The viscous behaviour and optical properties of poly (-p-phenylene terephthala-mide) (PPTA) in pure sulfufic acid solution have been studied at varied temperatures and concentrations by Hoppler rheometer

depolarized light transmission and small angle light scattering methods. The anisotropic solution of PPTA shows nema-tic as well as cholesteric mesophase characteristics at different temperatures. This means that the liquid crystals of aromatic polyamides possess similar mesophase transition as the low molecular compounds do. Liquid crystals of PPTA in sulfuric acid solution is changed from nematic at lower temperature to cholesteric mesophase at higher temperature. This change does not take place directly from nematic to cho-lesteric and is essentially a monotropic one.