Structure and Properties of Phosphorous-Containing Thermotropic Liquid-Crystalline Aliphatic-Aromatic Copolyesters

A series of thermotropic liquid crystalline aliphatic-aromatic copolyesters derived from various ratios of dodecane-1,12-diol (1), terephthaloyl bis-(4-oxybenzoyl-chloride) (2), and 2-(6-oxido-6H-dibenz < c,e > < 1,2 > oxaphosphorin-6-yl)-1,4-naphthalene diol (3), has been synthesized. The chemical structures of the monomers and polymers have been confirmed by elemental analyses, and FT-IR and H-1 NMR spectroscopy. The mesomorphic properties of polymers have been investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction measurements. The influence of the content of the aliphatic unit on the phase behavior of the polymers has been examined. The polymers that contain >30 mol-% aliphatic did l showed smectic phases while the polymers that contained <30 mol-% aliphatic diol displayed nematic phases. The polymers revealed a reversible mesomorphic phase transition, wide mesophase temperature ranges, and high thermal stability. The degree of crystallinity increased upon increasing the content of aliphatic moieties. The char yield at high temperature increased by increasing the content of phosphorous-containing bisphenol.