Transport and physicochemical parameters of polypentenamer

Physicochemical properties of a cis-polypentenamer—a hydrocarbon polymer with a low glass transition temperature (T g = 168.8 K)—have been studied. Measurements of permeability coefficients P in rubbery material for a wide range of gases (He, H2, O2, N2, CO2, CH4, C2H6, C3H8, and n-C4H10) indicate a high permeability of this polymer for which the values of P are only slightly lower than those of the most permeable rubber—poly(dimethylsiloxane). The method of inverse gas chromatography has been employed to estimate solubility coefficients S for n alkanes C3–C10 and cycloalkanes in cis-polypentenamer in the range from 25 to 150°C. It has been shown that the solubility coefficients linearly increase in lnS-T cr 2 coordinates, where T cr is the critical temperature of a solute. In terms of the above correlation, the solubility coefficients of light gases have been estimated and the diffusion coefficients D of gases in the same polymer have been calculated via the formula P=DS. The free volume in cis-polypentenamer has been studied by positron annihilation lifetime spectroscopy. The temperature dependence of the positronium lifetime τ 3 that characterizes the size of the free volume element in a polymer demonstrates saturation at temperatures above 250 K. This effect is probably related to a rapid migration of fluctuation holes in the rubbery polymer at temperatures remote enough from its glass transition temperature.