How alkyl branching shapes structure in imidazolium and pyrrolidinium NTf 2 ionic liquids

Emerson, Matthew S. [Brookhaven National Laboratory (BNL), Upton, NY (United States)]; Fetherolf, Jonathan [Rutgers, The State University of New Jersey, Piscataway, NJ (United States)]; Wu, Boning [Rutgers, The State University of New Jersey, Piscataway, NJ (United States)]; Ramati, Sharon [Brookhaven National Laboratory (BNL), Upton, NY (United States); City University of New York, Bayside, NY (United States)]; Mukhlall, Joshua [City University of New York, Bayside, NY (United States)]; Fernandez, Eddie D. [City University of New York, Bayside, NY (United States)]; Gohdo, Masao [Brookhaven National Laboratory (BNL), Upton, NY (United States); Japan Atomic Energy Agency (JAEA), Tokai-Mura Ibaraki (Japan)]; Lall-Ramnarine, Sharon I. [City University of New York, Bayside, NY (United States)]; Castner, Jr., Edward W. [Rutgers, The State University of New Jersey, Piscataway, NJ (United States)]; Wishart, James F. [Brookhaven National Laboratory (BNL), Upton, NY (United States)]

doi:10.1016/j.jil.2026.100209

DOE OSTI · 3377351

How alkyl branching shapes structure in imidazolium and pyrrolidinium NTf 2 ionic liquids

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Abstract

High-energy X-ray scattering experiments and molecular dynamics (MD) simulations were carried out on ionic liquids (ILs) consisting of 1-alkyl-3-methylimidazolium and 1-alkyl-1-methylpyrrolidinium cations. These cations were paired with bis(trifluoromethylsulfonyl)amide anions and identical alkyl tails were used for both cationic species. The goal of this work is to investigate how the nanoscale structure of the ionic liquid changes with the length and with the degree of branching of the alkyl tail, for ILs having a common anion. We investigate spatial correlations in the intermolecular region, focusing on the intrinsic charge-charge interactions that characterize all ionic liquids, as well as the nanoscale domain segregation that is present in IL species with significant nonpolar components.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY Alkyl branching Density First sharp diffraction peak Fragility Glass transition Imidazolium Ionic conductivity Ionic liquids Molecular dynamics Pyrrolidinium Viscosity X-ray scattering

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Emerson, Matthew S. [Brookhaven National Laboratory (BNL), Upton, NY (United States)], Fetherolf, Jonathan [Rutgers, The State University of New Jersey, Piscataway, NJ (United States)], Wu, Boning [Rutgers, The State University of New Jersey, Piscataway, NJ (United States)], Ramati, Sharon [Brookhaven National Laboratory (BNL), Upton, NY (United States); City University of New York, Bayside, NY (United States)], Mukhlall, Joshua [City University of New York, Bayside, NY (United States)], Fernandez, Eddie D. [City University of New York, Bayside, NY (United States)], Gohdo, Masao [Brookhaven National Laboratory (BNL), Upton, NY (United States); Japan Atomic Energy Agency (JAEA), Tokai-Mura Ibaraki (Japan)], Lall-Ramnarine, Sharon I. [City University of New York, Bayside, NY (United States)], Castner, Jr., Edward W. [Rutgers, The State University of New Jersey, Piscataway, NJ (United States)], Wishart, James F. [Brookhaven National Laboratory (BNL), Upton, NY (United States)]. 2026-06-01. How alkyl branching shapes structure in imidazolium and pyrrolidinium NTf 2 ionic liquids. https://doi.org/10.1016/j.jil.2026.100209

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