Polycondensation reaction was carried out for synthesizing rigid-rod polymer hPBI. Various molar ratios (50:1, 25:1, and 15:1) of 2-hydroterephthalic acid and 5-hydroisophthalic acid were also introduced in the synthesis for articulated rigid-rod polymer a-hPBI. The polymers were further derivatized with 1,3-propanesulton for pendants of lithium ionomer to become water soluble polyelectrolytes hPBI-PS(Li+) and a-hPBI-PS(Li+), respectively. Lithium salt doped cast film of the rigid-rod polyelectrolyte hPBI-PS(Li+) showed a room-temperature DC conductivity parallel to film surface as high as 4.02¡Ñ10-3 S/cm. Molecular weight of the rigid-rod polyelectrolyte was low indicating a small molecular aspect ratio. In cast film, the molecules were randomly distributed and highly isotropic facilitated Li cations mobility for a high film conductivity. The conductivity was also insensitive to the anion of lithium salt. No apparent layered structure was revealed by scanning electron microscope suggesting that the cast films had near three-dimensionally isotropic structure and conductivity.