WO2023003890A1 - Methods for beta-lactone copolymerization - Google Patents

Abstract

A copolymer of a beta lactone and a lactone having 5 or more ring members may be formed by polymerizing the beta lactone and the lactone having 5 or more ring members in the presence of a catalyst comprised of a metal triflate/alcohol catalyst. A copolymer of a beta propiolactone and another lactone comprising a substituted beta lactone or a lactone having 5 or more ring members may be formed in a like manner. The copolymer(s) may be a random, gradient or block copolymer.

Description

METHODS FOR BETA-LACTONE COPOLYMERIZATION

BACKGROUND

[0001 ] Polyester polymers have proven to be versatile materials with a wide range of uses.

Polyesters based on petroleum-derived aromatic monomers are among the most widely utilized polymers, for example polyethylene terephthalate (PET) is produced on massive scale to produce water bottles, textiles and other consumer goods. Unfortunately, PET is not biodegradable and as such has become a major contributor to the growing problem of environmental contamination by residual post-consumer plastic wastes, including damage to marine ecosystems. In recent years there has been increasing interest in biodegradable polyesters, examples include polylactic acid (PLA) and poly-3-hydroxybutyrate (PHB). These polymers’ high cost and properties have made it difficult to serve large volume applications to displace incumbent high- volume polymers. There remains a need for high performance biodegradable polyesters and for methods of making such polymers from flexible feedstock sources that allow manufacturers to balance the cost and sustainability profiles of their products.

[0002] Conventional polymerization of lactones follows a nucleophilic ring-opening of the acyl-C(C=0)-0 bond mechanism with an alcohol/alkoxide propagating group. Most lactones can be copolymerized via this mechanism (e.g., beta-butyrolactone (bBL) and epsilon-caprolactone (eCL)) described in Polym. Int. 2002, 51, 859 and Macromolecules 2004, 37, 9798. However, ring opening polymerization of beta-propiolactone (bPL) is unique and follows an alkyl-C-0 bond cleavage mechanism described in ACS Catal. 2016, 6, 8219. The propagating carboxylate is incompatible for copolymerization with other lactones. Therefore, methods of building copolymers of beta-lactones, and beta-propiolactone in particular, is challenging. One method is the polymerization lactide from a pre-established poly(propiolactone), as described in WO2020197148. However, this will result in block polymers exclusively. Another method is through an acid-catalyzed ring-opening polymerization of beta-lactones with lactide, described in Int. 1. Mol. Sci. 2017, 18, 1312. This method is effective for lactide/beta-lactone copolymerization but is not sufficient in the copolymerization of beta-lactones with gamma-, delta-, or epsilon-lactones. Cationic polymerization can also be used for beta-lactone copolymerizations with cyclic ethers, such as tetrahydrofuran (THF) and other lactones (e.g., epsilon-caprolactone) as described in Polymer Science USSR 1980, 12, 2902. Similarly, beta- lactones have been copolymerized in the presence of neodymium triflate described in Macromolecules 2013, 46, 6765. However, this has been only shown in substituted beta-lactones (e.g. beta-butyrolactone and beta-malolactone), which resemble the ring-opening mechanism and reactivity of other lactones, such as delta-valerolactone and epsilon-caprolactone. To date, a catalyst for the random or gradient copolymerization of beta-propiolactone with other lactones has yet to be established.

[0003] Accordingly, it would be desirable to provide a method that overcome previously described limitations to form copolymers from beta-lactones and other lactone monomers to tailor the physical and end-of-life properties (e.g., composting).

SUMMARY

[0004] A method has been discovered enabling random, gradient, or block copolymerization of lactones having differing number ring members allowing for tailoring of the polymeric properties. In particular, it has been discovered that particular catalysts allow for the copolymerization of beta-lactones, even beta-propiolactone, with other lactones having a differing number of ring members (e.g., delta- and epsilon-lactones), even though lactones with more than 4 ring members are generally more stable. This may allow for greater tailoring of the polymer properties while retaining the compostability and use of lower cost, higher volume monomers.

[0005] A first aspect of the invention is a polymerization method comprising, polymerizing a beta-lactone and a lactone have 5 or more ring members in the presence of a catalyst comprised of a metal triflate/alcohol catalyst. The method may produce a random copolymer of the beta lactone and lactone having 5 or more ring members when the monomers are reacted simultaneously, or a block copolymer may be formed by the sequential addition of differing monomers. [0006] A second aspect of the invention is a copolymer comprised of the ring opened reaction product of a beta lactone and a lactone having 5 or more ring members. The copolymer may be a random copolymer or block copolymer.

[0007] A third aspect of the invention is a copolymer comprised of the ring opened reaction product of beta-propiolactone and a substituted beta-lactone or lactone having 5 or more ring members.

[0008] A fourth aspect of the invention is a polymerization method comprising polymerizing a beta-propiolactone and one or more of a substituted beta-lactone or lactone having 5 or more ring members in the presence of a catalyst comprised of metal triflate/alcohol catalyst. The method may produce a random copolymer of the bPL and other lactones (e.g., substituted beta lactone or lactone with 5 or more ring members) when the monomers are reacted simultaneously, or a block copolymer may be formed by the sequential addition of differing monomers. The polymerizations (second and fourth aspects) may be performed at temperatures ranging from about ~-20 °C to about 80 °C.

DETAILED DESCRIPTION

Definitions

[0009] Definitions of specific functional groups and chemical terms are described in more detail below. For purposes of this invention, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75^th Ed., inside cover, and specific functional groups are generally defined as described therein. Additionally, general principles of organic chemistry, as well as specific functional moieties and reactivity, are described in Organic Chemistry, Thomas Sorrell, University Science Books, Sausalito, 1999; Smith and March March's Advanced Organic Chemistry, 5^th Edition, John Wiley & Sons, Inc., New York, 2001; Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., New York, 1989; Carruthers, Some Modern Methods of Organic Synthesis, 3^rd Edition, Cambridge University Press, Cambridge, 1987; the entire contents of each of which are incorporated herein by reference. [0010] Certain polymers disclosed can comprise one or more asymmetric centers, and thus can exist in various stereoisomeric forms, e.g., enantiomers and/or diastereomers. The polymers and compositions thereof may be in the form of an individual enantiomer, diastereomer or geometric isomer, or may be in the form of a mixture of stereoisomers. The polymers disclosed may be enantiopure compounds. Disclosed are mixtures of enantiomers or diastereomers.

