Study on the interfacial adhesion mechanism between polydopamine and coal: Experimental demonstration and molecular simulation

Abstract

Understanding the adhesion mechanism between polydopamine (PDA) and coal surface is crucial for implementing the mussel strategy in self-adhesive gel for fire suppression. In this study, a combination of experiments and molecular simulations was utilized to explore the interfacial adhesion mechanism between PDA and coal. Initially, the adhesion potential of varying concentrations of PDA solutions was evaluated using a UV–Vis spectrophotometer, and in conjunction with contact angle/surface tension measurements, it was observed that adhesion strength did not show a direct correlation with PDA concentration. Subsequently, the adhesion sites of PDA on the coal surface were identified through spectroscopic analysis and confirmed using Dmol3 simulations. The study revealed that the amino and phenolic hydroxyl groups in the PDA structure could establish hydrogen bonds with oxygen-containing functional groups on the coal surface (e.g., COOH, OH, R-O-R'), while the aromatic rings in the molecules engaged in π-π stacking interactions. These non-covalent forces collectively facilitated the adhesion process. Molecular dynamics (MD) simulations were then employed to validate the relationship between PDA solution concentration and adhesion strength, which aligned with the experimental findings. Furthermore, the MD simulations elucidated how the concentration of PDA solution influenced its interfacial adhesion strength with coal by considering water molecule diffusion. Overall, this research offers a theoretical foundation for designing self-adhesive gel for fire suppression.