刚柔三嵌段共聚物自组装行为的模拟研究

采用耗散粒子动力学模拟方法研究了刚柔三嵌段共聚物(coil-rod-coil,CRC)在溶剂环境下的自组装.通过观察C₄R₈C₄共聚物囊泡结构形成的动力学过程,发现体系先自组装成球形或柱状胶束,然后逐渐融合为盘状结构,再进一步弯曲形变,形成闭合的双层膜囊泡结构.当共聚物浓度为6%~25%时,C₄R₈C₄自组装成不同尺寸的囊泡相,其均方半径2>随共聚物浓度的增加而增大,而双层膜厚度T基本保持不变.最后,改变溶剂性质,从亲棒到中性再到亲链,体系自组装结构从囊泡相转变为球形胶束相.尤其在等效的中性溶剂环境下,体系呈现层状结构,其中棒与棒嵌段呈高度有序的液晶相排列.

Simulation on the self-assembly of coil-rod-coil triblock copolymer

Self-assembled vesicles formed by symmetrical coil-rod-coil triblock copolymer in selective solvents are investigated by dissipative particle dynamics method. The kinetic process of vesicle formation is also observed. The micelles firstly experience the fusion, elongation and deformation, and then encompass the solvents, finally close up to a vesicle membrane, where the cylindrical and disc phase are the intermediate phases transited from solid micelle to hollow vesicle. Furthermore, the effects of polymer concentration and solvent properties are discussed. Vesicle structure is only observed in the range of f_p from 6%to 25%. Meanwhile, the vesicle size exhibits a well linear increase with the polymer concentration. Finally, varying the solvent properties from rod-selective to neutral then to coil-selective, the self-assembled structure of system is transited from vesicle to micelle. Under the neutral case, the lamellar structure is observed, where the rods are arranged in a highly ordered liquid crystalline phase.