1,3,5-TRIISOPROPYLBENZENE DIFFUSION IN POLYSTYRENE SOLUTIONS

Self-diffusion coefficients of 1,3,5-triisopropylbenzene (TIB) in bina ry solutions with poly styrene and ternary mixtures comprised of TIB, toluene, and polystyrene have been measured by static gradient nuclear magnetic resonance (SG-NMR) techniques. These data, as well as mutual -diffusion coefficient data measured by capillary column inverse gas c hromatography (CCIGC), have been analyzed here with the Vrentas-Duda f ree-volume diffusion model. Although both binary and ternary diffusion coefficient data can be accurately correlated with the model, the res ults contradict those of an earlier investigation, which suggested tha t TIE diffuses as a single unit in polystyrene solutions. The new data suggest that either: 1) TIE diffuses by piece-wise displacements in p olystyrene solutions, or 2) a diffusive activation energy ceiling valu e has been reached. The implications of both possibilities are discuss ed in the context of established free-volume principles. (C) 1996 John Wiley & Sons, Inc.