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Functional Wet/Underwater Adhesives Enabled by Hydrogen-Bonding Interaction-Driven Coacervation
- Author / Creator
- Peng, Qiongyao
Robust instant and repeatable underwater adhesion is a great challenge for the development of adhesives as water is a notorious destroyer to prevent the intimate contact of adhesives and substrates by forming hydration layers on surfaces. Long-lasting and strong underwater adhesion of sessile organisms has inspired substantial research attraction in biomimetic underwater adhesives, whose formation involves a critical biological process named coacervation. Coacervation is a liquid-liquid phase separation phenomenon where a material-rich dense coacervate phase and a co-existing immiscible dilute supernatant simultaneously generated from a homogeneous aqueous solution consisting of one (simple coacervation) or two different types of (complex coacervation) macromolecules (e.g., proteins, polymers, and colloids). Current coacervation-derived wet/underwater adhesives usually suffer from complex polymer synthesis, delicate formation conditions, weak mechanical properties, and low yields. Additionally, increasing demands of advanced and smart materials impels the fabrication of wet/underwater adhesives with multifunctionalities, which is rarely achieved. In this thesis, a review of recent advances in coacervation and underlying noncovalent intermolecular interactions is presented first, followed by three original studies regarding the development of multifunctional wet/underwater adhesives based on hydrogen-bonding interaction-driven coacervates.
Wet adhesives have been recognized as attractive candidates of tissue glues and wound dressings. In the first project, an instant paintable antimicrobial hemostatic agent was developed based on hydrogen-bonding interaction-enabled coacervates. The fabrication of the coacervate was achieved via one-step mixing of silicotungstic acid (SiW) and poly(ethylene glycol) (PEG) aqueous solutions, which is extremely facile and could be scaled up. Phase behaviors, rheological properties, and associated intermolecular interaction of the coacervates were investigated. This work demonstrates that coacervation can occur in salt-free environments via non-electrostatic interactions, providing a new platform for engineering multifunctional coacervate materials as tissue glues, wound dressings, and membrane-free cell systems.
Instant underwater adhesives have gained special interest as paintable electrodes in the development of next-generation aqueous batteries. In the second project, coacervation-driven instant paintable underwater adhesives with tunable optical and electrochromic properties were prepared. The formation of the adhesives was induced through the facile one-step mixing of SiW and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) micelles aqueous solutions, which was driven by hydrogen-bonding and hydrophobic interactions. The as-prepared adhesive possesses instant and excellent underwater adhesion (up to 479.6 kPa on poly(methyl methacrylate)) and can be readily painted underwater on diverse substrates, showing resistance to water flush as well as repeatable stretching and bending of the substrates. The adhesive also exhibited outstanding stability in aqueous solutions of high salinity up to 3 M for at least 1200 h. The introduction of P123 endows the adhesives with thermo-responsive optical property, while the innate reduction-related color switch of SiW offers the electrochromic property. The functional adhesives hold great promise in bioengineering applications and for the fabrication of novel flexible electronics such as smart aqueous batteries and low-power electrochromic windows.
In the third project, novel instant and repeatable underwater adhesives with anticancer and antibacterial properties were fabricated via the one-step mixing of tannic acid (TA) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F68) micelles aqueous solutions. This coacervation phenomenon was also driven by hydrogen-bonding and hydrophobic interactions. Meanwhile, the coacervates could be facilely painted on different substrates, exhibiting robust and instant underwater adhesion (with adhesion strength up to 1.1 MPa on porcine skin) and excellent repeatability (at least 1000 cycles). Due to the biological activities of TA, the underwater adhesive displayed innate anticancer and antibacterial properties against different types of cancer cells and bacteria, showing great potential for diverse biomedical applications, such as injectable drug carriers, tissue glues and wound dressings.
Three novel functional wet/underwater adhesives have been developed in this work, which are based on coacervation driven by hydrogen-bonding interaction. This work expands the applicability of hydrogen-bonding interaction to different multifunctional materials such as antibacterial hemostatic agent and paintable electrodes, providing new insights and approaches to the development of advanced functional materials based on hydrogen-bonding interaction for diverse biomedical and engineering applications.
- Graduation date
- Fall 2021
- Type of Item
- Doctor of Philosophy
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