Membranes containing polymerized ionic liquid for use in gas separation

A dense poly(ionic liquid)-based membrane suitable for gas separation obtainable by copolymerization via UV-curing of a mixture comprising:

• a) 10 to 50 wt %, of a IL monomer trialkyl[(4-vinylphenyl)alkyl]phosphonium with X− as counterion ([TAVPAP]X) of the following formula:
• wherein each R represents an alkyl chain having 3 to 20 carbon atoms, L represents a linker consisting of a simple alkanediyl C1-C20 chain, or an ethereal chain containing 1-20 carbon atoms and 1-10 oxygen atoms, and X− represents an anion selected from the group consisting of:
• BF4−, PF6−, SbF6−, TsO−, CF3—SO3−, NC—N−—CN, (MeO)2PO2−, EtSO4− or F3CO2SN−—SO2CF3
• b) 30 to 70% wt % of one or more ethylenically unsaturated co-monomers;
• c) 1 to 35 wt % of a surfactant;
• d) 0.5-20% wt %, of one or more cross-linkers,
• e) 0.001 to 5 wt % of a photo-initiator;
• f) the remainder of the mixture being water.