Semiflexible main-chain thermotropic liquid crystalline polyesters (TLCPs) are applied in functional materials like heat dissipation sheets because of their good processability and ability to form nanostructures. Poly(pentylene 4,4'-bibibenzoate) (BB-5) is a commonly investigated biphenyl-based TLCP that forms a SmCA phase. The functional application of BB-5 is limited by its high isotropization temperature (Ti). This study aims to lower the Ti of BB-5 and enhance the processability of poly(pentylene 4,4''-terphenyl dicarboxylate) (T-5) compounds, which contain photo/electronic-functional mesogens. Six fluorinated BB-5 (F-BB-5) compounds are synthesized with Ti values at least 35 °C lower than that of BB-5. Fluorinated T-5 (F-T-5) compounds show isotropic phases before thermal decompositions, unlike T-5. Moreover, F-BB-5 and F-T-5 form not only amorphous and SmCA phases, but also crystalline and higher-order smectic phases, which is unexpected from low-molecular-weight liquid crystals. Mesogenic fluorination of semiflexible TLCPs results in low Ti and even unique morphologies, opening up their new possibilities.
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