Patent ID: 7893163

Claim:
A gradient copolymer comprising at least two different monomer units: a) the first (M 1 ), the homopolymer of which has a Tg 1 of less than 20° C., representing at least 50% by weight of the total weight of the copolymer and selected from the group consisting of linear and branched C 1 -C 12 alkyl acrylates, polyethylene glycol acrylate, polyethylene glycol methacrylate and dienes, b) the second (M 2 ), the homopolymer of which has a T g2 of greater than 20° C., representing at most 50% by weight of the total weight of the copolymer and selected from the group consisting of styrene, styrene derivatives, acrylic acid, methacrylic acid, norbornyl acrylate, methyl methacrylate, acrylonitrile and methacrylonitrile, wherein at least 5% by weight of the total weight of the copolymer is represented by a hydrophilic monomer unit selected from the group consisting of polyethylene glycol acrylate, polyethylene glycol methacrylate, acrylic acid and methacrylic acid, said gradient copolymer comprising at least one monomer M i such that the probability of encountering M i in any standardized position x situated on the polymer chain is nonzero; and wherein said gradient copolymer is soluble or dispersible in both water and in organic solvents at a concentration greater than or equal to 5%, and wherein said copolymer has number average and weight average masses of between 5,000 g/mol and 1,000,000 g/mol and a polydispersity index of between 1.1 and 2.5, said copolymer further comprising nitroxide residue unit.