Strain-Stiffening, Self-Healing, and Low-Hysteresis Physically Dual-Cross-Linked Hydrogels Derived from Two Mechanically Distinct Hydrogen Bonds

Abstract

Herein, we propose a facile strategy to fabricate high-performance hydrogels combining strain-stiffening mechanical behavior with self-healing ability and low hysteresis, which feature a unique structure with two mechanically distinct polymeric networks. The stereocomplex micelles sc−PEG-PLA are first obtained from the mixtures of poly(ethylene glycol)-b-poly(Llactide) (PEG−PLLA) and poly(ethylene glycol)-b-poly(D-lactide) (PEG−PDLA), then the hydrogels PAA/sc−PEG-PLA are fabricated from the one-pot free radical polymerization process of poly(acrylic acid) (PAA) with sc−PEG-PLA as a physical dynamic cross-linker. Two kinds of mechanically distinct hydrogen bonds, strong hydrogen bonding between PAA and sc−PEG-PLA and weak hydrogen bonding between PAA chains, are attributed to the creation of dual-cross-linked networks of the hydrogels. The special structure imparts the hydrogels with unique strain-stiffening behavior, self-healing capability (98.5% efficiency), and low hysteresis. When exploited as a strain sensor, the fabricated hydrogel sensor demonstrates superior sensitivity even for ultralow strains ranging from 0.5 to 10%. During mimicking practical wearable testing, the hydrogel-based sensor shows high sensitivity and reliability for the detection of diverse human motions like wrist, elbow, and knee movements. This work well elucidates the structure−property relationship of materials and further provides new insights into the development of high-performance hydrogels for broadening their applications.

Facile fabrication of highly-stretchable, low-hysteresis and notch-insensitive ionogels for strain sensors

“…2B). 34,43–46 Meanwhile, all the ionogels showed good frequency tolerance over a wide frequency range (Fig. 2C).…”

“…It is noted that low hysteresis is essential for ionogel-based soft electronic devices to rapidly and fully recover their deformed structure, significantly decreasing fatigue and improving their durability and reliability. 32–34 For the fabrication of high-performance ionogels, strategies to tailor the network structure and cross-linking mechanism are highly desirable to mitigate, and perhaps eliminate, the toughness-low hysteresis conflict.…”

Low hysteresis zwitterionic supramolecular polymer ion-conductive elastomers with anti-freezing properties, high stretchability, and self-adhesion for flexible electronic devices

“…The remarkable low-hysteresis and good elasticity of the PCBUIA-LiCl-4-20 elastomer can be ascribed to its densely entangled network and strong hydrogen-bond cross-linked structure on the side chains. 32,33,41 The ultra-high monomer concentration (4 mol L −1 , 54.66 wt%) resulted in the dense entanglements of polymeric chains after polymerization, which enables the maintenance of the network integrity under stretching. 32 The strong hydrogen-bond cross-linked structure built by the ureido group of zwitterionic polymer side chains can effectively eliminate temporary entanglements and reduce energy dissipation.…”

Engineering Rapeseed Germination and Root Growth with Mechanical Strength of Polysaccharide Hydrogel

“…In contrast, the use of transparent or translucent culture substrates has enabled convenient observation of plant roots and data collection using standard optical photographic equipment. With good biocompatibility and adjustable properties, hydrogels have broad application prospects in the fields of material science and biomedicine. − For example, regulating the mechanical properties of hydrogels can induce stem cell differentiation into different tissues . Consequently, transparent gel cultivation, notably utilizing media like agar and low acyl gellan gum (GG), − has emerged as a prominent approach for studying root growth. − …”