Reconfiguration of Langmuir Monolayers of Thermo-Responsive Branched Ionic Polymers with LCST Transition
Reconfiguration of Langmuir Monolayers of Thermo-Responsive Branched Ionic Polymers with LCST Transition
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DOI：
10.1021/acs.langmuir.2c01940
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发表时间：
2022-09-23
期刊：
影响因子：
3.9
通讯作者：
Tsukruk, Vladimir V.
中科院分区：
文献类型：
--
作者：
Flouda, Paraskevi;Stryutsky, Alexandr V.;Tsukruk, Vladimir V.
热响应性离子聚合物具有形成自适应和可转换形态的能力，这可能在储能和催化应用中提供更好的控制。目前的热响应性聚合物由共价连接的热响应部分组成，限制了它们的移动性和整体动态响应。在此，我们报道了具有胺封端的聚（N - 异丙基丙烯酰胺）（PNIPAM）大阳离子弱离子键合臂的对称和不对称两亲性热响应支化聚合物在水 - 空气界面的合成与组装。正如我们所观察到的，对称支化聚合物形成多分子纳米尺寸的胶束组装体，而相应的不对称聚合物形成大型的、相互连接的蠕虫状聚集体。局部和大规模化学成分的显著变化证实了在低临界溶液温度（LCST）以下和以上移动的PNIPAM大阳离子的可逆吸附和解吸，以及它们在聚合物单分子层内的不均匀再分布。将温度升高到LCST以上会导致形成大型相互连接的胶束聚集体，这是因为在水亚相中疏水化的PNIPAM大阳离子末端链以胶束为中心聚集。总体而言，这项工作深入了解了具有弱离子键合热响应末端链的支化离子聚合物化学成分的动态性质，以及它在LCST转变时对单分子层的形态和局部/表面化学的影响。
Thermo-responsive ionic polymers have the ability to form adaptive and switchable morphologies, which may offer enhanced control in energy storage and catalytic applications. Current thermoresponsive polymers are composed of covalently attached thermoresponsive moieties, restricting their mobility and global dynamic response. Here, we report the synthesis and assembly at the water-air interface of symmetric and asymmetric amphiphilic thermo-responsive branched polymers with weakly ionically bound arms of amine terminated poly(N-isopropylacrylamide) (PNIPAM) macro-cations. As we observed, symmetric branched polymers formed multimolecular nanosized micellar assemblies, whereas corresponding asymmetric polymers formed large, interconnected worm-like aggregates. Dramatic changes in localized and large-scale chemical composition confirmed the reversible adsorption and desorption of the mobile PNIPAM macro-cations below and above the low critical solution temperature (LCST) and their non-uniform redistribution within polymer monolayer. Increasing the temperature above LCST led to the formation of large interconnected micellar aggregates because of the micelle-centered aggregation of the hydrophobized PNIPAM macro-cationic terminal chains in the aqueous subphase. Overall, this work provides insights into the dynamic nature of the chemical composition of branched ionic polymers with weakly ionically bound thermo-responsive terminal chains and its effect on both morphology and local/surface chemistry of monolayers at LCST transition.