Freezing-Tolerant Supramolecular Organohydrogel with High Toughness, Thermoplasticity, and Healable and Adhesive Properties

Abstract

Hydrogels based on supramolecular noncovalent interactions have attracted great research interest but are still limited by relatively low mechanical strength and performance deterioration at subzero temperatures because of the formation of ice crystallization. In this study, an antifreezing and mechanically strong gelatin supramolecular organohydrogel is prepared via a simple strategy of immersing a gelatin pre-hydrogel in the citrate (Cit) water/glycerol mixture solution. In the organohydrogel, a part of water molecules are replaced by glycerol, which inhibits the formation of ice crystallization even at extremely low temperature. In addition, the formation of noncovalent interactions such as the hydrophobic aggregation induced by the salting-out effect, ionic interactions between the −NH 3 + of gelatin and Cit 3− anions, and hydrogen bonding between gelatin chains and glycerol endows the organohydrogels with high mechanical strength and toughness. The supramolecular organohydrogel can maintain its mechanical flexibility even at −80 °C or be stored for a long time. Moreover, the nature of noncovalent interactions endows the organohydrogel with intriguing thermoplasticity, good healable ability, and excellent adhesive behavior at various substrate surfaces.

Resilient yet entirely degradable gelatin-based biogels for soft robots and electronics

“…Bio-derived hydrogels [22][23][24] based on starch, alginate or collagen are cheap and offer fast degradation rates but typically fail to provide sufficient mechanical integrity under high loads. Strategies based on photo-crosslinking 25 , inclusion of additional monomers 26,27 , or salt treatment 28,29 help to overcome this issue but on the cost of processability, degradability, and price (Table 1).…”

Physical Organohydrogels With Extreme Strength and Temperature Tolerance

“…The tensile strength (Figure 3B), fracture strain ( Figure 3C), and Young's modulus (Figure 3D) of the organohydrogels were higher than that of original Eu-alginate/PVA hydrogel, which can be ascribed to the synergistic effect of the multiple hydrogen bonds and the dense polymer networks. For instance, the tensile strength of OHG SB increases from 0.58 ± 0.06 MPa to as high as 5.62 ± 0.41 MPa, fracture strain raised from 4.07 ± 0.04 to as high as 7.63 ± 0.02 and Young's modulus ascended from 0.16 ± 0.01 to 1.08 ± 0.03 MPa as the displacement time gradually increased to 6 h. The tensile strength is higher than many of the previously reported organohydrogels, such as polydopamine decorating carbon nanotubes (PDA-CNT)/copolymer of acrylamide (AM) and acrylic acid (AA) (PAM-co-PAA) organohydrogel (0.07 MPa stress, 7.01 strain, Han et al, 2017), PVA/poly(3,4ethylenedioxythiophene):polystryrene sulfonate (PEDOT:PSS) organohydrogel (2.1 MPa stress, 7.60 strain, Rong et al, 2017), and gelation organohydrogel (2.06 MPa stress, 6.88 strain, Qin et al, 2019), as shown in Figure S1. The dramatic enhancement in mechanical properties of the organohydrogels is directly related to crosslinking density, which dominated by the largely increased hydrogen bonds between the cryoprotectant molecules and polymer chains in the organohydrogels (Pan et al, 2018).…”

Highly Elastic and >200% Reversibly Stretchable Down‐Conversion White Light‐Emitting Diodes Based on Quantum Dot Gel Emitters

“…Even though some of the gels had complex shapes, they were all colorless and transparent. The different shapes of the gels, with excellent dimensional stability, indicate that the gelation of the polymer proceeded without significant volume changes in the mold, whereas the high transparency of the gel shows that the gelation conditions were suitable for achieving the desired textural properties of the gel, especially in terms of crystallinity and porosity . The gels obtained from the binary solvent system were more transparent and robust compared to a gel prepared from water only (see Figure S4, Supporting Information).…”