Dielectric relaxations in polymers with pendent phenyl or pyridine groups at temperatures from 4°K to 80°K

Isochronal measurements of dielectric loss are made for polystyrene (PS), poly(4‐vinyl pyridine) (P4VP), poly(2‐vinyl pyridine) (P2VP), poly(L‐phenylalanine) (PLPA), and poly(γ‐benzyl‐L‐glutamate) (PBLG) at temperatures ranging from 4°K to 80°K and at frequencies from 10 Hz to 100 kHz. PS, P4VP, and PLPA show loss peaks around 50°K (10 kHz) while P2VP exhibits a loss peak around 20°K (10 kHz). PBLG has no detectable peak in this temperature range. The 50°K and 20°K peaks are ascribed to wagging and rotation, respectively, of phenyl or pyridine groups between two energy minima. The barrier height and energy difference between the minima evaluated from the experimental data are reasonably explained by assuming that the double minima are caused by interaction between a pair of phenyl or pyridine groups, each belonging to adjacent chains which pack irregularly.