SELF-DIFFUSION OF OLIGO(ETHYLENE GLYCOL)S AND POLY(ETHYLENE GLYCOL)S IN POLY(VINYL ALCOHOL) AQUEOUS-SOLUTIONS AS STUDIED BY PULSED-GRADIENTNMR-SPECTROSCOPY

We have measured the self-diffusion coefficients of a series of solute probes, including ethylene glycol and its oligomers and polymers in a queous solutions and gels of poly(vinyl alcohol) (PVA) using the pulse d-gradient spin-echo NMR techniques. In an effort to link the diffusio n properties of small and large molecules in polymer systems, we have selected this group of diffusant probes with various molecular weights , ranging from 62 to 4000. The self diffusion coefficients of the solu te probes decrease with increasing PVA concentrations (from 0 to 0.38 g/mL) and with increasing molecular size of the probes. The temperatur e dependence of the self-diffusion coefficients has also been studied for ethylene glycol and poly(ethylene glycol)s of molecular weights 60 0 and 2000. Energy barriers of 30.0, 36.5, and 39.0 kJ/mol have been c alculated respectively for the probes, in the temperature range 23-53 degrees C. The experimental data are used to fit a new physical model of diffusion (Petit et al. Macromolecules, 1996, 29, 6031), which is s hown to be successful in describing the effects of polymer concentrati on, temperature, and molecular size of the diffusants on the self-diff usion coefficients of small and large molecular probes in the polymer system.