[0011] The term "beta lactone", as used herein, refers to a substituted or unsubstituted cyclic ester having a four-membered ring comprising an oxygen atom, a carbonyl group and two optionally substituted methylene groups. When unsubstituted, the beta lactone is referred to as propiolactone (bPL). The beta lactones may be monosubstituted, disubstituted, trisubstituted, and tetrasubstituted. Such beta lactones may be further optionally substituted as defined herein. The beta lactones comprise a single lactone moiety. The beta lactones may comprise two or more four-membered cyclic ester moieties. Examples of beta lactones are shown in Table A (between paragraphs 65 and 66) of PCT Pub. W02020/033267 incorporated herein by reference.

[0012] The term "polymer", as used herein, refers to a molecule of high relative molecular mass, the structure of which comprises the multiple repetition of units derived, from ring opened molecules of cyclic lactone monomers with lower molecular mass. The polymers may be a copolymer, terpolymer, heteropolymer, block copolymer, or tapered heteropolymer incorporating two or more different monomers. With respect to the structural depiction of such polymers, the convention of showing enchainment of different monomer units or polymer blocks separated by a slash may be used herein. For example, a structure:

could be used to represent a copolymer of beta-propiolactone and beta-butyrolactone. Such structures are to be interpreted to encompass copolymers incorporating any ratio of the different monomer units depicted unless otherwise specified. This depiction is also meant to represent random, tapered, block copolymers, and combinations of any two or more of these all of which are implied unless otherwise specified. [0013] The terms "halo" and "halogen" as used herein refer to an atom selected from fluorine (fluoro, -F), chlorine (chloro, -Cl), bromine (bromo, -Br), and iodine (iodo, -I). The term "aliphatic" or "aliphatic group", as used herein, denotes a hydrocarbon moiety that may be straight-chain (i.e., unbranched), branched, or cyclic (including fused, bridging, and spiro-fused polycyclic) and may be completely saturated or may contain one or more units of unsaturation, but which is not aromatic. Aliphatic groups may contain 1-40 carbon atoms, 1-20 carbon atoms, 2-20 carbon atoms, 1-12 carbon atoms, 1-8 carbon atoms, 1-6 carbon atoms, 1-5 carbon atoms, 1-4 carbon atoms, 1-3 carbon atoms orl or 2 carbon atoms. Exemplary aliphatic groups include, but are not limited to, linear or branched, alkyl, alkenyl, and alkynyl groups, and hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or (cycloalkyl)alkenyl. The term "heteroaliphatic," as used herein, refers to aliphatic groups wherein one or more carbon atoms are independently replaced by one or more atoms selected from the group consisting of oxygen, sulfur, nitrogen, or phosphorus. One to six carbon atoms may be independently replaced by one or more of oxygen, sulfur, nitrogen, or phosphorus. Heteroaliphatic groups may be substituted or unsubstituted, branched or unbranched, cyclic or acyclic, and include saturated, unsaturated, or partially unsaturated groups. The term "unsaturated", as used herein, means that a moiety has one or more double or triple bonds. The terms "cycloaliphatic", "carbocycle", or "carbocyclic", used alone or as part of a larger moiety, refer to a saturated or partially unsaturated cyclic aliphatic monocyclic or polycyclic ring system, as described herein, having from 3 to 12 members, wherein the aliphatic ring system is optionally substituted as defined below and described herein. Cycloaliphatic groups include, without limitation, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, cycloheptenyl, cyclooctyl, cyclooctenyl, norbornyl, adamantyl, and cyclooctadienyl. A cycloaliphatic group may have 3-6 carbons. The terms "cycloaliphatic", "carbocycle" or "carbocyclic" also include aliphatic rings that are fused to one or more aromatic or nonaromatic rings, such as decahydronaphthyl or tetrahydronaphthyl, where the radical or point of attachment is on the aliphatic ring.

[0014] The term "alkenyl," as used herein, denotes a monovalent group derived from a straight- or branched-chain aliphatic moiety having at least one carbon-carbon double bond. The term "alkynyl," as used herein, refers to a monovalent group derived from a straight- or branched-chain aliphatic moiety having at least one carbon-carbon triple bond. The term "alkoxy", as used herein refers to an alkyl group, as previously defined, attached to the parent molecule through an oxygen atom. Examples of alkoxy, include but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, neopentoxy, and n-hexoxy. The term "acyl", as used herein, refers to a carbonyl-containing functionality, e.g., -C(=0)R^', wherein R^' is hydrogen or an optionally substituted aliphatic, heteroaliphatic, heterocyclic, aryl, heteroaryl group, or is a substituted (e.g., with hydrogen or aliphatic, heteroaliphatic, aryl, or heteroaryl moieties) oxygen or nitrogen containing functionality (e.g., forming a carboxylic acid, ester, or amide functionality). The term "acyloxy", as used here, refers to an acyl group attached to the parent molecule through an oxygen atom. The term "aryl" used alone or as part of a larger moiety as in "aralkyl", "aralkoxy", or "aryloxyalkyl", refers to monocyclic and polycyclic ring systems having a total of five to 20 ring members, wherein at least one ring in the system is aromatic and wherein each ring in the system contains three to twelve ring members. The term "aryl" may be used interchangeably with the term "aryl ring" wherein "aryl" refers to an aromatic ring system which includes, but is not limited to, phenyl, biphenyl, naphthyl, anthracyl and the like, which may bear one or more substituents. Also included within the scope of the term "aryl", as it is used herein, is a group in which an aromatic ring is fused to one or more additional rings, such as benzofuranyl, indanyl, phthalimidyl, naphthimidyl, phenantriidinyl, or tetrahydronaphthyl, and the like, where the radical or point of attachment is on the aryl ring. The terms "heteroaryl" and "heteroar-", used alone or as part of a larger moiety, e.g., "heteroaralkyl", or "heteroaralkoxy", refer to groups having 5 to 14 ring atoms, preferably 5, 6, or 9 ring atoms; having 6, 10, or 14 p electrons shared in a cyclic array; and having, in addition to carbon atoms, from one to five heteroatoms. The term "heteroaryl" may be used interchangeably with the terms "heteroaryl ring" and "heteroaryl group", any of which terms include rings that are optionally substituted. The term "heteroatom" refers to nitrogen, oxygen, or sulfur, and includes any oxidized form of nitrogen or sulfur, and any quaternized form of a basic nitrogen. Heteroaryl groups include, without limitation, thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl, purinyl, naphthyridinyl, benzofuranyl and pteridinyl. The terms "heteroaryl" and "heteroar-", as used herein, also include groups in which a heteroaryl ring is fused to one or more aryl, cycloaliphatic, or heterocyclyl rings, where the radical or point of attachment is on the heteroaryl ring. Nonlimiting examples include indolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4/-/— quinolizinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and pyrido[2,3-b]-l,4-oxazin- 3(4H)-one. A heteroaryl group may be mono- or bicyclic. The term "heteroaralkyl" refers to an alkyl group substituted by a heteroaryl, wherein the alkyl and heteroaryl portions independently are optionally substituted. In certain embodiments, the term "5- to 10-membered heteroaryl" refers to a 5- to 6-membered heteroaryl ring having 1 to 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8- to 10-membered bicyclic heteroaryl ring having 1 to 4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. The term "partially unsaturated" refers to a ring moiety that includes at least one double or triple bond. The term "partially unsaturated" is intended to encompass rings having multiple sites of unsaturation but is not intended to include aryl or heteroaryl moieties, as herein defined.

