Membranes with a 1:1 ratio of LiMTFSI to co-monomer and 2.5 wt% EDGMA crosslinker were used to assess the alkyl co-monomer effect on the formation of solid membranes; with different degrees of flexibility (see entries 1, 2 and 5 in Table ). As expected, MMA produced hard and brittle membranes with low flexibility, while BMA produced very flexible/ductile membranes (Figure ). On the other hand, using IBMA co-monomer resulted surprisingly in relatively stretchy membranes, with flexibility between the hard MMA-containing membranes and the very flexible BMA-containing membranes (Figure ). In this way, IBMA was chosen to copolymerise the LiTFSI-based monomers and evaluate their behaviour, according also to the percentage of crosslinker employed, regarding one of the most important properties when electrodialysis evaluation is needed: water uptake.