Sidechain liquid crystal polymers derived from oxetane monomers containing 2 or 3fluorophenyl moieties in the core of the mesogen
作者:Stephen J. Cowling、Kenneth J. Toyne、John W. Goodby
DOI:10.1039/b009426i
日期:——
Two series of side-chain liquid crystalline polymers were prepared by cationic ring-opening of oxetane substituted mesogens. Each of the terminally appended side chain polymers prepared had a flexible spacer length of six methylene units separating a mesogenic aromatic core from the polymer backbone. The core unit was designed to incorporate either a 2-fluoro- or a 3-fluoro-phenyl unit possessing either an (R)-(−)-1-methylheptyl, (S)-(+)-2-methylbutyl or a 1-propylbutyl terminal chain. The materials produced in this study were compared with the previously reported unsubstituted parent materials in order to assess the affect of having a lateral fluoro substituent in the core. Low melting points, smectic C/C* and smectic A/A* phases were exhibited by most of the monomers. The behaviour of the 3-fluorophenyl monomers was found to be similar to their unfluorinated parents, whereas the 2-fluoro analogues
were shown to have significantly lower transition temperatures. All of the polymers exhibited smectic C/C* and smectic A/A* phases over wide temperature ranges and had relatively low Tg values. Some of the polymers were found to exhibit exceptionally large temperature ranges for the smectic C/C* phase, e.g. from 0.8 °C to 190 °C.
通过阳离子开环反应制备了两类侧链液晶聚合物,这些聚合物由取代的氧杂环烷烃构成。每个末端附加的侧链聚合物都有一个由六个亚甲基单元组成的柔性间隔器,将液晶芳香核与聚合物主链分隔开。核心单元设计为包含一个2-氟或3-氟苯基单元,并具有(R)-(−)-1-甲基庚基、(S)-(+)-2-甲基丁基或1-丙基丁基的末端链。本研究中产生的材料与之前报道的未取代母体材料进行了比较,以评估核心中侧向氟取代基的影响。大多数单体表现出低熔点,呈现出层状相C/C*和层状相A/A*。发现3-氟苯基单体的行为与其未氟化的母体相似,而2-氟的类似物显示出显著较低的相变温度。所有聚合物在较宽的温度范围内表现出层状相C/C*和层状相A/A*,且具有相对较低的玻璃化转变温度(Tg)。一些聚合物展现出异常大的层状相C/C*的温度范围,例如从0.8°C到190°C。