美国加州大学伯克利分校Omar M. Yaghi团队报道了共价有机框架对模板聚合物纠缠的倾向。相关研究成果发表在2024年3月22日出版的《科学》。

将分子编织的三维（3D）共价有机框架（COF）晶体引入不同类型的聚合物中，引起填料和聚合物之间不同形式的接触。尽管编织的COF与无定形和脆性聚甲基丙烯酸甲酯的组合导致了表面相互作用，但液晶聚合物聚酰亚胺的使用诱导了聚合物COF结的形成。

这些连接是通过聚合物链穿过纳米晶体的孔而产生的，从而实现聚合物链的空间排列。这为在应力下解开聚合物链提供了一种可编程的途径，并导致高纵横比纳米纤维的原位形成，从而在断裂过程中耗散能量。聚合物COF结还通过添加少量（~1wt%）编织的COF纳米晶体来增强填料-基体界面并降低复合材料的渗流阈值，从而提高复合材料的强度、延展性和韧性。聚合物链与编织框架紧密相互作用的能力被强调为形成这些连接的主要参数，从而影响聚合物链的渗透和构象。

附：英文原文

Title: The propensity for covalent organic frameworks to template polymer entanglement

Author: S. Ephraim Neumann, Junpyo Kwon, Cornelius Gropp, Le Ma, Raynald Giovine, Tianqiong Ma, Nikita Hanikel, Kaiyu Wang, Tiffany Chen, Shaan Jagani, Robert O. Ritchie, Ting Xu, Omar M. Yaghi

Issue&Volume: 2024-03-22

Abstract: The introduction of molecularly woven three-dimensional (3D) covalent organic framework (COF) crystals into polymers of varying types invokes different forms of contact between filler and polymer. Whereas the combination of woven COFs with amorphous and brittle polymethyl methacrylate results in surface interactions, the use of the liquid-crystalline polymer polyimide induces the formation of polymer-COF junctions. These junctions are generated by the threading of polymer chains through the pores of the nanocrystals, thus allowing for spatial arrangement of polymer strands. This offers a programmable pathway for unthreading polymer strands under stress and leads to the in situ formation of high-aspect-ratio nanofibrils, which dissipate energy during the fracture. Polymer-COF junctions also strengthen the filler-matrix interfaces and lower the percolation thresholds of the composites, enhancing strength, ductility, and toughness of the composites by adding small amounts (~1 weight %) of woven COF nanocrystals. The ability of the polymer strands to closely interact with the woven framework is highlighted as the main parameter to forming these junctions, thus affecting polymer chain penetration and conformation.

DOI: adf2573

Source: https://www.science.org/doi/10.1126/science.adf2573