Ion‐Specific Effects on Ion and Polyelectrolyte Solvation

• Published in: Chemphyschem 2024-08, Vol.25 (15), p.e202400244-n/a
• Main Authors: Kastinen, Tuuva, Batys, Piotr, Tolmachev, Dmitry, Laasonen, Kari, Sammalkorpi, Maria
• Format: Article
• Language: English
• Subjects: ab initio molecular dynamics; Binding; Molecular dynamics; molecular modelling; poly(diallyldimethylammonium); poly(styrene sulfonate); polyelectrolyte; Polyelectrolytes; Polystyrene resins; Simulation; Solvation
• ISSN: 1439-4235; 1439-7641; 1439-7641
• DOI: 10.1002/cphc.202400244

Ion‐specific effects on aqueous solvation of monovalent counter ions, Na + ${^+ }$ , K + ${^+ }$ , Cl - ${^- }$ , and Br - ${^- }$ , and two model polyelectrolytes (PEs), poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were here studied with ab initio molecular dynamics (AIMD) and classical molecular dynamics (MD) simulations based on the OPLS‐aa force‐field which is an empirical fixed point‐charge force‐field. Ion‐specific binding to the PE charge groups was also characterized. Both computational methods predict similar response for the solvation of the PEs but differ notably in description of ion solvation. Notably, AIMD captures the experimentally observed differences in Cl - ${^- }$ and Br - ${^- }$ anion solvation and binding with the PEs, while the classical MD simulations fail to differentiate the ion species response. Furthermore, the findings show that combining AIMD with the computationally less costly classical MD simulations allows benefiting from both the increased accuracy and statistics reach. Hydration and counter ion interactions of poly(styrene sulfonate) and poly‐(diallyldimethylammonium) are studied with ab initio molecular dynamics (AIMD) and classical molecular dynamics (MD) simulations. AIMD improves accuracy over MD significantly capturing the anion binding difference that explains the experimentally measured trends in polyelectrolyte material swelling response.