pH‐Triggered Self‐Assembly of Cellulose Oligomers with Gelatin into a Double‐Network Hydrogel

Abstract

Multicomponent systems for self‐assembled molecular gels provide huge opportunities to generate collective or new functions that are not inherent in individual single‐component gels. However, gelation tends to require careful and complicated procedures, because, among a myriad of kinetically trapped structures related to the degree of mixing of multiple components over a wide range of scales, from molecular level to macroscopic scale, a limited number of structures that exhibit the desired function need to be constructed. This study presents a simple method for the construction of double‐network (DN) hydrogels with improved stiffness composed of crystalline cellulose oligomers and gelatin. The pH‐triggered self‐assembly of cellulose oligomers leads to the formation of robust networks composed of crystalline nanofibers in the presence of dissolved gelatin, followed by cooling to allow for the formation of soft gelatin networks. The resultant DN hydrogels exhibit improved stiffness; the improvement in gel stiffness with double networking is comparable to that of previously reported DN hydrogels produced via a time‐consuming enzymatic reaction.

In-Paper Self-Assembly of Cellulose Oligomers for the Preparation of All-Cellulose Functional Paper

“…Significantly, the formation of crystalline assemblies is not limited to macromolecular cellulose; cellulose oligomers with a degree of polymerization (DP) of more than six potentially form crystalline assemblies due to a loss of water solubility . In fact, the self-assembly of the oligomers through homogeneous nucleation in bulk solutions was induced by enzymatic synthesis of the oligomers and was also triggered by neutralization-driven pH changes of aqueous alkaline solutions of the oligomers, , thus producing hydrogels composed of crystalline nanoribbon networks. We hypothesized from the observations that the self-assembly of oligomers on the surface of general-purpose materials via heterogeneous, but not homogeneous, nucleation has the potential to functionally modify the surfaces of materials with robust assemblies.…”

Double network hydrogels for energy/environmental applications: challenges and opportunities

“…63,126,155 Physically crosslinking gels prepared from natural biological macromolecules have good adsorption performances for heavy metals and other pollutants due to their rich hydroxyl, carboxyl, and amino functional groups, and physical crosslinking provides excellent fatigue resistance and self-healing properties. 60,145 The commonly used natural macromolecules include alginate, 156,157 agar, 158,159 chitosan, 65,160 gelatin, 54 cellulose, 161 carrageenan, 48,109 starch and curdlan. 162 In current studies, natural macromolecules are the most commonly used materials for the synthesis of DN hydrogels,.…”

Recent advances in enzymatic synthesis of β-glucan and cellulose

“…Insoluble cello-oligosaccharides (ca. DP 10) dissolved in alkaline solution (1 N NaOH) self-assembled upon pH decrease (7.4) in the presence of a warm acidic solution of gelatin to yield a hydrogel with improved stiffness, which was assumed to be based on entanglement between the networks of gelatin and the nanoribbon-shaped fibres of cellulose oligomers [ 95 ]. The pH neutralisation approach was also studied in the presence of a more complex mixture, such as serum-containing cell culture media, resulting in a physically cross-linked hydrogel of cellulose nanoribbon networks with anti-biofouling properties.…”