Temperature Dependence of Volumetric and Dynamic Properties of Imidazolium-Based Ionic Liquids

Khabaz, Fardin; Zhang, Yong; Xue, Lianjie; Quitevis, Edward L.; Maginn, Edward J.; Khare, Rajesh

doi:10.1021/acs.jpcb.7b12236

Cited by 21 publications

(26 citation statements)

References 51 publications

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“…It can be seen that the T g values calculated from simulations are higher than the experimental values for GalEAm and DMA linear polymers by 38 and 111 K, respectively. Similar observations have been reported in literature for a wide range of systems, such as asphalt, ionic liquids, linear polyacrylates, and crosslinked epoxies that differ in their molecular weight, connectivity, and interactions. Specifically, T g value differences of 113 K (asphalt), 77 K (ionic liquids), 70–106 K (linear polyacrylates), and 27 K (crosslinked epoxies) were observed and were attributed to significantly faster cooling rates used in simulations compared to experiments which lead to higher T g values in simulations compared to experiments.…”

Section: Resultssupporting

confidence: 90%

“…Specifically, T g value differences of 113 K (asphalt), 77 K (ionic liquids), 70–106 K (linear polyacrylates), and 27 K (crosslinked epoxies) were observed and were attributed to significantly faster cooling rates used in simulations compared to experiments which lead to higher T g values in simulations compared to experiments. The Williams–Landel–Ferry (WLF) equation, which characterizes the temperature dependence of relaxation time, has been used to estimate the expected shift in T g due to these differences in cooling rates . Specifically, using the universal WLF parameters ( C 1 = 17.44 and C 2 = 51.6 K), for the cooling rate used in simulations in this work, the calculated shift in T g is 84 K, which is in the same order as the observed differences (38 and 111 K for GalEAm and DMA, respectively).…”

Section: Resultsmentioning

confidence: 64%

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Water structure and mobility in acrylamide copolymer glycohydrogels with galactose and siloxane pendant groups

Fogel

Ravichandran

Mani

et al. 2019

J Polym Sci B Polym Phys

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Glycohydrogels containing 2′‐acrylamidoethyl‐β‐d‐galactopyranoside and varying levels of N,N′ methylene bisacrylamide and 3‐acrylamidopropyltris(trimethylsiloxy)silane were synthesized to determine the effects of crosslinker and amphipathic balance on equilibrium water content (EWC), bound water population, and hydrogen bonding dynamics at the water–polymer interface. Analogous dimethylacrylamide hydrogels were synthesized for comparison with a system containing lower hydrogen bonding propensity. An approach combining experiment (proton nuclear magnetic resonance, thermogravimetric analysis, differential scanning calorimetry, and dynamic vapor sorption analysis) and molecular dynamics simulations was employed to examine the relationship between bulk hydrogel properties, molecular water mobility, and hydrogen bonding characteristics. It was found that copolymer composition (hydrophobic content) and crosslink concentration in high water content glycohydrogels affect EWC, and by extension, structural water population. The organization of water at the polymer interface is greatly impacted by the surrounding environment, where hindered molecular water mobility promotes water–polymer binding and decreases water–water clustering. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 584–597

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 64%

Water structure and mobility in acrylamide copolymer glycohydrogels with galactose and siloxane pendant groups

Fogel

Ravichandran

Mani

et al. 2019

J Polym Sci B Polym Phys

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“…Note that the system is coarse-grained and the quenching rate has a minimal impact on the volumetric data obtained in simulations as opposed to all-atom MD simulations. 51,52…”

Section: Oldmentioning

confidence: 99%

“…At extremely high temperatures ( T ̃ ≥ 1.8), the probability plateaus, which shows that temperature does not affect the rate of the bond exchange anymore. Note that the system is coarse-grained and the quenching rate has a minimal impact on the volumetric data obtained in simulations as opposed to all-atom MD simulations. , …”

Section: Simulations Detailsmentioning

confidence: 99%

Volumetric and Rheological Properties of Vitrimers: A Hybrid Molecular Dynamics and Monte Carlo Simulation Study

Perego

Khabaz

2020

Macromolecules

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Contrary to thermosets, vitrimers adjust their topology upon heating without loss of network integrity. Here, the proposed simulation methodology utilizes coarse-grained molecular dynamics in conjunction with a Monte Carlo method to capture the network integrity and flowability of vitrimers at high temperatures. The model vitrimer shows two transition temperatures. In addition to the conventional glass transition temperature, the topology freezing temperature is detected from the volumetric and rheological data. In the glassy state, the mobility of the vitrimer and thermoset is identical, whereas increasing the temperature results in a diffusive behavior in the vitrimer. The rheological data capture the main feature of vitrimers, which is the terminal regime of the elastic modulus at low frequencies. The zero-shear viscosity of the model vitrimer follows an Arrhenius-like temperature dependence at temperatures above the topology freezing temperature. The horizontal shift factors obtained from collapsing the rheological data onto master curves also display the same temperature dependence. Simulations reveal that the lifetime of the exchangeable bonds determines the rheology and dynamics of these networks. When the rate of the deformation is higher than the rate of the bond exchange, the system behaves as a typical thermoset, while at lower rates, the vitrimer behaves as a viscous liquid.

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“…Since the first development of water stable room temperature ILs, computer simulations have been used for this task, being able not only to explain but also often to predict their properties before experiments. 1 Molecular dynamics simulations of ionic liquids are normally performed with fullyatomistic force fields [2][3][4] and help to explain, at a molecular level, physical properties like the viscosity, 5,6 the melting point, 7 dielectric response, 8,9 sound modes, 10 and bulk and shear moduli 11 of ILs. Traditional non-polarizable force fields keep the partial charges on the atoms fixed, with polarization represented implicitly by an effective Lennard-Jones or similar potential.…”

Section: Introductionmentioning

confidence: 99%

Ion pair free energy surface as a probe of ionic liquid structure

Bernardino

Goloviznina

Gomes

et al. 2020

The Journal of Chemical Physics

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Numerous combinations of cations and anions are possible for the production of ionic liquids with fine-tuned properties once the correlation with the molecular structure is known. In this sense, computer simulations are useful tools to explain and even predict the properties of ionic liquids. However, quantum mechanical methods are usually restricted to either small clusters or short time scales so that parameterized force fields are required to study the bulk liquids. In this work, a method is proposed to enable a comparison between the quantum mechanical system and both polarizable and nonpolarizable force fields by means of the calculation of free energy surfaces for the translational motion of the anion around the cation in gas phase. This method was tested for imidazolium-based cations with 3 different anions, [BF4]−, [N(CN)2]−, and [NTf2]−. Better agreement was found with the density functional theory calculations when polarizability is introduced in the force field. In addition, the ion pair free energy surfaces reproduced the main structural patterns observed in the first coordination shell in molecular dynamics simulations of the bulk liquid, proving to be useful probes for the liquid phase structure that can be computed with higher level methods and the comparison with forcefields can indicate further improvements in their parameterization.

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Temperature Dependence of Volumetric and Dynamic Properties of Imidazolium-Based Ionic Liquids

Cited by 21 publications

References 51 publications

Water structure and mobility in acrylamide copolymer glycohydrogels with galactose and siloxane pendant groups

Water structure and mobility in acrylamide copolymer glycohydrogels with galactose and siloxane pendant groups

Volumetric and Rheological Properties of Vitrimers: A Hybrid Molecular Dynamics and Monte Carlo Simulation Study

Ion pair free energy surface as a probe of ionic liquid structure

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