Strong,Tough, Conductive Cellulose/Paa Gel Enabled by In-Situ Esterification and Noncovalent Crosslinking for Adaptive Sensor

Abstract

Cellulose-based gel with flexibility, structural tunability and biocompatibility are applied in advanced filed. However, most of cellulose-based gels are still limited in insufficient mechanical strength and tedious preparation process. We have developed a tough and flexible cellulose/polyacrylic acid (cellulose/PAA) gel through a simple process involving in-situ esterification and photopolymerization within a polymerizable deep eutectic solvent (PDES: ZnCl2/acrylic acid/H2O). In this process, cellulose undergoes highly efficient dissolution (>7wt% within 30 min) while simultaneously capturing acrylic acid (AA) in PDES by in situ esterification, endowing cellulose/PAA gel with a double-network structure through synergistic ester covalent crosslinking and dense hydrogen bond interaction. The hydrogen donor-acceptor capability of PDES, coupled with ester bond formation, induce a delocalization effect in AA, enabling spontaneous radical generation for photopolymerization without requiring external initiator and crosslinker. The resulting cellulose/PAA gel exhibit exceptional tensile strength (12.6 MPa) and toughness (4.24 MJ/m³), which is about 17.67 times than that of the pure cellulose gel. Furthermore, the synergistic presence of carboxyl groups and Zn2+ ions within cellulose/PAA gel impart high electric conductivity (4.7 mS/cm), enabling real-time detection of diverse physiological motions. The simple and effective method we present provides a pathway for the preparation of high-performance conductive gel from renewable biopolymer for flexible sensors applications.

Keywords: cellulose, acrylic acid, in-situ esterification, polymerization, deep eutectic solvent