Process for the free radical polymerization of thionolactones or thionocarbonates

1 . 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:

wherein:

X is an oxygen atom or a —CH 2 — group;

Y is chosen from —CH 2 —, —CH 2 —O—CH 2 —, —O—CH 2 —CH 2 , —CH 2 —CH 2 —O—CH 2 —CH 2 and CH 2 —O—CH 2 —CH 2 groups;

n is an integer greater than or equal to 1;

wherein:

when Y represents a —CH 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 2 —CH 2 — group; and

when X represents a —CH 2 — group, and when Y represents an —O—CH 2 —CH 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:

wherein:

R 1 , R 2 and R 3 are identical and represent a hydrogen atom,

R 4 represents a hydrogen atom, an alkyl radical, or a group chosen from imidazole, alkylimidazolium, carbazole, —OC(O)R 5 groups, or a group of formula (III) below:

R 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 6 and R 7 , which are identical or different, represent a hydrogen atom, an alkyl, cycloalkyl, arylalkyl, aryl, glycidyl radical, or else R 6 and R 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.

2 . The process as claimed in claim 1 , 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.

3 . The process as claimed in claim 1 , wherein the monomers of formula (II) are chosen from vinyl esters of formula (II-1) below:

wherein R 5 represents an alkyl, haloalkyl, trifluoroalkyl, aryl or arylalkyl radical.

4 . The process as claimed in claim 3 , 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.

5 . The process as claimed claim 1 , wherein the monomers of formula (II) are chosen from those wherein R 4 represents a linear or branched alkyl radical.

6 . The process as claimed in claim 5 , wherein the monomers of formula (II) are chosen from ethylene and octene.

7 . The process as claimed in claim 1 , wherein the monomers of formula (II) are chosen from N-vinyl monomers of formula (II-2) below:

wherein R 6 and R 7 , which are identical or different, represent a hydrogen atom, an alkyl, cycloalkyl, arylalkyl, aryl, glycidyl radical, or else R 6 and R 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.

8 . The process as claimed in claim 7 , 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.

9 . The process as claimed in claim 1 , 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).

10 . The process as claimed in claim 1 , 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).

11 . The process as claimed in claim 1 , 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.

12 . The process as claimed in claim 1 , 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.

13 . The process as claimed in claim 1 , wherein the polymerization is carried out at a temperature of from 5° C. to 150° C.

14 . The process as claimed in claim 1 , wherein the polymerization is carried out in the presence of a polymerization control agent.