Synergy of Host–Guest and Cation−π Interactions for an Ultrastretchable, pH-Tunable, Surface-Adaptive, and Salt-Resistant Hydrogel Adhesive

Abstract

The adhesion to wet, acidic, and saline biointerfaces with large deformation is important in the fields of wound dressing and motion monitoring but has proven to be extremely challenging. There is a need for a facile method to improve the stretchability and salt resistance simultaneously. Here, an ultrastretchable, pH-tunable, surface-adaptive, and salt-resistant hydrogel adhesive is reported. The hydrogel adhesive is prepared through cross-linking acrylamide with a supramolecular complex of poly­(β-cyclodextrin) (PCD) and benzimidazole (BI). The dynamic association between PCD and BI causes an extra energy dissipation and improves the breaking strain to be larger than 4000%. The hydrogel exhibits stable adhesiveness to varieties of surfaces due to the multiple types of hydrogel–surface interactions, including ionic bond, π–π stacking, and hydrogen bond. Notably, the adhesive strength of the hydrogel gets significantly enhanced in an acidic environment and shows no attenuation in a saline environment. This is due to the unique adjacent cation−π structure of BI: the imidazole can be protonized upon acidification, and the phenyl group can repel water and enhance the ionic attraction with the substrates. The ultrastretchability, the stable adhesion on biointerfaces, and the salt resistance render the hydrogel a promising candidate for the surgical patch and motion sensors that serve in wet, acidic, and dynamic environments.

Promising Delivery Platform for Smart Pest Control with High Water-Retaining Capacity

“…P­(β-CD) was synthesized by the condensation polymerization according to the previous studies. − For the sake of clarity, only reactions on the primary alcohols are shown (Figure A). Briefly, β-CD (10.0 g, 8.8 mmol) was first dissolved in 15 mL of NaOH aqueous solution (15 wt %) and stirred at room temperature overnight.…”

Engineered cyclodextrin-based supramolecular hydrogels for biomedical applications

“…Studies have shown that CD-based supramolecular self-assembly systems can effectively react to external stimuli, leading to the assembly and dissociation of the system. For example, the pH sensitivity of the b-CD/benzimidazole system, [151][152][153] the redox responsiveness of the b-CD/Fc, 56,154 and the UV light sensitivity of the b-CD/Azo have been investigated. 67,68 These host-guest interactions offer promising conditions for the exploitation of stimuli-responsive CD-based supramolecular hydrogels.…”

Engineering cohesion and adhesion through dynamic bonds for advanced adhesive materials

“…[ 83 ] The host–guest complexation between β ‐cyclodextrin and benzimidazole was employed by Zhao's group to prepare hydrogel adhesives. [ 84 ] In the system, β ‐cyclodextrins were polymerized to serve as macromolecular cross‐linkers, which formed dynamic cross‐links with the benzimidazole pendant groups in the poly(acrylamide)‐based copolymer chains. The dynamic host–guest complexes afforded bulk toughness for cohesion, and the pendant groups in the copolymer chains interacted with substrates through other physical interactions to achieve interfacial adhesion.…”