Sorption and transport of hydrocarbons and alcohols in addition-type poly(trimethyl silyl norbornene). I: Experimental data

Abstract

The sorption and transport properties of n-alkane and alkyl-alcohol vapors in addition-type poly(trimethyl silyl norbornene) (PTMSN) were studied at 35 °C and at various activity values. PTMSN is a high free volume polymer that shows very high solubility to the condensable vapors and can be considered a promising material for several applications, such as gas/vapor membrane separations. Sorption and diffusion experiments with n-alkanes ( n-C 4, n-C 5, n-C 6) and alkyl alcohols (CH 3OH, C 2H 5OH, n-C 3H 7OH) were performed as well as dilation measurements with n-C 5 and n-C 6, at 35 °C. The behavior of the alcohol vapors differs from that of alkanes, mainly for the shape of the solubility, diffusivity and mobility isotherms: this phenomenon, as well as the diffusion trend of the different vapors, was explained by the different interactions between the penetrants and the hydrocarbon-based polymer. The permeability isotherms were also estimated from solubility and diffusivity data, showing that the permeability of PTMSN lies in between those of AF2400 and PTMSP. Finally, the dependence of the transport parameters of n-alkanes in PTMSN on penetrant pressure and molecular weight was analyzed, and compared to that observed in other high free volume glassy polymers. The activity-based solubility coefficients as well as permeabilities of alkanes in PTMSN show a weak dependence on molecular weight, while in PTMSP permeability increases and in AF2400 decreases with increasing the number of carbon atoms.