Live poly(n-vinyl lactam) reactive stabilizers for dispersed phase polymerization

1. A process for preparing a polymer, comprising a step (E1) of dispersed-phase polymerization in the presence of a reactive stabilizer, wherein the following are placed in contact in an aqueous phase:

at least one ethylenically unsaturated monomer;

a redox initiator comprising tert-butyl hydroperoxide as oxidizing agent, combined with a reducing agent selected from the group consisting of ascorbic acid and sodium sulfite; and

a reactive stabilizer comprising a polymer chain including N-(vinyllactam) monomer units and a thiocarbonylthio group —S(C═S)—;

wherein step (E1) is performed in the absence of surfactants.

2. The process as claimed in claim 1 , wherein in said step (E1), the ethylenically unsaturated monomer is in dispersed form.

3. The process as claimed in claim 1 , wherein said step (E1) is performed at a temperature below 40° C.

4. The process as claimed claim 1 , wherein in the reactive stabilizer used in said step (E1), N-(vinyllactam) monomer units generally correspond to the following formula:

wherein n is an integer ranging from 2 to 6.

5. The process as claimed in claim 4 , wherein in the reactive stabilizer used in said step (E1), is monomers N-vinylpyrrolidone, N-vinylpiperidone or N-vinylcaprolactam.

6. The process as claimed in claim 1 , wherein the thiocarbonylthio group present on the reactive stabilizer is a xanthate or a dithiocarbamate.

7. The process as claimed in claim 1 , wherein the ethylenically unsaturated monomers used in said step (E1) are vinyl ester monomers of formula CH2═CH—O—(C═O)—R a , wherein R a represents:

an optionally substituted alkyl, acyl, aryl, aralkyl, alkene or alkyne group,

a saturated or unsaturated, aromatic, optionally substituted carbocycle or heterocycle.

8. The process as claimed in claim 1 , wherein the ethylenically unsaturated monomers used in said step (E1) comprise halogenated vinyl compounds, corresponding to the formula R b R c C═CX 1 X 2 , wherein: X 1 ═F or Cl

X 2 ═H, F or Cl

each one from among R b and R c represents, independently:

H, Cl, F; or

an alkyl group.

9. A polymer dispersion obtained according to the process of claim 1 .

10. The dispersion as claimed in claim 9 is a latex comprising dispersed particles formed from block polymers derived from the controlled radical polymerization as obtained after said step (E1) of claim 1 .

11. A method for producing paints, coatings and adhesives, for preparing construction materials, in cosmetic or body care compositions, in plant protection formulations or for the agricultural sector, or in petroleum extraction fluids, said method comprising a step of using said dispersion as claimed in claim 10 .

12. The dispersion as claimed in claim 9 comprises block polymers derived from the controlled radical polymerization as obtained after said step (E1) of claim 1 , organized in the form of micelles, which may be used as a site of polymerization for controlled radical polymerizations.