Stretchy polymer lights up under stress

Stretchy polymer lights up under stress

This rubbery material lights up when stretched. Materials like this that respond to stress
could be used as sensors to detect forces to gauge strain in a material, or to form
electronic skin. Researchers have built other colorful force
sensors, but those change hues when chemical bonds break, making the change hard to reverse,
limiting the materials’ reusability. This polymer, made by an international group
of researchers, produces reversible color changes with the help of mechanically interlocking
molecules called rotaxanes. Rotaxanes contain a cyclic compound with a
rod-shaped molecule threaded through it. The ring can slide along the rod but is held
on the rod by two bulky end groups. To turn a rotaxane into a force sensor, researchers
tagged their ring with a fluorescent dye that glows green, blue, or orange, then inserted a rod containing a quencher
molecule that blocks the dyes from glowing. Hydroxy groups on the ends of the ring and
the rod enable them to add the customized rotaxane to a polyurethane chain. In the polymer chains, the quenchers start
out close to the dyes, preventing them from glowing. When researchers stretch the material, the
rod slips along the ring, separating the dye from the quencher and allowing it to glow,
seen here under UV light. Relaxing the material instantly reverses the
effect. The team showed how the color response can
be tailored by blending the blue-, green-, and orange-emitting polymers to make a polymer
that emits white light. The researchers are working to simplify the
synthesis of the glowing rotaxane structures so they can be made on larger scales.

2 thoughts on “Stretchy polymer lights up under stress

  1. Who wanted them to actually hold it at the outstretched point to see if it stayed glowing? … Hmm. Maybe at the very end.

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