Pressure sensitive adhesives for strong adhesive strength and rapid strain recovery by introducing H6XDI-PEG diacrylate

Abstract

The development of flexible electronic technology has led to convenient devices, including foldable displays, wearable, e-skin, and medical devices, increasing the need for flexible adhesives that can quickly recover their shape while connecting the components of the device. Conventional pressure sensitive adhesives (PSAs) can improve recoverability via crosslinking, but often have poor adhesive strength. In this study, new types of urethane-based crosslinkers are synthesized using m-xylylene diisocyanate (XDI) or 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI) as a hard segment, and poly(ethylene glycol) (PEG) group as a soft segment. The PSA with the synthesized H6XDI-PEG diacrylate (HPD) demonstrates a significantly improved recoverability compared to XDI-PEG diacrylate and a conventional crosslinker 1,6-hexanediol diacrylate (HDDA) while maintaining high adhesion strength (~25.5 N 25mm-1). The excellent recovery property of the PSA crosslinked with HPD is further confirmed by 100k folding tests and 10k multi-directional stretching tests exhibiting high folding and stretching stability. PSA with HPD also shows high optical transmittance (> 90%) even after 20% straining, suggesting its applicability in fields that simultaneously require high flexibility, recoverability, and optical clarity such as foldable displays.