USE OF MAGNETIC-RESONANCE-IMAGING TO STUDY TRANSPORT OF METHANOL IN POLY(METHYL METHACRYLATE) AT VARIABLE-TEMPERATURE

The transport kinetics of methanol in PMMA have been studied over the temperature range 25-60 degrees C, using magnetic resonance imaging. I t is shown that transport behavior changes from being relaxation contr olled (Case II) at the lowest temperature to approaching Fickian behav ior at the higher temperatures. It is also shown that the change of th e exponent of time, n, describing the methanol uptake, with the swelli ng temperature can be compared with a change of the mechanical behavio r of the polymer matrix in the presence of the penetrant. From DSC and DMA measurements, it can be concluded that the transition from Case I I toward Fickian diffusion takes place at a temperature around the eff ective T-g of the imbibed material.