Block copolymers that can be used as plasticisers

1. A method for preparing a block copolymer comprising:

at least one block A consisting of poly (alkylene oxide) groups, and

at least one block B obtained by polymerization of a monomer B1 or of a mixture of monomers with ethylenic unsaturation comprising at least one monomer B1, wherein a monomer B1 is a monomer with ethylenic unsaturation comprising at least one phosphonate function

comprising the steps of:

providing a poly(alkylene oxide),

grafting at one end of said poly(alkylene oxide) a group of formula —S(C═S)R 10 to obtain a

compound of the following formula (V):

wherein:

block A consists of poly (alkylene oxide) groups,

L is absent or is a binding group connecting covalently the block A and the group —S—(CS)R 10 ,

R 10 represents an alkyl, an arylalkyl, an aryl, an alkylaryl or a group OR 11 , NR 12 R 13 or SR 14 ,

R 11 , R 12 , R 13 and R 14 represent independently an alkyl or an alkenyl, an arylalkyl, an aryl, an alkylaryl, wherein R 12 and R 13 may be connected together in order to form a ring with the nitrogen atom bearing them,

effecting controlled radical polymerization, or several successive controlled radical polymerizations, comprising putting into contact:

the compound of formula (V),

a monomer B1 or a mixture of monomers with ethylenic unsaturation comprising at least one monomer B1, wherein a monomer B1 is a monomer with ethylenic unsaturation comprising at least one phosphonate function, and

a source of free radicals.

2. The preparation method according to claim 1 , wherein the monomer B1 has the following formula (IV):

wherein:

Y represents:

a linear or branched alkyl having from 1 to 6 carbon atoms,

a group —W—(CH 2 ) z —P(═O)(OR 1 )(OR 2 ), or

a group (CH 2 ) x —R 25 , wherein x represents an integer comprised between 0 and 4 and R 25 represents a hydrogen atom, a phenyl or a group —CN or —CO 2 R 9 ,

z represents an integer comprised between 0 and 4,

W represents a simple bond or a group —COO— or —CONH—, wherein when z represents 0, W represents a simple bond,

R 1 , R 2 and R 9 represent independently H, a phenyl or a linear or branched alkyl having from 1 to 6 carbon atoms and optionally substituted with one or several halogens.

3. The preparation method according to claim 2 , wherein W represents a simple bond and z represents 0.

4. The preparation method according to claim 3 , wherein the monomer B1 is vinyl phosphonic acid.

5. The preparation method according to claim 1 , wherein, during said effecting controlled radical polymerization, the mixture of monomers with ethylenic unsaturation comprising at least one monomer B1 comprises:

at least one monomer B1 with ethylenic unsaturation comprising at least one phosphonate function, and

at least one monomer B2 selected from acrylic acid, methacrylic acid, a monomer with ethylenic unsaturation comprising an aminomethylene bisphosphonic or gem-bisphosphonic function or a monomer with ethylenic unsaturation comprising a sulfonic or sulfonate function.

6. The preparation method according to claim 1 , comprising, after said effecting controlled radical polymerization, an oxidation step.