[0015] As described herein, compounds disclosed may contain "optionally substituted" moieties. The term "substituted", whether preceded by the term "optionally" or not, means that one or more hydrogens of the designated moiety are replaced with a suitable substituent. Unless otherwise indicated, an "optionally substituted" group may have a suitable substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned are those that result in the formation of stable or chemically feasible compounds. The term "stable", as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and, in certain embodiments, their recovery, purification, and use for one or more of the purposes disclosed herein. As used herein the term "alkoxylated" means that one or more functional groups on a molecule (usually the functional group is an alcohol, amine, or carboxylic acid, but is not strictly limited to these) has appended to it a hydroxy-terminated alkyl chain. Alkoxylated compounds may comprise a single alkyl group or they may be oligomeric moieties such as hydroxyl-terminated polyethers. Alkoxylated materials can be derived from the parent compounds by treatment of the functional groups with epoxides. Unless otherwise specified, "a," "an," "the," and "at least one" are used interchangeably and mean one or more than one.

Polymerization Method

[0016] The polymerization methods comprise of polymerizing a beta -lactone with a lactone having 5 or more ring members (e.g., delta-valerolactone or epsilon-caprolactone) or beta-propiolactone with another lactone (e.g., beta-butyrolactone, or epsilon-caprolactone) in the presence of a catalyst such as a metal triflate/alcohol catalyst (MTFA catalyst herein). The ratio of monomers to MTFA catalyst is selected to form the desired polymer. For example, the mole ratio may be 10:1 or greater, 100:1 or greater, 1,000:1, or greater, 2,000:1 or greater, 3,000:1 or greater, 4,000:1 or greater, 5,000:1 or greater, 7,500:1 or greater, 10,000:1 or greater, 15,000:1 or greater. 20,000:1 or greater, 30,000:1 or greater, 40,000:1 or greater, 50,000:1 or greater, 75,000:1 or greater or 100,000:1 or greater. The MTFA catalyst is contacted with the monomers for a sufficient time to form the desired polymers.

[0017] The polymerization may be carried out in the presence of the MTFA catalyst for any useful time to form the desired copolymer. The time may be from several minutes, 1, 2, 4, or 8 hours to several days (3 or 4 days). The progress of the polymerization reaction may be monitored (for example by analyzing aliquots from the reaction mixture by a suitable technique such as GPC, or by utilizing in situ monitoring techniques). The method may include stopping the reaction when the molecular weight of the polymer composition (or a proxy for molecular weight such as reaction viscosity) reaches a desired value or exceeds a predetermined threshold. The method may include the step of monitoring the depletion of monomers until their concentration reaches a desired concentration or falls below a predetermined threshold. The method may include the step of stopping the reaction when the concentration of monomers reaches a desired concentration or falls below a predetermined threshold.

[0018] The MTFA may be comprised of any useful metal triflate such as those known in the art with an alcohol, wherein the metal is desirably a rare earth, transition metal, aluminum or bismuth and more desirably a lanthanide. Triflate is a trifluoromethanesulfonate anion functional group (e.g., CF3SO3- also represented by -OTf). The metal is desirably a lanthanide comprised of one or more of Nd, Ce, Pr, or Yb. The metal may be a transition metal, such as Sc, Y, or Hf or other metal such as Bi or Al. The MTFA catalyst may be formed by known methods starting with a triflate and metal compound such as salt. An example of a particular MTFA is Nd(OTf)₃.

[0019] The MTFA is also comprised of an alcohol. The alcohol may be any alcohol, but desirably the alcohol has a lower molecular weight such as below about 10,000, 5000, 100 or 500 g/mole. It is also desirable that the alcohol has more than one hydroxyl alcohol such as a glycol or polyol. Examples include methanol, ethanol, butanol, propanol, ethylene glycol, 1,4- butanediol,l,4-benzenedimethanol, propylene glycol, glycerol, dihydroxy-telechelic poly (ethylene oxides), and dihydroxy-telechelic polyolefins. The amount of alcohol and metal triflate (MTF) may be any useful amount. For example, the ratio of triflate groups to alcohol groups may be from about 0.1 or 0.2 to 10 or 5 by mole.

[0020] The beta lactone may be represented by the following general formula:

wherein R¹, R², R³, R⁴ are hydrogen, a hydrocarbyl moiety or a fluorocarbyl moiety; the hydrocarbyl or fluorocarbyl moieties may optionally contain at least one heteroatom or at least one substituent. If substituted it is desirable for at least one R¹, R², R³, R⁴to be present as a hydrocarbyl or fluorocarbyl moiety which may enhance the polymer's usefulness in coatings or films. At least one R¹, R², R³, R⁴are hydrocarbyl or fluorocarbyl groups may contain one or more of unsaturated groups, electrophilic groups, nucleophilic groups, anionic groups, cationic groups, zwitterion containing groups, hydrophobic groups, hydrophilic groups, halogen atoms, natural minerals, synthetic minerals, carbon based particles, an ultraviolet active group, a polymer having surfactant properties, and polymerization initiators or reactive heterocyclic rings. The functional groups may be linked to the ring by a linking group (M) which functions to link the functional portion of the groups to the cyclic ring. Exemplary linking groups may be hydrocarbylene, fluorocarbylene groups, ethers, thioethers, polyethers (such as polyalklene ether).

[0021] Examples of substituted lactones may include one or more of the following:

where R¹⁰ is as defined above for R¹ to R⁴.

