Freezing-Tolerant Hydrogel Composed of Sulfonated Chitosan and Poly(vinyl alcohol) Featuring Excellent Stretchability and High Proton Conduction

Abstract

Antifreezing and highly proton-conductive hydrogels show promising applications in flexible electrochemical devices owing to their inherent stretchability and safety. In this study, we chose an ethylene glycol/water (EG/H2O) binary mixture as the solvent, sulfonated chitosan (CS-SO3H) as the proton-conducting component, and the blend of CS-SO3H and poly­(vinyl alcohol) (PVA) as a gelator to prepare double-network hydrogels, CS-SO3H@PVA-X (X represents the mass ratio of CS-SO3H and PVA with a value of 0, 0.5, 1.0, and 1.5), which are characterized by different techniques, including microanalysis, IR, 1H and 13C NMR spectra, TG, PXRD, and so on. CS-SO3H@PVA-X hydrogels exhibit excellent tensile strength, toughness, and a freezing-tolerant feature. Importantly, CS-SO3H@PVA-1.5 hydrogel displays not only high proton conduction in a wide range of temperatures from −35 to 70 °C, with proton conductivities of 7.2 × 10–4 S cm–1 at −35 °C and 4.56 × 10–2 S cm–1 at 70 °C and ambient humidity, but also exceptional mechanical performance, with a tensile strength of 3.11 MPa and an elongation at break of 423%, indicative of a potential application in electrochemical devices relying on proton transport and operating at extreme conditions. It is also discovered for the first time that the double-network micelles are entangled together to form the spiral crimped texture in hydrogels CS-SO3H@PVA-X (X = 1.0 and 1.5).

Construction of shrimp shell (SS) waste-based carbon electrode-gel polymer electrolyte (GPE) system for flexible symmetric supercapacitors

“…A double network hydrogel of sulfonated chitosan and polyvinyl alcohol (PVA) has been prepared, yielding a conductivity of 7.2 × 10 −7 S cm −1 . 35 The electrical conductivity of the double network gel electrolyte formed by cross-linking carboxylated chitosan with polyvinyl alcohol (PVA) was 2.561 × 10 −2 S cm −1 , which can be attributed to the carboxyl group in carboxylated chitosan that is conducive for improved electrical conductivity. 36 Although SS-derived and modified chitosan have been used for the preparation of GPE, they mostly cannot be separated from other synthetic polymers.…”

Study of a novel supramolecular hydrogel electrolyte for aqueous zinc ion batteries

“…[36][37][38] Hydrogel electrolytes are classified as chemical cross-linking hydrogel electrolytes and physical cross-linking hydrogel electrolytes. 39 Chemical cross-linking hydrogels such as polyvinyl alcohol (PVA), 40 polyethylene glycol (PEG), 41 and polyacrylamide (PAM) 42 hydrogels as electrolytes in ZIBs have been reported in the literature. 43 This type of hydrogel electrolyte is usually obtained by immersing pre-prepared hydrogels in zinc salt solutions until swelling equilibrium is reached, which means that high requirements are placed on the shape and swelling degree of the hydrogel.…”

Sustainable and mechanically robust epoxy resins derived from chitosan and tung oil with proton conductivity

“…Among them, chitosan with multiple active groups, is one of the most abundant polysaccharides in nature, and a promising material to prepare sustainable, mechanically reinforced biobased resins due to its degradability, biodiversity, thermoplasticity, and easy film formation characteristics 23,24 . Meanwhile, introduction of additional functions into the composites by chitosan, allowed the formation of advanced materials for property‐targeting applications, such as food packaging, proton exchange membranes and flame retardants etc 22,24,25 . However, in most cases, the performance of the composites was hindered by the poor interface compatibility and dispersion challenge when blending chitosan with polymer matrix, which can be solved by grafting polymers from chitosan.…”

“…23,24 Meanwhile, introduction of additional functions into the composites by chitosan, allowed the formation of advanced materials for property-targeting applications, such as food packaging, proton exchange membranes and flame retardants etc. 22,24,25 However, in most cases, the performance of the composites was hindered by the poor interface compatibility and dispersion challenge when blending chitosan with polymer matrix, which can be solved by grafting polymers from chitosan. Also, Grafting polymerization based on controlled/"living" radical (e.g., reversible addition-fragmentation chain transfer, RAFT) polymerizations stands out as one of the most successful strategies in the fabrication of chitosancontaining functional materials.…”