This invention discloses a class of soluble poly(arylene-oxadiazole) polymers and copolymers comprising at least 20 repeat units, which may be the same or different, represented by the formula: ##STR00001## wherein Arom can be a fluorene group, an aromatic hydrocarbon ring, an aromatic C.sub.2+ heterocyclic ring, or two aromatic rings linked by a single bond, ethenyl bond, or ethynyl bond. A process for preparing the polymers and copolymers by reacting dicarboxylic acids and hydrazine salt is provided. The polymers are useful in electroluminescent devices, photovoltaic cells, and diodes.