PROCESS FOR THE FREE RADICAL POLYMERIZATION OF THIONOLACTONES OR THIONOCARBONATES

Abstract

A process for preparing preferably degradable copolymers by free radical ring-opening polymerization using thionolactone monomers or thionocarbonate monomers, in the presence of a radical polymerization initiator. Also, the copolymers, which include thioester or thiocarbonate bonds, that are obtained by carrying out the process including the free radical ring-opening polymerization using thionolactone monomers or thionocarbonate monomers.

Claims

1-20. (canceled)

21. A process for preparing copolymers, said process comprising at least one step of radical ring-opening polymerization of at least one cyclic monomer with at least one monomer comprising an ethylenic unsaturation, in the presence of a radical polymerization initiator, wherein: (i) the cyclic monomer is chosen from thionolactones and thionocarbonates of formula (I) below: ##STR00012## wherein: X is an oxygen atom or a —CH.sub.2— group; Y is chosen from —CH.sub.2—, —CH.sub.2—O—CH.sub.2—, —O—CH.sub.2—CH.sub.2, —CH.sub.2—CH.sub.2—O—CH.sub.2—CH.sub.2 and CH.sub.2—O—CH.sub.2—CH.sub.2 groups; n is an integer greater than or equal to 1; wherein: when Y represents a —CH.sub.2— group, then n is greater than or equal to 4, when X represents an oxygen atom, then Y is other than an —O—CH.sub.2—CH.sub.2— group; and when X represents a —CH.sub.2— group, and when Y represents an —O—CH.sub.2—CH.sub.2— group, then the oxygen atom of the Y group is connected to X; and (ii) the monomer comprising an ethylenic unsaturation is chosen from the monomers of formula (II) below: ##STR00013## wherein: R.sup.1, R.sup.2 and R.sup.3 are identical and represent a hydrogen atom, R.sup.4 represents a hydrogen atom, an alkyl radical, or a group chosen from imidazole, alkylimidazolium, carbazole, —OC(O)R.sup.5 groups, or a group of formula (III) below: ##STR00014## R.sup.5 represents an alkyl, haloalkyl, trifluoroalkyl, aryl or arylalkyl radical, the asterisk (*) represents the anchoring point of the group of formula (III) to the carbon atom of the compound of formula (II), R.sup.6 and R.sup.7, which are identical or different, represent a hydrogen atom, an alkyl, cycloalkyl, arylalkyl, aryl, glycidyl radical, or else R.sup.6 and R.sup.7, together with the nitrogen and carbon atoms of the group of formula (III) to which they are bonded, form a heterocycle comprising from 4 to 7 carbon atoms.

22. The process as claimed in claim 21, wherein the thionolactones or thionocarbonates of formula (I) are chosen from ε-thionocaprolactone, ω-pentadecathionolactone, nonadecathionolactone, tricosathionolactone, crown ethers comprising a thionoester, tetramethylene thionocarbonate and diethylene glycol thionocarbonate.

23. The process as claimed in claim 21, wherein the monomers of formula (II) are chosen from vinyl esters of formula (I-1) below: ##STR00015## wherein R.sup.5 represents an alkyl, haloalkyl, trifluoroalkyl, aryl or arylalkyl radical.

24. The process as claimed in claim 23, wherein the monomers of formula (II-1) are chosen from vinyl acetate, vinyl pivalate, vinyl trifluoroacetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl neodecanoate and vinyl trifluorobutyrate.

25. The process as claimed claim 21, wherein the monomers of formula (II) are chosen from those wherein R.sup.4 represents a linear or branched alkyl radical.

26. The process as claimed in claim 25, wherein the monomers of formula (II) are chosen from ethylene and octene.

27. The process as claimed in claim 21, wherein the monomers of formula (II) are chosen from N-vinyl monomers of formula (II-2) below: ##STR00016## wherein R.sup.6 and R.sup.7, which are identical or different, represent a hydrogen atom, an alkyl, cycloalkyl, arylalkyl, aryl, glycidyl radical, or else R.sup.6 and R.sup.7, together with the nitrogen and carbon atoms of the group of formula (III) to which they are bonded, form a heterocycle comprising from 4 to 7 carbon atoms.

28. The process as claimed in claim 27, wherein the monomers of formula (II-2) are chosen from N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylpyrrolidone, N-vinylpiperidone, and N-vinylcaprolactame.

29. The process as claimed in claim 21, wherein the monomer(s) of formula (I) represent at most 50% by number relative to the total number of monomers of formulae (I) and (II).

