Department of Chemistry, Washington & Jefferson College, Washington, Pennsylvania 15301, United States.
Langmuir. 2012 Mar 20;28(11):5048-58. doi: 10.1021/la204100d. Epub 2012 Mar 9.
Polystyrene-block-poly(ethylene oxide) (PS-PEO) is an amphiphilic diblock copolymer that undergoes microphase separation when spread at the air/water interface, forming nanosized domains. In this study, we investigate the impact of PS by examining a series of PS-PEO samples containing constant PEO (~17,000 g·mol(-1)) and variable PS (from 3600 to 200,000 g·mol(-1)) through isothermal characterization and atomic force microscopy (AFM). The polymers separated into two categories: predominantly hydrophobic and predominantly hydrophilic with a weight percent of PEO of ~20% providing the boundary between the two. AFM results indicated that predominantly hydrophilic PS-PEO forms dots while more hydrophobic samples yield a mixture of dots and spaghetti with continent-like structures appearing at ~7% PEO or less. These structures reflect a blend of polymer spreading, entanglement, and vitrification as the solvent evaporates. Changing the spreading concentration provides insight into this process with higher concentrations representing earlier kinetic stages and lower concentrations demonstrating later ones. Comparison of isothermal results and AFM analysis shows how polymer behavior at the air/water interface correlates with the observed nanostructures. Understanding the impact of polymer composition and spreading concentration is significant in leading to greater control over the nanostructures obtained through PS-PEO self-assembly and their eventual application as polymer templates.
聚苯乙烯-聚（环氧乙烷）（PS-PEO）是一种两亲性嵌段共聚物，当在空气/水界面上展开时会发生微相分离，形成纳米尺寸的畴。在这项研究中，我们通过检查一系列含有恒定 PEO（~17,000 g·mol(-1)）和可变 PS（从 3600 到 200,000 g·mol(-1)）的 PS-PEO 样品，通过等温特性和原子力显微镜（AFM）来研究 PS 的影响。这些聚合物分为两类：主要疏水性和主要亲水性，PEO 的重量百分比约为 20%，作为两者的分界线。AFM 结果表明，主要亲水性 PS-PEO 形成点，而更疏水性的样品则产生点和面条的混合物，并且在约 7% PEO 或更少的情况下出现大陆状结构。这些结构反映了聚合物铺展、缠结和玻璃化过程随着溶剂蒸发的混合。改变铺展浓度可以深入了解这一过程，较高的浓度代表较早的动力学阶段，而较低的浓度则表明较晚的阶段。等温结果和 AFM 分析的比较表明，聚合物在空气/水界面上的行为如何与观察到的纳米结构相关。了解聚合物组成和铺展浓度的影响对于通过 PS-PEO 自组装获得更大的纳米结构控制及其作为聚合物模板的最终应用具有重要意义。
