Soft colloids make strong glasses

Glasses can be classified as either fragile or strong, according to whether they show a marked dependence of their relaxation time with temperature when approaching the glass transition. It has been difficult so far to study this behaviour in molecular liquids and to understand where it stems from. Now Mattsson et al. show that colloids incorporating deformable particles can also exhibit this rich behaviour: previously they had been thought to produce only fragile glasses. The fragility of these colloids is dependent on the elasticity of the particles, with softer particles leading to stronger behaviour. Since colloids are easy to study by imaging and other techniques, this model system could help unravel the origin of fragility in glasses.