfide added according to step d) of the process according to the invention is sufficient in principle to reduce metal cations to the metal. However, it should be noted that, for example, silver cations only need one electron to be reduced to silver, while two electrons are required for the reduction of Cu ²⁺ ions to elemental copper. At the same concentration of Cu ²⁺ or Ag ⁺ -SaIz and sulfide is therefore less Cu ²⁺ reduced to Cu than Ag ⁺ to Ag. It is known to those skilled in the art that the amount of reducible metal salt depends, inter alia, on the concentrations of the metal salt and the reducing agent, their respective redox potential and the number of electrons that must be transferred. If the solution of the at least one metal salt according to step e) of the process according to the invention is a sufficiently dilute solution of the salt of a noble metal, then it may be that, owing to the small amount of salt

Salt concentration the redox potential is not high enough to drain the reduction to the metal. In this case, even when using a salt of a noble metal, the addition of a homogeneous reducing agent according to step f) is required.

In a preferred embodiment, the at least one organosoluble metal salt is a salt or salts of metals which are more noble than hydrogen, and a homogeneous reducing agent is added in step f) of the process according to the invention.

The precipitation of the formed by the method according to the invention with

Polymer-coated metal-containing nanoparticles is carried out with the aid of a precipitant, for example water, methanol, ethanol, n-propanol, isopropanol, acetone, diethyl ether, methyl acetate, ethyl acetate, hydrocarbons such as pentane, hexane, heptane, cyclohexane, cycloheptane, furthermore petroleum ether and mixtures of these solvents. In a preferred embodiment, the precipitation is carried out with the aid of water, methanol or ethanol, which are optionally previously acidified or treated with an acid salt such as calcium chloride.

The person skilled in the art knows which solvents and precipitants are suitable for which polymers.

"Precipitant" refers to that solvent or solvent mixture which is used for the precipitation of the polymer-containing metal-containing nanoparticles.

In the present invention, the precipitant is selected to dissolve with the solvent in which macroinitiator and anionically polymerizable monomer are dissolved. The precipitant is further selected so that it does not dissolve the polymer formed during the reaction.

The process according to the invention can be carried out both batchwise (batch process) and continuously, for example in a microreactor.

In discontinuous implementation of the process as a batch process, the preparation is carried out as described above in a single reaction vessel.

In an advantageous embodiment, the macroinitiator and the sulfide are used in the ratio 1: 1 (equivalent / equivalent).

The macroinitiator and the at least one anionically polymerizable monomer are advantageously used in the ratio initiator: monomer = 1: 10 to 1: 100 (equivalent / equivalent).

In a preferred embodiment, the metal salt is the salt of a noble metal, and no reducing agent according to step f) of the method according to the invention is added. In this case, 2-3 equivalents of metal salt are used per equivalent of the monomer, preferably 2.3 equivalents. Furthermore, in this embodiment, as described above, one equivalent of macroinitiator and one equivalent of sulfide are used per equivalent of monomer.

In a particularly preferred embodiment, each one equivalent of monomer, sulfide and macroinitiator and each 1 to 8 equivalents of metal salt and homogeneous Reducing agent used, with as much equivalents of metal salt as reducing agents are used.

When the process is carried out continuously, for example in a microreactor, steps a) to d) are prepared in a first vessel in accordance with the above method. In a second vessel, the solution of the at least one organosoluble metal salt is provided in an aprotic organic solvent. Subsequently, these two solutions are continuously brought together, for example in a microreactor, and the product solution forming continuously removed. The precipitation of the particles formed from the product solution according to step f) takes place in a third vessel. Subsequently, the precipitated particles are separated according to step g) and dried.

The polymer-coated nanoparticles according to the invention have diameters of about 2 nm to 300 nm, with the variation around the mean being 30% to 70%. The metal particles have inside diameter of about 1 nm to 10 nm, and the thickness of the polymer layer is about 0.5 nm to 300 nm.