[0022] The substituted beta lactone may be.

where Ar is any optionally substituted aryl group, R¹² is selected from the group consisting of: -H, optionally substituted Ci-40 aliphatic, optionally substituted Ci-20 heteroaliphatic, and optionally substituted aryl, and R¹³ is a fully or partially unsaturated C2-20 straight chain aliphatic group.

[0023] The beta lactone may be:

where each R¹⁴ is independently selected from the group consisting of: optionally substituted Ci-40 aliphatic, optionally substituted Ci-20 heteroaliphatic, and optionally substituted aryl and both R¹⁴ groups may be optionally taken together to form an optionally substituted ring optionally containing one or more heteroatoms.

The one or more substituted propiolactones may be:

[0024] One or more of R¹, R², R³, R⁴ may be a halogen substituted alkyl group, a sulfonic acid substituted alkyloxy group; an alkyl sulfonate alkyloxy group; alkyl ether substituted alkyl group; a polyalkylene oxide substituted alkyl group, an alkyl ester substituted alkyl group; an alkenyloxy substituted alkyl group; an aryl ester substituted alkyl group; an alkenyl group; a cyano substituted alkyl group; an alkenyl ester substituted alkyl group; a cycloalkyl substituted alkyl group; an aryl group; a heteroatom containing cycloalkenyl, alkyl ether substituted alkyl group; a hydroxyl substituted alkyl group, a cycloaliphatic substituted alkenyl group; an aryl substituted alkyl group; a haloaryl substituted alkyl group; an aryloxy substituted alkyl group; an alkyl ether substituted alkaryl group; a hetero atom containing cycloaliphatic group substituted alkyl group; a hetero atom containing aryl substituted alkyl group, an alkyl amide substituted alkyl group, an alkenyl substituted cycloaliphatic group; two of R¹ or R² and R³ or R⁴form a cyclic ring, which may optionally contain one or more unsaturated groups; an alkyl group substituted with a beta propiolactone group which may optionally contain one or more ether groups and/or one or more hydroxyl groups; a glycidyl ether group, ora benzocyclobutene substituted alkyl group, optionally substituted with one or more ether groups. An unsubstituted beta lactone corresponds to the formula wherein all of R¹, R², R³and R⁴ are hydrogen. [0025] The lactone having more than 4 ring members may be any cyclic ester having 5 to

20 ring members. Said lactone may have more ring members such as macro cyclic esters. These lactones may be substituted at each carbon member of the ring as described above for the beta lactone. Desirably said lactone has 6 or 7 to 12 or 11 ring members.

[0026] The polymerization method may be performed with or without an additional solvent. If an additional solvent is used, it may be any solvent that does not react or impede the polymerization. For examples, the solvent may comprise a C4-12 aliphatic hydrocarbon, aromatic solvent, ether solvent or a chlorinated hydrocarbon. The solvent may comprise, isobutane, pentanes, hexanes, or heptanes, or higher aliphatic hydrocarbons. The solvent may comprise, diethylether, tert-butyl methyl ether, or cyclopentyl methyl ether, toluene, benzene, a chlorobenzene or mixture thereof. The solvent may be substantially anhydrous (e.g., less than 10 ppm water by weight) or any other grade of solvent.

[0027] The polymerization may be carried out at least in part in a gas phase. The polymerization may be performed essentially in a liquid or liquid and solid (e.g., slurry). A gas containing beta lactone or bPL vapor may be contacted with condensed MTFA catalyst and or the lactones having more than 4 ring members or another lactone, respectively. The gas comprising monomer vapor may comprise of a mixture of monomers with air or an inert gas such as nitrogen or argon. Any condensed ingredient's particles may be suspended in a flow of such a gas. The condensed particles may be separated from the gas flow as they gain mass due to the formation of the polymer. Additional MTFA or monomer may be added to the gas flow (either continuously or in discrete portions) to replace separated and removed products or catalyst from the stream. The gas stream may be maintained at a sub-atmospheric pressure. The gas stream may be maintained at an elevated temperature. The gas stream may be maintained at an elevated temperature and sub-atmospheric pressure.

[0028] The polymerization may be performed at any useful temperature depending on the desired polymer and other circumstances. The polymerization may be any temperature from about 30 °C, 40 °C, 50 °C, to about 60 °C, 70 °C, or 80 °C. The polymerization may also be performed at ambient temperature (e.g., ~20 to ~30 °C. The polymerization temperature may be at a temperature below about 20 °C, below about 15 °C below about 10°C, below about 5 °C, below about 0 °C, to about -20 °C. The method may include changing the temperature of the polymerization mixture over time during the process.

[0029] The polymerization may be conducted at any suitable pressure and may be conducted at elevated pressure. This can allow processes to be conducted at temperatures above the boiling point of certain reaction mixture components (e.g., solvents or monomers) and/or may aid in separation of volatile components when the pressurized process stream or reaction vessel is depressurized. The polymerization may be conducted at a pressure above 1 bar, about 2 bar or greater, about 3 bar or greater, about 5 bar or greater or about 10 bar or greater, about 15 bar or greater, about 20 bar or greater, about 30 bar or greater or about 40 bar o greater. The pressure may be a about 50 bar or less, about 60 bar or less, about 70 bar or less, about 80 bar or less, about 90 bar or less or about 100 bar or less. The pressure may be applied by pressurizing a reactor headspace in contact with the reaction mixture (e.g., by introducing a pressurized inert gas). The pressure may be applied by heating the mixture in contained volume. The pressure may be maintained by applying pressure to a hydrostatically filled reaction vessel. Two or more of these approaches may be used. The pressure may be controlled by application of a back-pressure regulator or other pressure relief system.

[0030] The polymerization may be performed in a batch process, continuous process, a hybrid of batch and continuous processes (e.g., fed batch reactions). The method may comprise the step of feeding one or more components to the polymerizing mixture over time. Monomers, oligomers, end capping agents, chain extenders, chain transfer agents, or crosslinking agents may be added to the polymerization mixture overtime (either continuously, or in one or more discrete additions) the composition of monomers added to such a fed reaction may be changed over time. Such methods are characterized in that the polymer composition produced comprises a tapered copolymer or block copolymer (e.g., sequential addition to realize block copolymers).

[0031] The lactone having 5 or more ring members may be added at the beginning of the process along with the beta lactone. For example, a batch polymerization may be performed using a defined mixture of beta lactone and the lactone having 5 or more ring members. Likewise, the bPL and the other lactone may be added together or sequentially depending on the desired polymer. The methods may include changing the monomer composition over time by the

IB addition of additional monomers to the polymerization mixture. Such additions may comprise of continuous or batch-wise addition of the beta lactone and the lactone having 5 or more ring members or mixtures of the beta lactone and the lactone having 5 or more ring members may lead to random copolymers, tapered copolymers, or block copolymers.

