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arXiv 0709.2875cond-mat.softcond-mat.stat-mech
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两嵌段共聚物液体中桥长尺度的理论粗粒化方法

Theoretical coarse-graining approach to bridge length scales in diblock copolymer liquids

E. J. Sambriski, M. G. Guenza

摘要:

本文基于液相积分方程的解,建立了一个将两嵌段共聚物粗粒化为哑铃状相互作用软胶粒的微观理论。求解Ornstein-Zernike方程,以在嵌段质量中心水平和聚合物质量中心水平上提供二嵌段共聚物系统的介观描述。分析形式的总关联函数的块块,块单体,和质量中心对得到的液体的结构对称的二嵌段共聚物作为温度,密度,链长,和链组成的函数。该理论正确地预测了作为温度的函数($chi$参数)的双嵌段到微区中的热驱动偏析。粗粒度的描述包含密度和浓度波动的贡献,随着温度的降低,后者成为主导。数值计算的块粗粒总关联函数,作为一个功能的系统接近其相变,提出。与联合原子分子动力学模拟的比较进行了无热制度,模拟和理论定量地同意,不需要可调的参数。

英文摘要:

A microscopic theory for coarse graining diblock copolymers into dumbbells of interacting soft colloidal particles has been developed, based on the solution of liquid-state integral equations. The Ornstein-Zernike equation is solved to provide a mesoscopic description of the diblock copolymer system at the level of block centers of mass, and at the level of polymer centers of mass. Analytical forms of the total correlation functions for block-block, block-monomer, and center-of-mass pairs are obtained for a liquid of structurally symmetric diblock copolymers as a function of temperature, density, chain length, and chain composition. The theory correctly predicts thermodynamically-driven segregation of diblocks into microdomains as a function of temperature ($chi$ parameter). The coarse-grained description contains contributions from density and concentration fluctuations, with the latter becoming dominant as temperature decreases. Numerical calculations for the block coarse-grained total correlation functions, as a function of the proximity of the system to its phase transition, are presented. Comparison with united atom molecular dynamics simulations are carried out in the athermal regime, where simulations and theory quantitatively agree with no need of adjustable parameters.

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