Patent ID: 8580917

Claim:
A method for purifying a block copolymer comprising the steps of: (a) providing an arborescent block copolymer comprising a polyisobutylene-based thermoplastic elastomer having polystyrene based end blocks; (b) dissolving the block copolymer in a first solvent system to provide a first solution, wherein the first solvent system comprises one or more solvents capable of dissolving a polyisobutylene-based polymer; (c) combining the first solution with a second solvent system, wherein the second solvent system is a (C 3 to C 10 ) ketone, to provide a precipitated block copolymer in a mother liquor; (d) adding acetone to the precipitated block copolymer in the mother liquid to provide a mixture of the precipitated block copolymer in the mother liquid and acetone; (e) adding a third solvent system to the mixture of the precipitated block copolymer in the mother liquid and acetone, wherein the third solvent system is a non-solvent with respect to at least two types of blocks of the purified block copolymer, to provide a mixture of the precipitated block copolymer in the mother liquid and the mixture of solvents; and (f) separating the precipitated block copolymer from the mother liquid and the mixture of solvents to provide a purified block copolymer.