Process for the free radical polymerization of thionolactones or thionocarbonates

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 —CH2— group;
• Y is chosen from —CH2—, —CH2—O—CH2—, —O—CH2—CH2, —CH2—CH2—O—CH2—CH2 and CH2—O—CH2—CH2 groups;
• n is an integer greater than or equal to 1;
• wherein:
• when Y represents a —CH2— group, then n is greater than or equal to 4,
• when X represents an oxygen atom, then Y is other than an —O—CH2—CH2— group;
• and
• when X represents a —CH2— group, and when Y represents an —O—CH2—CH2— 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:
• R1, R2 and R3 are identical and represent a hydrogen atom,
• R4 represents a hydrogen atom, an alkyl radical, or a group chosen from imidazole, alkylimidazolium, carbazole, —OC(O)R5 groups, or a group of formula (III) below:
• R5 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),
• R6 and R7, which are identical or different, represent a hydrogen atom, an alkyl, cycloalkyl, arylalkyl, aryl, glycidyl radical, or else R6 and R7, 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.