Photohardenable Pressure-Sensitive Adhesives using Poly(methyl methacrylate) containing Liquid Crystal Plasticizers

Realizing Vat-Photocycloaddition 3D Printing with Recyclable Synthetic Photorheological Silicone Fluids

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.