Bottlebrush polymers are a special class of nonlinear polymers with a high density of polymeric side chains. Bottlebrush homopolymers typically do not interact and instead self-segregate as single macromolecules, where low chain entanglement results from the high steric repulsion between side chains. We report here the synthesis of poly(3-hexylthiophene) (P3HT) bottlebrush polymers and the unusual observation that these interesting molecules self-assemble by end-on-end linear assembly into long fibers. As-cast bottlebrush polymers are disordered and disperse freely as expected; however, thermal annealing promotes the evolution of long fibers. The use of P3HT allows for noncovalent interactions that are absent in other bottlebrush polymers, including π–π interaction and n-hexyl interdigitation. Optical spectroscopy provides evidence of these interactions that appear to drive end-on-end linear assembly. Interestingly, only end-on-end linear assembly is observed by TEM width analysis, since it is more favorable than side-to-side assembly due to steric constraints. This is further confirmed in solution when using a poor solvent to self-assemble bottlebrush polymers. To the best of our knowledge, this end-on-end linearly assembled morphology has not been previously observed for bottlebrush polymers and is a direct result of incorporating π-conjugated materials.

中文翻译：

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聚（3-己基噻吩）牙刷聚合物的自组装成端对端线性纤维形态

洗瓶刷聚合物是一类特殊的非线性聚合物，具有高密度的聚合物侧链。洗瓶刷均聚物通常不相互作用，而是自分离为单个大分子，其中低链缠结归因于侧链之间的高位阻。我们在这里报告了聚（3-己基噻吩）（P3HT）洗瓶刷聚合物的合成，以及不同寻常的观察结果，这些有趣的分子通过端对端线性组装成长纤维而自我组装。浇铸的牙刷聚合物杂乱无章，可自由分散。然而，热退火促进长纤维的发展。P3HT的使用允许其他洗瓶刷聚合物中不存在的非共价相互作用，包括π–π相互作用和n-己基互指。光谱学提供了这些相互作用的证据，这些相互作用似乎推动了端对端线性组装。有趣的是，通过TEM宽度分析只能观察到端对端线性装配，因为由于空间限制，它比侧面装配更有利。当使用不良溶剂自组装牙刷聚合物时，可以在溶液中进一步证实这一点。据我们所知，这种端对端线性组装的形态以前从未在瓶刷聚合物中观察到，这是掺入π共轭材料的直接结果。