Photomanipulable Liquid Pressure-Sensitive Adhesives Based on the Reversible Cyclic–Linear Topological Transformation of Synthetic Silicones

For the next generation of materials science toward a sustainable future, it is quintessential to provide recyclability to polymeric materials that cannot be readily replaced by inherently degradable polymers. Silicones are widely utilized in various fields, such as adhesives, medical devices, microfluidics, and food. Although the highly flexible and durable nature of silicones has led to irreplaceable applications by other carbon-based nondegradable and degradable polymers, these properties also make it difficult to provide recyclability. Here, we exploit cyclic polydimethylsiloxane (PDMS) linked with hexaarylbiimidazoles (HABIs) in the chains as a photoreversible liquid pressure-sensitive adhesive (PSA). Based on cyclic-to-linear topological transformation based on the photochemistry of HABI, the adhesion force between a glass and a polymer film attached with cyclic PDMS as a liquid PSA decreased by a factor of 55 upon photoirradiation only at irradiated parts. Furthermore, the dramatic change in the adhesion force was reasonably linked to a change in the viscosity of the liquid PSA by exploiting a newly developed ultratrace microviscometer, demonstrating a decrease in viscosity by a factor of more than 35.