[0032] The method may comprise a quenching step of the polymerization. A quenching agent may be added after a specified reaction time, or when the polymer composition has reached a desired molecular weight (e.g., when the Mn of the formed polymer composition exceeds a predetermined threshold). The quenching agent may be added when the desired molecular weights are achieved. When the method is performed in a continuous process such as in a plug-flow reactor, a quenching agent may be added at a particular point along the length of the reactor. The quench agent may be one or more of mineral acids, organic acids, and acidic resins or solids.

[0033] Any suitable quenching agent may be used such as those known in the art including weak bases and metal chelated compounds. Quenching agents may include, for example, ethers (e.g., glyme), water, phenols, catechols or mixtures thereof.

[0034] The polymerization method may include adding an end-capping agent to quench the polymerization, as disclosed in PCT application WO2019241596A1, the entirety of which is incorporated herein by reference. The monomers may be polymerized such that the terminal end of the formed polymer chains have an alcohol end-group. The terminal end groups are reacted with the end capping agent. The end capping agent may render the formed polymers more stable. The end capping agents may comprise electrophilic organic compounds. The end capping agents may comprise one or more of an organohalide, organosulfonate, a haloalkyl silane, an aniline derivative, a phosphate derivative, and an isophthalic acid derivative.

[0035] The end capping agent may comprise an alkyl halide, such as an aliphatic chloride, bromide, or iodide. In certain embodiments, a quench agent comprises a compound of formula Rⁿ-X^h, where Rⁿ is an optionally substituted Ci-40 aliphatic group and X^h is selected from Cl, Br, or I. In certain embodiments, the end capping agent comprises R^p-CH2-X^h, where R^p is -H or an optionally substituted radical selected from the group consisting of aliphatic, aryl, heterocyclic, and heteroaryl. In certain embodiments, the end capping agent is selected from the group consisting of methyl bromide, methyl iodide, allyl chloride, and allyl bromide, benzyl chloride, and benzyl bromide.

[0036] The end capping agent may comprise an organosulfonate. The organosulfonate may correspond to the formula RⁿOS0₂R^q, where each of R^q and Rⁿ is as defined above and in the genera and subgenera herein. The end capping agent may comprise a dialkylsulfate, such as dimethylsulfate or diethylsulfate.

[0037] The end capping agent may comprise a compound that contains a silyl or siloxy group. Such end capping agents may correspond to one of the formulas:

/ where X^h is as defined above, each R¹ is methyl, ethyl or propyl, and each R^s is -H, methyl, or ethyl. X^h may be -triflate or tosylyate. R¹ may be methyl or ethyl. R^s may be methyl.

[0038] Thermally stable aniline derivatives may include azoles such as those selected from the group consisting of benzothiazole, benzoxazole, benzimidazole, 2-aminothiophenol, o- phenylenediamine, and 2-aminophenol. Exemplary end-capping agents may further include phosphates such as aliphatic phosphates (e.g., trimethylphosphate). Exemplary end-capping agents may even further include other additives and stabilizers such as isophthalic acid.

[0039] The methods may comprise a step of adding a chain extender or cross-linking agent to the polymerization reaction. The chain extender or cross-linking agent may be added as a quench agent. Analogs of the end capping agents described above having two or more suitable reactive functional groups in a single molecule are utilized as quench agents, they may act as chain extenders or cross-linking agents respectively. Quenching with a difunctional chain extender results in reaction with the carboxylate ends of two separate polymer chains leading to the formation of a dimeric chain extended product. It will be appreciated that difunctional analogs of any of the quench agents described above can be utilized to similar effect. [0040] Chain extenders suitable for methods disclosed comprise compounds of formula

X'-L'-X' where each X' is independently as defined above and L' comprises a bivalent moiety. L'- is an optionally substituted Ci-Cioo aliphatic group, - an optionally substituted C₁-C₄₀ aliphatic group; an optionally substituted Ci-₂₄ aliphatic group, an optionally substituted C₁-C₂₀ aliphatic group an optionally substituted C₁-C₁₂ aliphatic group, an optionally substituted C₂- C₁₀ aliphatic group; an optionally substituted C₄-C₈ aliphatic group, an optionally substituted C₄-C₆ aliphatic group, an optionally substituted C₂-C₄ aliphatic group, an optionally substituted C₁-C₃ aliphatic group, an optionally substituted C₆-C₁₂ aliphatic group, or an optionally substituted Ci, C_2, C_3, C_4, C_5, C_6, C₇ or Ce aliphatic group.

[0041] L'- may be an optionally substituted straight alkyl chain or optionally substituted branched alkyl chain. -L'- may be a Ci to C₂₀ alkyl group having one or more methylene groups replaced by -C(R^aR^b)- where R^aand R^b are each independently C₁-C₄ alkyl groups. L'- may be an aliphatic group having 2 to 30 carbons including one or more gem-dimethyl substituted carbon atoms. L'-may include one or more optionally substituted rings such as saturated or partially unsaturated carbocyclic, saturated or partially unsaturated heterocyclic, aryl, and heteroaryl. L'- may be a substituted ring (i.e., the X' groups are directly linked to atoms composing the ring in -L'-). The ring may be part of an -L'- moiety having one or more non-ring heteroatoms or optionally substituted aliphatic groups separating one or more of the X' group(s) from the ring. L'- may contain one or more heteroatoms in its main chain (i.e., in the group of covalently linked atoms separating the site(s) of attachment of the -X' groups). L'- may comprise a moiety corresponding to the structure resulting from replacing one or more sp² carbon atoms of an optionally substituted C₄-C₄₀ aliphatic moiety with a group selected from: -0-, -NR¹-, -S-, -S(O)-, -S(0) -, -OC(O)-, -0C(0)0-, -NR¹C(0)-, -NR^OjO-, -NR¹C(0)NR¹-, -N =N-, -NR^NJNR¹-, -SC(O)-, -SC(0)S-, -SC(S)S-, -NR^OJS-. and -NR^SjO-, where R¹ is as defined above and in the genera and subgenera herein and with the proviso that the -L'- moiety resulting from such replacements have a structure consistent with the recognized principles defining the structures of stable organic molecules. Where more than one such substitution is present, they are separated by at least one aliphatic carbon atom, at least two aliphatic carbon atoms. L'-may comprise one or more ether linkages one or more ester linkages, one or more urethane linkages and/or one or more amide linkages. L'- may comprise an oligomer or a polymer. The polymer may be one or more of polyolefins, polyethers, polyesters, polycarbonates, polyamides, and polyimides. Where -L'- comprises a polymer, the X' groups may be present on the ends of the polymer chains.

