美国布朗大学Benjamin R. McDonald研究团队报道了，超密集瓶刷聚合物的精确合成揭示了溶变有序的独特趋势。相关研究成果于2024年12月24日发表在《美国化学会杂志》。

具有多尺度纤维结构的生物大分子网络具有优异的力学性能，使其成为合成材料的有吸引力的结构。然而，缺乏能够形成类似结构网络的合成聚合物构建块。瓶刷状聚合物（BBPs）是各向异性接枝聚合物，有可能模拟和替代原胶原等生物大分子，用于制造合成纤维网络。

然而，BBPs的一个长期局限性是缺乏，获得支撑胶原网络形成的溶致性有序所需的刚性。虽然BBPs刚度和接枝密度之间的相关性已经很好地建立起来，但通过增加接枝密度来硬化BBPs的综合方法还不发达。

为了解决合成能力方面的这一差距，研究人员报告了新型大分子引发剂的合成，这些引发剂提供了定义明确的BBPs，具有前所未有的高接枝密度。一套光散射技术用于将大分子刚性与接枝结构和密度相关联，并首次证明聚（降冰片烯）BBPs因其棒状特性而表现出长程溶致有序性。

具体来说，新报道的可在多尺度上制备的，超密集接枝结构形成六边形阵列，而传统的BBPs则没有，尽管显示出长程空间相关性。这些结果揭示了密度和纠缠在BBPs溶液相组装中的核心作用，并提供了与BBPs衍生材料的制造和性能，广泛相关的新见解，涵盖了生物医学研究、光子材料和热管理技术。

此外，这些新报道的液晶BBPs提供了一个结构模板，用于探索半柔性网络自下而上组装的未开发潜力，并最终为分层结构的仿生材料提供模块化路线。

附：英文原文

Title: The Precise Synthesis of Ultradense Bottlebrush Polymers Unearths Unique Trends in Lyotropic Ordering

Author: Timea Kolozsvary, Phillip Kohl, Tianyu Li, David Gillespie, Youli Li, Benjamin R. McDonald

Issue&Volume: December 24, 2024

Abstract: Biomacromolecular networks with multiscale fibrillar structures are characterized by exceptional mechanical properties, making them attractive architectures for synthetic materials. However, there is a dearth of synthetic polymeric building blocks capable of forming similarly structured networks. Bottlebrush polymers (BBPs) are anisotropic graft polymers with the potential to mimic and replace biomacromolecules such as tropocollagen for the fabrication of synthetic fibrillar networks; however, a longstanding limitation of BBPs has been the lack of rigidity necessary to access the lyotropic ordering that underpins the formation of collagenous networks. While the correlation between BBP rigidity and grafting density is well established, synthetic approaches to rigidify BBPs by increased grafting density are underdeveloped. To address this gap in synthetic capability, we report the synthesis of novel macroinitiators that provide well-defined BBPs with an unprecedentedly high grafting density. A suite of light scattering techniques are used to correlate macromolecular rigidity with grafting architecture and density and demonstrate for the first time that poly(norbornene) BBPs exhibit long-range lyotropic ordering as a result of their rodlike character. Specifically, the newly reported ultradensely grafted structures, preparable on multigram scale, form hexagonal arrays while conventional BBPs do not, despite showing long-range spatial correlations. These results implicate the central role of density and entanglement in the solution phase assembly of BBPs and provide new fundamental insight that is broadly relevant to the fabrication and performance of BBP-derived materials, spanning biomedical research to photonic materials and thermal management technologies. Furthermore, these newly reported liquid crystalline BBPs provide a structural template to explore the untapped potential of the bottom-up assembly of semiflexible networks and are ultimately intended to provide a modular route to hierarchically structured biomimetic materials.

DOI: 10.1021/jacs.4c13759

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c13759