Patent ID: 7655735

Claim:
A multi-block copolymer comprising at least two ABA-type tri-block copolymers which are covalently connected through a biodegradable dicarboxylic linkage, wherein A is a polyethyleneoxide block, B is a polypropyleneoxide block, a polybutyleneoxide block or a combination thereof, and wherein said multi-block copolymer has an ionic group at both terminal ends, wherein the ionic group is a member selected from the group consisting of monovalent or divalent metal salt of —SO 3 − , —PO 3 2− , and —C(═O)—R—C(═O)—O − , wherein, R is —(CH 2 ) m — or an aryl having C m ′, m is an integer ranging from 0 to 20, and m′ is an integer ranging from 6 to 12.