Nanocellulose-Mediated Electroconductive Self-Healing Hydrogels with High Strength, Plasticity, Viscoelasticity, Stretchability, and Biocompatibility toward Multifunctional Applications

Abstract

Conducting polymer hydrogels (CPHs) have emerged as a fascinating class of smart soft matters important for various advanced applications. However, achieving the synergistic characteristics of conductivity, self-healing ability, biocompatibility, viscoelasticity, and high mechanical performance still remains a critical challenge. Here, we develop for the first time a type of multifunctional hybrid CPHs based on a viscoelastic polyvinyl alcohol (PVA)-borax (PB) gel matrix and nanostructured CNFs-PPy (cellulose nanofibers-polypyrrole) complexes that synergizes the biotemplate role of CNFs and the conductive nature of PPy. The CNF-PPy complexes are synthesized through in situ oxidative polymerization of pyrrole on the surface of CNF templates, which are further well-dispersed into the PB matrix to synthesize homogeneous CNF-PPy/PB hybrid hydrogels. The CNF-PPy complexes not only tangle with PVA chains though hydrogen bonds, but also form reversibly cross-linked complexes with borate ions. The multi-complexation between each component leads to the formation of a hierarchical three-dimensional network. The CNF-PPy/PB-3 hydrogel prepared by 2.0 wt % of PVA, 0.4 wt % of borax, and CNF-PPy complexes with a mass ratio of 3.75/1 exhibits the highest viscoelasticity and mechanical strength. Because of a combined reinforcing and conductive network inside the hydrogel, its maximum storage modulus (∼0.1 MPa) and nominal compression stress (∼22 MPa) are 60 and 2240 times higher than those of pure CNF/PB hydrogel, respectively. The CNF-PPy/PB-3 electrode with a conductivity of 3.65 ± 0.08 S m has a maximum specific capacitance of 236.9 F g, and its specific capacitance degradation is less than 14% after 1500 cycles. The CNF-PPy/PB hybrid hydrogels also demonstrate attractive characteristics, including high water content (∼94%), low density (∼1.2 g cm), excellent biocompatibility, plasticity, pH sensitivity, and rapid self-healing ability without additional external stimuli. Taken together, the combination of such unique properties endows the newly developed CPHs with potential applications in flexible bioelectronics and provides a practical platform to design multifunctional smart soft materials.

Fabrication and electrochemical properties of flexible transparent supercapacitor electrode materials based on cellulose nanofibrils and reduced graphene oxide

“…The intercept of the Nyquist plots at the real axis represents the internal resistance ( R s ), which is mainly dependent on the intrinsic electrical resistance of the electrode material, in addition to the contact and ionic resistance of the electrolyte . While the charge transfer resistance ( R ct ) reflects the electronic and ionic resistance at the electrode‐electrolyte interface . The EIS curve was found to be nearly perpendicular to the X axis at the low‐frequency area, which proved that the supercapacitor based on the CNFs/RGO (18) composite film electrode possessed an ideal capacitive behavior.…”

Poly(vinyl alcohol)–Carbon Nanodots Fluorescent Hydrogel with Superior Mechanical Properties and Sensitive to Detection of Iron(III) Ions

“…Compared with the original hydrogel, the healing efficiency at 1 h and 48 h recovered to 21% and 72%, respectively. Since the self‐healing properties of the hydrogel was contributed to the reversible hydrogen bonds by cross‐linking between PVA and CNDs, which accelerated the self‐recovery process and lead to an improvement in the healing efficiency . Thus, the self‐healing hydrogel could fuse into its original shape after damage and further restored its original properties.…”

“…The cylindrical hydrogel samples (length 20 mm ( l ), width 14 mm ( r )) were subjected to compression test with speed of 2 mm −1 . In this experiment, the nominal tensile stress (σ) and the nominal tensile strain (ε) were determined from the fracture point of the stress–strain curve . In order to study the change in stress performance, the stress ( s ) computed according to Equation .…”

Mussel‐inspired bio‐based water‐resistant soy adhesives with low‐cost dopamine analogue‐modified silkworm silk Fiber

“…Natural reinforcing biomaterials have emerged as a potential green, sustainable alternative for composite enhancement . Natural fibers make excellent composite enhancers due to their high length‐to‐diameter ratio and good mechanical performance .…”

“…10,11 Natural reinforcing biomaterials have emerged as a potential green, sustainable alternative for composite enhancement. 12 Natural fibers make excellent composite enhancers due to their high length-to-diameter ratio and good mechanical performance. 13,14 In a previous study conducted in our laboratory, kenaf fiber was used to enhance the mechanical properties of a soy-based adhesive; kenaf fiber can release internal stress to improve the toughness of the adhesive, although the biocompatibility between kenaf fiber and the soy matrix is not ideal.…”