Unique Combination of Mechanical Strength, Thermal Stability, and High Ion Conduction in PMMA-Silica Nanocomposites Containing High Loadings of Ionic Liquid

A report on ionogel ternary systems based on a covalently bonded polymer-silica hybrid matrix and an ionic liquid was studied. A sol-gel synthesis involving modified poly(methylmethacrylate) (PMMA), silicon tetraethyloxide (TEOS), and 1-butyl-3-methyl imidazolium bis(trifluoromethane sulfonyl) imide ([BMIm][NTf2]) was implemented. The modified PMMA contained about 5 mol % units bearing pendant hydrolyzable silicon groups arising from methacryloxypropyltrimethoxysilane (MPTMS) monomer. A series of hybrid ionogels loaded with various amounts of [BMIm][NTf2] were prepared. Ionic liquid contents were determined by weighting and further checked by thermogravimetric analyses (TGA). After extracting the IL, the degree of condensation was valued around 77% by means of MAS 29Si NMR spectroscopy. An increase in ionic conductivity was observed when increasing the ionic liquid content. Hybrid ionogels exhibited high thermal stabilities around 530 K.