Abstract: Amphiphilic diblock copolymer poly(N-isopropylacrylamide)-b-poly(diacetone acrylamide)(PNIPAM-b-PDAAM), which composed of N-isopropylacrylamide and diacetone acrylamide, was synthesized by reversible addition-fragmentation chain transfer(RAFT) polymerization. Its structure and composition were confirmed by FTIR spectroscopy, 1H nuclear magnetic resonance spectroscopy(1H NMR) and gel permeation chromatography(GPC). This copolymer can self-assemble into stable polymeric micelles. The critical micelle concentration values of the self-assembled micelles are about 7.0 mg/L in distilled water relying on fluorescent probe technique. The results measured by dynamic light scattering(DLS) and scanning electron microscopy(SEM) show that the self- assembled PNIPAM-b-PDAAM micelles exhibit spherical core-shell structure with well-defined dispersancy. The mean diameter of micelles estimated by SEM is around 150 nm. The model drug folic acid(FA) was loaded into the micelles as drug carrier material and the in vitro drug release behavior was investigated at body temperature. The results show that the FA-loaded content and the entrapment efficiency reach up to 25% and 72%，respectively. Compared with those at 25 ℃, in vitro release rates of FA from polymeric micelles in phosphate buffer solution(PBS) at temperatures 37 ℃，and different pH 4.0, 6.86 and 9.18， are all relatively faster within 20 h，and increase with increasing pH value and the largest accumulation release percentage is 31%， 67% and 72%， respectively.

Key words: amphiphilic block copolymer, reversible addition-fragmentation chain transfer, thermosensitivity, folic acid controlled release