[0042] If a tri-functional or higher-functional end-capping agent is utilized, a star or comb polymer composition may be obtained. Such end-capping agents may have a formula L"(X')_n where X' is as defined above and herein and L" is a multivalent linker having any of the formulae enumerated for L', and n is at least S to any practical amount such as 50, 25, 10 or 7. L" may comprise a polymer that has a large number (i.e. dozens or hundreds) of attached X' groups (as for example if the X' groups are present as substituents on monomers comprising a polymer L").

[0043] The quenching, end capping, crosslinking agent or chain extending agent may be added to the reaction mixture in an amount of less than 10 molar equivalents relative to the amount of MTFA catalyst added to the polymerization process, for example from 0.1 to 10 molar equivalents relative to the amount of MTFA catalyst, from 0.1 to 2 molar equivalents, or from 1 to 2 molar equivalents or about 1 molar equivalent.

[0044] The polymerization may also be comprised of chain transfer agents, and/or crosslinking agents. Chain transfer agents, in this context are defined as any substance or reagent capable of terminating growth of one polymer chain and initiating polymerization of a new polymer chain. In a living polymerization this is typically a reversible process, and the net effect is that, on average in the composition, all chains grow at similar rates. Chain transfer agents can be used to control the molecular weight of the produced polymer composition, to optimize the amount of catalyst used, and/or to control the polydispersity of the produced polymer composition. Chain transfer agents can also be used to introduce additional functional groups at chain ends (e.g., for subsequent cross-linking or chain extension reactions, or to impart particular physical properties such as hydrophilicity or hydrophobicity etc.) examples of the latter would include chain transfer agents having radically polymerizable functional groups such as vinyl groups, perfluorinated moieites or siloxy groups). [0045] The chain transfer agent may be provided at a molar ratio of from about 1:1 to about 10,000:1 relative to MTFA catalyst, or from about 1:1 to about 10:1, e.g., 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1 or 10:lorfrom about 10:1 to about 100:1, e.g., 20:1, 30:1, 40:1, 50:1, 75:1, or 100:1,. about 100:1 to about 1,000:1, e.g., 200:1, 300:1, 400:1, 500:1, 750:1, or 1000:1

[0046] The polymerization methods may be integrated into a process for production of beta lactones. Such integrated processes can have advantages in terms of energy efficiency and can lead to higher quality polymer products due to reduced introduction of water, oxygen or other impurities. The methods may include a step of reacting ethylene oxide with carbon monoxide to form beta propiolactone. Exemplary catalysts and methods for such processes are described in Published Patent Applications: W02013/063191, W02014/004858,

W02003/050154, W02004/089923, WO2012/158573, W02010/118128, W02013/063191, and W02014/008232; in U.S. Pat. Nos. 10,662,283, 5,359,081 and 5,310,948 and in the publication "Synthesis of beta-Lactones" J. Am. Chem. Soc., vol. 124, 2002, pages 1174-1175. the entire contents of each of which is incorporated herein by reference.

[0047] The methods may comprise the steps of: contacting one or more epoxides (e.g., ethylene oxide or propylene oxide) with carbon monoxide in the presence of a carbonylation catalyst and a solvent to provide reaction stream comprising beta lactone; separating a product stream comprising the beta lactone from the reaction stream, and feeding the beta lactone- containing reaction stream into a polymerization reactor with the lactone having 5 or more ring members and contacting it with the MTFA catalyst to provide a second reaction stream containing a biodegradable polyester. Such integrated carbonylation/polymerization processes may be characterized in that substantially all carbonylation catalyst is removed from the reaction stream comprising beta propiolactone prior to feeding the stream into the polymerization reactor. Such integrated carbonylation/polymerization processes are characterized in that at least a portion of the solvent in which the carbonylation process is performed is present in the reaction stream comprising beta lactone and is fed into the polymerization reactor. The method may comprise separating the solvent from the second reaction stream containing the polymer. The method may comprise recycling the separated solvent back to the carbonylation reaction. The processes may be characterized in that the reaction stream comprising beta propiolactone contains residual ethylene oxide and the beta propiolactone ethylene oxide mixture is fed into the polymerization reactor.

[0048] The copolymer (polyester) comprised of the reaction product of the beta lactone and lactone having 5 or more ring members, or beta-propiolactone with any other lactone monomers, may be multimodal and include one or more peaks representing a distinct population of low molecular weight oligomers (e.g., polyester chains) having a molecular weight of about 5,000 g/mol or less, about 4,500 or less, about 4,000 or less, about 3,500 or less, about 3,000 or less, about 2,500 or less, about 2,000 less, about 1,500 or less or about 1,000 g/mol or less. The ratio of the area of peaks resulting from polymer chains having an Mn above 50,000 g/mol to the area of peaks representing oligomers with Mn below 5,000 g/mol may be at least 10:1. The polymer or the higher weight molecular weight fraction may have a number average molecular weight M_n of 2,000 g/mol, 5,000 g/mol, 10,000 g/mol to 150,000 g/mol, 200,000 g/mol, 250,000 g/mol or greater, 300,000 g/mol, 400,000 g/mol, 500,000 g/mol, 600,000 g/mol, 700,000 g/mol. Mn of the polymer composition refers to that measured by gel permeation chromatography (GPC) using CHCU as the solvent and referenced to polymethyl methacrylate standards.

[0049] The copolymer may have a low polydispersity such as a polydispersity index (PDI) of 3.5 or less, 3.0 or, 2.5 or less or 2.2 or less the polymer may have a PDI of 1.05 or greater, 1.1 or greater, 1.2 or greater, 1.5 or greater or 2.0 or greater the PDI values recited refer to that measured by GPC. The PDI values may be calculated without inclusion of GPC peaks arising from oligomers having Mn below about 5,000 g/mol, less than about 4,500, less than about 4,000, less than about 3,500, less than about 3,000, less than about 2,500, less than about 2,000, less than about 1,500, or less than about 1,000 g/mol.

[0050] The copolymer may have an M_N between 2,000 g/mol and 200,000 g/mol and a

PDI less than 1.5. In certain embodiments, the method is characterized in that the polymer composition formed has an M_N between 5,000 g/mol and 50,000 g/mol and a PDI less than 1.5. The polymer may have an M_N between 50,000 g/mol and 100,000 g/mol and a PDI less than 1.5.

