Two novel unsymmetric diamine isomers, 6-amino-2-(4-(4-aminophenoxy)phenyl)-1H-benzimidazole (3p) and 6-amino-2-(3-(4-aminophenoxy)phenyl)-1H-benzimidazole (3 m), were synthesized and employed to react with several aromatic dianhydrides to yield two new series of poly (benzimidazole imide)s (PBIPIs), PI-4 (a-e) and PI-5 (c-e) through two-step and one step polymerization method, respectively. The effect of chain isomerism on molecular packing and physical properties of PBIPIs is investigated. Both series exhibited excellent thermal stability (T-5%= 503-559 degrees C), high T-g values (276 -383 degrees C) and good mechanical properties (tensile strengths of 98-151 MPa and tensile moduli of 3.5 -5.2 GPa). The PI-5 (c-e) showed high solubility compared to PI-4 (a-e) series. Such improved solubility attributed to the flexible ether connecting groups with non-coplanarity. Furthermore, controlled molecular weight (Mw) polymer PI-5e-PA derived from 3 m, demonstrated good solution and melt processability. (C) 2018 Published by Elsevier Ltd.