Dynamic mechanical and dielectric relaxations in liquid crystalline copolymers formed from hydroxynaphthoic acid, terephthalic acid and p-aminophenol

Dynamic mechanical and dielectric measurements were carried out in the temperature range −120 to 160°C on nematic random copolymers formed from 60% hydroxynaphthoic acid, 20% terephthalic acid and 20% p-aminophenol. Only two relaxation transitions were observed both mechanically and dielectrically: the β and α relaxations. The virtual absence of the low-temperature γ relaxation is attributed to the existence of hydrogen bonding anticipated in this copolymer. The appearance of a pronounced dielectric α relaxation confirms that some electric dipoles were inactive at low temperatures and become active when hydrogen bonds are broken at high temperatures.