KINETICS OF DIFFUSION OF WATER AND DIMETHYLMETHYLPHOSPHONATE THROUGH POLY(DIMETHYLSILOXANE) MEMBRANE USING COATED QUARTZ PIEZOELECTRIC SENSOR

The mass sensing principle of quartz crystal has successfully been emp loyed to study the diffusion of dimethylmethylphosphonate (DMMP) and w ater through a poly( dimethylsiloxane) (PDMS) membrane. For this study a new permeation cell has been fabricated which houses a Cu(II) butyr ate ethylenediamine-coated quartz crystal sensor. This development was motivated by the desire to measure the diffusion coefficients rapidly , precisely, and at different temperatures. Temperature dependence dif fusion coefficients of DMMP and water are also evaluated using the sam e cell, which enables calculation of the activation energies for the d iffusion process. From the diffusion and solubility data permeability coefficients of DMMP and water have been calculated. It is observed th at PDMS membrane offers a selectivity for DMMP over water roughly by 1 3 : 1 (i.e., P-DMMP/P-water > 13). (C) 1997 John Wiley & Sons, Inc.