Polyethylene glycol penetration into clay films: real time experiments

The real time uptake of polyethylene glycol (PEG) into montmorillonite thin films is tracked by absorbance and clay-modified electrodes. The data indicate that there is a discontinuity in behavior observed between 600 and 1600 PEG related to the size of the PEG as compared to the interlayer dimensions within the clay film. Lower molecular weight PEG penetrate rapidly with little impact on co-diffusing probe molecules. At later times, the PEG slows penetration of the co-diffusing probe. Larger molecular weight PEG penetrate more slowly at all stages. In the initial stage the higher molecular weight species tend to disrupt the clay films, accelerating penetration of the co-diffusing probe molecule. Decrease in diffusion of the co-diffusing probe molecule is related to the formation of PEG domains within the interlayer region of the clay.