4,3’-Diamino-3,5-diphenyl-biphenyl and 4-amino-4’-carboxy 3,5-diphenyl-biphenyl were synthesized from the corresponding pyrylium slats. A novel class of rigid-rod polyamides and polyimides containing phenyl pendent groups were synthesized and characterized by viscosities, elemental analyses, H-1 n.m.r., C-13 n.m.r., X-ray, t.m.a., t.g.a. and isothermal gravimetric analysis. They were amorphous or semicrystalline and dissolved in polar aprotic solvents and certain other solvents. Some of the polymers showed T-g at 225-256 degrees C. The polymers were stable up to 375-426 degrees C in N-2 and 336-376 degrees C in air and afforded anaerobic char yields of 59-79% at 800 degrees C.