Surface polarity of porous polymers at different coverages

Abstract

ABSTRACTAt different surface coverages (θs), the dispersion component (ΔFdisp) and specific components (induction and orientation interactions; ΔFio and donor‐acceptor interactions; ΔFda) of the sorption free energy and the polarities were calculated for three porous polymers: the microporous styrene–divinylbenzene copolymer Dowex L‐285, the microporous hypercrosslinked polystyrene MN‐200, and the macroporous styrene–divinylbenzene copolymer Polysorb‐1. Two methods were used to calculate ΔFdisp, ΔFio and ΔFda: the linear free energy relationship method and the Dong polarization method. For styrene–divinylbenzene sorbents, ΔFdisp decreased with θ, whereas ΔFio and ΔFda increased; this caused the polarity to rise. This phenomenon was caused by the sorbat–sorbat lateral interactions on the polymer's surface; these were stronger for polar molecules. In the case of hypercrosslinked polystyrene, ΔFdisp and ΔFio varied equally, and the polarity was almost constant. This trend could be explained by the absorption of the molecules into the bulk of the polymer; this prevented lateral interactions. We concluded that the lateral interactions were a function of the porous polymer's surface properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44146.