Two LiTFSI-based monomers were considered for this work comprised of either a methacrylate or a styrene functional group (LiMTFSI or LiSTFSI). Three different co-monomers were explored based on their structural features, namely a short sidechain methyl methacrylate (MMA) monomer, a longer sidechain butyl methacrylate (BMA) monomer and a bulkier and hydrophobic alkyl sidechain isobornyl methacrylate (IBMA) (Scheme 1). Ethylene glycol dimethylacrylate (EGDMA) was employed as a crosslinker at 2.5 wt% with respect to the total monomer composition in order to assess the ease of handling and the water uptake properties of the CEMs. The monomers, crosslinker and photoinitiator were dissolved in a small amount of ethanol and exposed to UV-light radiation for 300 seconds. This UV curing process results in the quantitative random copolymerisation of the co-monomers to obtain a fully solid CEM. The different lengths and geometries of the alkyl chains confers the monomers with different mechanical and chemical properties, which we expect to be imparted onto the final CEM to some degree. For instance, the MMA was expected to increase the robustness of the membrane due to the high Tg of the homopolymer while maintaining some hydrophilicity for water uptake. BMA can increase the flexibility of the membrane due to the lower Tg, while water uptake could be reduced due to the longer and thus more hydrophobic alkyl chain. In the case of the IBMA monomer, a biobased monomer, the larger number of methyl groups and resultant steric effects around the methacrylate group can further reduce the water uptake of the membrane. IBMA homopolymers present a very high Tg which should further contribute to increasing the rigidity of the membrane. Lastly, EGDMA was used as a dimethacrylate polymeric chain crosslinker to form a more robust solid membrane with sufficient mechanical strength as well as to reduce membrane swelling. To understand the interplay between the different components and their overall effect on the CEM properties, a number of combinations were prepared as summarised in Error! Reference source not found..