Patent ID: 8318204

Claim:
A pH-sensitive block copolymer comprising a polyethylene glycol-based block (A) and a pH-sensitive block (B); wherein the polyethylene glycol-based block (A) comprises a functional group selected from the group consisting of acrylate and methacrylate, and has a molecular weight of 500-5,000; wherein the pH-sensitive block (B) is at least one poly(amino acid) compound selected from the group consisting of a poly(β-amino ester), a poly(amido amine), and a copolymer thereof, and formed by polymerization of an amine compound (E) and a bisacrylate or bisacrylamide compound (F); wherein the bisacrylate or bisacrylamide compound (F) and the amine compound (E) are used in a molar ratio of 1:0.5-2.0, and wherein said pH-sensitive block copolymer is a AB diblock type copolymer, wherein the ratio of the polyethylene glycol-based block (A): the pH-sensitive block (B) is 10-40 wt %:90-60 wt %, and wherein the pH-sensitive block copolymer forms micelles by self-assembly at a pH ranging from 7.2 to 7.4, said micelles collapsing at a pH ranging from 6.5 to 7.0.