Cross-linked polymer-ionic liquid composite materials

A series of composites, some with permanent porosity, comprising polymers and ionic liquids have been prepared by in-situ polymerization. The characteristics of both composites and isolated polymers have been investigated. Slow mass and phase transfer characterize the interaction with a range of polymers (1-17) in the NN-dialkylimidazolium ionic liquids, [emim]BF4, [bmim]PF6, or [omim]N(SO2CF3)(2). Freeradical homopolymerization of 1-vinyl-2-pyrrolidinone in [bmimlPF(6) or of 4-vinylpyridine in [omim]N(SO2CF3)(2) gave viscous solutions from which polymer (M-w = 162 500 and 71 500 g mol(-1), respectively) could be isolated. Detectable ionic liquid residues were retained in the isolated polymers despite five reprecipitations from methanol. Copolymerization of 4-vinylpyridine (VP) with > 5% divinylbenzene (DVB) or trimethylolpropane trimethacrylate (TRIM) in [omim]N(SO2CF3)(2), and hornopolymerizations of the cross-linking monomers on their own, led with 90-100% monomer conversion to a series of gel-like composite materials, B-H, from which cross-linked polymers, B'-H', could be isolated by Soxhlet extraction of the ionic liquid. Copolymers of VP with 5-30% DVB (E', F) showed a low degree of permanent porosity in the dry state. However, poly(DVB) (G') and poly(TRIM) (H') have bulk densities (<0.6 g cm(-3)), intrusion volumes (>0.9 cm(3) g(-1)), BET surface areas (70-320 m(2) g(-1)), and morphology (from SEM studies) which demonstrate the porogenic character of the ionic liquids used. Comparisons with the related products I and J obtained in toluene reveal the sensitivity of these systems both to the properties of the porogen solvent and to the monomer used.