It should be emphasized that all metal-containing nanoparticles coated with polymers accessible by means of the process according to the invention do not aggregate or agglomerate and therefore retain their physical and chemical properties for a very long time. For example, the particles according to the invention are UV-stable, since they can be exposed to solar radiation for several months without changing. The chemical stability could be demonstrated by exposing the particles to semi-concentrated nitric acid for several days without any change in the particles.

The process according to the invention allows the use of the entire spectrum of anionically polymerizable monomers. The resulting particles are u.a. so stable because each polymer chain is individually coordinatively bonded to the metal surface.

The metal-containing nanoparticles coated with polymers and accessible by means of the process according to the invention can be used as non-aggregating antibacterial substances. They can either be further processed directly or added as additives for antibacterial and / or antistatic finishing of other polymers. Thus, the nanoparticles can be used directly or as additives in films or Coatings, workpieces (extrudates, pressings), fibers (macro, micro, nano fibers, electrospun fibers) can be used. They can be used for example in antibacterial paints, antibacterial textiles, antibacterial filters, antibacterial membranes, antibacterial components.

The metal-containing nanoparticles coated with polymers according to the invention are likewise used for the production of antistatic films, workpieces, fibers, granules or masterbatches as antistatic additives. The polymer-stabilized metal-containing nanoparticles can be mixed together with a first polymer matrix. The mixture may be a powder, granules, a liquid or a paste. In an extruder, this mixture is processed with other additives and polymers to granules. Thus, a mixture of silver nanoparticles with polystyrene was prepared. This mixture was then extruded with more polystyrene. In this case, a uniform distribution of the silver nanoparticles was achieved. This antibacterial and / or antifungal properties could be introduced into a granule. The granules also show antistatic properties. The further processing of the granules can be carried out, for example, but not exclusively, to melt-spun fibers, melt-blown microfibers or films.

The polymer-stabilized metal-containing nanoparticles can also be used as viscous pastes having antibacterial and / or antifungal properties. These pastes, which also have antistatic properties, can e.g. used in the construction industry. The polymer-stabilized metal-containing nanoparticles can also be used as aprotic solutions having antibacterial and / or antifungal properties. Thus, a solution of the polystyrene-clad silver nanoparticles in toluene could be prepared.

Furthermore, the polymer-coated metal-containing nanoparticles according to the invention can be used for the production of inks. This is particularly advantageous when the metals are gold, silver, copper or alloys thereof. In the manufacture of electronic components, ink-jet printing processes provide an alternative to conventional photolithography. When the polymer or polymers of the nanoparticles of the present invention are thermally degradable polymers, these polymers may optionally be removed after printing, for example by pyrolysis. In this way, very thin metal lines are obtained. If the particles according to the invention are silver particles, see above can be produced silver lines that are antibacterial, electrically conductive and thermally conductive.

The inks are prepared according to the invention so that in the presence of a polymer which is provided with so-called thiol groups at the chain ends, the respective metal nanoparticles are prepared from the corresponding metal salts by reduction in solution. This leads to the formation of metal nanoparticles that are chemically bound to the thioterminated polymers. In this way, the metal nanoparticles can no longer aggerize. As a result, they can be processed by removing the solvent into powders. The powders thus obtained can then be re-introduced into a solvent to prepare the inks and redispersed without aggregation. Depending on the desired use, the inks can then be further adjusted individually by adding further substances, for example dyes or viscosity-modifying substances.

Another use of polymer-coated nanoparticles prepared by the process according to the invention, whose outer metal is silver, copper or gold, is due to their plasmon resonance. The plasmon resonance effect can be used, for example, in immunosensors in kinetics and bioanalytics: The abovementioned polymer-coated gold, silver or copper maleic particles according to the invention can adsorb foreign molecules. This change in the ligand shell changes the plasmon resonance frequency of the particle. By means of plasmon resonance measurement, therefore, very low concentrations of foreign molecules, for example of biomolecules, can be detected.

The polymer-coated metal-containing nanoparticles can, provided they have a reversible thermochromic effect, which is due to the altered interference of the plasmon resonances, also be used in thermally switchable windows and in the sensor.

