Model considerations and examples of enantiotropic liquid crystalline polymers. Polyreactions in ordered systems, 14
Model considerations and examples of enantiotropic liquid crystalline polymers. Polyreactions in ordered systems, 14
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DOI：
10.1002/macp.1978.021790129
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发表时间：
1978
影响因子：
2.5
通讯作者：
H. Finkelmann;H. Ringsdorf;J. Wendorff
中科院分区：
文献类型：
--
作者：
H. Finkelmann;H. Ringsdorf;J. Wendorff
在过去的几年里，由于液晶聚合物的理论和技术方面的原因，有关液晶聚合物的研究越来越引起人们的兴趣。作为起始化合物，使用了具有传统液晶典型结构的介晶可聚合单体。对于通过缩合反应形成的聚合物，例如将低相对分子质量的介晶单体构建到主链中，描述了向列相和近晶相的聚合物3)。在带有介晶侧链的乙烯基聚合物的范围内，虽然已经进行了大量的实验，但只得到了一些对映异构型液晶聚合物。在大多数情况下，它只能冻结在液晶结构中，这种结构在玻璃化转变温度以上就不可逆转地消失了。在传统的液晶相中，分子的运动仅受与其邻体的各向异性相互作用的限制。这导致了取向长程有序的形成。如果介晶基团像侧链一样直接固定到主链上，那么移动和定向的能力就会发生很大的变化。在聚合物的液态，统计链构象的倾向阻碍了侧链的取向。如果侧链的各向异性相互作用强到足以形成中间相，仍然可以形成液晶结构，但只能与主链的有限运动相一致。前人的研究结果表明，侧基在平面上有序的情况下，近晶结构更受青睐。一个例子是4-乙氧基-N-(4-甲基丙烯酰氧基苯亚胺)6的聚合物。X射线研究表明，主链在近晶层内呈平面排列。
In the last few years studies concerning liquid crystal polymers have become of increasing interest because of their theoretical and technological aspects'). As starting compounds, mesogenic polymerizable monomers were used which have the typical structure') of conventional liquid crystals. For polymers formed by condensation reactions, eg building the low molecular weight mesogenic monomer into the main chain, nematic as well as smectic polymer phases have been described3).Within the scope of vinyl polymers with mesogenic side chains only some enantiotropic liquid crystalline polymers have been obtained4), although numerous experiments have been made. In most cases it was only possible to freeze in the liquid crystalline structure, which was irreversibly lost above the glass transition temperature5). In conventional liquid crystalline phases the motions of a molecule are restricted only by the anisotropic interactions with its neighbours. This leads to the formation of the orientational long range order. If the mesogenic groups are directly fixed like side chains to the main chain, the ability to move and orient is changed drastically. In the liquid state of the polymer, the tendency of statistical chain conformation hinders an orientation of the side chains. If the anisotropic interactions of side chains are strong enough to form the mesophase, a liquid crystalline structure can nevertheless be formed, but only in accordance with the limited motions of the main chain. Previous results show that smectic structures are favored where the side groups are ordered in planes. An example is the polymer of 4-ethoxy-N-(4-methacryloyloxybenzy-lidene) aniline6). X-ray investigations indicate that the main chain is ordered in planes within the smectic layers.