Natural abundance NMR methods were employed to analyze static and dyna
mic properties of poly(p-benzamide), the parent compound of the aramid
e family of polymers, dissolved in absolute sulfuric acid. Quantitativ
e determinations of order in the liquid crystal phases arising in thes
e systems were carried out with the aid of bidimensional C-13 NMR data
collected in the solid phase and of total line shape simulations, and
the parameters thus obtained were monitored as a function of temperat
ure, concentration, and polymer molecular weight. These measurements r
evealed that by contrast to what had been inferred from previous macro
scopic order determinations, the alignment of polymer molecules in the
ir nematic domains is essentially independent of temperature. Existing
measurements can still be explained in terms of a temperature-depende
nt isotropic reversible arrow nematic equilibrium, whose presence and
thermodynamics were unambiguously characterized by NMR. Dynamic aspect
s of this interphase equilibrium as well as of the intraphase molecula
r diffusion in the nematic region were explored by bidimensional and p
ulsed-gradient NMR methods. Spectroscopic results were analyzed in ter
ms of thermal and athermal theories predicting the appearance of nemat
ic phases in rigid anisometric polymers and compared with recent NMR o
bservation on other lyotropic aramide solutions.