PLA-b-PEO-b-PLA三嵌段共聚物分子聚集体性质的研究

采用开环聚合的方法 ,合成了组成不同的PLA b PEO b PLA三嵌段共聚物 .滴加选择性溶剂水于共聚物的良溶剂溶液中 ,制备了共聚物以水为介质的“平头”聚集体胶束溶液 .把聚集体胶束溶液浇铸在云母片上 ,采用扫描探针显微镜 (SPM)表征了其形貌和表面微粘弹性 .发现脱离了极性介质水的聚集体的表面性质发生了不均一化 ,聚集体的顶部比相连接的部分具有较高的储能模量 .聚集体环境的改变使聚集体中不同嵌段的迁移导致了这种表面粘弹性的不均一 .另外 ,采用动态光散射的方法测量了体系溶液中聚集体胶束的尺寸 .实验发现光散射所得到的聚集体的尺寸远远大于SPM所得到尺寸 .增加聚合物的起始浓度使聚集体胶束的尺寸以及多分散性都在不同程度上增大 .然而聚合物的不同 ,这种增加的程度会有比较大的差别

THE STUDY ON THE PROPERTIES OF AGGREGATES OF PLA-b-PEO-b-PLA TRIBLOCK COPOLYMERS IN AQUEOUS MEDIA

PLA b\|PEO b\|PLA triblock copolymers with different compositions were prepared by ring\|open polymerization using OH\|capped PEO as macroinitiators. T he “crew\|cut” aggregates of PLA b\|PEO b\|PLA triblock copolymers i n aqueous media were fabricated by dropping water into block copolymer solutions in common solvents. The surface morphology and micro\|viscoelasticity of aggreg ates cast on mica sheets from colloids were investigated by scanning probe micro scopy (SPM). It was observed that the micelles with a diameter of about 45?nm w ere formed and organized into relatively single layer on mica surface. Intersted ly, inhomogeneity of surface modulus appeared as the water of colloids evaporate d. The top of aggregates had relatively higher modulus than that of the peripher a l parts of aggregates. The changes of environments of aggregates from polar wate r to unpolar air on mica sheets were suggested to be responsible for the surface modulus inhomogeneity. In addition, the experimental data showed that the sizes of aggregates measured from dynamic light scattering were greatly larger than t hose from SPM observations. At the same time, increasing the initial concentrati on of copolymers in common solvents resulted in the increase of aggregate sizes and higher polydispersities.