Rheology of phosphonium ionic liquids: a molecular dynamics and experimental study

Sarman, Sten; Wang, Yong‐Lei; Rohlmann, Patrick; Glavatskih, Sergei; Laaksonen, Aatto

doi:10.1039/c7cp08349a

Cited by 19 publications

(20 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this work, we adopted a similar scheme by down‐scaling unity charges (±1e) for tetraalkylphosphonium cations and [NTF 2 ] anions using a factor of 0.8 to account for polarization and charge transfer effects between ion species . This scaling factor is effective in providing reliable liquid viscosities of [P 6,6,6,14 ][BMB] (bis(mandelato)borate) and [P 6,6,6,14 ]Cl (chloride) ILs as those obtained from experimental measurements within a wide temperature interval of 373–463 K . It should be noted that such a charge scaling procedure is not universal.…”

Section: Ion Models and Computational Methodologymentioning

confidence: 99%

The Effect of Phenyl Substitutions on Microstructures and Dynamics of Tetraalkylphosphonium Bis(trifluoro‐ methylsulfonyl)imide Ionic Liquids

Wang

Laaksonen

et al. 2020

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

Extensive atomistic simulations demonstrated that a gradual substitution of hexyl chains with phenyl groups in tetraalkylphosphonium cations results in remarkable changes in hydrogen bonding interactions, liquid structures and scattering structural functions, and rotational dynamics of hexyl chains and phenyl groups in tetraalkylphosphonium bis(trifluoromethylsulfonyl)imide ionic liquids. Hydrogen donor sites in hexyl chains present competitive characteristics with those in phenyl groups in coordinating anions, as well as their continuous and intermittent hydrogen bonding dynamics. Cation‐cation and anion‐anion spatial correlations show concomitant shift to short distances with decreased peak intensities with variations of cation structures, whereas cation‐anion correlations have a distinct shift to large radial distances due to decreased associations of anions with neighboring cations. These microstructural changes are qualitatively manifested in shifts of prominent peaks for prevalent charge alternations and adjacency correlations between ion species in scattering structural functions. Meanwhile, rotational dynamics of hexyl chains speed up, which, in turn, slow down rotations of phenyl groups, whereas anions exhibit imperceptible changes in their rotational dynamics. These computational results are intrinsically correlated with conformational flexibilities, molecular sizes, and steric hindrance effects of phenyl groups in comparison with hexyl chains, and constrained distributions of anions around cations in heterogeneous ionic environments.

show abstract

Section: Ion Models and Computational Methodologymentioning

confidence: 99%

The Effect of Phenyl Substitutions on Microstructures and Dynamics of Tetraalkylphosphonium Bis(trifluoro‐ methylsulfonyl)imide Ionic Liquids

Wang

Laaksonen

et al. 2020

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

show abstract

“…The preliminary results of atomistic simulations on these ILs have shown that the viscosities of [P 6,6,6,14 ][BMB] IL system do not change within statistical uncertainty when system size is increased from 96 to 735 ion pairs [116]. This is advantageous when the Green-Kubo relation is evaluated since thermal fluctuations are larger in smaller systems, which means that the time correlation functions converge faster.…”

Section: Simulation Algorithms For Calculation Of Ionic Liquid Viscositymentioning

