PURPOSE: To prepare the titled polymer having excellent mechanical strength, heat resistance, electrical properties, and dimensional stability, by reacting an aromatic dicarboxylic acid dihalide with an aromatic ether in the presence of a Lewis acid using an aprotic organic solvent.

CONSTITUTION: An aromatic dicarboxylic acid dihalide of formula I (where R1W R8 each represents H, a halogen, a hydrocarbon radical, or an alkoxy; n is 1W5; X is a halogen) (e.g. diphenyl ether-4,4'-dicarboxylic acid dichloride) is reacted with an aromatic polyether of formula II (where R9WR22 are the same as R1W R8; m is 0W5) (e.g. diphenyl ether) in the presence of a Lewis acid (e.g. AlCl3) using an aprotic organic solvent (e.g. ethylene chloride). A polymer of high polymerization degree having excellent mechanical strength such as tensile and flexural strength, heat resistance, thermal decomposition temperature, electrical properties, and dimensional stability, and low moisture and water absorption, can be prepared under such mild conditions as -10W150°C. It may be used in the form of tilms, molding articles, and fibers.