Poly(benzyl acrylate) structural and thermodynamic properties in imidazolium-based ionic liquids: A molecular dynamics simulations study

Abstract

Molecular dynamics simulations were performed to investigate the structural and thermodynamic properties of poly(benzyl acrylate) (PBA) in eight imidazolium-based ionic liquids (ILs), each sharing a common cation, 1-ethyl-3-methylimidazolium ([EMIM]⁺), and different in anions chemistry: acetate [OAc]⁻, benzoate [Bz]⁻, bis(trifluoromethane)sulfonimide [NTf₂]⁻, tetrafluoroborate [BF₄]⁻, formate [FRM]⁻, methyl Sulfate [MeSO₄]⁻, nitrate [NO₃]⁻ and hexafluorophosphate [PF₆]⁻. The results demonstrate that both the size and chemical nature of the anions influence the conformation and solvation environment of the PBA chain. In particular, larger or more strongly interacting anions promote polymer swelling, as confirmed by an increase in radius of gyration and end-to-end distance relative to water. Swelling ratios, calculated with respect to water, provide quantitative evidence of anion-specific structural perturbations. The results are further quantified by using the radial distribution functions (RDFs), reduced density gradient (RDG) calculations, and solvent accessible surface area (SASA). The solvation enthalpy (ΔH_solv) and excess molar volume (V_E^m) of the PBA chain are in accordance with structural changes. Overall, these results provide the effect of IL combinations on the solvation and structural behaviour of the PBA, offering insights relevant for polymer design and IL-based processing.