This study presents a novel approach utilizing total internal reflection microscopy (TIRM) to effectively characterize the swelling and collapse of polymer brushes in aqueous solutions. Zwitterionic poly(carboxybetaine methacrylate) (PCBMA) and nonionic poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA) brushes are chosen as model systems. By investigation of an intriguing theory–experiment discrepancy observed during the measurement of near-wall hindered diffusion, valuable insights into the compressibility of polymer brushes are obtained, revealing their conformational information in aqueous solution. The results demonstrate that zwitterionic PCBMA brushes exhibit minimal antipolyelectrolyte effects in 0.1–10 mM NaCl solution but undergo significant swelling with increasing pH. On the other hand, nonionic POEGMA brushes exhibit similar responses to ionic strength as weak polyelectrolyte brushes. These unexpected findings enhance our understanding of polymer brushes beyond classical theories. The TIRM-based approach proves to be effective for characterizing polymer brushes and other soft nanomaterials.

中文翻译：

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一种基于全内反射显微镜 （TIRM） 的方法，用于直接表征水溶液中聚合物刷状构象的变化


本研究提出了一种利用全内反射显微镜 （TIRM） 有效表征聚合物刷在水溶液中的膨胀和塌陷的新方法。选择两性离子聚（羧基甜菜碱甲基丙烯酸酯）（PCBMA）和非离子聚[寡聚（乙二醇）甲基醚酯] （POEGMA） 刷作为模型系统。通过调查在测量近壁受阻扩散过程中观察到的有趣的理论-实验差异，获得了对聚合物刷可压缩性的宝贵见解，揭示了它们在水溶液中的构象信息。结果表明，两性离子 PCBMA 刷在 0.1–10 mM NaCl 溶液中表现出最小的抗聚电解质效应，但随着 pH 值的增加而发生明显的溶胀。另一方面，非离子型 POEGMA 电刷对离子强度的反应与弱聚电解质电刷相似。这些意想不到的发现增强了我们对聚合物刷的理解，超越了经典理论。基于 TIRM 的方法被证明对表征聚合物刷和其他软纳米材料是有效的。