Bioinspired fully physically cross-linked double network hydrogels with a robust, tough and self-healing structure

Abstract

The conventional covalently cross-linked double network (DN) hydrogels with high stiffness often show low toughness and self-healing property due to the irreversible bond breakages in their networks. Therefore, scarcity of hydrogels that possess simultaneous features of stiffness, toughness, and autonomous self-healing properties at the same time remains a great challenge and seriously limits their biomedical applications. While, many natural materials acquire these features from their dynamic sacrificial bonds. Inspired by biomaterials, herein we propose a novel strategy to design stiff, tough and self-healing DN gels by substitution of both covalently cross-linked networks with strong, dynamic hydrogen bond cross-linked networks. The prepared fully physically cross-linked DN gels composed of strong agar biopolymer gel as the first network and tough polyvinyl alcohol (PVA) biopolymer gel as the second network. The DN gels demonstrated multiple-energy dissipating mechanisms with a high modulus up to 2200kPa, toughness up to 2111kJm, and ability to self-heal quickly and autonomously with regaining 67% of original strength only after 10min. The developed DN gels will open a new avenue to hydrogel research and holds high potential for diverse biomedical applications, such as scaffold, cartilage, tendon and muscle.

Synthesis of poly(acrylic acid)–Fe3+/gelatin/poly(vinyl alcohol) triple‐network supramolecular hydrogels with high toughness, high strength and self‐healing properties

“…(a) that the tensile strength of the PAA‐Fe 3+ (0.20)/Gelatin5%/PVA10% triple‐network hydrogel could reach 186.1 kPa, which is significantly higher than that of single‐ or double‐network hydrogels. This is attributed to a multi‐energy dissipative mechanism . It can be also observed from Fig.…”

“…And the reversibility of metal coupling also gives the hydrogels good self‐healing properties. Sabzi et al . synthesized physically crosslinked agar/poly(vinyl alcohol) double‐network hydrogels, and found that the modulus and toughness can reach 200 kPa and 2200 kJ m −2 , respectively.…”

Synthesis of multifunctional high strength, highly swellable, stretchable and self‐healable pH‐responsive ionic double network hydrogels

“…To measure the self‐healing property, hydrogel samples with different water contents (20, 40 and 60 wt%) were cut into two parts; the two cut surfaces were kept firmly in contact and stored in sealed sample bags to prevent loss of water from the samples, which were kept at room temperature for 24 h. The mechanical properties of the healed samples were measured and compared with the mechanical properties of the original sample to study the self‐healing property . The healing efficiency was thus calculated from the ratio of the tensile strength of the healed sample to that of the original sample (expressed as a percentage).…”

Facile synthesis of extremely biocompatible double‐network hydrogels based on chitosan and poly(vinyl alcohol) with enhanced mechanical properties

“…Indeed, DN hydrogels are composed of two networks: the first one, as the brittle gel, is generally high density and crosslinked, and the second one, the loose and stretchable network, is loosely crosslinked or is not even crosslinked. Furthermore, the molar concentration of the second network must be more than 20–30 times that of the first network . This structure can be synthesized with a general consecutive two‐step method.…”