Novel side-chain liquid-crystalline polyesters have been synthesized by direct polyesterification of phthalic anhydride, pentaerythritol, and 4-methoxy-4′-oxybiphenyl-substituted monocarboxylic acids with different lengths of spacers. The polyesters were characterized by 1H- and 13C-NMR spectroscopy, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and optical polarized light microscopy. The polymerizations reached high conversion, the number-average molecular masses were 2900-3300 g/mol, and the polydispersity indices were 4.7-12.1, respectively. The thermal properties of the polyesters varied greatly. They had one to four endothermic transitions on heating and one or two exotherms on cooling. After the first heating cycle, subsequent heating and cooling cycles on each polymer gave virtually identical DSC thermograms. Mesophases are presumed to be of the smectic type.
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Hamara et al. (1994) studied this question.
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