Synthesis and mesomorphic properties of side-chain polynorbornenes containing mono-, di- and tri-calamitic mesogenic pendant groups
Synthesis and mesomorphic properties of side-chain polynorbornenes containing mono-, di- and tri-calamitic mesogenic pendant groups
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含有单、二、三棒介晶侧基的侧链聚降冰片烯的合成和介晶性质
DOI：
10.1039/c6py00632a
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发表时间：
2016
影响因子：
4.6
通讯作者：
Chen Xiaofang
中科院分区：
文献类型：
--
作者：
Ma Shenhao;Cai Yongchen;Tu Yuanyang;Guan Yan;Chen Xiaofang
合成并表征了含有烷氧基联苯基介晶侧基的侧链聚芳撑（PNB），其重复单元内的取代基数目和位置可控。在该体系中发现了近晶A相（SmA）、具有中心矩形柱状晶格的调制近晶相（Φr-c）和六方柱状相（Φh）等多种热致性中间相。系统地研究了烷氧基联苯基团的数目和位置对PNB自组装行为的影响。随着取代基数目的增加，PNB的中间相由PNB-4-CmBA的SmA变为PNB-3，4-CmBA的Φr-c和PNB-3，4，5-CmBA的Φh（m = 12，16）。自组织结构由脂肪族和芳香族分离区域之间的界面曲率决定。随着介晶基团数目的增加，界面变得越来越弯曲，从而引起结构改变。当取代基位置由PNB-3，4-CmBA变为PNB-3，5-CmBA（m = 12，16）时，由于侧链更加灵活，相结构由Φr-c变为无定形相。该棒状液晶基元是一种强有力的侧链结构单元，可用于构建具有复杂超分子自组装结构的侧链聚合物。
Side-chain polynorbornenes (PNBs) containing alkoxy biphenyl mesogenic side groups with a controlled number and substituted position within each repeating unit were synthesized and characterized. Various thermotropic mesophases including the smectic A (SmA) phase, the modulated smectic phase with a centered rectangular columnar lattice (Φr-c), and the hexagonal columnar (Φh) phase have been verified in this system. The influence of the number and position of alkoxy biphenyl groups on the self-assembly behavior of PNBs has been systematically studied. When increasing the number of substituted mesogenic groups, the mesophase of PNBs changes from SmA of PNB-4-CmBA to Φr-c of PNB-3,4-CmBA and Φh of PNB-3,4,5-CmBA (m = 12, 16). The self-organized structure is determined by the curvature of the interface between the aliphatic and aromatic segregated regions. With increases in the mesogenic group numbers, the interface becomes increasingly curved giving rise to structure alteration. When changing the substituent position from PNB-3,4-CmBA to PNB-3,5-CmBA (m = 12, 16), the phase structure changes from Φr-c to the amorphous phase because of the more flexible side chain. The calamitic mesogen shown here is a powerful side-chain building block to construct side-chain polymers with complex supramolecular self-assembled structures.