Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996-1600, USA.
Institut Charles Sadron, CNRS-UdS, 23 rue du Loess, 67034 Strasbourg Cédex 2, France.
J Chem Phys. 2017 Feb 7;146(5):054905. doi: 10.1063/1.4975022.
Copolymers are commonly used as interface modifiers that allow for the compatibilization of polymer components in a blend. For copolymers to function as a compatibilizer, they must diffuse through the matrix of the blend to the interface between the two blend components. The diffusivity of a copolymer in a blend matrix therefore becomes important in determining good candidates for use as compatibilizers. In this work, coarse-grained Monte Carlo simulations using the bond fluctuation model modified with an overlap penalty have been developed to study the diffusive behavior of PS/PMMA random copolymers in a PMMA homopolymer blend. The simulations vary the connectivity between different monomers, the thermodynamic interactions between the monomers which manifest within a chain, and between copolymer and homopolymer matrix and define the monomer friction coefficient of each component independently, allowing for the determination of the combined effect of these parameters on copolymer chain diffusion. The results of this work indicate that PS-r-PMMA copolymer diffusion is not linearly dependent on the copolymer composition on a logarithmic scale, but its diffusion is a balance of the kinetics governed by the dominant motion of the faster styrene monomers and thermodynamics, which are governed by the concentration of styrene monomer within a given monomer's local volume.
共聚物通常用作界面改性剂，允许共混物中的聚合物组分相容。为了使共聚物能够作为相容剂发挥作用，它们必须扩散通过共混物的基质到达两种共混物组分之间的界面。因此，共聚物在共混物基质中的扩散率对于确定用作相容剂的良好候选物变得很重要。在这项工作中，使用键波动模型与重叠惩罚相结合的粗粒度蒙特卡罗模拟，研究了 PS/PMMA 无规共聚物在 PMMA 均聚物共混物中的扩散行为。模拟改变了不同单体之间的连接性、单体之间在链内表现出的热力学相互作用以及共聚物和均聚物基质之间的相互作用，并独立定义了每个组分的单体摩擦系数，从而可以确定这些参数对共聚物链扩散的综合影响。这项工作的结果表明，PS-r-PMMA 共聚物的扩散在对数标度上与共聚物组成不成线性关系，但其扩散是由动力学平衡决定的，动力学由更快的苯乙烯单体的主导运动和热力学决定，而热力学则由给定单体局部体积内苯乙烯单体的浓度决定。
