Method for free radical reduction of dithiocarbonylated or dithiophosphorylated functions borne by a polymer

1. A method for preparing a polymer which comprises a stage comprising bringing into contact:

(A) at least one living organic polymer exhibiting, at the chain end, at least one reactivatable dithiocarbonyl or dithiophosphoryl functional group;

(B) at least one source of free radicals; and

(C) at least one organic compound carrying a labile hydrogen atom.

2. The method of claim 1 , wherein the reactivatable dithiocarbonyl or dithiophosphoryl functional group present at the chain end on the polymer (A) employed is an —S(C═S)—R or —S(P=S)—R functional group, where R denotes:

(i) an alkyl, haloalkyl, perfluoroalkyl, alkenyl, alkynyl, acyl, aryl, arylalkyl, arylalkenyl or arylalkynyl group, or else a carbonaceous ring or a heterocycle, or a polymer chain; or

(ii) an —OR a radical, in which R a denotes a group selected from the group consisting of:

alkyl, haloalkyl, perfluoroalkyl, alkenyl, alkynyl, acyl, aryl, arylalkyl, arylalkenyl, arylalkynyl, a carbonaceous ring, a heterocycle, a polymer chain and a —CR b R c PO(OR d )(OR e ) group, in which:

R b and R c each represent, independently of one another, a hydrogen atom, a halogen atom, a perfluoroalkyl group, a carbonaceous ring or a heterocycle, or else an —NO 2 , —NCO or —CN group or a group —R f , —SO 3 R f , —OR f , —SR f , —NR f R g , —OOCR f , —CONR f R g ;

R f and R g each independently denote an alkyl, alkenyl, alkynyl, aryl, aryl, arylalkyl, arylalkenyl or arylalkynyl group;

or R b and R c form, together with the carbon to which they are attached, a C═O or C═S group, or a hydrocarbonaceous ring or a heterocycle; and

R d and R e each represent, independently of one another, a radical having one of the definitions given above for the R f group;

or R d and R e together form a hydrocarbonaceous chain comprising from 2 to 4 carbon atom optionally interrupted by an —O—, —S— or —NR h -group, where R h has one of the definitions given above for the R f group; or

(iii) an —NR i R j group, where:

R i and R j represent, independently of one another, a radical selected from the group consisting of an alkyl, haloalkyl, alkenyl, alkynyl, acyl, ester, aryl, arylalkyl, arylalkenyl or arylalkynyl group and a carbonaceous ring; or

R i and R j together form a hydrocarbonaceous chain comprising from 2 to 4 carbon atom optionally interrupted by an —O—, —S— or —NR H -group, where R H corresponds to one of the definitions given above for the R f group, said hydrocarbonaceous chain forming a 5-membered ring with nitrogen to which R i and R j are attached.

3. The method of claim 2 , wherein R denotes a —NR i R j group (iii), wherein the R i and R j radicals induce an electron-withdrawing effect or a delocalization effect with regard to the electron density of the nitrogen atom to which they are bonded.

4. The method of claim 1 , wherein the living organic polymer (A) is a polymer resulting from a process employing a living radical polymerization using at least one reversible addition-fragmentation transfer agent of dithioester, xanthate, dithiocarbamate, thioether-thione, trithiocarbonate or dithiophosphoric ester type.

5. The method of claim 4 , wherein the polymer (A) results from a polymerization or copolymerization process comprising at least one stage of controlled radical polymerization employing a reversible addition-fragmentation transfer agent selected from the group consisting of a xanthate, a dithiocarbamate and a dithioester.

6. The method of claim 1 , wherein the source of free radicals (B) employed comprises a peroxide selected from the group consisting of the compounds having one of the following formulae (I) to (IV):

wherein the R′ and R′ groups are identical or different and represent linear or branched alkyl groups, aryl groups or aralkyl groups which are substituted or non-substituted.

7. The method of claim 5 , wherein the source of free radicals (B) employed comprises a peroxide selected from the group consisting of diisobutyryl peroxide, cumyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, di(2-ethylhexyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, dibutyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, tert-butyl peroxyneoheptanoate, tert-amyl peroxypivalate, didecanoyl peroxide, tert-amyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrate, 1,4-di(tert-butylperoxycarbo)cyclohexane, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, di(tert-amyl) peroxide, tert-butyl cumyl peroxide, bis(tert-butyl) peroxide, dicumyl peroxide, dilauroyl peroxide and di(4-(tert-butyl)cyclohexyl) peroxydicarbonate.

8. The method of claim 1 , wherein the source of free radicals (B) is introduced in an amount such that the amount of free radicals which it is capable of releasing is between 50 mol % and 200 mol % with respect to the total molar amount of dithiocarbonyl or dithiophosphoryl functional groups carried by the combined living organic polymers (A) employed.

9. The method of claim 1 , wherein the organic compound (C) carrying a labile hydrogen is selected from the group consisting of:

secondary alcohols of formula (HO)CH(R I )(R II ),

mercaptans of formula R III SH,

phosphites of formula (O═)PH(—OR IV )(—OR V ),

silanes of formula R VI R VII R VIII SiH, and

acetals of formula R IX CH(OR X )(OR XI ),

where the R I , R II , R III , R IV , R V , R VI , R VII , R VIII , R IX , R X and R XI groups each independently represent an alkyl, cycloalkyl, alkoxy, alkene, acyl, aryl, aralkyl, aralkenyl or aralkynyl radical, these radicals being substituted or non-substituted.

10. The method of claim 1 , wherein the compound (C) is employed in a proportion of 1 to 50 000 molar equivalents with respect to the polymer (A).

11. The method of claim 10 , wherein compound (C) is employed in a proportion of 2 to 10 000 molar equivalent with respect to polymer (A).

12. The method of claim 1 , wherein the stage of bringing into contact the living polymer (A), the source of free radicals (B) and the organic compound carrying the labile hydrogen (C) is carried out at a temperature of between 0° C. and 200° C.