The polymer may have an M_N between 100,000 g/mol and 200,000 g/mol and a PDI less than 1.5.

The polymer may have an M_N between 200,000 g/mol and 500,000 g/mol and a PDI less than 1.5.

The polymer may have an M_N between 400,000 g/mol and 800,000 g/mol and a PDI less than 1.5. [0051] The copolymer of the beta lactone and lactone having 5 or more ring members, or beta-propiolactone with any other lactone monomers, may be block copolymers, random copolymers or one or more chains may be grafted to the polymer backbone. The copolymers of this invention may include triblock, pentablock, multiblock, tapered block, and star block ((AB)_n) polymers, designated A(B'A')_xB_y, where in each and every occurrence A is block comprised of the residue of the beta lactone, B is the residue of the lactone having 5 or more ring members, A, in each occurrence, may be the same as A or of different components or Mw, B', in each occurrence, may be the same as B or of different components or Mw, n is the number of arms on a Star and ranges from 2 to 10, in one embodiment 3 to 8, and in another embodiment 4 to 6, x is > 1 and y is 0 or 1. In one embodiment the block polymer is symmetrical such as, for example, a triblock with a beta lactone block of equal Mw, on each end. Typically, the block copolymer will be an A- B-A or A-B-A-B-A type block copolymer.

[0052] The block copolymers can have blocks with individual weight average molecular weighted blocks, M_w, of from about 6,000, especially from about 8,000, to sum-total weighted blocks of about 15,000, to about 45,000. The sum-total, weight average molecular weight of the blocks comprised of the lactones having 5 or more members unit block(s) can be from about 20,000, especially from about 30,000, more especially from about 40,000 to about 150,000, and especially to about 130,000.

Examples 1-3 and Comparative Examples 1-4

[0053] Each Example and Comparative Example is made in 40 mL were equipped with stir-bars and pressure-relief caps, that are loaded with lactones, neodymium triflate (Nd(OTf)3 catalyst and ethylene glycol (EG) initiator as shown in Table 1. The vials are stirred and maintained at 50 °C and sampled for NMR analysis over time. Table 1:

[0054] The b-propiolactone (bPL) of Comparative Example 2 is completely converted to poly(propiolactone) (PPL) within 24 hours. Given the ratio of bPL to EG, the calculated polymer molecular weight (M_n) is~ 1500 g/mol, which is reasonably close to the diffusion NMR measured M_w of 1800 g/mol. From DSC, the solid polymer product has a melting transition of 47°C, again reasonable for a low molecular weight PPL. TGA showed an onset of decomposition temperature of 229°C.

[0055] The b-butyrolactone (bBL) of Comparative Example 3 polymerized rather more slowly, reaching full conversion within 4 days. The resulting polymer has an NMR diffusion-based M_w of 2000 g/mol which compares well to the calculated M_n of 1800 g/mol. DSC analysis of the polymer did not show a melting transition and TGA gave an onset of decomposition temperature of 223°C.

[0056] The d-valerolactone (dVL) of Comparative Example 4 took longer than 4 days to polymerize, eventually giving a product with an NMR diffusion-based M_w of 1300 g/mol compared to the calculated M_n of 2100 g/mol. DSC showed a melting transition at 58°C and TGA an onset of decomposition of 153°C.

[0057] The e-caprolactone (eCL) of Comparative Example 5 is the slowest reaction observed, reaching full conversion after 4 weeks. The solid product has an M_w from NMR diffusion measurement of 5,600 g/mol, compared to a calculated M_n of 2300 g/mol. The diffusion data did not suggest a very broad molecular weight distribution, so this discrepancy is probably due to a low number of catalyst active sites (perhaps poor solubility of the catalyst in eCL, the least polar lactone in this series), which would also be consistent with the long reaction time. The solid product showed a melting transition of 52°C in DSC and an onset of decomposition of 273 °C from TGA.

[0058] The copolymers of Examples 1-3 all show comparatively fast reactions, with complete conversion of both bPLand the co-lactone within 24 hours. All produced liquid products with no DSC melting transition and all show onsets of decomposition close to that of polypropiolactone. All also display carboxylic acid chain ends, as evidenced by broad ¹H NMR signals in the 0 10-12 ppm region of the spectra (the same signal is seen in the bPL homo polymerization with this catalyst/initiator system, but not in the other homopolymerizations). This implies that bPL forces this polymerization system to flip its regiochemistry from carbonyl carbon attack in the case of bBL, dVL and eCL to ester carbon attack in the case of bPL and bPL copolymerizations. The copolymers's lack of melting points is evidence that these reactions have produced random copolymers.

Examples 4-8

[0059] In each of these examples, the reaction temperature is 60 °C and the reaction time is 24 hours. The lactones are mixed with the alcohol either ethylene glycol (EG) or 1-4-butanediol (BDO). This metal triflate catalyst is added to the vial and the reaction carried out for the reaction time shown in Table 2 and tracked until free bPL is not observed using gas chromatography with a flame ionization detector. The molar ratios of the lactone 1, lactone 2, alcohol, and metal triflate catalyst (Lactone l:Lactone 2:Alcohol: triflate catalyst) are listed below. The molar ratios for examples 4-6 is 250:250;1:0.05. The molar ratio for Example 7 is 12:7:1:0.2. The molar ratio for Example 8 is 13:9:1:0.2 and the reaction time is 96 hours. The properties of the resultant polymers are shown in Table 2. The number molecular weight average Mn and polydispersity index (PDI) is determined by gel permeation chromatography in CHCI3. The structure of the polymer of each these Examples are random copolymers as determined by 13C NMR and proton diffusion spectroscopy. The % by mole of bPL in each polymer is determined by 1H NMR spectroscopy. The decomposition temperature of the polymer (Tdec) is determined by TGA at 10 °C/min in nitrogen with the Tdec corresponding to the temperature where there has been a 5% loss in mass. These examples show the metal triflate effectiveness to make random copolymers of bPL and other lactones having more ring members.

Examples 9-8

[0060] Examples 9 and 10 and Comparative Example 6 are performed at the same ratios as Examples 4-6 and procedures with differing catalysts as shown in Table 3. The reaction time is 168 hours for Example 9; 48 hours for Examples 10. These examples show that certain catalysts may form copolymers of bPL and other lactones having differing ring opening polymerization mechanisms, but they fail to form random copolymers. DPP when copolymerizing bBL and bPL fails to have a reaction under the same conditions (Comp. Ex. 6), whereas TBD and DPP form a copolymer as shown by Examples 9 and 10 when reacting bPL and eCL, displaying essentially block copolymers. In contrast, all of the copolymer Examples made using the metal triflate catalysts, result in essentially random copolymers.

