Stretchable Heterogeneous Polymer Networks of High Adhesion and Low Hysteresis

Abstract

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 acrylateco-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.

Unique Polymer-Stabilized Liquid Crystal Structure Prepared by Addition of a Reversible Addition–Fragmentation Chain Transfer Agent

“…One evidence is the viscoelasticity of polymer networks. The measured tan δ of sample A3 is half that of sample B, indicating a more elastic polymer network (Figure d) …”

“…The results of the hysteresis effect agree well with the measured irrecoverable strains for samples B and A3. The observed contrast can be explained by the difference in the polymer network structures . The uniform structure in sample A3 leads to lower viscoelasticity (Figure d) and better recovery as compared to sample B, which is crucial for PSLCs to be used for high-precision optics like augmented and virtual reality. , …”

“…The measured tan δ of sample A3 is half that of sample B, indicating a more elastic polymer network (Figure 4d). 38 In addition, SEM is used to directly visualize the structures of the formed polymer networks from these two polymerization mechanisms. Both cross-sectional (Figure 4e) and topview (Figure 4f) figures are collected for comparison.…”

“…The observed contrast can be explained by the difference in the polymer network structures. 38 The uniform structure in sample A3 leads to lower viscoelasticity (Figure 4d) and better recovery as compared to sample B, which is crucial for PSLCs to be used for high-precision optics like augmented and virtual reality. 47,48 Last but not least, the aging performances of PSLC devices prepared by the two polymerization mechanisms are compared, including both the ON/OFF switching test and long-term power-on test.…”