Transient techniques in NMR of H-1 and C-13 were used to study the chemical and physical structures of solid poly(p-phenylene) (PPP), poly(2,6-dimethyl-p-phenylene oxide) (PDMPO), poly(p-phenylene sulfide) (PPS), poly(p-biphenylene sulfide) (PPBS), poly(p-phenylene selenide) (PPSe), poly(p-biphenylene selenide) (PPBSe), poly(2,5-thienylene) (PT), poly (3-methyl-2,5-thienylene) (PMT), and poly (p-phenylene-co-2,5-thienylene) (PPPT) of different monomer ratios. C-13 NMR confirmed the expected chemical structure for homopolymers, and indicated a random distribution of monomer units in PPPT. Relative fractions of crystalline and interfacial regions were determined by measurements of H-1 magnetic relaxation, C-13 CP/MAS NMR, and XRD. (c) 1994 John Wiley & Sons, Inc.