A new prediction method for organic liquids sorption into polymers

Abstract

A new prediction method for sorption of low-molecular organic liquids (non-solvents) in polymers is presented. It was derived from the gravimetric data for sorption of linear and cyclic alkanes, aromatics and alcohols into various kinds of polymers (glassy polystyrene, rubbery polydimethylsiloxane, semicrystalline low-density polyethylene, ion exchange Nafion, and copolymeric poly(styrene–butadiene–styrene) in temperature range 5–50°C. Our method is based on a normalised function φQ(t) evaluated from series of the equilibrium mass swelling degrees Qm of a model liquid in one polymer at each temperature from the indicated temperature interval to the corresponding Qm at the highest temperature of this interval. A knowledge of the proper function φQ(t) for given polymer enables to predict a sorption of any other liquid with the same properties or interactions with given polymer in given temperature range just from a knowledge of a single experimental Qm value at any temperature from the indicated temperature interval. The steepest temperature dependent normalised function φQ(t) exhibited LDPE+liquid systems. Contrarily, PDMS+liquid systems were practically temperature independent. The thermodynamic analysis of the sorption process in studied polymer–liquid systems comprised evaluation of the appropriate values of the sorption enthalpy ΔsH and the sorption entropy ΔsS. The values of the resulting Gibbs energy of sorption ΔsG were negative in all cases and thus confirmed the spontaneity of liquids sorption in polymers over the whole temperature range.