Abstract: A low birefringent organic optical component prepared from a resin consisting essentially of one or more repetitive structural units selected from the group consisting of structures represented by general formula (1); ##STR1## wherein A is either of the groups below. ##STR2## The organic optical component can exhibit excellent transparency, heat resistance and mechanical strength as well as a low birefringence. Also provided is a novel aromatic polyamide with a low permitivity and excellent transparency, processability and thermal stability, besides excellent heat resistance inherent in an aromatic polyamide.

Abstract: A sliding material and a heat resistant filament which primarily comprises a liquid crystal polyimide, a liquid crystal polyamide or a liquid crystal polyamide-imide copolymer having at least one recurring structural unit selected from the formula (1) and the formula (2) and is excellent in heat resistance, mechanical characteristics and other fundamental properties of polyimides, and relates to significant improvement of heat-resistance by heat-treating the sliding material, the filament and the molded items. The liquid crystal polyamide-imide copolymer which comprises in a polymer molecule 0.05.about.0.95 mole ratio of the recurring structural units of the formula (1) and 0.95.about.0.