Self-diffusion studies in polymer-solvent systems by pulsed-gradient spin-echo nuclear magnetic resonance

Pulsed gradient NMR techniques have been used to study self-diffusion in polymer solutions. The systems studied include toluene, cyclohexane, ethylbenzene, chloroform, t-butyl acetate, and methyl ethyl ketone in polystyrene; methyl methacrylate in poly(methyl methacrylate); poly(ethylene oxide) in water; and water in biological tissue. The polymer diffusion data are evaluated in terms of scaling theory as they relate to the scaling of the polymer diffusion coefficient with molecular weight. The solvent diffusion data are evaluated with kinetic and free-volume theories. In addition a relatively simple dependence of diffusion coefficient on polymer volume fraction is derived from free-volume theory. The solvent diffusion data are employed in a model which simulated the drying of a coating by solvent evaporation. Solvent volatility is determined from solvent activity at the surface. Diffusion within the film is handled by the solution of Fick\u27s second Law by the Crank-Nickolson implicit method. Without using any adjustable parameters the model can do an excellent job of predicting the drying curves for a good solvent-polymer two component system. The model is less successful with poorer solvents --Abstract, page iii