Li Yunqi, Sun Zhaoyan, Shi Tongfei, An Lijia
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
J Chem Phys. 2004 Jul 8;121(2):1133-40. doi: 10.1063/1.1758938.
The gelation of physically associating triblock copolymers in a good solvent was investigated by means of the Monte Carlo simulation and a gelation process based on the conformation transition of the copolymer that was described in detail. In our simulative system, it has been found that the gelation is closely related with chain conformations, and there exist four types of chains defined as free, dangling, loop, and bridge conformations. The copolymer chains with different conformations contribute to the formation of gel in different ways. We proposed a conformational transition model, by which we evaluated the role of these four types of chains in sol-gel transition. It was concluded that the free chains keeping the conformation transition equilibrium and the dangling conformation being the hinge of conformation transition, while the chain with loop conformation enlarges the size of the congeries and the chain with bridge conformations binds the congeries consisted of the copolymer chains. In addition, the effects of temperature and concentration on the physical gelation, the association of the copolymer congeries, and the copolymer chain conformations' distribution were discussed. Furthermore, we employed the structure factor analysis to study the association of copolymer conformations and long-range order of the simulation system and found our results are in agreement with the previous experimental conclusions.
通过蒙特卡罗模拟研究了在良溶剂中物理缔合三嵌段共聚物的凝胶化过程，并详细描述了基于共聚物构象转变的凝胶化过程。在我们的模拟体系中，发现凝胶化与链构象密切相关，存在自由、悬垂、环和桥四种链构象类型。不同构象的共聚物链以不同方式促进凝胶的形成。我们提出了一个构象转变模型，据此评估这四种链构象类型在溶胶-凝胶转变中的作用。得出的结论是，自由链保持构象转变平衡，悬垂构象是构象转变的关键，而具有环构象的链增大了聚集体的尺寸，具有桥构象的链则将由共聚物链组成的聚集体连接起来。此外，还讨论了温度和浓度对物理凝胶化、共聚物聚集体缔合以及共聚物链构象分布的影响。此外，我们采用结构因子分析研究共聚物构象的缔合以及模拟体系的长程有序，发现我们的结果与先前的实验结论一致。
