ABC三嵌段共聚物在受限孔道中自组装行为的Monte Carlo模拟

Self-assembly behavior of ABC triblock copolymer in cylindrical pore: A Monte Carlo study

采用Monte Carlo模拟方法研究了在本体条件下形成四角排列柱状相的ABC线型三嵌段共聚物在受限孔道中的自组装行为.模拟结果表明共聚物的自组装结构依赖受限孔道的尺寸.在尺寸较大的孔道中,自组装结构与体系的初始态无关,表现出单一的套索结构;而在尺寸较小的孔道中,自组装结构与体系的初始态有关,表现出双螺旋、平行柱、堆积盘等结构.进一步研究结果表明,当孔道直径与体系在本体条件下的平衡周期不匹配时,体系相互作用能密度高的结构出现的概率高;而二者相匹配时,相互作用能密度高的结构出现的概率低.此外,对同一螺旋结构的统计分析表明,随着孔道尺寸的增加,体系中高分子链的均方末端距也随之增加,并且高分子链在圆柱孔道中由小孔道尺寸下沿垂直圆柱长轴方向排列逐渐转变为大孔道尺寸下沿圆柱长轴方向排列.

The spacially confined environment can greatly affect the self-assembly behavior of block copolymers, which provides an effective way for fabricating nanomaterials with novel structures and functionalities. Understanding the self-assembly behavior of block copolymers under various confined environments is of great importance for both fundamental studies and practical applications. In this work, the self-assembly behavior of tetragonal-packed cylinder-forming linear ABC triblock copolymers in cylindrical pore is studied using Monte Carlo simulation. Simulation results show that the self-assembly structures of the triblock copolymers depend on the pore size. In larger pore, the self-assembly structure is independent of the initial state of the system, only complex lariat structures are formed. While in smaller pore, the self-assembly structures depend on the initial state of the system. Double helices, parallel pillars and stacked disks can be obtained from different initial states. Further investigations indicate that when the pore size is incommensurate with the equilibrium period of the system in bulk, the occurring probability of the structure with higher interactive energy is high. However, when the pore size is commensurate with the equilibrium period, the occurring probability of the structure with higher interactive energy is low. Moreover, the statistical analysis at the level of micro-scale for the same double helices reveals that with the increase in the pore size, the mean-square end-to-end distance of the polymer chains in cylindrical pore increases, and the orientation of the polymer chains changes from the direction that is perpendicular to the pore axis to the direction that is parallel to the pore axis. The simulation results not only offer new insights into the self-assembly behavior of block copolymers under confined environment, but also provide a theoretical basis for corresponding experiments.