Ionic liquid-assisted construction of carboxymethyl konjac glucomannan hydrogels with strain sensing and actuating capabilities

Expanding the application of carboxymethyl konjac glucomannan (CMK) beyond the fields of food and medicine is very important for enhancing the high-value utilization of konjac glucomannan (KGM) derivatives. Herein, we used CMK and poly(vinyl alcohol) (PVA) as the matrices and ionic liquids (ILs)/glycol (Eg)/water as the mixed solvents to construct a hydrogel with multi-dissipative structures. Eg acted as plasticizer, leading to the swelling of the CMK/PVA chain entanglements. This was able to compensate for the loss of PVA crystallinity caused by the CMK-PVA hydrogen bonding, and also favored enhancing electrostatic interactions and hydrogen bonding between ILs and CMK/PVA chains simultaneously. Owing to this synergism, the mechanical properties of hydrogel were remarkably improved. The strength and elongation of the hydrogel with optimized ILs/Eg ratio (1/4) are 1.3 MPa and 1266.9 %, respectively, much higher than those of the hydrogels only with ILs (PCB, 0.7 MPa and 738.1 %) and only with Eg (PCE, 0.7 MPa and 690.5 %). The anti-freezing ability, and the tolerance to dehydration and swelling, were also significantly improved. Thus, the flexible strain sensor prepared could be well applied in harsh environments. Furthermore, by controlling the heterogeneity of ILs, the actuating ability of hydrogel could be activated through a bilayer structuring strategy. This work opens up new application scenarios of CMK-based hydrogels in the fields other than the traditional hydrocolloid areas. • Eg/IL had synergistic effect to improve tensile property/environmental tolerance. • Hydrogel was well used as strain sensor under normal condition and underwater. • Actuating ability was activated by tuning heterogeneity of IL in bilayer hydrogel. • New application of the CMK based hydrogel other than food area was opened up.