Understanding Urea-Linked Dicatechol Chemistry for Developing Micrometer-Thick Surface Coatings

Catechol-containing molecules, such as dopamine, are widely explored as effective surface-coating agents. However, the development of dicatechol derivatives remains under-investigated. Here, we report the synthesis of urea-linked dicatechol derivatives and their ability to form micrometer-thick surface coatings under oxidative conditions. The representative urea-linked dicatechol derivative yielded coatings over 30-fold thicker than those from dopamine in the presence of sodium periodate. Mechanistic studies revealed that at least one free catechol group is essential for initiating the coating. Substituting one catechol with a simple phenyl group still enhanced coating thickness through π-π stacking interactions. By contrast, derivatives that lack free catechol groups or aromatic moieties failed to form coatings on substrates. Spectroscopic and surface analyses confirmed that coating proceeds via rapid catechol oxidation, followed by intermolecular cross-linking through covalent and noncovalent pathways. These findings establish key structure-function relationships in catechol-based coating chemistry and provide a strategic framework for next-generation thick and functional surface coatings.