in this article a new synthesis of 3,3'-diaminobiphenyl (3,3'-DABP) is described, along with the preparation and characterization of polyamides and polyimides based on it. Reactivity of this monomer was calculated by a molecular simulation study, using ab initio quantum-mechanical methods. Terephthaloyl and isophthaloyl chloride were used for the synthesis of polyamides, while 3,3',4,4'-biphenylenetetracarboxylic acid dianhydride and 4,4'-(hexfluoroisopropylidene) diphthalic anhydride were used far the synthesis of polyimides. Medium to high molecular weight polymers were attained, with inherent viscosities near or higher than 1.0 dL/g, the solubility of the 3,3'-DABP polymers was much better than that of the homologous polymers from benzidine (4,4'-DABP), the glass-transition temperatures were lower, by about 40 degrees C, and the thermal resistance, as measured by thermogravimetry, was virtually the same. Amorphous films, made from cast polymer solutions, showed excellent mechanical properties, comparable to conventional aromatic polyamides and polyimides. Theoretical calculations demonstrated that the radius of giration, end-to-end distance and density of poly(3,3'-DABP-isophthalamide) were lower than those of poly(4,4'-DABP-isophthalamide), as a consequence of the chain folding induced in the backbone by the m-substitution in 3,3'-DABP.