A series of poly(N-isopropylacrylamide) (PNIPAM)-blocked polycarbonates

P(MAC-co-DTC)-b-PNIPAM

were designed as thermosensitive micelles for drug delivery.The amphiphilic block copolymers were synthesized by enzymatic ring-opening copolymerization of HO-PNIPAM

5-methyl-5-allyloxycarbonyl-trimethylene carbonate (MAC) and 5

5-dimethyltrimethylene carbonate (DTC).The novel block copolymers were characterized by1H-NMR and GPC-MALLS analyses.All the amphiphilic copolymers were able to self-assemble into nano-sized micelles in aqueous solutions with hydrophilic PNIPAM shells and hydrophobic polycarbonates cores.The critical micelle concentration (CMC) determined by fluorescence spectroscopy using pyrene as a probe was around 20~60 mg/L.Transmission electron microscopy (TEM) measurements showed that the micelles presented even spherical shape and the diameters of them were about 20~70 nm.The micelles exhibited thermosensitivity at lower critical solution temperature (LCST) of around 38~43℃

which was related to the hydrophilic PNIPAM blocks.In vitro experiments demonstrated that the P(MAC-co-DTC)- b -PNIPAM showed low cytotoxicity.Furthermore

the micelles were loaded with hydrophobic drug of prednisone acetate (PA) and in vitro drug release investigation also displayed thermosensitivity.The results suggested that P(MAC-co-DTC)-b-PNIPAM copolymers would be a promising thermosensitive carrier for drug delivery.