Pervaporation properties to aromatic/non-aromatic hydrocarbon mixtures of cross-linked membranes of copoly(methacrylates) with pendant phosphate and carbamoylphosphonate groups

A series of copoly(methacrylates) with pendant phosphate and carbamoylphosphonate groups were synthesized. The copolymer membranes were cross-linked by the chemical reaction of either ethylene glycol diglycidyl ether (EGDE) or toluene diisocyanate with hydroxyl or secondary amine groups in copolymer segments at 423 K. Pervaporation (PV) and sorption of aromatic/non-aromatic hydrocarbon mixtures for the membranes were investigated. The membranes were in rubbery state and preferentially permeable to aromatics. The membranes cross-linked with flexible EGDE residues and having diethyl phosphate and/or carbamoylphosphonate groups displayed higher PV performance to benzene/n-hexane (Bz/Hx) mixtures with excellent durability. They had lower specific permeation flux and higher PV selectivity αPV, compared with poly(ethylene oxide imide) segmented block copolymer membranes. The higher αPV was due to a small, but positive contribution of diffusivity selectivity as well as reasonably high solubility selectivity. The lower specific permeation flux was due mainly to the lower diffusion coefficient. This diffusion behavior can be explained by dense polymer-chain packing due to the hydrogen bonding between carbonyl and hydroxyl groups of polymer side-chain as well as relatively high cross-linking density. Sorption isotherms of Bz/Hx mixtures could be represented by the Flory–Rehner model, but the model overpredicted the sorption amounts of Hx, leading to a little small predictions of solubility selectivity.