Patent ID: 8637622

Claim:
A process for the preparation of a copolymer comprising: a) preparing an aqueous fluid B comprising: at least one ethylenically unsaturated monomer B, wherein monomer B is hydrophobic (B phobic ) and/or amphiphilic (B amphi ), and optionally a surfactant, wherein, if the monomer B is a hydrophobic monomer B phobic , then the aqueous fluid B comprises a surfactant, wherein monomer B is included in micelles comprising surfactant and/or monomer B amphi , wherein: the number of monomers in the micelles is greater than 2.6; the ratio in moles of the surfactant to the monomer B is less than or equal to 28; and/or the ratio by weight of the surfactant, if present, to the monomer B is less than or equal to 30 b) carrying out a polymerization by combining in an aqueous medium: the micelles of the aqueous fluid B, monomers A Z or A Z precursor and optionally other hydrophilic monomers A other dissolved in an aqueous medium, wherein: monomers A Z comprise a betaine group, said betaine group comprising a cationic group and an anionic group, monomers A Z precursor comprise a precursor capable of forming betaine groups A Z by a reaction subsequent to the polymerization, and a source of free radicals; and c) optionally converting A Z precursor to betaine groups A Z if present.