Chameleon-inspired elastomer stiffens and changes color when stretched

Trying to mimic chameleon skin with a synthetic material presents scientists with a twofold challenge: The material must change color and must possess skin’s ability to go rapidly from a soft, compliant state to a stiff one that prevents tearing. Scientists led by Sergei S. Sheiko of the University of North Carolina, Chapel Hill, and Andrey V. Dobrynin of the University of Akron managed to marry these two features—color shifting and stiffening upon strain—into a moldable elastomer made from polymers with brushlike architecture (Science 2018, DOI: 10.1126/science.aar5308). The polymer has linear ends and a central region that resembles a bottle brush, in which polydimethylsiloxane chains extend like bristles from a linear polymer backbone. These polymers form a physically cross-linked network that is soft but, like skin, stiffens upon deformation. The network also scatters light of different hues, from turquoise to a vibrant blue, depending on the stretched state of the elastomer. For now, the stiffness and color change are coupled, but the researchers note they would like to create a material in which these features can be controlled independently.