Fast Healing of Covalently Cross-Linked Polymeric Hydrogels by Interfacially Ignited Fast Gelation

Abstract

We report a new design concept that utilizes the Ag+/Fe3+-catalyzed fast gelation of acrylic acid (AA) or AA/comonomer aqueous solutions (e.g., 56 s for the gelation of the 20 wt % AA solution) to achieve fast healing of covalently cross-linked polymer hydrogels. The fast-generated poly(acrylic acid) (PAA) or AA copolymer hydrogel with a covalent network is highly active for the interfacially igniting gelation (IIG) of AA or the AA/comonomer in water through a frontal polymerization process. Using the AA or AA/comonomer aqueous solution as the “repairing liquid,” the fast-generated hydrogels (polymer concentration of 20 wt %) are repeatedly healed at room temperature through the IIG reaction without extra energy input. This IIG reaction-mediated healing (IIG-healing) has healing efficiencies higher than 90%. The healing time can be shortened from ∼60 min to only ∼1 min by increasing the solid concentration of the fast-generated hydrogel to 92 wt %. The IIG reaction also enabled the coating of a hydrophobic polymer layer on the hydrogel, resulting in higher tensile strength, toughness, and much better water retention capacity. We expect that this Ag+/Fe3+-catalyzed fast gelation strategy will pave a facile and energy-efficient pathway to fabricate versatile and multifunctional healing polymers.

Highly Stretchable and Self-Healable Tough Polymer Elastomer through Dy3+ and Cu2+ Coordination Cross-Linking

“…By encapsulating healing agents − or incorporating dynamic bonds, including dynamic covalent bonds, − hydrogen bonds, − and coordination bonds, − synthetic polymer materials are able to self-heal autonomously. Among those dynamic bonds, the coordination bond is quite attractive for making self-healing polymers. − Compared with dynamic covalent and hydrogen bonds, coordination bonds are more easily tuned by changing the metal ion, metal oxidation state, or counterion .…”

Biomorphogenesis-Inspired Three-Dimensional Shape Transformation of Bilayer Polymer Sheets

“…According to the PLTG in Figure 1a-iii, we fabricated the BSM material for the gourd shape transformation. Using the Ag + -catalyzed fast gelation reaction developed in our previous report, 53 we first prepared the Ag-PAA hydrogel sheet (active layer thickness (L a ) of 2 mm, polymer content of 10 wt %) as the active layer. Hereafter, all active layers throughout this work had a constant L a of 2 mm.…”

“…The Ag-PAA hydrogel was prepared according to our previous reports. 52,53 The P(MMA-co-BA) layer was created by the interfacially initiated copolymerization of methyl-methacrylate (MMA) and n-butyl acrylate (n-BA). Based on the UV mapping of the mesh model for the target shape, we utilized the laser engraving method to create the passive layer thickness gradient (PLTG).…”

“…The BSM material was composed of a Ag + -containing poly­(acrylic acid) (Ag-PAA) hydrogel and a hydrophobic poly­(methyl-methacrylate- co - n -butyl acrylate) (P­(MMA- co -BA)). The Ag-PAA hydrogel was prepared according to our previous reports. , The P­(MMA- co -BA) layer was created by the interfacially initiated copolymerization of methyl-methacrylate (MMA) and n -butyl acrylate ( n -BA). Based on the UV mapping of the mesh model for the target shape, we utilized the laser engraving method to create the passive layer thickness gradient (PLTG).…”

Reversible White-Light-Driven Photochromic Polymer Hydrogels with High Stretchability and Adhesiveness

“…After 10 min of incubation in a Teflon mold, the AgPAI hydrogel was prepared. In the as-prepared aqueous solution, the presence of Ag + and APS, on the one hand, led to the generation of hydroxyl radicals, , which initiated the copolymerization of AA and IDHPMA (Figure a and Figure S1); on the other hand, it triggered the oxidative decarboxylation reaction of AA, which produced covalent cross-links of P­(AA- co -IDHPMA) (blue region in Figure a). − Finally, the aqueous solution became a transparent hydrogel (Figure S2). Due to the coexistence of Ag + ions and IDA, Ag + –IDA complexes as the physical cross-links were formed in the P­(AA- co -IDHPMA) network (gray region in Figure a).…”