The use of polymer-coated nanoparticles produced by the process according to the invention can be carried out in the form of powders, dispersions, pastes and solids. Among others, the following applications are conceivable: antibacterial and / or antistatic finishing of workpieces, films or fibers, the

Use as silent additives for example in security ink, use in the Production of electrical conductors, which may be particularly interesting in the field of near-field electrospinning or inkjet printing, the use in the production of special optical encodings - for example, if scanbars with additional functions are desired. In addition, the polymer-coated nanoparticles produced according to the invention could find use in the production of metal alloys. In this case, the good miscibility of the polymer-coated nanoparticles would be of particular advantage. For the same reason, the production of composites with glasses is conceivable.

Figure legends

Fig. 1

FIG. 1 shows TEM images (transmission electron microscopy) of silver nanoparticles prepared according to Embodiment 1. FIG. In Fig. 1a) particles are shown after stirring in an ultrasonic bath, in Fig. 1b) those after stirring with a magnetic stirrer.

While the silver nuclei made by magnetic stirrer are 5 nm in size (Figure 1b) and are single, those produced in the ultrasonic bath agglomerate to form 200 nm (Figure 1a).

Fig. 1a): The bar at the bottom right of the screen corresponds to 2.6 microns. Fig. 1b): The bar at the bottom right edge of the picture corresponds to 2 nm.

Fig. 2

The structure of the core-shell particles was investigated by means of AFM, for which

Analytical method Particles were used with the molecular weight of Oligostyrolhülle of 326 g / mol.

Based on Fig. 2, the postulated structure of the core-shell particles can be demonstrated. The AFM images were taken at different magnifications:

Fig. 2a): magnification Ag / St = 0.1; M = 326 g / mol

Fig. 2b): magnification Ag / St = 4.35; M = 326 g / mol.

St = styrene; M = 326 g / mol refers to the molecular weight of Oligostyrolhülle.

At the lower magnification one recognizes that all particles are identically constructed, each one has a core (silver) and a shell (styrene chain).

Fig. 3

Shown is the antibacterial effect of films of industrial polystyrene (M _n = 100,000) and core-shell silver nanoparticles according to Embodiment 2. Fig. 3a) shows the antibacterial effect on E. coli. Fig. 3b) shows the antibacterial effect on M. luteus.

B ₂ denotes a blend of the above-mentioned industrial polystyrene and core-shell silver nanoparticles having a molecular weight of the shell polymer of 326 g / mol. The weight ratio of the blend is 12 to 88. B ₄ denotes a blend of the above-mentioned industrial polystyrene and core-shell silver particles having a molecular weight of the shell polymer of 1980 g / mol. The weight ratio of the blend is 11 to 89.

B ₆ denotes a blend of the above-mentioned industrial polystyrene and core-shell silver nanoparticles having a molecular weight of the shell polymer of 116590 g / mol. The weight ratio of the blend is 14 to 86.

Fig. 4

4 shows an SEM image of the polystyrene film with core-shell silver nanoparticles according to exemplary embodiment 2. The white bar on the lower right-hand edge of the image corresponds to 600 nm.

Fig. 5

TEM image of microreaction synthesized silver polyphenylene-containing silver particles.

5 shows an overview of a plurality of polymer drops at the edge of a grid hole. The

Silver particles are weakly recognizable in the drops.

The scaling bar at the upper right edge of the picture corresponds to 100 nm.

Fig. 6

TEM image of microreaction synthesized silver particles with

Polystyrene shell.

Fig. 6 shows a single polymer droplet with several silver particles. The scaling bar at the upper right edge of the picture corresponds to 5 nm. Fig. 7

TEM image of microreaction synthesized silver nanoparticles with polystyrene shell.

Fig. 7 shows a single silver particle with recognizable lattice planes. The scaling bar at the lower left edge of the picture corresponds to 1 nm.

Fig. 8

TEM images of silver particles with polystyrene or polymethacrylate sheath. The scaling bar at the top right of the screen is 50 nm.

