Materials both Tough and Soft

Tough elastomers are created by adapting an approach previously used for hydrogels. [Also see Report by Ducrot et al. ] Hydrogels and elastomers are soft materials that have similar network structures but very different affinities to water. Consisting mostly of water, hydrogels resemble biological soft tissues and have great potential for use in biomedical applications; they tend to be very brittle, like fragile jellies. Elastomers are formed of nonhydrated polymer networks and are widely used as load-dispersing and shock-absorbing materials. They are stretchable but break easily along a notch. On page 186 of this issue, Ducrot et al. ( 1 ) show that the toughness of elastomers can be improved substantially by combining two different network materials, an approach previously applied to hydrogels.