Impact of comonomer chemistry on phase behavior of polymerizable lyotropic ionic liquid crystals: a pre- and post-polymerization study

The design and characterization of polymerizable lyotropic ionic liquid crystals with an intact alkyl chain bilayer are described. The bilayer is left intact to enable further inclusion of peptide-based channels to mimic biological protein membranes for potential separation applications. Impact of comonomer concentration and chemistry on the mesophase formed pre- and post-polymerization is characterized. An optimum comonomer concentration of 20 wt% is found for the poly(ethylene glycol) diacrylate (PEGDA) system, before full disruption of the discontinuous cubic phase occurs. Little impact on the discontinuous cubic phase is observed by varying comonomer chemistry from PEGDA to either poly(ethylene glycol) dimethacrylate or 2-hydroxyethyl acrylate, with exception of variation in the thermal stability of the resulting mesophase. Surprisingly, the use of 2-hydroxyethyl methacrylate as comonomer results in formation of the 2D hexagonal phase, which is of interest for the design of biological protein membranes. Unfortunately, mesostructure retention is not observed in any systems studied. A sequence of structural changes, modeled as a change from a spherical micelle to a cylindrical micelle, and to finally a lamellar architecture, is rather observed using in situ small-angle X-ray scattering polymerization measurements, suggesting a reduction of the headgroup area, likely caused by cross-linking of the acrylate moiety.