Self-Activated Healable Hydrogels with Reversible Temperature Responsiveness

Abstract

The self-healable polymer hydrogel along with reversible temperature responsiveness was prepared through self-catalyzed dynamic acylhydrazone formation and exchange without any additional stimulus or catalyst. The hydrogel was prepared from a copolymer of N-isopropylacrylamide and acylhydrazine P(NIPAM-co-AH) cross-linked by PEO dialdehyde. Besides self-healed under catalysis of acid and aniline, the hydrogel can also self-heal activated by excess of acylhydrazine groups. Without interference of catalyst during the hydrogel formation and self-healing, this kind of hydrogel prepared from biocompatible polymers can be used in more areas including biotechnology and be more persistent. The hydrogel with a large part of the PNIPAM segment also showed temperature responsiveness around body temperature influenced by the variation in group ratio. This self-healable hydrogel has great potential application in areas related to bioscience and biotechnology.

Transiently malleable multi-healable hydrogel nanocomposites based on responsive boronic acid copolymers

“…It should be noted that regardless of the application of any stimulus, all the hydrogels exhibit remarkably rapid healing capabilities compared to other structurally and mechanically similar gels that require hours or even days for full recovery. 24,62,105 Photographs of the thermal-and optical-initiated healing process, in Fig. 7, display the self-healing properties of the gels with or without the application of stimuli.…”

“…[5][6][7][8] The latter approach is particularly interesting and challenging in that suitable chemistries must be adopted that do not compromise the end-functionality of the designed material. Notable approaches of this method include the construction of healable polymer networks based on the exploitation of hydrogen bonds, [9][10][11] π-π stacking type of interactions, 12,13 host-guest recognition events, [14][15][16][17] electrostatic interactions, 18,19 metal coordination, [20][21][22] acylhydrazones, 23,24 reversible (hetero) Diels-Alder reaction motifs [25][26][27][28] and disulfide bonds. [29][30][31] Indeed, all these approaches have their own merits, however, the healing process is not always ex vi termini perfect as autonomous/automatic healing must be accompanied by gravitational force or mechanical/manual rejoining of the damaged material.…”

Three‐dimensional extrusion bioprinting of single‐ and double‐network hydrogels containing dynamic covalent crosslinks

“…The hydrazone bond is a unique dynamic covalent bond that is formed between an electron‐dense, nucleophilic hydrazide (R‐NHNH 2 ) and an electron‐deficient, electrophilic aldehyde (R‐CHO). Hydrazone crosslinked hydrogels and imine variants of the hydrazone bond have previously been explored for their injectable, shear‐thinning and self‐healing properties . They have further been shown to protect cells during extrusion through a needle, adding to the advantages of using this system for 3D printing .…”

Cross‐linking induced thermoresponsive hydrogel with light emitting and self‐healing property

“…TPE bearing one phenolic hydroxyl group (TPE‐OH) was synthesized from 4‐hydroxybenzophenone and benzophenone following previous report and used to synthesize TPE ethanol by reaction with 2‐bromoethanol . The RAFT agent of S‐1‐Dodecyl‐S ′ ‐(R,R ′ ‐dimethyl‐R ″ ‐acetic acid) trithiocarbonate (DDMAT) was synthesized in our lab . PEO 23 ( M n = 1000) was purchased from Guangfu fine chemical research institute and used to prepare PEO 23 DBH and PEO 23 DNH .…”

“…The self‐healing hydrogel can be based on a series of dynamic covalent bonds and each has its own advantages. The amine groups are existed in sustainable chitosan while the acylhydrazide group can be easily transformed through hydrazinolysis of ester bond . On the other side, fluorescent imaging is an useful tool to visualize the hydrogels during its bioapplication processes .…”