聚乳酸基可降解形状记忆聚合物的制备、结构与性能

Synthesis,Structure,and Properties of Polylactide-Based Degradable Shape Memory Polymers

以三枝化低不饱和度聚环氧丙烷/聚乳酸两嵌段共聚物(POLA)为原料,甲苯二异氰酸酯(TDⅠ)交联制备可降解聚环氧丙烷/聚乳酸基聚氨酯(POLA-PU).通过对POLA共聚物序列结构的调控,制备了由高模量低断裂伸长率的脆性到低模量高断裂伸长率的韧性POLA-PU可降解形状记忆材料.由TMA测得POLA-PU的形变温度为96～153℃.POLA-PU试样在140℃的形状记忆恢复时间不超过20 s.在200%拉伸形变条件下,POLA-PU的形变固定率在65%～100%之间,形变回复率均可达100%.实验表明,形状记忆行为取决于链的交联密度,记忆效应归属于不同温度下柔性链的构象熵变化.降解实验结果表明,聚乳酸链段的引入赋予了该形状记忆材料良好的降解性能,且随着聚乳酸含量的降低而下降.

A series of degradable poly（propylene oxide）-poly（L-lactide）-polyurethane（POLA-PU） shape memory polymers were synthesized by crosslinking triarm POLA diblock copolymers with tolylene diiso-cyanate（TDI）.The mechanical properties of POLA-PU could be conveniently adjusted through variation of composition to prepare materials from high modulus and low elongation at break to low modulus and high elongation at break.The transition temperatures of POLA-PU were between 96 and 153 ℃ by thermome-chanical analysis（TMA） and the restoration time was less than 20 s in 140 ℃.When the deformations from the permanent to the temporary shape were up to 200%,POLA-PU samples had a shape fixity rate between 65% and 100% and a shape recovery rate of 100%.Shape memory behavior relies on the cross-linking den-sities,and this effect can be achieved with changing conformational entropy of soft chains in different tem-peratures.The degradation of POLA-PU was investigated in 10% NaOH at 80 ℃.The results showed that the PLLA segments were introduced to novel shape memory materials with the degradable property,and the rate of degradation was decreased with decreasing the PLLA segments content.