Synthesis and Characterization of Three-Arm Poly(ε-caprolactone)-Based Poly(ester-urethanes) with Shape-Memory Effect at Body Temperature

Novel biodegradable star poly(ester-urethanes) containing three-arm poly(epsilon-caprolactone) (PCL) as switching segment were prepared as shape-memory polymers (SMPs) with switching temperature (T-s) around body temperature. PCL-triols with molecular weight (M-n) of 2700-4200 g/mol and T-m of 45-47 degrees C were synthesized in 55-67% yield by Novozym 435-catalyzed ring-opening polymerization of epsilon-caprolactone with glycerol as initiator, and their three-arm structures were confirmed by H-1 and C-13 NMR analysis. Reaction of the PCL-triols with methylene diphenyl 4,4'-diisocyanate isocynate and 1,6-hexanediol gave three-arm PCL-based poly(ester-urethane)s (tPCL-PUs) in 83-92% yield, with 65-75% soft segment. The structure of tPCL-PUs was confirmed by H-1 NMR analysis, and the thermal properties were analyzed by DSC with T-s of 36-39 degrees C. tPCL-PUs showed excellent shape-memory effects at 38 degrees C during cyclic thermomechanical tensile tests: shape recovery within 10 s, shape fixity rate of 92%, and shape recovery rate of 99%. The novel biodegradable star SMPs are potentially useful in biomedical applications.