Abstract: This invention discloses a unique process for the preparation of N-substituted phenyl polybenzimidazole polymers from unsubstituted polybenzimidazole polymers. An unsubstituted polybenzimidazole polymer is first reacted with an alkali hydride to produce a polybenzimidazole anion which is then reacted with a substituted or an unsubstituted phenyl fluoride to produce N-substituted phenyl polybenzimidazole polymer. The N-substituted phenyl polybenzimidazole polymer produced by this process can be formed into a wide range of products, such as membranes, films resins or fibers. The produce can be designed to meet special applications by the choice of the substitutent. These N-substituted phenyl polybenzimidazole polymers can be utilized for numerous applications including reverse osmosis, ultrafiltration, microfiltration, electrodialysis, ion exchange and affinity chromatography.