PURPOSE: To obtain a liq.-crystalline arom. polymer which is treatable from melt, has high strengths, modulus, and thermal shock resistance, and is used for fibers, etc., by thermally polymerizing an arom. monomer to a desired degree of polymn., adding a triazine compd. to the polymn. system, continuing the polymn., cooling the resultant product, and subjecting it in the solid state to post-condensation at a high temp.

CONSTITUTION: In melt reacting an arom. monomer with a triazine compd. represented by the formula [wherein R1 is amino; R2 and R3 are each (alkyl) carboxyl, (alkyl)hydroxy, and/or amino], the triazine compd. is added when a desired degree of polymn. is reached while regarding the max. conversion of 96% as the standard; then, the reaction is continued for a short time; and after the resultant product is cooled, it is subjected to post condensation at an elevated temp., if necessary in the solid state. Thus is obtd. a liq.-crystalline arom. polymer which is treatable from melt and has at least one trifunctional triazine unit of the formula.