An intrinsically self-healing and biocompatible electroconductive hydrogel based on nanostructured nanocellulose-polyaniline complexes embedded in a viscoelastic polymer network towards flexible conductors and electrodes

Electroconductive hydrogels (ECHs) that integrate gel features and electrochemical properties are considered as promising tissue-like flexible materials important for broad applications. Nevertheless, realizing the synergistic features of self-healing capability, conductivity, biocompatibility, stretchability and malleability is challenging. Herein, a novel kind of versatile ECHs built on a borax-crosslinked polyvinyl alcohol (PVA) hydrogel system and conducting PANI@CNF (polyaniline-cellulose nanofiber) nanocomplexes which synergize the conductivity of PANI and the template feature of CNFs is reported. The PANI@CNF nanocomplexes are firstly prepared via in situ polymerization of anilines on CNFs, which are then evenly distributed into borax-crosslinked PVA gel system to fabricate free-standing PANI@CNF-PVA composite ECHs. Sustainable and renewable CNFs serve as flexible biotemplates and mediate the development of PANI into integrated PANI@CNF with good dispersity, enabling the establishment of an integrated conducting and reinforcing network. The dynamic multi-complexation and chain entanglements between PANI@CNF complexes, borax and PVA chains contribute to the development of a hierarchical network structure. The maximum compression stress (similar to 48.8 kPa) and storage modulus (similar to 31.5 kPa) of PANI@CNF-PVA hydrogel are about 3.5 and 400 times greater than those of pure PVA gel. These hydrogels also demonstrate appealing biocompatibility, mouldability, pH sensitivity, thermo-reversibility and fast self-healing ability within 15s. The hydrogel-based electrode with a conductivity of similar to 5.2 S m(-1) shows a maximum specific capacitance of 226.1 F g(-1) and a capacitance retention of 74% after 3000 cycles. The integration of such remarkable features enables the promising applications of the as-prepared versatile ECHs in flexible, self-healing and implantable electronic devices. (C) 2019 Elsevier Ltd. All rights reserved.