Elastic films and shaky gels help implement nasal electronics, soft robotics and biocompatible fabrics. But too much force can cause these polymers to break down without warning. To detect stress before it’s too late, researchers report in Journal of the American Chemical Society show that they have developed a compound with “wings” that cause these materials to change color when stretched or crushed.
Plastic films and polymer gels—Soft 3D networks filled with liquid – can be flexible, stretched or compressible. And so far most polymer movies only split when pulled too far, many gels are not very strong, crack under relatively low pressure. However, there is no way to predict how durable the spongy material will be. In previous studies, Shohei Saito and colleagues developed V-shaped molecules known as waving molecular probes (FLAP). FLAPs have two lateral structures resembling wings that flatten under pressure, causing a color change from blue to green fluorescence. This probe worked as expected when included in the polyurethane film, but when added to a liquid-impregnated polymer gel, the compound spontaneously turned fluorescent green without any external force. Thus, Saito and Takuya Yamakada decided to improve the FLAP molecule so that it accurately detects mechanical loads in both the polymer gel and the film.
The researchers modified their earlier version by replacing the two anthracenimide wings with pyrenimid ones by attaching them to opposite sides of the same flexible central cyclooctatetraene joint. When they added the probe to the polymer film and stretched the material, its fluorescence greatly shifted from blue to green. It also caused a color change that was visible to the naked eye. Next, the researchers included a new FLAP probe in a polyurethane gel impregnated organic solvent, creating a yellow cylinder that fluoresces blue and then compresses the material. The fluorescence of the cylinder became noticeably greener as the pressure increased. In their latest test, the researchers placed metal FLAP letters on a rectangular block of gel. They used green and blue fluorescence ratio maps to calculate the pressure of each letter on the gel below, which ranged from 0 to 1 MPa. The researchers say the study could help them develop stronger gel materials and nanosized tension probes for cell membranes.
Takuya Yamakado et al., Ratiometric Waving Force Probe Working in Polymer Gels, Journal of the American Chemical Society (2022). DOI: 10.1021 / jacs.1c12955
American Chemical Society
Citation: Brightly exposed polymer films in stress, gels before their rupture (2022, February 23) obtained February 23, 2022 from https://phys.org/news/2022-02-colorfully-stressed-out-polymer-gels .html
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