confidence: 99%

4. Multigranular modeling of ionic liquids

Wang¹,

Sarman²,

Laaksonen³

et al. 2019

Ionic Liquids

Self Cite

View full text Add to dashboard Cite

Ionic liquids (ILs) are a special category of molten salts with melting points near ambient temperatures (or by convention below 100°C). Owing to their numerous valuable physicochemical properties as bulk liquids, solvents, at surfaces and in confined environments, ILs have attracted increasing attention in both academic and industrial communities in a variety of application areas involving physics, chemistry, material science and engineering. Due to their nearly limitless number of combinations of cation-anion pairs and mixtures with cosolvents, a molecular level understanding of their hierarchical structures and dynamics, requiring strategies to connect several length and time scales, is of crucial significance for rational design of ILs with desired properties, and thereafter refining their functional performance in applications. As an invaluable compliment to experiments from synthesis to characterization, computational modeling and simulations have significantly increased our understanding on how physicochemical and structural properties of ILs can be controlled by their underlying chemical and molecular structures. In this chapter, we will give examples from our own modeling work based on selected IL systems, with focus on imidazolium-based and tetraalkylphosphonium-orthoborate ILs, studied at several spatio-temporal scales in different environments and with particular attention to applications of high technological interest. We start by describing studies performed using ab initio methods on force field development for tetraalkylphosphonium-orthoborate ILs, and computational studies on thermal decomposition of these ILs. The delicate interplay between hydrogen bonding and π-type interactions in an imidazolium-orthoborate IL was studied by performing ab initio molecular dynamics simulations. On the atomistic level, atomistic simulations were performed with constructed force field parameters to study intrinsic molecular interactions between residual water molecules and tetraalkylphosphoniumorthoborate ionic species. For a typical trihexyltetradecylphosphonium bis(oxalato) borate IL at varied concentrations, microstructures and dynamics were systematically analyzed as water concentration increases. The liquid viscosities of typical trihexyltetradecylphosphonium-based ILs were estimated through equilibrium atomistic simulations using Green-Kubo relation with charge scaling factors on ionic species.Additionally, atomistic simulations were combined with X-ray scattering experiments to investigate phase behavior and ionic structures in IL mixtures with varied concentrations. Peculiar features of X-ray scattering spectra of IL mixtures with organic solvent are also discussed with an example dealing with ethyl ammonium nitrate and acetonitrile mixtures. On the mesoscopic level, a united-atom model for trihexyltetradecylphosphonium cation and coarse-grained models for butylmethy-limidazolium hexafluorophosphate were proposed, and effective interactions between coarse-grained beads were validated against experimental...

show abstract

“…For example, Holm and co‐workers calculated the charge of ions in [C 2 C 2 im][Cl], at the MP2 (second order Møller–Plesset) level of theory and also by first‐principles MD simulations, finding values in the range 0.8–0.6 e , depending on the computational protocol, in any case much lower than unity . It is also well known that a scaling of the total ionic charge in classical Force Fields (FF) of ILs leads to a better agreement of the results of the MD simulations with experimental dynamic properties; this also supports the idea of a significantly reduced effective charge of the ions.…”

Section: Structure Of Ionic Liquidsmentioning

confidence: 99%

Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation

Saielli

2018

Advcd Theory and Sims

View full text Add to dashboard Cite

Computational spectroscopy" refers to quantum chemistry protocols capable of predicting the electronic and/or magnetic spectra of molecules. The most common techniques used for structural assignment are infrared, electronic, and NMR spectroscopies. Chemists can normally deduce the chemical structure of an unknown substance by using a vast collection of empirical relationships linking the spectral features with the presence or absence of functional groups and, this part mostly by NMR, the connectivity between them and the relative stereochemistry. Computational spectroscopy is a powerful aid for structural elucidation when empirical relationships do not suffice to unambiguously assign the structure. In these cases, the calculated spectrum of a putative structure is compared with the experimental one and the match, or lack thereof, between the two, measured by several statistical parameters, indicates whether or not that structure is the correct one. Is it possible to extend such protocols to bulk phases of complex fluids, such as ionic liquids, rather than covalent molecules, in order to get insights into the average structure of the fluid? It is the aim of this Progress Report to highlight recent advances in this field through the discussion of specific case studies.

show abstract

Rheology of phosphonium ionic liquids: a molecular dynamics and experimental study

Abstract: We have studied the rheological behavior of the ionic liquid trihexyl(tetradecyl)phosphonium bis(mandelato)-borate, [P 66614

Cited by 19 publications

References 62 publications

The Effect of Phenyl Substitutions on Microstructures and Dynamics of Tetraalkylphosphonium Bis(trifluoro‐ methylsulfonyl)imide Ionic Liquids

The Effect of Phenyl Substitutions on Microstructures and Dynamics of Tetraalkylphosphonium Bis(trifluoro‐ methylsulfonyl)imide Ionic Liquids

4. Multigranular modeling of ionic liquids

Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation

Contact Info

Product

Resources

About