Transparent, flexible, and paramagnetic ionogels based on PMMA and the iron-based ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate(III) [Bmim][FeCl4]

The iron-containing ionic liquid (IL) 1-butyl-3-methylimidazolium tetrachloroferrate(III) [Bmim][FeCl4] has been used as a building block in the synthesis of transparent, ion-conducting, and paramagnetic ionogels. UV/Vis spectroscopy shows that the coordination around the Fe(III) ion does slightly change upon incorporation of the IL into PMMA. The thermal stability of the PMMA increases significantly with IL incorporation. In particular, the onset weight loss observed at ca. 265 degrees C for pure PMMA is completely suppressed. The ionic conductivity shows a strong temperature dependence and increases with increasing IL weight fractions. The magnetic properties are similar to those reported for the pure IL and are not affected by the incorporation into the PMMA matrix. The resulting ionogel is thus an interesting prototype for soft, flexible, and transparent materials combining the mechanical properties of the matrix with the functionality of the metal-containing IL, such as magnetism.