高等学校化学学报 ›› 2006, Vol. 27 ›› Issue (1): 156-160.

• 研究论文 • 上一篇    下一篇

高分子相分离的分子动力学模拟

魏东山, 李奕杰, 廖琦, 金熹高   

  1. 中国科学院化学研究所, 高分子物理与化学国家重点实验室, 北京 100080
  • 收稿日期:2005-01-24 出版日期:2006-01-10 发布日期:2006-01-10
  • 通讯作者: 廖琦(1970年出生), 男, 博士, 副研究员, 主要从事高分子物理计算机模拟研究. E-mail: qiliao@iccas.ac.cn
  • 基金资助:

    中国科学院创新基金(批准号:  KJCX2-SW-H07)和国家科学技术部“九七三”计划(批准号:  2003CB615604)资助.

Molecular Dynamics Simulation on  Phase Separation of Polymer Blend Systems

 WEI Dong-Shan, LI Yi-Jie, LIAO Qi, JIN Xi-Gao   

  1. State Key Laboratory of Polymer Physics and Chemistry,  Institute of Chemistry,Chinese Academy of Sciences,  Beijing 100080,  China
  • Received:2005-01-24 Online:2006-01-10 Published:2006-01-10
  • Contact: LIAO Qi,E-mail: qiliao@iccas.ac.cn

摘要:

用粗粒化分子动力学(MD)模拟方法从分子层次研究两组分聚合物共混体系相分离过程中的动力学. 在相分离初期, 相区尺寸不随时间增加而变化; 在相分离中期, 相区尺寸与时间有很好的标度关系, 标度指数(α=1/3)符合Lifshiz-Slyozov提出的以扩散为主导的蒸发-凝聚机理的标度预测; 在相分离后期, 体系实现宏观相分离, 相区尺寸不再随时间改变而变化. 体积分数小的高分子链尺寸在相分离过程中先收缩再扩张, 在实现宏观相分离后, 高分子链尺寸又回到本体状态尺寸.

关键词: 高分子相分离; 结构因子; 相区尺寸; 分子动力学模拟

Abstract:

A molecular dynamics simulation(MD) is performed to study the phase separation of binary symmetric polymer blend systems. The blend systems comprise of two kind of polymers with equal chain length of 20 and total chain number of 1 000. By adjusting chain numbers of polymer A,  a series of volume fractions φ from 0.1 to 0.5 were obtained. Polymer chains were simulated by a coarse-grained bead-spring model. The interaction potential between monomers is purely repulsive Lennard-Jones 12-6 potential and the bond potential between neighbor monomers along the sequence of the chain is FENE potential. The collective structure factor evolving with time,  S(q,t),  is obtained by the fast Fourier transform(FFT) of the concentration fluctuation function. As the phase separation proceeds,  the maximum of the collective structure factor increase with the increase of  time. The average phase domain size R(t) keeps constant at the early stage. At the intermediate stage,  R(t) increase with the increase of  time and a scaling relation  of R(t) vs. t1/3 is observed. At the last stage of the phase separation,  R(t) is time independent again. The time evolution of polymer chain size,  as well as the coordination number of monomer is also investigated during the phase separation. All these indicate that MD simulation is an effective and advantageous method for studying the dynamics of phase separation of polymer blend systems.

Key words: Polymer phase separation;  Structure factor;  Domain Size;  Molecular dynamics simulation

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