30. The process as claimed in claim 21, wherein the monomer(s) of formula (I) represent from 5% to 30% approximately by number, relative to the total number of monomers of formulae (I) and (II).

31. The process as claimed in claim 21, wherein the radical ring-opening polymerization of the monomers of formulae (I) and (II) is carried out in bulk or in solution in a solvent.

32. The process as claimed in claim 21, wherein the polymerization is carried out in a solvent and in that the total amount of monomers of formulae (I) and of formula (II) varies from 30% to 60% by mass relative to the total mass of the reaction medium.

33. The process as claimed in claim 21, wherein the polymerization is carried out at a temperature of from 5° C. to 150° C.

34. The process as claimed in claim 21, wherein the polymerization is carried out in the presence of a polymerization control agent.

35. A copolymer comprising thioester or thiocarbonate bonds, wherein said copolymer results from the radical ring-opening polymerization of: (i) at least one cyclic monomer chosen from thionolactones and thionocarbonates of formula (I) below: ##STR00017## wherein: X is an oxygen atom or a —CH.sub.2— group; Y is chosen from —CH.sub.2—, —CH.sub.2—O—CH.sub.2—, —O—CH.sub.2—CH.sub.2, —CH.sub.2—CH.sub.2—O—CH.sub.2—CH.sub.2 and CH.sub.2—O—CH.sub.2—CH.sub.2 groups; n is an integer greater than or equal to 1; wherein: when Y represents a —CH.sub.2— group, then n is greater than or equal to 4, when X represents an oxygen atom, then Y is other than an —O—CH.sub.2—CH.sub.2— group; and when X represents a —CH.sub.2— group, and when Y represents an —O—CH.sub.2—CH.sub.2— group, then the oxygen atom of the Y group is connected to X; and (ii) at least one monomer comprising an ethylenic unsaturation chosen from the monomers of formula (II) below: ##STR00018## wherein: R.sup.1, R.sup.2 and R.sup.3 are identical and represent a hydrogen atom, R.sup.4 represents a hydrogen atom, an alkyl radical, or a group chosen from imidazole, alkylimidazolium, carbazole, —OC(O)R.sup.5 groups, or a group of formula (III) below: ##STR00019## R.sup.5 represents an alkyl, haloalkyl, trifluoroalkyl, aryl or arylalkyl radical, the asterisk (*) represents the anchoring point of the group of formula (III) to the carbon atom of the compound of formula (II), R.sup.6 and R.sup.7, which are identical or different, represent a hydrogen atom, an alkyl, cycloalkyl, arylalkyl, aryl, glycidyl radical, or else R.sup.6 and R.sup.7, together with the nitrogen and carbon atoms of the group of formula (III) to which they are bonded, form a heterocycle comprising from 4 to 7 carbon atoms, in the presence of a radical polymerization initiator.

36. The copolymer as claimed in claim 35, wherein the copolymer results from the polymerization of ε-thionocaprolactone and vinyl acetate or from the copolymerization of ε-thionocaprolactone and vinyl acetate in the presence of a xanthate as radical polymerization control agent.

37. The copolymer as claimed in claim 35, wherein the copolymer is a statistical copolymer.

38. The copolymer as claimed in claim 35, wherein the copolymer has a number-average molar mass of from 2000 to 200 000 g/mol.

39. The copolymer as claimed in claim 35, wherein the copolymer has a polymolecularity index of from 1.2 to 4.

40. The copolymer as claimed in claim 35, wherein the content of thioester or thiocarbonate bonds in the main chain of the copolymer is from 2% to 15% by number relative to the total number of bonds of the main chain.

Description

EXAMPLES

Example 1: Synthesis of a Degradable Copolymer Based on Vinyl Acetate and ε-Thionocaprolactone According to the Process of the Invention

1) First Step: Synthesis of ε-thionocaprolactone (Product of Formula (I-1))

[0104] Introduced into a 500-ml two-necked round-bottomed flask topped with a condenser were P.sub.4S.sub.10 (21.9 mmol, 0.25 eq), ε-caprolactone (87.91 mmol, 1 eq), hexamethyldisiloxane (HMDSO) (146.31 mmol, 1.67 eq) and 90 ml of anhydrous acetonitrile. After inerting for 10 minutes with a flow of argon, the mixture was heated at 82° C. for 2 hours. Next, the reaction medium was cooled to 0° C. 22.5 ml of a 5M solution of K.sub.2CO.sub.3 were added slowly to the medium, this medium being maintained at 0° C. for 30 min after the end of the introduction. Next, the mixture was diluted with 200 ml of diethyl ether, then the product was extracted with 2×100 ml of water, and then with 100 ml of brine. The organic phase was then dried over magnesium sulfate and then the solvent was evaporated under vacuum. The product was purified by column chromatography (7/3 cyclohexane/ethyl acetate eluent). The yield was 60%. The final product was a yellow liquid.

