Polyelectrolyte (PE) brushes have ubiquitous applications as surface modifiers which regulate various structural and dynamic properties. Here, we apply a continuous-space self-consistent field theory to study the structural heterogeneity in PE brushes induced by competing electrostatic and hydrophobic interactions. For brushes with high grafting densities, we find a series of microphase-segregated morphologies with alternating polymer-rich and polymer-poor layers in the direction normal to the substrate. The transitions between multilayer morphologies with consecutive numbers of condensed layers as well as the melting transition to the fully swollen brush are all discontinuous. We also elucidate that the segregated layers are formed by different subpopulations of all chains, significantly different from the scenario of the pearl-necklace structure formed by a single PE in poor solvents. Furthermore, we bridge the microstructure of multilayer brushes to experimentally measurable reflectivity spectra, where the oscillation period and amplitude in the spectra are shown to be very sensitive to the number of layers and the sharpness of the polymer–solvent interface. The multilayer morphology predicted by our theory is in good agreement with the lamellae structure experimentally observed at hydrated Nafion film interfaces.

中文翻译：

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聚电解质刷中的微相偏析


聚电解质 （PE） 刷作为表面改性剂无处不在，可调节各种结构和动态特性。在这里，我们应用连续空间自洽场理论来研究由竞争性静电和疏水相互作用引起的 PE 刷中的结构异质性。对于具有高接枝密度的刷子，我们发现了一系列微相分离的形态，在垂直于基材的方向上具有交替的富含聚合物和贫聚合物的层。具有连续数量的冷凝层的多层形态之间的过渡以及向完全膨胀的刷子的熔化过渡都是不连续的。我们还阐明了分离层是由所有链的不同亚群形成的，这与在贫溶剂中由单个 PE 形成的珍珠项链结构的情况显着不同。此外，我们将多层刷的微观结构与实验可测量的反射率光谱联系起来，其中光谱中的振荡周期和振幅对层数和聚合物-溶剂界面的清晰度非常敏感。我们的理论预测的多层形态与在水合 Nafion 薄膜界面上实验观察到的薄片结构非常吻合。