Fig. 9

UV-VIS spectrum of A. uncoated and B: polystyrene-coated silver particles in water (solid line) and 1.8 M NaCl solution (dashed line).

Fig. 10 TEM images of silver particles in Teflon. The scaling bar at the bottom right of the screen corresponds to 30 nm.

Fig. 11

Palladium nanoparticles synthesized with thiol-end-functionalized polystyrene having a molecular weight Mn = 2600 g / mol and a molar ratio of polystyrene to palladium acetate of 1: 1, prepared according to Embodiment 6.

Fig. 12

Transmission electron micrograph of the palladium nanoparticles prepared according to Embodiment 6 in the polystyrene matrix after extrusion and hot pressing.

Fig. 13

Palladium nanowires synthesized with thiol-end-functionalized polystyrene having a molecular weight Mn = 2600 g / mol and a molar ratio of polystyrene to palladium acetate of 1: 3. Fig. 14

High-resolution TEM image of the nanoworms shown in FIG. 13 with subsequently drawn edges of the structure. Clearly visible is the crystalline region at the end of the structure.

Fig. 15

X-ray powder diffractograms of the palladium nanowires (W) shown in Figs. 13 and 14 and the spherical palladium nanoparticles (S) of Fig. 11. At 2θtha = 20 °, the amorphous halo of polystyrene can be seen. Clearly visible is the widespread reflection of palladium at 2Theta = 40 ° due to nanostructuring. The only difference is the intensity of the signal. This shows that the worm-like structures of FIGS. 13 and 14 are pure palladium.

Fig. 16 Polystyrene film after extrusion and hot pressing at 150 ⁰ C with a thickness of 0.5 cm and a Pd nanoparticle concentration of 0.01 percent by weight. Width of the picture about 10 cm.

embodiments

Embodiment 1

Preparation of polystyrene coated silver nanoparticles

The mixing of the reaction solution was ensured by means of a Magnetsrührers or ultrasonic bath. 10 ml of THF with initiator (s-BuLi / cyclohexane 1.3 M) were placed in a flask. The reaction temperature was 25 ^° C. The polymerization was started by the rapid addition of the monomer (St). The solution immediately turned dark red. After complete polymerization (about 5 minutes), the mixture was treated with an ethylsulfide-THF solution. The color disappeared after a few seconds. Subsequently, a solution of silver trifluroacetate in THF was added and the reaction mixture was stirred for 10 minutes. The resulting particles were precipitated from methanol. After the precipitated samples were filtered off, they were dried at 60 ^° C. in a vacuum oven for 20 hours.

The size of the particles was clarified by means of TEM (Transmission Electron Microscopy) or AFM (Atomic Force Microscope). The particle sizes were between 3 and 200 nm depending on silver content and production method. The TEM images of the particles are shown in FIG. The structure of the core-shell particles was investigated by AFM. This is shown in FIG. 2.

Embodiment 2: Antibacterial action of the core-shell particles

Due to the composition of the core-shell particles (silver core) an antibacterial effect was suspected. For this reason, films were made of industrial polystyrene (M _n = 100,000) and the particles:

From industrial PS (M = 100,000) and core-shell nanoparticles in THF, a solution was prepared. With this, the bottom of a Petri dish was poured or pulled with a squeegee on a glass plate, a film and allowed to stand for 20 h to dry out the solvent. The film was peeled off and used for further investigation. The antibacterial effect of the polymer films was tested against E. coli (Escherichia coli) and M. luteus (Micrococcus luteus). It could be stated that the films have an antibacterial effect due to the emission of silver ions. However, their concentration is insufficient to completely inhibit the growth of M. luteus. This is shown in FIG.

The polystyrene shell around the silver core complicates the release of the silver ions due to the strong hydrophobicity. The fact that these are separated at all depends on the structure of the film surface. The core-shell particles are defying the low concentration on the surface of the film (Fig. 4), which facilitates the interaction with water and thus makes the antibacterial effect possible.

