嵌段序列对聚合物囊泡形成过程影响的Monte Carlo模拟

采用Monte Carlo模拟方法研究了具有相同链长和组分比的不同嵌段序列的AB两嵌段共聚物与ABA三嵌段共聚物在选择性溶剂中形成囊泡的动力学过程. 模拟结果表明, AB两嵌段共聚物囊泡的形成与ABA三嵌段共聚物囊泡的形成的动力学过程不同. 在慢速退火条件下, ABA三嵌段共聚物囊泡是通过亲水链段向胶束的表面和中心扩散而形成的, 而AB两嵌段共聚物囊泡则由片层弯曲闭合而形成. 相对而言, 退火速度对AB两嵌段共聚物囊泡形成的动力学过程没有显著影响, 其改变仅影响亲水链段与疏水链段发生相分离的难易程度. 当退火速度较快时, 亲水链段和疏水链段发生相分离的速度较快且相分离发生在囊泡形成之前; 而当退火速度较慢时亲水链段和疏水链段之间的相分离在囊泡形成之后仍在进行.

Monte Carlo Simulation of Effect of Block Sequence on Kinetics of Vesicle Formation of Polymers

We studied the kinetics of the vesicle formation of ABA and AB amphiphilic block copolymers, which have the same chain length and composition but different block sequence, in selective solvent. The simulation results show that the kinetic of the formation of AB diblock copolymer vesicle is different from that of ABA triblock copolymer vesicle. At slow annealing rate, ABA triblock copolymer vesicles are formed via hydrophilic molecules diffusion into the center of spherical micelles, whereas AB diblock copolymer vesicles are formed via oblate membrane closing. The annealing rate does not affect the pathway of spontaneous vesicle formation of AB diblock copolymers. Vesicles of AB diblock copolymers in selective solvent are more likely to be formed by membrane closing. Annealing rates only affect microphase separation process between hydrophobic and hydrophilic blocks. At quick annealing rate, the phase segregation between hydrophobic and hydrophilic blocks is relatively quick and occurs before the formation of vesicle. However, the phase segregation is relatively slow at slow annealing rate and occurs after the formation of vesicle.