Salicylhydroxamic Acid as a Novel Switchable Adhesive Molecule

Area of Science:

• Materials Science
• Surface Chemistry
• Biomaterials

Background:

• Developing switchable adhesives is crucial for advanced applications.
• Catechol-based adhesives are effective but prone to irreversible oxidation.
• Need for robust, pH-responsive adhesive molecules with tunable properties.

Purpose of the Study:

• To investigate the pH-responsive, switchable adhesive capabilities of salicylhydroxamic acid (SHAM).
• To compare the adhesive performance and stability of SHAM with catechol.
• To elucidate the mechanism behind SHAM's tunable adhesion.

Main Methods:

• Utilized a custom-built Johnson-Kendall-Roberts contact mechanics test setup.
• Tested SHAM-containing adhesives on various surfaces (glass, titanium, polystyrene, amine-functionalized glass).
• Performed density functional theory (DFT) calculations to understand adhesion mechanisms.

Main Results:

• SHAM demonstrated strong wet adhesion at pH 5, comparable to catechol.
• Adhesion decreased by ~98% with increasing pH and fully recovered upon return to pH 5.
• SHAM retained adhesive properties even after exposure to pH 11, showing superior base stability.
• DFT calculations confirmed deprotonation of SHAM as the cause of tunable adhesion.

Conclusions:

• Salicylhydroxamic acid (SHAM) functions as a highly effective pH-responsive, switchable adhesive.
• SHAM offers superior stability and recovery compared to catechol, especially under basic conditions.
• The deprotonation mechanism provides a tunable and robust adhesion strategy for material applications.