可生物降解多嵌段聚(酯-氨酯)的合成及其热致形状记忆性质

以端羟基L-丙交酯/乙交酯共聚物(PLLG-diol)和端羟基ε-己内酯/乙交酯共聚物(PCG-diol)为硬段和软段,通过与二异氰酸酯反应制得了软、硬分子量和组成均可调的多嵌段聚(酯-氨酯),表征了它们的形状记忆行为.多嵌段聚(酯-氨酯)具有良好的形状记忆性质,应变固定率达98%~99.5%,应变恢复率达93%~98.5%;通过转变温度的调节,可使多嵌段聚(酯-氨酯)在37℃体温下不发生形状变化,而在稍高于体温的温度(40~50℃)下恢复原始形状,其形状恢复速率可通过温度和升温速率来调节.

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(ε-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 ε-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%～99.5% and strain recovery rate of 93%～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 40～50℃.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.