In situ photopolymerization of a gel ionic liquid electrolyte in the presence of iodine and its use in dye sensitized solar cells

We report for the first time an in situ photopolymerization of model co-monomers, 2-hydroxyethyl methacrylate (HEMA) and tetra (ethylene glycol) diacrylate (TEGDA), in an IL electrolyte containing I₂ for DSSCs. TiO₂ nanoparticles were used as the photo-initiator and co-gelator in a charge transfer polymerization reaction. The gel-IL polymer obtained was characterized in terms of the diffusion properties of the electrolyte. Preliminary results from DSSCs assembled using the gel-IL electrolyte showed energy conversion efficiency of 3.9% at 1 sun (AM1.5) and 5.0% at 0.39 sun illumination.

Structure retention in cross-linked poly(ethylene glycol) diacrylate hydrogel templated from a hexagonal lyotropic liquid crystal by controlling the surface tension

Retaining hexagonal lyotropic liquid crystal (LLC) structures in polymers after surfactant removal and drying is particularly challenging, as the surface tension existing during the drying processes tends to change the morphology. In this study, cross-linked poly(ethylene glycol) diacrylate (PEGDA) hydrogels were prepared in LLC hexagonal phases formed from a dodecyltrimethylammonium bromide (DTAB)/water system. The retention of the hexagonal LLC structures was examined by controlling the surface tension. Polarized light microscopy, X-ray diffraction and small angle X-ray scattering results indicate that the hexagonal LLC structure was successfully formed before polymerization and well retained after polymerization and after surfactant removal when the surface tension forces remained neutral. Controlling the surface tension during the drying process can retain the nanostructures templated from lyotropic liquid crystals which will result in the formation of materials with desired nanostructures.

Retention of the original LLC structure in a cross-linked poly(ethylene glycol) diacrylate hydrogel with reinforcement from a silica network

Cross-linked poly(ethylene glycol) diacrylate (PEGDA) hydrogels with uniformly controlled nanoporous structures templated from hexagonal lyotropic liquid crystals (LLC) represent separation membrane materials with potentially high permeability and selectivity due to their high pore density and narrow pore size distribution. However, retaining LLC templated nanostructures is a challenge as the polymer gels are not strong enough to sustain the surface tension during the drying process. In the current study, cross-linked PEGDA gels were reinforced with a silica network synthesized via an in situ sol-gel method, which assists in the retention of the hexagonal LLC structure. The silica precursor does not obstruct the formation of hexagonal phases. After surfactant removal and drying, these hexagonal structures in samples with a certain amount of tetraethoxysilane (TEOS) loading are well retained while the nanostructures are collapsed in samples without silica reinforcement, leading to the hypothesis that the reinforcement provided by the silica network stabilizes the LLC structure. The study examines the conditions necessary for a sufficient and well dispersed silica network in PEGDA gels that contributes to the retention of original LLC structures, which potentially enables broad applications of these gels as biomedical and membrane materials.