[0105] NMR: .sup.1H (CDCl.sub.3; 300 MHz): 1.79 ppm (m, 2H); 1.91 ppm (m, 4H); 3.20 ppm (m, 2H); 4.50 ppm (t, 2H).

[0106] .sup.13C (CDCl.sub.3; 300 MHz): 25.9 ppm; 28.51 ppm; 28.63 ppm; 46.17 ppm; 74.37 ppm; 227.47 ppm.

2) Second Step: Synthesis of the Copolymer

[0107] Introduced into a Schlenk tube were 0.017 g (0.103 mmol) of azobisisobutyronitrile (AIBN), 0.235 g (1.8 mmol) of the 6-thionocaprolactone obtained above in the preceding step and 1.622 g (18.85 mmol) of vinyl acetate. The ε-thionocaprolactone (monomer of formula (I-1)) represented 9.54% (mol %) relative to the vinyl acetate (monomer of formula (II)). The reaction medium was degassed then maintained under argon at a temperature of 70° C. for 5 hours and 20 minutes. The monomer conversion, determined by hydrogen nuclear magnetic resonance (.sup.1H NMR), was 100% for the 6-thionocaprolactone and 85% for the vinyl acetate. The reaction medium was taken up in a minimum amount of toluene then precipitated in petroleum ether. The number-average molar mass (Mn), and also the polymolecularity index (Mw/Mn) of the purified polymer thus obtained, in powder form, were measured by size exclusion chromatography (eluant: dimethylformamide (DMF)/10 mM LiBr) with a calibration curve based on polystyrene. Mn=32 800 g/mol; Mw/Mn=2.83.

Example 2: Synthesis of a Degradable Statistical Copolymer Based on Vinyl Acetate and ε-thionocaprolactone in the Presence of a Xanthate According to the Process of the Invention

[0108] Introduced into a Schlenk tube were 0.064 g of AIBN (0.388 mmol), 1.04 g (7.99 mmol) of ε-thionocaprolactone, as prepared above in step 1) of example 1, and 5.75 g (66.8 mmol) of vinyl acetate in the presence of 0.159 g of O-ethyl S-(1-methoxycarbonylethyl)dithiocarbonate (0.716 mmol), as polymerization control agent. The O-ethyl S-(1-methoxycarbonylethyl)dithiocarbonate was synthesized beforehand by according to the protocol indicated by Liu et al. (ACS Macro Mett, 2015, 4, 89-93). The reaction medium was degassed then maintained under argon at 70° C. for 7 h. The monomer conversion, determined by 1H NMR, was 95% for 6-thionocaprolactone and 69% for vinyl acetate. The reaction medium was taken up in a minimum amount of toluene and precipitated in petroleum ether. Next, the number-average molar mass and the polymolecularity index of the purified polymer, obtained in powder form, were measured as indicated above in example 1. Mn=6000 g/mol; Mw/Mn=1.54.

Example 3: Synthesis of a Degradable Copolymer Based on Vinyl Pivalate and ε-Thionocaprolactone in the Presence of a Xanthate According to the Process of the Invention

[0109] Introduced into a 500-ml two-necked round-bottomed flask were 3.285 g of AIBN (0.02 mol), 13 g (0.1 mol) of ε-thionocaprolactone, as prepared above in step 1) of example 1, and 115.35 g (0.9 mol) of vinyl pivalate in the presence of 5.4 g (0.026 mol) of O-ethyl S-(1-methoxycarbonylethyl)dithiocarbonate, polymerization control agent. The reaction medium was degassed then maintained under argon at 70° C. for 18 h. The monomer conversion, determined by 1H NMR, was 85% for ε-thionocaprolactone and 92% for vinyl acetate. The reaction medium was taken up in a minimum amount of toluene and precipitated in petroleum ether. Next, the number-average molar mass and the polymolecularity index of the purified polymer, obtained in powder form, were measured as indicated above in example 1. Mn=4500 g/mol; Mw/Mn=1.7.

