Temperature-Mediated Phase Separation Enables Strong yet Reversible Mechanical and Adhesive Hydrogels

L Zhang and SH Wang and ZM Wang and ZY Liu and X Xu and H Liu and D Wang and ZQ Tian, ACS NANO, 17, 13948-13960 (2023).

DOI: 10.1021/acsnano.3c03910

Hydrogelswith strong yet reversible mechanical and adhesivepropertiesfabricated in a facile and friendly manner are important for engineeringand intelligent electronics applications but are challenging to createand control. Existing approaches for preparing hydrogels involve complicatedpretreatments and produce hydrogels that suffer from limited skinapplicability. Copolymerized hydrogels are expected to present anintriguing target in this field by means of thermoresponsive features,while the perceived intrinsic flaws of brittleness, easy fracture,and weak adhesion enervate the development prospects. Herein, we reporta hydrogel with strong yet reversible mechanical and adhesive propertiesusing cellulose nanofibrils to simultaneously address multiple dilemmasinspired by a temperature- mediated phase separation strategy. Thisstrategy applies temperature- driven formation and dissociation ofhydrogen bonds between common copolymers and cellulose nanofibrilsto trigger the onset and termination of phase separation for dynamicallyreversible on-demand properties. The resulting hydrogel exhibits upto 96.0% (117.2 J/m(2) vs 4.8 J/m(2) for interfacialtoughness) and 85.7% (0.02 MPa vs 0.14 MPa for mechanical stiffness)adhesive and mechanical tunability when worked on skin, respectively.Our strategy offers a promising, simple, and efficient way to directlyachieve robust adhesion performance in one step using common copolymersand biomass resources, with implications that could go beyond strongyet adhesive hydrogels.

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