Effects of Polymer Chain Length and Stiffness on Phase Separation Dynamics of Semidilute Polymer Solution
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- 作者：Yung-Hsu Wu ; Da-Ming Wang ; Juin-Yi Lai
- 刊名：Journal of Physical Chemistry B
- 出版年：2008
- 出版时间：April 17, 2008
- 年：2008
- 卷：112
- 期：15
- 页码：4604 - 4612
- 全文大小：551K
- 年卷期：v.112,no.15(April 17, 2008)
- ISSN：1520-5207
文摘
Three-dimensional dissipative particle dynamics (DPD) simulations were performed to investigate the phaseseparation dynamics of semidilute polymer solutions with different polymer chain length and stiffness. Forthe polymer solution composed of shorter and more flexible chains, a crossover of the domain growth exponentfrom 1/3 to 2/3 was observed during the course of phase separation, indicating that the growth mechanismaltered from diffusion to interfacial-tension driven flow. When the chain flexibility was kept the same but thechain was lengthened to allow for the chain entanglement to occur, the growth exponent changed to 1/4 in thediffusion-dominating coarsening regime while the growth exponent remained 2/3 in the flow-dominating regime.When the chain length was kept short but the stiffness was increased, the growth exponent became 1/6 in thediffusion-dominating regime and little effect was observed in the flow-dominating coarsening regime. Theslow down of the phase separation dynamics in the diffusion-dominating coarsening could be explained bythat the polymer chains could only perform wormlike movement when chain entanglements occurred or whenthe chain motion was limited by chain stiffness during phase separation. Moreover, when both the effects ofchain length and stiffness were enhanced, polymer networks composed of longer and stiffer chains appearedand imposed an energy barrier for phase separation to occur. As a result, the polymer solution with stifferand longer chains required a larger quench depth to initiate the phase separation and caused the delay incrossover of the coarsening mechanism from diffusion to flow.