Example 4: Chemical Degradation of the Copolymer Based on Vinyl Pivalate and ε-thionocaprolactone from Example 3

[0110] 20 mg of the copolymer from example 3 were diluted in 10 ml of dichloromethane before addition of 10 ml of isopropylamine. The reaction medium was stirred overnight at ambient temperature. The solvent and the amine were then evaporated under reduced pressure, and then the residue was dissolved in THF and analyzed by size exclusion chromatography with apparatus equipped with two Styragel H3R and HR4E columns, a refractometer detector and a light scattering detector, for analysis in tetrahydrofuran (THF) at 35° C. and a flow rate of 1 mn/min. It appears that after degradation of the copolymer by isopropylamine, the molar mass distribution is greatly shifted to the range of low molar masses compared to the polymer before treatment, attesting to the degradation of the backbone resulting from the presence of the thioester bonds. It should be noted that it was verified that, under identical chemical treatment conditions, a sample of poly(vinyl pivalate) of the same molar mass did not undergo any detectable chemical modification.

Example 5: Synthesis of a Degradable Copolymer Based on Vinyl Acetate and ω-Pentadecathionolactone According to the Process of the Invention

1) First Step: Synthesis of ω-pentadecathionolactone (Product of Formula (I-2))

[0111] Introduced into a 500-ml two-necked round-bottomed flask topped with a condenser were P.sub.4S.sub.10 (21.9 mmol, 0.25 eq), ω-pentadecalactone (87.91 mmol, 1 eq), hexamethyldisiloxane (HMDSO) (146.31 mmol, 1.67 eq) and 90 ml of of anhydrous p-xylene. After inerting for 10 minutes with a flow of argon, the mixture was heated at 140° C. for 4 hours. Next, the reaction medium was cooled to 0° C. 22.5 ml of a 5M solution of K.sub.2CO.sub.3 were added slowly to the medium, this medium being maintained at 0° C. for 30 min after the end of the introduction. Next, the mixture was diluted with 200 ml of diethyl ether, then the product was extracted with 2×100 ml of water, and then with 100 ml of brine. The organic phase was then dried over magnesium sulfate and then the solvent was evaporated under vacuum. The product was purified by column chromatography (9/1 cyclohexane/ethyl acetate eluent). The yield was 70%. The final product was a yellow liquid.

[0112] NMR: .sup.1H (CDCl.sub.3; 300 MHz): 1.33 ppm-1.25 (m, 24H); 2.81 ppm (t, 2H); 4.47 ppm (t, 2H).

2) Second Step: Synthesis of the Copolymer

[0113] Introduced into a Schlenk tube were 0.038 g (0.16 mmol) of azobisiso(cyanocyclohexane) (VAZO-88), 0.4 g (1.5 mmol) of ω-pentadecathionolactone obtained in the preceding step and 0.8 g (15 mmol) of vinyl pivalate. The ω-pentadecathionolactone (monomer of formula (I-2)) represents 20% (mol %) relative to the vinyl acetate (monomer of formula (II)). The reaction medium was degassed then maintained under argon at a temperature of 88° C. for 5 hours and 20 minutes. The monomer conversion, determined by hydrogen nuclear magnetic resonance (1H NMR), was 25% for the ω-pentadecathionolactone and 92% for the vinyl pivalate. The reaction medium was taken up in a minimum amount of toluene then precipitated in petroleum ether. The number-average molar mass (Mn), and also the polymolecularity index (Mw/Mn) of the purified polymer thus obtained, in powder form, were measured by size exclusion chromatography (eluant: dimethylformamide (DMF)/10 mM LiBr) with a calibration curve based on polystyrene. Mn=2200 g/mol; Mw/Mn=3.8.

Example 6: Chemical Degradation of the Copolymer Based on Vinyl Acetate and on ε-Thionocaprolactone from Example 1

[0114] 20 mg of the copolymer from example 1 were diluted in 2 ml of dichloromethane before addition of 2 ml of isopropylamine. The reaction medium was stirred overnight at ambient temperature. The solvent and the amine were then evaporated under reduced pressure, and then the residue was dissolved in THF and analyzed by size exclusion chromatography with apparatus equipped with two Styragel H3R and HR4E columns, a refractometer detector and a light scattering detector, for analysis in tetrahydrofuran (THF) at 35° C. and a flow rate of 1 mn/min, Mn=1.5 kDa, D=3.83. It appears that after degradation of the copolymer by isopropylamine, the molar mass distribution is greatly shifted to the range of low molar masses compared to the polymer before treatment, attesting to the degradation of the backbone resulting from the presence of the thioester bonds.