Enhancing Adhesion On-Demand in Bottlebrush Pressure Sensitive Adhesives

There is significant interest in pressure sensitive adhesives that can alter their tackiness on demand without the use of additives or chemical agents. Towards this end, we have explored the potential of altering bottlebrush network architecture, via a mild external stimulus, to induce shifts in the viscoelastic properties of a material. Specifically, by controllably decreasing the cross-link density of a bottlebrush network via exposure to UV light over a short period of time, we have achieved quantitatively predictable shifts in the network’s plateau modulus and Rouse relaxation time. This was achieved through the incorporation of UV-triggered cleavable crosslinks in a set of bottlebrush pressure sensitive adhesives. Concurrently enhancing softness and dissipation induced increases to PSA work of adhesion by more than 3 orders of magnitude for peel rates ranging from ca. 10^–3 to 10 s^–1. The work of adhesion measured as a function of the deformation rate covers three distinct regimes from viscoelastic bulk- to interface-dominated adhesion with increasing cross-linking density.