LAUSR

Synthetic silicone rubbers are finding a broad spectrum of applications, yet there has been a demand for developing greener silicone rubbers with processability, recyclability, and reversible tunability in their mechanical properties. Here, a recyclable photorheological silicone fluid (RPSF) is developed, which realizes completely reversible wavelength-selective liquid-rubber conversion upon photoirradiation, relying on the reversible photocycloaddition of coumarin upon alternating irradiation of light with wavelengths of 365 nm (UV365 ) and 254 nm (UV254 ). Rheological studies demonstrate that the storage modulus of the developed RPSF increases by a factor of more than 100,000 upon UV365 irradiation to reach 20-50 kPa, while it decreases to ca. 0.01 kPa upon UV254 irradiation. The reversibility of the photocycloaddition of coumarin enables the application of RPSF as a photodismantlable adhesive. Furthermore, unprecedented vat-photocycloaddition 3D printing of silicone rubber is realized by taking advantage of the excellent photocurability, i.e., dramatic increase in viscoelasticity upon UV365 irradiation. This article is protected by copyright. All rights reserved.