A Universal and Reversible Wet Adhesive via Straightforward Aqueous Self-Assembly of Polyethylenimine and Polyoxometalate

A solvent-free processed low-temperature tolerant adhesive

Ultra-low temperature resistant adhesive is highly desired yet scarce for material adhesion for the potential usage in Arctic/Antarctic or outer space exploration. Here we develop a solvent-free processed low-temperature tolerant adhesive with excellent adhesion strength and organic solvent stability, wide tolerable temperature range (i.e. -196 to 55 °C), long-lasting adhesion effect ( > 60 days, -196 °C) that exceeds the classic commercial hot melt adhesives. Furthermore, combine experimental results with theoretical calculations, the strong interaction energy between polyoxometalate and polymer is the main factor for the low-temperature tolerant adhesive, possessing enhanced cohesion strength, suppressed polymer crystallization and volumetric contraction. Notably, manufacturing at scale can be easily achieved by the facile scale-up solvent-free processing, showing much potential towards practical application in Arctic/Antarctic or planetary exploration.

A Nature-Inspired Versatile Bio-Adhesive

The application of most hydrogel bio-adhesives is greatly limited due to their high swelling, low underwater adhesion, and single function. Herein, a spatial multi-level physical-chemical and bio-inspired in-situ bonding strategy is proposed, to develop a multifunctional hydrogel bio-glue using polyglutamic acid (PGA), tyramine hydrochloride (TYR), and tannic acid (TA) as precursors and 4-(4,6-dimethoxytriazine-2-yl) -4-methylmorpholine hydrochloride(DMTMM) as condensation agent, which is used for tissue adhesion, hemostasis and repair. By introducing TYR and TA into the PGA chain, it is demonstrated that not only can the strong adhesion of bio-glue to the surface of various fresh tissues and wet materials be realized through the synergistic effect of spatial multi-level physical and chemical bonding, but also this glue can be endowed with the functions of anti-oxidation and hemostasis. The excellent performance of such bio-glue in the repair of the wound, liver, and cartilage is achieved, showing a great potential in clinical application for such bio-glue. This study will open up a brand-new avenue for the development of multifunctional hydrogel biological adhesive.

Scalable Underwater Adhesives with High-Strength, Long-Term, and Harsh-Environment Adhesion Enabled by Heterocyclic Chemistry

Developing scalable and high-performance underwater adhesives is important in various biomedical and industrial applications. However, despite massive efforts, the realization of such adhesives remains a challenging task, as mainly imposed by the difficulty in balancing the interfacial and bulk properties via an efficient way. Here, we report a facile yet effective strategy to construct a novel underwater adhesive with multiple advantaged performances by virtue of heterocyclic chemistry. This adhesive is designed with the cooperation of a heterocycle-based versatile adhesive functionality and an eco-friendly hydrophilic matrix with cross-linkable sites, which allows water absorption to destroy hydration layer, diverse molecular interactions to enhance interfacial adhesion, and abundant covalent crosslinks to strengthen bulk cohesion. Such a rational design endows the adhesive with strong underwater adhesion (up to 1.16 MPa for wood and 0.36 MPa for poly(tetrafluoroethylene) (PTFE)), long-term durability (maintaining pristine strength even after 4 months), and harsh-environment stability (salt, acidic/alkaline, low/high-temperature solutions). This strategy is also generic to derive more adhesive formulas, which offers a new direction for designing the next-generation underwater adhesives with high performance and scalability for practical applications.

An Instant Underwater Tissue Adhesive Composed of Catechin-Chondroitin Sulfate and Cholesterol-Polyethyleneimine

Due to the safety issue and poor underwater adhesion of current commercially available bioadhesives, they are hard to apply to in vivo physiological environments and more diverse medical use conditions. In this study, a novel and facile bioadhesive for underwater medical applications are designed based on the coacervation of electrostatic interactions and hydrophobic interactions, with the introduction of catechin as a provider of catechol moieties for adhesion to surrounding tissues. The orange-colored bio-adhesive, named PcC, is generated within seconds by mixing catechin-modified chondroitin sulfate and cholesterol chloroformate-modified polyethyleneimine with agitation. In vitro mechanical measurements prove that this novel PcC bio-adhesive is superior in underwater adhesion performance when applied to cartilage. Animal experiments in a rat mastectomy model and rat cartilage graft implantation model demonstrate its potential for diverse medical purposes, such as closing surgical incisions, reducing the formation of seroma, and tissue adhesive applied in orthopedic or cartilage surgery.