Reversible liquid-soft solid polymer gels can combine with ionic liquids to provide an alternative to traditional liquid electrolytes. Timothy Lodge and Yiyong He, from the University of Minnesota, US, made 'ion gels', networks of a three-part polymer molecule swollen with a large amount of ionic liquid. 

'Compared to other approaches, our gels require significantly less polymer (4% by weight) and offer improved ionic conductivity,' said Lodge. 'In addition, they avoid the leakage and flammability issues of organic solvent-based electrolytes.' 

The thermoreversible nature of the ion gels, the ability to reverse polymer cross-linking with a change in temperature, enables the material to be processed in the liquid state, but used in the solid state. Lodge said that the ability to fine-tune the physical properties of the polymer was 'achieved through judicious selection of polymer and ionic liquid'. 

The ionic conductivity of Lodge's system was only a few percent below that of the pure ionic liquid but it possessed good mechanical strength, even under heavy strain, and offered the advantage of solvent-free processing.

Lodge expects the ion gels to find diverse applications, including sensors, transistors, electromechanical systems, light-emitting cells and gas separation. Pradip Bhowmik of the University of Nevada agreed: 'These ion gels will definitely find applications in many new technologies and the design of smart materials in the near future.'

Michael Spencelayh