Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden, Germany.
J Chem Phys. 2010 Jan 14;132(2):024907. doi: 10.1063/1.3277670.
We study the behavior of random AB-copolymer melts near a selective surface. We consider the case where the copolymers do not display phase segregation behavior in the bulk but the surface is strongly selective for the A-component and the probability of finding an A-monomer along the chain is p<<1. Using self-consistent field theory and scaling arguments, we discuss some aspects of conformational rearrangements and composition selection in the surface layer. For strong selectivity we discuss the formation of a polydisperse brush on the surface. Next, we consider selection mechanisms of chains and sequences of A-species in the surface layer. We used the bond-fluctuation method to simulate copolymer melts at different values of the surface selectivity. Several aspects of the surface layer are analyzed, such as the composition profiles, chemical composition of chains on the surface, chain extension, and dynamics. We find evidence for conformational rearrangements in the surface layer according to the polydisperse brush model, as well as enrichment of A-monomers in the adosorbed chains, stretching of chains in the direction perpendicular to the surface, and selection of multiple A-sequences. Slight but systematic variation of the properties of surface layer at long simulation times indicates that selection processes require very long time scales as expected from theoretical arguments.
我们研究了随机 AB 嵌段共聚物熔体在选择性表面附近的行为。我们考虑了这样一种情况，即在本体中嵌段共聚物没有表现出相分离行为，但表面对 A 组分具有很强的选择性，并且沿链找到 A 单体的概率为 p<<1。我们使用自洽场理论和标度分析讨论了表面层中构象重排和组成选择的一些方面。对于强选择性，我们讨论了在表面形成多分散性刷的情况。接下来，我们考虑了表面层中 A 种链和序列的选择机制。我们使用键涨落方法模拟了不同表面选择性的嵌段共聚物熔体。分析了表面层的几个方面，如组成分布、表面链的化学组成、链延伸和动力学。我们根据多分散性刷模型发现了表面层构象重排的证据，以及吸附链中 A 单体的富集、垂直于表面方向上链的拉伸和多个 A 序列的选择。在长时间模拟中，表面层的性质略有但系统地变化表明，选择过程需要非常长的时间尺度，这与理论论点一致。
