SYNTHESIS AND THERMAL INDUCED SHAPE MEMORY PROPERTIES OF BIODEGRADABLE SEGMENTED POLY(ESTER-URETHANE)S

It is very important to manipulate the switch temperature, mechanical properties and degradation rate of biodegradable shape memory polymers(BSMPs) from the viewpoint of practical applications. This can be realized through molecular design of the microstructure of the building blocks of BSMPs. In this study, hydroxy-telechelic poly(L-lactide-co-glycolide) (PLLG-diol) and poly (epsilon-caprolactone-co-glycolide) (PCG-diol) copolymers with adjustable composition, molecular weight and thermal transition temperature were synthesized via ring opening copolymerization of L-lactide/glycolide and epsilon-caprolactone/glycolide, respectively. Biodegradable segmented poly(ester-urethane) s were then synthesized via reaction with diisocyanate using them as hard and soft segments, respectively. Their molecular weight distribution, thermal transition and thermal induced shape memory behaviors were studied with GPC, DSC and thermomechanical. characterization, respectively. Segmented poly(ester-urethane) s exhibit excellent. shape memory properties, with strain fixity rate of 98 % similar to 99.5 % and strain recovery rate of 93 % similar to 98.5 % The strain fixity rate is independent of the composition and molecular weight of the segments, but the strain recovery rate increases with increasing the molecular weight or decreasing the GA content in the segments. With controlling the transition temperature of the soft segments, the shape recovery does not occur at body temperature but takes place at a little higher temperature in the range of 40 similar to 50 degrees C This character is very desired for and beneficial to clinical applications. The shape recovery speed can be adjusted by the environmental temperature or the heating rate.