Interfacial polymerization of dopamine with diamines for ultrastable Janus nanofiltration membranes and adhesives

The polymerization of dopamine can yield nature-inspired materials for diverse applications. Polydopamine (PDA) is used for modifying hydrophilic surfaces via deposition techniques; however, it lacks film-formation ability. In this study, we demonstrate the interfacial polymerization of dopamine with diamines via aza-Michael addition, which results in the formation of films possessing thicknesses in the range of nano- to micrometers with Janus properties for the latter. Experimental and in silico mechanistic investigations were conducted to determine the effects of the diamine chain length, monomer concentration, heteroatom, and solvent medium on film formation. The nanofilms exhibited exceptional stability in harsh organic solvents, ionic liquids, and strong acids. A 5-nm thick nanofilm composed of PDA and biomass-derived priamine exhibited controllable nanofiltration performance, demonstrating a high N,N-dimethylformamide solvent permeance of 26 L m⁻² h⁻¹ bar⁻¹ and molecular weight cutoff of 540–704 g mol⁻¹. Furthermore, the membrane was successfully applied in high-temperature nanofiltration. Additionally, the nanofilms demonstrated single- and double-sided adhesion on diverse surfaces, including wood and glass surfaces, which possess different wettability and roughness characteristics. This study provides a comprehensive understanding of the structure–property relationship, polymerization mechanism, membrane separation, and adhesive applications of PDA–diamine freestanding films.