A rheology modifier copolymer of formula wherein a, b, c, and d represent the percentage by weight that each repeating unit or derived monomer is contained within the copolymer, these percentages being: a ranges from 0.5 to 25% by weight of the copolymer; b ranges from 70 to 98% by weight of the copolymer; c ranges from 0.1 to 15% by weight of the copolymer; and d ranges from 0 to 5% by weight of the copolymer; A is a macromonomer pre-formed by catalytic chain transfer comprising at one end a polymerizable group reactive during polymerization with at least one of B, C and D monomers, the reactive group at the one end of the macromonomer being attached to a chain formed of a homo- or co-polymer of C 1 -C 22 alkyl acrylates, C 1 -C 22 alkyl methacrylates, methacrylic acid, acrylic acid and combinations thereof, the macromonomer having a number average molecular weight ranging from 500 to 10,000; and B is acrylic or methacrylic acid or a salt thereof; C is a polyacidic vinyl monomer selected from the group consisting of maleic, fumaric, itaconic, citraconic acid and combinations thereof and anhydrides and salts thereof; and D is a cross linking monomer for introducing branching and controlling molecular weight, the cross linking monomer comprising polyfunctional units carrying multiple reactive functionalization groups selected from the group consisting of vinyl, allylic and functional mixtures thereof, the groups A, B, C and D being covalently bonded one to another in a random, a block, or a cross-linked copolymer format. wherein a, b, c, and d represent the percentage by weight that each repeating unit or derived monomer is contained within the copolymer, these percentages being: a ranges from 0.5 to 25% by weight of the copolymer; b ranges from 70 to 98% by weight of the copolymer; c ranges from 0.1 to 15% by weight of the copolymer; and d ranges from 0 to 5% by weight of the copolymer; a ranges from 0.5 to 25% by weight of the copolymer; b ranges from 70 to 98% by weight of the copolymer; c ranges from 0.1 to 15% by weight of the copolymer; and d ranges from 0 to 5% by weight of the copolymer; A is a macromonomer pre-formed by catalytic chain transfer comprising at one end a polymerizable group reactive during polymerization with at least one of B, C and D monomers, the reactive group at the one end of the macromonomer being attached to a chain formed of a homo- or co-polymer of C 1 -C 22 alkyl acrylates, C 1 -C 22 alkyl methacrylates, methacrylic acid, acrylic acid and combinations thereof, the macromonomer having a number average molecular weight ranging from 500 to 10,000; and B is acrylic or methacrylic acid or a salt thereof; C is a polyacidic vinyl monomer selected from the group consisting of maleic, fumaric, itaconic, citraconic acid and combinations thereof and anhydrides and salts thereof; and D is a cross linking monomer for introducing branching and controlling molecular weight, the cross linking monomer comprising polyfunctional units carrying multiple reactive functionalization groups selected from the group consisting of vinyl, allylic and functional mixtures thereof, the groups A, B, C and D being covalently bonded one to another in a random, a block, or a cross-linked copolymer format.