Interestingly, the water uptake for all membranes based on LiSTFSI:IBMA is higher than the LiMTFSI co-monomer analogues in the studied parameter ranges (Figure ). This observation is counterintuitive to a prediction based on the polarity of the styrene and methacrylate groups, with a higher dipole moment expected for the latter and hence a stronger interaction with water. However, π-π interactions between the styrene rings could lead to the clustering of interacting styrene moieties, with aggregated LiSTFSI groups facilitating water uptake in these aggregates, with less hydrophobic alkyl monomers nearby affecting the interactions with water molecules.