Phase behaviour and solvent diffusion in the system poly(methyl methacrylate)/methanol

The diffusion of methanol into atactic poly(-methyl methacrylate) is contro lled by the interference of the demixing curve with the concentration depen dence of the glass transition. Below the temperature of intersection of the two curves, the sample is always in the glassy state and diffusion is of c ase II. Above this temperature, absorption of methanol brings the sample th rough the glassy state into the solution state. With increasing temperature , diffusion changes from case II into Fickian. The maximum degree of absorp tion is determined by the position of the demixing curve in the temperature -concentration plane.