Scientists from Japan and India have produced a temperature-sensitive film from guar gum.
 
Guar gum, a polysaccharide, is a cheap and environmentally friendly material produced naturally by a leguminous shrub. A range of industries use the gum but its inability to form gels and high-quality films has limited its use. 

Now, Jun-ichi Kadokawa from Kagoshima University and colleagues have discovered a way to produce a thin film from the gum. They did this by treating the gum with an ionic liquid, 1-butyl-3-methyl-imidazolium chloride, and heating the mixture until the gum had dissolved. They then cooled the mixture and treated it with organic liquids. The team compressed the resulting gel to form a stable film. The film has a high tensile strength and Kadokawa says it can conduct electricity as efficiently as semi-conductors.   

Uniquely, the film hardens upon heating but becomes soft again as it cools. These properties mean that it could be used to produce temperature sensors. The method could also be extended to produce films from other polysaccharides and solvents, but first Kadokawa and his team want to understand the gel's structure and properties. 

Yoshiaki Yuguchi, an expert in polysaccharide gels at the Osaka Electro-Communication University in Japan, says: 'This research has the potential of producing an advanced novel material. Polysaccharides are usually used in the food industry, but this technology is developing a new field.'   

Harriet Brewerton 

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