Embodiment 3

Synthesis of polystyrene-coated silver nanoparticles via microreaction system

a) Synthesis of the macroinitiator A 25 mL nitrogen flask, heated under reduced pressure, is charged under argon with 10 mL cyclohexane (distilled over calcium hydride) and 6.5 mL butyllithium (1.3 mol / L in cyclohexane, 8.5 mmol) and heated to 40 ^° C. with stirring , 2 mL of styrene (distilled over calcium hydride, 17 mmol) are added quickly. The solution immediately turns deep red. The solution is stirred for another 10 minutes at 40 ⁰ C and stored until use at -20 ⁰ C.

b) Synthesis of the thiolate-functionalized polystyrene

A 1 liter nitrogen flask heated in vacuo is charged under argon with 400 ml of THF (dried over potassium hydroxide, distilled over phosphorus pentoxide). It is added with stirring at 25 ⁰ C as much macroinitiator solution until the red color persists, then a further 26 ml_ (11.9 mmol) macroinitiator are added. 15.5 ml styrene (135 mmol) are added quickly, the deep red solution is stirred for a further 10 minutes at 25 ⁰ C. 0.71 mL of ethylene sulfide (12 mmol) is added to the solution, which then turns pale yellow in color. The solution is stored at -20 ⁰ C until use.

c) Preparation of the silver trifluoroacetate solution

3.06 g of silver trifluoroacetate (11.9 mmol) are dissolved under argon in 446 ml of THF _abs . The solution is to use protected with aluminum foil from light and stored at -20 ⁰ C.

d) Construction of the microreaction plant

Two syringe pumps (Syknm S1610, teflon pump head, internal volume of glass syringes each 10 mL) are connected via stainless steel cannulas to a pressure sensor and a microreactor (Ehrfeld LH25, 50/50 μm mixing plate, 50 μm fusing plate). The output of the microreactor is connected to a stainless steel cannula (length about 2 meters, internal volume 1.92 mL).

e) Execution of the synthesis via microreaction

Both syringe pumps are initially flushed to remove any impurities each with 500 mL water, 500 mL THF, 150 mL of cyclohexane and 300 mL _{of absolute} THF. Pump 1 is rinsed with 180 mL of the solution of the functionalized polymer (solution 1), and pump 2 is rinsed with 180 mL of the silver trifluoroacetate solution (solution 2). The pumps are set to the respective pumping speed and switched on. 5 ml of the product solution are discarded, 40 ml of the product solution are collected in a vessel. The product is precipitated in 400 ml of methanol, aged for 2 hours, filtered off and dried in a vacuum oven at 60 ^° C. overnight.

Example of pumping rates. Approach SB160508-2: Polystyrene solution (solution 1): 10.00 mL / min. Silver trifluoroacetate solution (solution 2): 13.20 mL / min

For other approaches, the pumping speeds are varied as needed. FIGS. 5 to 7 show TEM images of micro-reaction-synthesized silver particles with polystyrene shell.

Embodiment 4

Preparation of poly (styrene-block-co-M MA) Ag with magnetic stirrer

20 mL of THF were heated to 25 ^° C. in a water bath. The freshly synthesized macroinator solution (c = 0.5 mol / L) according to 3.a) was added to the THF until the red color of the macroinitiator was stable. Thereafter, another 0.65 mL of macroinitiator (c = 0.50 mol / L, 0.33 mmol, 1.00 eq.) Was added to the solution. 3.01 g of styrene (3.4 mL, 28.9 mmol, 87.58 eq) were added quickly to the solution. After five minutes, 90.1 mg of 1, 1-diphenylethylene (0.50 mmol, 1.5 eq.) Was added to the deep red solution. After another five minutes, 460.6 mg of methyl methacrylate (0.49 mL, 4.60 mmol, 13.94 eq.) Was added to the solution. After another five minutes, 50.0 mg of ethylene sulfide (0.84 mmol, 2.48 eq.) Was added to the solution. To the solution was added 10 mL of silver trifluoroacetate solution (c = 34.9 mmol / L, 0.349 mmol, 1.16 eq. In THF). After five minutes, the solution was introduced into ten times the excess of methanol. The brown precipitate was filtered off, washed with water and methanol and dried for 12-16 h in a vacuum oven at 60 ⁰ C.

