Ultrastrong underwater adhesion on diverse substrates using non-canonical phenolic groups

Abstract

Robust underwater adhesion is challenging because a hydration layer impedes the interaction between substrates and adhesives. Phenolic adhesives inspired by marine creatures such as mussels were extensively studied, but these adhesives have not reached the adhesion strength and substrate diversity of Man-made dry adhesives. Here, we report a class of ultrastrong underwater adhesives with molecular phenolic designs extending beyond what nature has produced. These non-canonical phenolic polymers show versatile adhesion on various materials, with adhesion strengths exceeding 10 MPa on metal. Incorporating even just a small amount (<10%) of non-canonical phenolic groups into a polymer is sufficient for dramatically enhancing underwater adhesion, suggesting that this new class of phenolic materials will be incorporated into various industrial polymer systems in the future.

Photoswitchable Adhesives of Spiropyran Polymers

“…To date, photoswitchable adhesives have been developed by utilizing a variety of photoresponsive systems including large structural changes of azobenzenes, − conjugation changes of diarylethenes, , dimerization of anthracenes, − photothermal effects of supramolecular motifs and dyes, − and other reactions. − Reversibly switchable polymer adhesives are particularly attractive because of their strong adhesion and recyclability. Similarly, large polarity changes in the photoisomerization between noncharged spiropyran (SP) and zwitterionic merocyanine (MC) seem highly suitable for photocontrol of adhesion (Figure a) , because molecular polarity and related interactions between adhesives and substrate surfaces are dominant factors to generate adhesion force. − The dipole moment (μ) drastically changes between 4–6 D for SP and 14–18 D for MC. , However, to the best of our knowledge, SP has been only used as additives in polymer adhesives ,, or as low-molecular-weight adhesives . In the additive approach, there is a concern about phase separation between a polymer matrix and SP small molecules particularly after isomerization to MC due to the large difference in the polarity between them, which degrades the performance and undermines the reliability.…”

Robust and multifunctional natural polyphenolic composites for water remediation

“…The adhesion strengths on metal could exceed 10 MPa, surpassing all commercial and literature underwater adhesives. 47 It is important to highlight that the superb adhesion ability enables natural polyphenols to admirably integrate with many other types of substrates to exploit the multifunctional composite materials that can be used for water treatment and other applications.…”

Water‐Triggered Spontaneously Solidified Adhesive: From Instant and Strong Underwater Adhesion to In Situ Signal Transmission

“…[35,36] Inspired by these creatures, a postgelation strategy is employed to design amorphous adhesive liquids (glue) for better conforming to the special morphology of substrates and providing robust binding. [37][38][39] Among them, water-triggered postgelation is specifically preferred for its spontaneous characteristic without the additional requirements of external stimuli, [40] usually achieved by waterinduced polymerization, [41,42] substance outflow, [43] solvent exchange, [44] pH change, [45] or water-triggered coacervation. [46] However, in these cases, substance exchange between the glue and external water is always inevitable for regulating the internal environment to initiate the gelation, [47] which may inversely aggravate the loss of the small conductive ions/ particles.…”