聚消旋丙交酯-b-聚氧乙烯星形嵌段聚合物的受限结晶行为

Confined Crystallization of Six-Armed Star-Shaped Poly(D, L-Lactide)-b-Poly(Ethylene Oxide) Copolymer

通过阳离子活性开环聚合和大分子酯化反应的两步法,合成两亲性的聚消旋丙交酯-b-聚氧乙烯(sPDLLA-b-PEO)六臂星形嵌段聚合物。通过差示扫描量热法研究了聚合物本体结晶行为。结果表明,无定形链段PDLLA的引入和特定的星形结构,使得PEO链段的结晶受到限制,出现了冷结晶现象,并且最高结晶温度随着升温速率的增大而升高。通过偏光显微镜研究了六臂嵌段聚合物的结晶形貌,发现六臂sPDLLA-b-PEO生长产生环带球晶。并且通过调控聚合物与溶剂的比例和聚合物膜的厚度,发现溶剂可以减小球晶生长中积累的应力,使环带结构消失;但六臂聚合物对于几何受限的响应性较强,当膜厚减小时,环带结构重新出现。

Amphiphilic six-armed star-shaped poly（D, L-lactide）-b-poly（ethylene oxide） （SPDLLA-b-PEO） was synthesized by combination of ring opening polymerization and macromolecular esterification to investigate its confined crystallization and micellization behavior due to its novel structure. The composition and structure of star-shaped copolymer were characterized by 1H-NMR, GPC and FT-IR. The bulk crystallization behaviors of sPDLLA-b-PEO were determined by DSC. sPDLLA-b-PEO exhibits specific cold crystallization process due to chain end restriction from both the star-shaped molecular architecture and amorphous PDLLA block. Moreover, the maximum cold crystallization temperature increases with heating rates increasing. It is also found by POM that sPDLLA-b-PEO has banded spherulites. The band periodicity in the spherulites of the block copolymers in solution cast films changes with evaporation rate, and becomes larger or even disappears.