Wet/Dry Bottlebrush Pressure Sensitive Adhesives via a Dangling Defect-Driven Design.

A series of bottlebrush pressure sensitive adhesives (PSAs) containing progressively greater numbers of large dangling ends were synthesized using ring-opening metathesis polymerization. These defects were engineered into PSAs by promoting the formation of loop defects and by manipulating the kinetic chain length such that large dangling defects are covalently bound to the bulk. The unique structure of these samples is shown to promote adhesion at interfaces by maximizing surface area contact and increasing local van der Waals forces. This design philosophy (termed defect-driven design, ) provides an easy route to synthesize bottlebrush PSAs ∼6 times stronger than commercial VHB1000 tape. Furthermore, the inherent tendency of water to dewet on poly(dimethylsiloxane) PSAs is exacerbated in these samples, resulting in PSAs capable of indefinite cycles of wet-dry-wet adhesion (tested up to 50 cycles, 7 months apart). Further development of the concept is expected to result in increased applications (e.g., dielectric actuators, wearable electronics, and especially soft robotics) as the unique design parameters are further explored.