Molecular chain structure of thermotropic p-oxybenzoate/ethylene terephthalate/vanillate or phenylene terephthalate terpolymers

Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (NM R) spectroscopies and wide-angle x-ray diffraction were used to analyze the molecular chain structures of thermotropic liquid-crystalline terpolymers from p-acetoxybenzoic acid, polyethylene terephthalate, and p-acetoxyvanill ic acid, or 1,4-diacetoxybenzene/terephthalic acid. The general features of FTIR spectra of the oriented terpolymer films and NMR spectra for the terp olymers in solution with the variation of terpolymer composition are discus sed. The assignments of the resonance peaks in FTIR and proton NMR spectra are given. The number-average degree of polymerization of the terpolymers i s estimated to be up to 34 by end-group analysis based on the NMR spectra. The meridional scans of x-ray diffraction of the as-drawn terpolymer ribbon s are being used to characterize the aperiodic characteristics and persiste nce length of the terpolymer chain. The persistence length of the terpolyme rs seems to increase with an increase in the p-oxybenzoate unit content and reaches the largest value of 5.56 nm at the p-oxybenzoate unit content of 70 mol%.