Thermoresponsive ionogels with switchable adhesion in air and aqueous environments induced by LCST phase behavior

Abstract

The rapid development of wearable devices is in urgent demand for materials with switchable adhesion both in air and aqueous environments. Herein, we report a thermoresponsive ionogel with switchable adhesion against various substrates both in air and aqueous environments. The switchable adhesion of ionogels is realized by a phase separation induced collapse of the polymer network and the subsequent extrusion of ionic liquids (ILs) on ionogel surfaces. The hydrophobic poly(butyl acrylate) (PBA) network and ILs endow the ionogels with excellent water-resistance ability, which enables the application of ionogels in aqueous environments. As a result, the adhesion strength of ionogels against rubber can reach an on/off ratio of 75-fold (45 kPa versus 0.6 kPa) and 7.7-fold (21 kPa versus 2.7 kPa) in air and aqueous environments, respectively. By varying the ratio of two structurally similar ILs in their blends, the responsive temperature of ionogels can be tuned within a wide temperature range from 32 °C to 100 °C. Furthermore, we show a demonstration of an underwater on demand capture and release by taking advantage of the switchable adhesion of ionogels. These nonvolatile ionogels with tunable responsive temperatures and high on/off adhesion strength ratio both in air and aqueous environments show broad applications in the fields related to wearable devices, soft robots and submersible sensors.