Microphase Segregation in Polyelectrolyte Brushes

IF 5.1 1区化学 Q1 POLYMER SCIENCE

Macromolecules Pub Date : 2024-12-17 DOI:10.1021/acs.macromol.4c01820

Takashi J. Yokokura, Chao Duan, Rui Wang

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Abstract

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.

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聚电解质刷中的微相分离

聚电解质（PE）电刷作为调节各种结构和动态性能的表面改性剂有着广泛的应用。本文应用连续空间自一致场理论研究了静电和疏水相互作用引起的PE电刷结构非均质性。对于高接枝密度的电刷，我们发现了一系列微相分离的形貌，在与衬底垂直的方向上，富聚合物层和贫聚合物层交替存在。具有连续凝聚层数的多层形态之间的转变以及熔化到完全膨胀的电刷之间的转变都是不连续的。我们还阐明了分离层是由所有链的不同亚群形成的，这与单一PE在不良溶剂中形成的珍珠项链结构的情况有很大不同。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结构与实验中观察到的水合Nafion膜界面的片层结构吻合较好。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Macromolecules 工程技术-高分子科学

CiteScore

9.30

自引率

16.40%

发文量

942

审稿时长

2 months

期刊介绍： Macromolecules publishes original, fundamental, and impactful research on all aspects of polymer science. Topics of interest include synthesis (e.g., controlled polymerizations, polymerization catalysis, post polymerization modification, new monomer structures and polymer architectures, and polymerization mechanisms/kinetics analysis); phase behavior, thermodynamics, dynamic, and ordering/disordering phenomena (e.g., self-assembly, gelation, crystallization, solution/melt/solid-state characteristics); structure and properties (e.g., mechanical and rheological properties, surface/interfacial characteristics, electronic and transport properties); new state of the art characterization (e.g., spectroscopy, scattering, microscopy, rheology), simulation (e.g., Monte Carlo, molecular dynamics, multi-scale/coarse-grained modeling), and theoretical methods. Renewable/sustainable polymers, polymer networks, responsive polymers, electro-, magneto- and opto-active macromolecules, inorganic polymers, charge-transporting polymers (ion-containing, semiconducting, and conducting), nanostructured polymers, and polymer composites are also of interest. Typical papers published in Macromolecules showcase important and innovative concepts, experimental methods/observations, and theoretical/computational approaches that demonstrate a fundamental advance in the understanding of polymers.