AbstractPolyimides with different proportions ofm‐phenylene andp‐phenylene (orp,p′‐biphenylene) were prepared by polymerizing different molar ratios ofm‐phenylene diamine andp‐phenylene diamine (orp,p′‐diaminobiphenyl) with pyromellitic dianhydride in dimethylformamide at 0°C. Chemical cyclodehydration of polyamic acids resulted in the corresponding polyimides. Polymers were characterized by infrared (IR), viscosity, and density measurements. Viscosity and density of polymers decreased with an increase onm‐phenylene groups in the backbone. The thermal and thermooxidative stabilities were investigated by dynamic thermogravimetry. Stability decreased whenm‐phenylene groups were introd