[0061] Examples 11-13 are made in the same manner as Examples 4 to 6. These examples show the metal triflate catalysts are also effective in making copolymers of bPL and substituted beta lactones.

Table 2:

ND = Not determined.

Table 3:

DPP = Diphenyl phosphate TBD = Triazabicyclodecene

Claims

CLAIMS We claim:

1. A polymer composition comprised of a polyester of the ring opening polymerization reaction product of a beta propiolactone and a substituted beta lactone or a lactone having 5 or more ring members.

2. The polymer composition of claim 1, wherein said polymer composition is comprised of the residue of a metal catalyst.

3. The polymer composition of claim 2, wherein the metal catalyst is comprised of a lanthanide metal, transition metal, aluminum or bismuth.

4. The polymer composition of claim 2, wherein the metal is Nd, Al, Sc, Bi or mixture thereof.

5. The polymer composition of any one of the preceding claims, wherein the lactone having 5 or more ring members has 6 to 12 ring members.

6. The polymer composition of claim 5, wherein the lactone having 5 or more ring members has 6 to 9 ring members.

7. The polymer composition of claim 6, wherein the lactone having 5 or more ring members is a substituted or unsubstituted caprolactone.

8. The polymer composition of any one of the preceding claims wherein the polyester is a random or gradient copolymer.

9. The polymer composition of any one of claims 1 to 7, wherein the polyester is a block copolymer.

10. The polymer composition of claim 9, wherein the block copolymer is a triblock, pentablock, multi-block, linear or star copolymer architectures.

11. A method to form a copolymer comprising polymerizing a beta lactone and a lactone having 5 or more ring members in the presence of a catalyst.

12. A method according to Claim 11 wherein the beta lactone and lactone having 5 or more ring members and the metal triflate/alcohol catalyst are present in a ratio of said lactones/catalyst a ratio of about 100 to 1 to about 1,000,000 to 1.

IB. The method of any one of claims 11 or 12, wherein the polymerization is performed at a temperature from about -20 °C to about 80 °C.

14. The method of any one of claims 11 to 13, wherein the polymerization is performed at a pressure of between about 1 bar and about 20 bar.

15. The method of any one of claims 11 to 14, wherein an end-capping agent is added.

16. The method of any one of claims 11 to 15, wherein the catalyst is a metal triflate/alcohol catalyst that is comprised of one or more of a rare earth metal, transition metal, Al or Bi.

17. The method of claim 16, wherein the rare earth metal is a lanthanide metal.

18. The method of claim 17, wherein the rare earth metal is neodymium, Sc, Al, Bi or mixture thereof.

19. The method of any one of claims 11 to 18, wherein the metal triflate/alcohol catalyst is comprised of an alcohol that is a polyol.

20. The method claim 19, wherein the alcohol has a molecular weight of at most about 500 g/mole.

21. The method of claims 19 or 20, wherein the alcohol is a glycol or glycerol.

22. The method of any one of claims 16 to 18, wherein the metal triflate/alcohol catalyst has an amount of triflate groups and alcohol groups to give a ratio of triflate groups/alcohol groups of 0.1 to 10 by mole.

23. A polymer composition comprised of a polyester of the ring opening polymerization reaction product of a beta propiolactone and another lactone comprised of one or more of a substituted beta lactone or a lactone having 5 or more ring members.

24. The polymer composition of claim 23, wherein said polymer composition is comprised of the residue of a metal catalyst.

25. The polymer composition of claim 24, wherein the rare earth metal catalyst is comprised of a lanthanide metal, transition metal, Al or Bi.

26. The polymer composition of claim 25, wherein the metal is comprised of one or more of Nd, Al, Bi, or Sc.

27. The polymer composition of any one of the claims 23 to 26, wherein the other lactone is the lactone having 5 or more ring members.

28. The polymer composition of claim 27, wherein the lactone having 5 or more ring members has 6 to 9 ring members.

29. The polymer composition of claim 28, wherein the lactone having 5 or more ring members is a substituted or unsubstituted caprolactone.

30. The polymer composition of any one of the claims 23 to 29 wherein the polyester is a random or gradient copolymer.

31. The polymer composition of any one of claims 23 to 29, wherein the polyester is a block copolymer.

32. The polymer composition of claim 31, wherein the block copolymer is a triblock or pentablock copolymer.

33. The polymer composition of claim 23, wherein the other lactone is a substituted beta lactone.

34. The polymer composition of claim 33, wherein the substituted beta lactone is beta butyrolactone.

35. A method to form a copolymer comprising polymerizing a beta propiolactone and another lactone comprised of one or more of a substituted beta lactone or lactone having at 5 or more ring members in the presence of a catalyst.

36. A method according to Claim 35 wherein the beta propiolactone and other lactone and the metal triflate/alcohol catalyst are present in a ratio of said lactones/catalyst a ratio of about 100 to 1 to about 1,000,000 to 1.

37. The method of any one of claims 35 or 36, wherein the polymerization is performed at a temperature from about 20 °C to about 80 °C.

38. The method of any one of claims 35 to 37, wherein the polymerization is performed at a pressure of between about 1 bar and about 20 bar.

39. The method of claim 35, wherein the other lactone is an aliphatic substituted beta lactone and the aliphatic substituent has 1 to 30 carbons.

40. The method of claim 39, wherein the aliphatic substituent has 1 to 10 carbons.

41. The method of claim 35, wherein the catalyst is a metal triflate/alcohol catalyst that is comprised of one or more of a lanthanide metal, transition metal, Al or Bi.

42. The method of claim 41, wherein the rare earth metal is Nd, Sc, Bi, Al or mixture thereof.

43. The method of any one of claims 35 to 42, wherein the metal triflate/alcohol catalyst is comprised of an alcohol that is a polyol.

44. The method claim 43, wherein the alcohol has a molecular weight of at most about 500 g/mole.

45. The method of claims 43 or 44, wherein the alcohol is a glycol or glycerol.

46. The method of any one of claims 35 to 45, wherein the metal triflate/alcohol catalyst has an amount of triflate groups and alcohol groups to give a ratio of triflate groups/alcohol groups of 0.1 to 10 by mole.