Stretchable Heterogeneous Polymer Networks of High Adhesion and Low Hysteresis

Adhesives are ubiquitous, but the mutual exclusion between hyperelasticity and adhesiveness impedes their uses in emerging techniques such as flexible/stretchable electronics. Herein, we propose a strategy to synthesize hyperelastic adhesives (HEAs), by designating hyperelasticity and adhesiveness to the bulk and the surface of a polymer network, respectively. The bulk is hyperelastic but nonadhesive, and the surface is viscoelastic but adhesive, while the HEA is hyperelastic and adhesive. We exemplify the principle by synthesizing poly(butyl acrylate) as the bulk and poly(butyl acrylate-co-isobornyl acrylate) as the surface. The resulting HEA exhibits a low hysteresis of 4% at 100% strain and an adhesion energy of 270 J m^-2. Moreover, the HEA is optically transparent, thermally stable, spontaneously adhesive to various materials, and mechanically stable against cyclic load, relaxation, and creep. We demonstrate two applications enabled by the unique combination of hyperelasticity and adhesiveness. The proposed strategy is generic, paving new avenues for stretchable yet resilient adhesives for diverse applications.