2',6',3''',5'''-Tetraphenyl- or tetra(4-biphenylyl)-4,4-''''-diamino-p-quinquephenyls were synthesized from the corresponding pyrylium salts. Using them as starting materials, rigid-rod polyamides and polyimides containing phenyl or 4-biphenylyl side groups on the p-quinquephenyl segments of the backbone were prepared. They were characterized by inherent viscosity, elemental analysis, H-1-NMR, C-13-NMR, X-ray analysis, differential scanning calorimetry, thermomechanical analysis, thermogravimetric analysis, isothermal gravimetric analysis, and water uptake measurements. The polymers with 4-biphenylyl pendent groups showed an enhanced solubility, lower crystallinity and hydrophilicity, and higher thermal stability in comparison to the corresponding polymers with phenyl pendent groups. Polyamides displayed strong blue fluorescence in the DMF solution. The polyamide containing 4-biphenylyl pendent groups possessed a well-defined chromophore, resulting from steric interactions in the polymer chain.