Experimental and theoretical studies on the permeation of argon through matrices of acrylic polymers containing 1,3-dioxane groups in their structure

摘要

The permeation of argon gas through membranes of poly(cis/trans 2-phenyl-5-ethyl-5-acryloxymethyl-1,3-dioxacyclohexane) (PAEDP) has been measured in the vicinity of the glass transition temperature of this polymer (approx T_g approx= 50 deg C). Both the permeation and the diffusion coefficients show only a slight dependence on temperature while the membrane remains in glassy state, but exhibit a sharp increase with temperature in the rubbery state. Theoretical calculations of the diffusion coefficient were performed according to the transition-state approach, i.e., assuming that the diffusant path is independent of the structural relaxation in the polymeric matrix, as a function of the smearing factor #DELTA# and temperature. Reasonably good agreement among theoretical and experimental values of the diffusion coefficient was obtained. Theoretical calculations were also performed for poly(cis/trans 2-phenyl-5-ethyl-5-methacryloxymethyl-1,3-dioxacyclohexane) (PMAEDP), the methacrylate analog of PAEDP, which indicate that the diffusion coefficient of glassy PMAEDP is lower than that of glassy PAEDP when the same temperature is taken as the basis of comparison, due to the higher values of T_g in methacrylate than in acrylate polymers which, in turn is a consequence of the rigidity conferred to the polymeric chain by the methyl group.