The obtained particles were examined by transmission electron microscopy. For this, a device JEM 3010 from JEOL was used. The measurements were taken with a LaB6 crystal as the cathode at a voltage of 300 kV. Sample preparation was performed on graphite coated 300 mesh copper grids by immersion in a highly diluted chloroform dispersion of the nanoparticles and drying in air. The evaluation was carried out with the device's own program Gatan Digital Microscope and the program ImageJ, Version 1.40g from the National Institute of Health, USA. Per sample diameter of 100 to 150 particles were measured. The average diameter and standard deviation were determined using the OriginPro 7.5 program.

Average diameter of the particles according to Embodiment 4: 4.3 nm Standard deviation: 1.5 nm (35%)

Embodiment 5: Polystyrene-clad copper nanoparticles

A solution of thiolate-functionalized polystyrene was prepared as described above (batch 150508-2, Mn = 4400 g-mol-1, c = 11, 1 mmol / L). 10 ml of this

Solution (0.11 mmol, 1.00 eq.) Was added with 71 mg of copper (II) acetylacetonate (0.27 mmol, 2.47 eq.) In 10 mL of THF. The solution was mixed with 1 mL hydrazine solution (c = 1 mol / L in THF, 1 mmol, 9.35 eq.). The resulting white precipitate was filtered off and discarded. The solution was placed in ten times excess methanol. The colorless product was filtered off, washed with water and methanol and dried overnight in a vacuum oven at 60 ⁰ C.

Yield: 263 mg (52%) The particles according to embodiment 5 were investigated by means of transmission electron microscopy as described under example 4.

Average diameter of particles according to Embodiment 5: 2.2 nm Standard deviation: 0.6 nm (27%)

The invention is not limited to one of the above-described embodiments, but can be modified in many ways. It will be appreciated, however, that the present invention provides a method of making polymer-coated metal-containing nanoparticles and particles obtainable therefrom.

In the process according to the invention, at least one anionic polymerizable monomer is polymerized in the presence of an anionic macroinitiator at room temperature. Subsequently, an aliphatic or aromatic sulfide is added first, then a solution of at least one organosoluble metal salt in an aprotic organic solvent and finally a homogeneous reducing agent. The metal cation is thereby reduced to the metal. The result is metal-containing nanoparticles that are covalently attached to the growing anionic polymers.

The metal salts are preferably salts of silver, copper, gold, tin, lead, chromium or zinc or mixtures thereof. Anionic polymerizable monomers are, for example Styrene (St), butadiene, isoprene, ethylene oxide, propylene oxide, caprolactone, lactide, glycolide, acrylates, methacrylates, bisacrylates, cyanoacrylates, amides, siloxanes, vinylpyridines or acrylonitrile.

The particles according to the invention can be used for antibacterial finishing of polymers in textiles and materials. Furthermore, they are suitable for the production of inks. If the underlying metals are those that show plasmon resonance, then the particles can also be used in sensors that use the plasmon resonance effect.

The metal-containing nanoparticles coated with polymers and accessible by means of the process according to the invention do not aggregate or agglomerate, and their physical and chemical properties remain unchanged for a long time.

Embodiment 6:

Synthesis of ultra-small palladium nanoparticles in a polystyrene matrix.

Thiolate end-functionalized polystyrene in THF (M _n = 4900 g / mol, 46 mmol / L, 0.15 mmol) is added to a stirred solution of palladium (II) acetate (100 mg, 0.45 mmol). After 5 minutes, a solution of triethylborohydride (1 mol / L in THF, 3 mL,

3 mmol) was added. After 20 minutes, the brown product is precipitated in methanol, washed and dried in vacuo. Yield: 98%.

