Comb copolymer and process for the preparation thereof

A method for the preparation of a comb copolymer, the comb copolymer comprising a backbone comprising 2-acrylamido-2-methylpropanesulfonic acid, with grafted poly(N-alkylacrylamide) or poly(N,N-dialkylacrylamide) side segments, the method comprising the following successive stages:

• (a) reaction of a compound of formula (II):
• CH2═C(R2)—C(═O)—N(R3)(R4) (II)
• in which
• R2 represents a hydrogen atom or a methyl group,
• R3 represents a hydrogen atom or a linear or branched alkyl radical comprising from 1 to 4 carbon atoms, and
• R4, which is identical to or different from R3, represents a linear or branched alkyl radical comprising from 1 to 4 carbon atoms,
• with a chain-limiting compound of formula (III):
• Z—R1—NH2 (III)
• in which
• R1 represents a divalent radical comprising from 1 to 4 carbon atoms and Z represents a functional group capable of acting as radical transfer agent,
• in the presence of a polymerization initiator, in a tert-butanol/water mixture, to obtain a poly(N-alkylacrylamide) or poly(N,N-dialkylacrylamide) telomer of formula (I):
• H2N—R1—Z—{CH2—C(R2)[C(═O)N(R3)(R4)]—}n'H (I)
• in which
• n represents an integer greater than or equal to 2 and less than or equal to 100 and Z represents a functional group capable of acting as radical transfer agent;
• optionally
• (b) isolation and/or of drying of said telomer of formula (I) obtained in stage (a);
• (c) reaction in tert-butanol of the telomer of formula (I) obtained in stage (a) or optionally in stage (b) with an acid chloride of formula (IV):
• CH2═C(R5)—C(═O)—Cl (IV)
• in which R5 represents a hydrogen atom or a methyl radical,
• in a (IV)/(III) molar ratio of 1 to 10 inclusive, while maintaining the pH of the reaction medium at a value of between 8 and 10, to obtain a solution of a macromonomer of formula (V):
• CH2═C(R5)—C(═O)NH—R1—Z—{CH2—C(R2)[C(═O)N(R3)(R4)]—}n—H (V),
• optionally
• (d) isolation and/or of drying of said macromonomer of formula (V) obtained in stage (c);
• (e) copolymerization in tert-butanol of the macromonomer of formula (V) resulting from stage (c) or from stage (d) with an ammonium salt of 2-acrylamido-2-methylpropanesulfonic acid, and optionally
• (f) purification of the comb copolymer obtained in stage (e).