Synthesis of a liquid crystalline semi-ordered aromatic polyester and high-resolution solid-state C-13 NMR investigation of local motions

A liquid crystalline sequence-ordered polyester was prepared from isophthalic acid and 4-hydroxyphenyl 4-hydroxybenzoate in a 1:1 mole ratio. The local motions of this polymer were investigated by high-resolution solid-state C-13 NMR and the results were compared to data obtained on liquid crystalline or semicrystalline random terpolyesters with very similar compositions. Whereas no motions of the hydroquinone rings could be detected below the glass-transition temperature of the semi-ordered polymer, the para-hydroxybenzoic acid units exhibit a certain degree of freedom in the temperature range between 450 K and 500 K.