Understanding the aggregation properties of polydopamine with polarizable forcefield molecular dynamics

Polydopamine (PDA) is a mussel-inspired wet adhesive biopolymer with a unique ability to form functional coatings independent of substrate surface chemistry. However, its complete insolubility in conventional solvents has limited characterization to solid-state techniques. Recent findings demonstrated that PDA can be solvated in the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]), forming supramolecular aggregates of monomers and covalent dimers. In this work, we advance the understanding of PDA dissolution and aggregation through Quantum Mechanical (QM) calculations and state-of-the-art polarizable Molecular Dynamics (pMD) simulations. The simulations reveal that ILs exhibit superior solvation ability compared to aqueous and organic solvents, aligning with experimental observations. Furthermore, we identify chloroform as the most effective anti-solvent for inducing PDA aggregation, allowing for the deposition of ultrasmooth PDA coatings. Additionally, predicted interaction energies between PDA dimers and IL ion pairs correlate well with experimental and MD dissolution results, offering a rapid screening method for identifying other viable ILs.