Side-chain liquid crystal polymers derived from oxetane monomers containing 2-or 3-fluorophenyl moieties in the core of the mesogen

Two series of side-chain liquid crystalline polymers were prepared by catio nic ring-opening of oxetane substituted mesogens. Each of the terminally ap pended side chain polymers prepared had a flexible spacer length of six met hylene units separating a mesogenic aromatic core from the polymer backbone . The core unit was designed to incorporate either a 2-fluoro- or a 3-fluor o-phenyl unit possessing either an (R)-(-)-1-methylheptyl, (S)-(+)-2-methyl butyl or a 1-propylbutyl terminal chain. The materials produced in this stu dy were compared with the previously reported unsubstituted parent material s in order to assess the affect of having a lateral fluoro substituent in t he core. Low melting points, smectic C/C* and smectic A/A* phases were exhi bited by most of the monomers. The behaviour of the 3-fluorophenyl monomers was found to be similar to their unfluorinated parents, whereas the 2-fluo ro analogues were shown to have significantly lower transition temperatures . All of the polymers exhibited smectic C/C* and smectic A/A* phases over w ide temperature ranges and had relatively low T-g values. Some of the polym ers were found to exhibit exceptionally large temperature ranges for the sm ectic C/C* phase, e.g. from 0.8 degreesC to 190 degreesC.