We measured the single-molecule interaction force between various hydroxybenzoic acids and a Si3N4 cantilever by atomic force microscopy in force curve mode. The adhesion properties of hydroxybenzoic acids with different numbers of hydroxyl groups in various positions on the aromatic ring were compared to determine the effect of the hydroxyl groups on single-molecule interactions. It was found that as the number of hydroxyl group increases, the number of single-molecule interactions increases and the interaction force also increases. A catecholic system with two hydroxyl groups on the aromatic ring, similar to that found in mussel adhesive, has been well studied. Here we demonstrate that gallic acid with three hydroxyl groups on the aromatic ring showed good adhesion and a large number of single-molecule interactions. We synthesized gallic acid adhesives that exhibited sufficiently strong adhesion (10 MPa) to be of practical use.
- Shougo Kinugawa
- Siqian Wang
- Daisaku Kaneko
