Controlling the structure and dynamics of thin films of ionizable polymers at water interfaces is critical to their many applications. As the chemical diversity within one polymer is increased, controlling the structure and dynamics of the polymer, which is a key to their use, becomes a challenge. Here molecular dynamics simulations (MD) are used to obtain molecular insight into the structure and dynamics of thin films of one such macromolecule at the interface with water. The polymer consists of an ABCBA topology with randomly sulfonated polystyrene (C), tethered symmetrically to flexible poly(ethylene-r-propylene) blocks (B), and end-capped by a poly(t-butylstyrene) block (A). The compositions of the interfacial and bulk regions of thin films of the ABCBA polymers are followed as a function of exposure time to water. We find that interfacial rearrangements take place where buried ionic segments migrate toward the water interface. The hydrophobic blocks collapse and rearrange to minimize their exposure to water. The water that initially drives interfacial reengagements breaks the ionic clusters within the film, forming a dynamic hydrophilic internal network within the hydrophobic segments.

中文翻译：

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水界面的结构化离聚物薄膜：分子动力学模拟洞察

在水界面控制可电离聚合物薄膜的结构和动力学对它们的许多应用至关重要。随着一种聚合物内化学多样性的增加，控制聚合物的结构和动力学（这是其使用的关键）成为一项挑战。在这里，分子动力学模拟（MD）用于获得分子对这种大分子在与水的界面处的薄膜的结构和动力学的了解。该聚合物由具有随机磺化聚苯乙烯（C）为ABCBA拓扑的，拴系对称于柔性聚（乙烯- [R由聚-丙烯）嵌段（B），和封端的（吨-丁基苯乙烯）嵌段（A）。遵循ABCBA聚合物薄膜的界面和本体区域的组成，作为暴露于水的时间的函数。我们发现界面重排发生在埋藏的离子段向水界面迁移的地方。疏水性嵌段会塌陷并重新排列，以最大程度减少其与水的接触。最初驱动界面重新结合的水会破坏薄膜内的离子簇，从而在疏水链段内形成动态的亲水内部网络。