聚合物单晶生长的三维相场模拟研究

利用元胞自动机方法与相场模型的结合建立新型三维模拟相场模型.同时,为模拟真实的、三维的高分子结晶的过程,采用元胞自动机方法离散方程,且元胞几何形状的选取符合真实聚合物晶格扩散方式的物理规律,以及新建立的相场模型套用间规聚丙烯的实验参数.利用该模型模拟了多种三维立方体或者薄层的晶体形貌及其相互之间的演化过程,包括正方形、长方形、菱形、六边形、多层单晶等.通过模拟结果与真实形貌作对比来证明所建立的相场模型真实可靠性.

SIMULATED THREE DIMENSIONAL MORPHOLOGICAL LANDSCAPE OF POLYMER SINGLE CRYSTALS BY PHASE-FIELD MODEL

The polymer crystallization process and mechanism were studied by computer simulation method.It is benefit to understand the crystallization kinetics by comparing the simulated results with the experimental results.Based on a nonconserved spatiotemporal Ginzburg-Landau equation TDGL model,a novel three dimensional phase field model was established by combining the cellular automaton method with the general phase field model.For simulating the real three dimensional polymer crystallization process,the cellular automaton method was modified by the different steric structures and discretization methods.The different steric structures or discretization methods are related to the lattice parameters of syndiotactic polypropylene single crystals and the crystal growth faces of polymer single crystals.It was suggested that the novel method is a way of building bridges between the diffusion equation and polymer characterization.Moreover,the diffusion equations are discretized according to the diffusion coefficient of every lattice site in various crystal growth faces,and the shape of lattice is selected based on the real proportion of the unit cell dimensions.Especially,the other physics parameters of syndiotactic polypropylene also were introduced into the phase field model.The spatio-temporal growth of syndiotactic polypropylene single crystals during isothermal crystallization was simulated by the novel three dimensional phase field model.Three dimensional numerical calculations are performed to elucidate the faceted single crystal growth including square,rectangular,lozenge-shaped,and hexagonal single crystals.The corresponding three dimensional results were illustrated by the MatLab.Our simulated patterns are in good agreement with the experimental morphologies,and the physical origin of polymer single crystal growth is discussed.