DIFFUSION OF SIMPLE LIQUIDS IN POROUS SOL-GEL GLASS

Diffusion coefficients of selected solvents (acetone, acetonitrile, chloroform, cyclohexane, toluene, water) in porous sol-gel glass were measured using the radioactive tracer diffusion method and the diaphragm technique. The concentrations of the solvents were determined using IR and scintillation measurements. Selected samples had their internal surface modified by replacing hydroxyl groups with trimethylsilane groups. It was shown that molecular translational motion inside the pores is hindered by pure geometrical restrictions and surface interactions. It was found that polar molecules diffuse faster than inert molecules. Experimental results were explained in terms of the model developed by Korb et al. Results obtained for cyclohexane were compared with molecular dynamics computer simulations, and the tortuosity factor was evaluated. The diffusion coefficient for acetone within the pores was studied over the temperature range 284-315 K, and the activation energy was determined.