Deformation Drives Alignment of Nanofibers in Framework for Inducing Anisotropic Cellulose Hydrogels with High Toughness

Abstract

Deformation-driven alignment of macromolecules or nanofibers leading to anisotropy is a challenge in functional soft materials. Here, tough cellulose hydrogels that exhibited deformation-induced anisotropy are fabricated by reacting cellulose with a small amount of epichlorohydrin (EPI) in LiOH/urea solution and subsequent treating with dilute acid. The loosely cross-linked network that was obtained via chemical cross-linking of cellulose with EPI as a large framework maintained the elasticity of hydrogels, whereas nanofibers produced by the acid treatment formed physical cross-linked networks through hydrogen bonds which could efficiently dissipated mechanical energy. Meanwhile, the nanofibers could further aggregate to form submicrobundles and participate in the formation of frameworks during the acid treatment. Under deformation, the nanofibers and submicrobundles in the physical networks synchronize easily to align with the large framework, generating the rapidly responsive birefringence behaviors with highly stable colors. Thus, the cellulose hydrogels possessing sensitively mechano-responsive behavior could be utilized as a dynamic light switch and a soft sensor to accurately detect small external force, respectively. This work opens a novel pathway to construct tough and mechanoresponsive hydrogels via a green conversion of natural polysaccharide.

Natural Biopolymer Alloys with Superior Mechanical Properties

“…44 For polymer materials, chemical reactions enable structural manipulation to achieve strong inter-/intramolecular or interfacial interactions (typically covalent bonding). 43,[45][46][47][48] We hypothesized that biopolymer alloys with strong mechanical properties could be obtained by maximizing the molecular interactions between chitosan and protein in a well-mixed system. In this work, we adopted an innovative, facile, "dry" approach to engineering such biopolymer alloys, which resulted in a homogeneous, well-dispersed structure yet still achieved outstanding mechanical properties.…”

Programmed Diffusion Induces Anisotropic Superstructures in Hydrogels with High Mechano‐Optical Sensitivity

“…The complex ordered structures afforded the hydrogel high mechano‐optical sensitivity, because the variation of patterned birefringence with abundant colors was more easily detectable than the monodomain gels, when subjected to the mechanical stress or strain. To characterize the mechano‐optical properties of the hydrogel with complex ordered structures, we improved the mechanical properties of the physical gel based on the double‐network (DN) principle .…”

Stimuli‐Responsive Biomolecule‐Based Hydrogels and Their Applications

“…Polysaccharides represent ab road class of biopolymers that originate from natural sources [42] and exhibit gelation capabilities.I na ddition, chemical modification of polysaccharides provides av ersatile means to prepare chemically functionalized scaffolds that can act as ar ich arsenal of gelation materials with unique physical properties. [3b] Hydrogelation of natural or chemically modified polysaccharides may proceed through hydrogen bonds, [43] ionic interactions, [44] and/or metal ion-assisted crosslinking [45] of polysaccharide chains.…”