Successive sorption runs of n-hexane vapor in supported amorphous poly(dimethyl silamethylene) films at 25degreesC are presented and discussed. Deviations from Fickian sorption kinetics were observed, and they were more distinct in the as-prepared films and in the lower n-hexane vapor pressure runs. Polymer films, gamma-irradiated to produce various degrees of crosslinking, exhibited closer conformity to Fickian sorption kinetics and enhanced diffusivity of n-hexane vapor. These results were consistent with the presence in the as-prepared polymer of some labile structural order (undetectable by differential scanning calorimetry or X-ray diffraction), which tended to be eliminated by radiation-induced crosslinking or strong swelling. (C) 2004 Wiley Periodicals, Inc.