The effect of high pressure on 2H n.m.r, spin relaxation in polystyrene is studied. Deuteron spin-lattice relaxation behaves non-exponentially both in chain- and ring-deuterated polystyrene at temperatures up to 20 K above the glass transition. The non-exponentiality is caused by the broad distribution of correlation times and the slowness of the spin diffusion process. The fast flipping phenyl rings are an effective relaxation mechanism both for the chain and for the phenyl deuterons. The distribution of correlation times is either due to a heterogeneity of local environments or to a change in time-scale of the motion over long time intervals. Denser packing of the polymer caused by high pressure results in a decrease in the spin-lattice relaxation time. The apparent transverse relaxation time can be used as a monitor of the glass transition.
Посилання на статтю:
2H n.m.r, study of high pressure effects on the molecular dynamics in polystyrene: 3. Spin relaxation studies / A. S. Kulik* and K. O. Prins // Polymer. – 1993. – Vol 34. – P. 4642-4648.