NUCLEAR-MAGNETIC-RESONANCE OBSERVATION OF CYCLOHEXANE SELF-DIFFUSION IN CONCENTRATED POLYBUTADIENE SOLUTIONS

The coefficient of self-diffusion of cyclohexane, in concentrated solu tions of polybutadiene, was measured using a pulsed magnetic field gra dient method. The polymer volume fraction was varied from 0.2 to 0.95, and the temperature range of observation was 260 K < T < 335 K. The c oncentration and temperature dependences of the solvent self-diffusion were analyzed according to a free volume description. These two depen dences were found to be well described by using either the Fujita or W LF equations or by applying the Vrentas-Duda model. The size of the po lymer jumping unit, derived from the Vrentas-Duda approach, was determ ined.