NMR study of molecular motion in solid and molten polystyrene: Application of the deuteron dilution technique

The proton spin‐lattice relaxation time T 1 was determined at 13,8, 55,2, and 90 MHz in polystyrene (PS‐ d 0 ) and polystyrene deuterated at the chain (PS‐ d 3 ) and the phenyl groups (PS‐ d 5 ), respectively, at temperatures between −130 and +230°C. Furthermore, T 1 was measured in isotopic mixtures of PS‐ d 3 and fully deuterated PS‐ d 8 where a separation into intramolecular and intermolecular contributions was possible through the deuteron dilution technique. Above 130°C, various distributions of correlation times provide a semiquantitative understanding of the different motins seen by the protons of the partially deuterated systems. Rotating frame relaxation times in PS‐ d 3 and PS‐ d 5 reveal librational motions in the solid glass (below 100°) where the amplitudes of the phenyl group librations are much larger than those of the chain oscillations, but the correlation times are of the same order of magnitude.