Abstract: Novel aromatic polymers containing a nitrogen-containing ring group which comprises at least 30 mol% of a recurring unit of the formula ##STR1## Preferably,, the nitrogen-containing ring group ##STR2## is a benzimidazolone, benzimidazolthione, benzimidazole, quinoxalidinedione, benzotriazole, benzothiazolidine, benzothiadiazolidine-S-oxide, benzothiadiazolidine-S-dioxide, benzodithiadiazine, benzodiazophosphole-p-oxide, benzodiazophosphole, benzodiazosilole, or benzodiazoborole ring.These polymers are soluble in various polar solvents. They find a wide range of applications ascribable to these ring groups, for example, as thermally stable resins and permselective membranes. These polymers can be prepared by reacting substantially linear aromatic polymers comprising at least 30 mol% of a recurring unit of the formula ##STR3## with reagents capable of forming 5- or 6-membered nitrogen-containing rings.

Abstract: Novel aromatic imine polymers containing as at least a part of its entire recurring units an aromatic imino group ##STR1## wherein .phi. is an aromatic ring group having a valence of at least two and has at least one electron-attracting group with respect to the group ##STR2## and R.sub.1 is a hydrogen atom or a non-aromatic hydrocarbon residue having a valence of at least 1. These polymers find a wide variety of applications by utilizing their thermal stability and various other desirable properties such as reducibility or photosensitivity. The polymers are prepared by reacting specific aromatic dihalogen compound with specific difunctional amino-containing compounds in an inert organic solvent in the presence of an acid acceptor. Copolymers can be obtained by carrying out the reaction using specific difunctional comonomers.