TEM: spherical nanoparticles with an average diameter of 1.6 nm.

Repetition of the synthesis with short-chain thiolate end-functionalized polystyrene (M _n = 2600 g / mol) and 0.15 mmol palladium (II) acetate also gave spherical

Nanoparticles with an average diameter of 1.6 nm. The material was additionally analyzed by gel permeation chromatography, X-ray powder diffraction and UV / Vis

Characterized spectroscopy. The palladium shown in FIG. 11 is formed.

Nanoparticles.

Embodiment 7:

Co-extrusion of polystyrene-stabilized palladium nanoparticles with polystyrene

Co-extrusion of polystyrene at 195 ^° C. shown in FIG. 1 with industrial polystyrene (M _n = 100,000 g / mol, BASF) provided a transparent, typical for palladium nanoparticles brown colored material (final concentration of palladium here 0.01% by weight) with a homogeneous distribution of palladium nanoparticles.

Exemplary Embodiment 8 Synthesis of Novel Structures Using the Example of Palladium Nanowarmers

-Thiolate end-functionalized polystyrene in THF (M _n = 2600 g / mol, 46 mmol / L, 0.15 mmol) is added to a stirred solution of palladium (II) acetate (100 mg, 0.45 mmol). After 5 minutes, a solution of triethylborohydride (1 mol / L in THF, 3 mL, 3 mmol) is added. After 20 minutes, the brown product is precipitated in methanol, washed and dried in vacuo. Yield: 96%.

Worm-like nanoscale structures of palladium were obtained, as shown in FIG.

All of the claims, the description and the drawings resulting features and advantages, including design details, spatial arrangements and method steps may be essential to the invention both in itself and in various combinations.

Claims

claims

1. A process for the preparation of polymer-coated, metal-containing

Nanoparticles, comprising the steps of: a) preparing a solution of an anionic macroinitiator in an aprotic organic solvent, b) adding at least one anionically polymerizable monomer to this solution, c) anionic polymerization at room temperature, d) adding an aliphatic or aromatic sulfide, e) Addition of a solution of at least one organosoluble metal salt in an aprotic organic solvent, f) addition of a homogeneous reducing agent, if the redox potential of the at least one organosoluble metal salt is insufficient to be reduced to the metal exclusively by the aliphatic or aromatic sulphide, g) precipitating the formed Particles with an organic solvent, h) separation and drying of the particles.

2. The method according to claim 1, characterized in that it is at least one organosoluble metal salt is a salt of silver, copper, gold, tin, lead, chromium, zinc, palladium and / or a mixture thereof.

3. The method according to any one of claims 1 or 2, characterized in that it is the at least one organosoluble metal salt is an acetate,

Trifluoroacetate, acetylacetonate, benzoate, iodide and / or a mixture thereof.

4. The method according to any one of claims 1 to 3, characterized in that the anionic macroinitiator is selected from alkali metal alcoholates, metal alkyls,

Amines, Grignard compounds (alkaline earth metal alkyls) and / or Lewis bases.

A process according to any one of claims 1 to 4, characterized in that the anionic polymerisable monomer is styrene or methacrylate.

6. The method according to any one of claims 1 to 5, characterized in that the aliphatic or aromatic sulfide is selected from ethylene sulfide, propylene sulfide and styrene oxide.

7. The method according to any one of claims 1 to 6, characterized in that polymers are used with sulfur-containing groups.

8. The method according to any one of claims 1 to 7, characterized in that by the use of sulfur-containing groups crosslinking of the polymers and at the same time stabilization of the metallic nanoparticles takes place.

9. metal-containing nanoparticles coated with polymers, obtainable by a process according to at least one of claims 1 to 8.

10. Use of polymer-coated metal-containing nanoparticles according to claim 9 for antibacterial or antistatic equipment.

11. The use of polymer-coated metal-containing nanoparticles according to claim 9 for the plasmon resonance measurement or for the production of inks.

12. Use of polymer-coated metal-containing nanoparticles according to claim 9 for masterbatches and / or granules.