Influence of the spacer length on the phase behaviors of mesogen-jacketed liquid crystalline polymers with a bulk side-chain
Influence of the spacer length on the phase behaviors of mesogen-jacketed liquid crystalline polymers with a bulk side-chain
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DOI：
10.1039/c5ra07155k
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发表时间：
2015-06
期刊：
影响因子：
3.9
通讯作者：
Yongbing Luo;Sheng Chen;Hailiang Zhang
中科院分区：
文献类型：
--
作者：
Yongbing Luo;Sheng Chen;Hailiang Zhang
设计并成功合成了一系列侧链上含有两个三苯甲基(Tr)基团的介元夹套液晶聚合物(poly{2，5-bis[(triphenylmethoxy-alkyl)oxycarbonyl]-styrenes})(记为PV-m-Tr，m=2，4，6，8，10，12，即侧链中对苯二甲酸二苯酯与Tr基团之间的亚甲基单元个数)。单体的化学结构经核磁共振氢谱和质谱仪确证。用核磁共振氢谱、凝胶渗透色谱和热重分析对聚合物进行了分子表征。用DSC、POM和一维/二维WAXD等技术研究了聚合物的相结构和相变温度。实验结果表明，所有聚合物都具有良好的热稳定性。聚合物的液晶相结构和行为强烈依赖于间隔基团的长度(M)。随着m的增加，由于烷基增塑作用，PV-m-Tr的玻璃化转变温度从116.7℃降至11.5℃。当m=2、4、6、8、10时，PV-m-Tr在Tg以上形成稳定的柱状向列相(ΦN)。当m=12时，PV-12-Tr在Tg以上为各向同性重入相，在较高温度下为LC相。这项工作为理解基于烷基间隔基和本体侧链的MJLCP的结构-性质关系提供了一个新的案例。
A series of mesogen-jacketed liquid-crystalline polymers (MJLCPs) containing two triphenylmethyl (Tr) units in the side chains, named poly{2,5-bis[(triphenylmethoxy-alkyl)oxycarbonyl]-styrenes} (denoted as Pv-m-Tr, m = 2, 4, 6, 8, 10, 12, which is the number of the methylene units between the terephthalate core and Tr moieties in the side chains), were designed and successfully synthesized via free radical polymerization. The chemical structures of the monomers were confirmed by 1H NMR and mass spectrometry. The molecular characterizations of the polymers were performed with 1H NMR, GPC and TG analysis. The phase structures and transition temperatures of the polymers were investigated by a combination of techniques including DSC, POM and 1D/2D WAXD. The experimental results revealed that all the polymers exhibited excellent thermal stabilities. The liquid crystalline (LC) phase structures and behaviors of the polymers were strongly dependent on the spacer length (m). With the increase of m, Tg of Pv-m-Tr decreased from 116.7 °C to 11.5 °C because of the alkyl plasticization. When m = 2, 4, 6, 8, 10, the Pv-m-Tr formed a stable columnar nematic (ΦN) phase above Tg. When m = 12, the Pv-12-Tr presented a re-entrant isotropic phase above Tg and a LC phase at higher temperature. This work provides a new case to understand the structure–property relationships of MJLCPs based on the alkyl spacer and bulk side-chain.