Solid electrolytes are crucial materials for lithium-ion or fuel-cell battery technology due to their structural stability and easiness for handling. Emergence of high conductivity in solid electrolytes requires precise control of the composition and structure. A promising strategy toward highly-conductive solid electrolytes is employing a thermally-stable inorganic component and a structurally-flexible organic moiety to construct inorganic-organic hybrid materials. Ionic liquids as the organic component will be advantageous for the emergence of high conductivity, and polyoxometalate, such as heteropolyacids, are well-known as inorganic proton conductors. Here, newly-designed ionic liquid imidazolium cations, having a polymerizable methacryl group (denoted as MAImC 1 ), were successfully hybridized with heteropolyanions of [PW 12 O 40 ] 3− (PW 12 ) to form inorganic-organic hybrid monomers of MAImC 1 -PW 12 . The synthetic procedure of MAImC 1 -PW 12 was a simple ion-exchange reaction, being generally applicable to several polyoxometalates, in principle. MAImC 1 -PW 12 was obtained as single crystals, and its molecular and crystal structures were clearly revealed. Additionally, the hybrid monomer of MAImC 1 -PW 12 was polymerized by a radical polymerization using AIBN as an initiator. Some of the resulting inorganic-organic hybrid polymers exhibited conductivity of 10 −4 S·cm −1 order under humidified conditions at 313 K.

The first syntheses of polyoxomolybdate hybrid crystals were achieved by using polymerizable ionic-liquid.

Conductive inorganic-organic hybrid monomers and polymers were successfully obtained by using a polymerizable imidazolium ionic-liquid with a methacryloyl group (denoted as MAImC 1) and inorganic polyoxometalate cluster anion ([SiW 12 O 40 ] 4− , SiW 12). The MAImC 1-SiW 12 hybrid monomer was synthesized as single crystals, the molecular and crystal structures of which were revealed by single crystal X-ray analysis. The obtained MAImC 1-SiW 12 hybrid monomer was found to be polymerized by a radical polymerization using AIBN as an initiator to form inorganic-organic homo-and copolymers. The hybrid copolymers of MAImC 1-SiW 12 polymerized with another polymerizable ionic-liquid (denoted as MAImC 8) exhibited high conductivity of 10 −3 S cm −1 order under humidified condition at near room temperature of 313 K.

Anionic metal−oxygen clusters known as polyoxometalates (POMs) have been widely researched as components of proton conductors. While proton conduction under non-humidified intermediate-temperature (100−250 °C) conditions is advantageous from the viewpoint...