Journal Description

Liquids

Liquids is an international, peer-reviewed, open access journal on all aspects of liquid material research published quarterly online by MDPI.

Open Access—free to download, share, and reuse content. Authors receive recognition for their contribution when the paper is reused.
Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 18.4 days after submission; acceptance to publication is undertaken in 3.8 days (median values for papers published in this journal in the second half of 2021).
Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.

Imprint Information Journal Flyer Open Access ISSN: 2673-8015

Latest Articles

Open AccessArticle

Liquid-State Volumetric Properties of a Set of Alcohols with Up to Five Carbon Atoms

and

Liquids 2022, 2(1), 1-13; https://doi.org/10.3390/liquids2010001 - 04 Jan 2022

Abstract

This work provides density data (~1300 values) of 14 alcohols with up to five carbon atoms at p ∈ [0.1–40] MPa and T ∈ [278–358] K. The information obtained is modeled with a convenient reformulation of the Tait equation from which the volumetric coefficients, α and β, are derived both analytically and numerically. The general EoS containing α and β is also used for checking the consistency of the hypothesis on the invariability of the cited thermophysic parameters. The results obtained can be considered reliable because of the low estimated errors between the experimental data and those of the literature, which are below 0.4% for volume, while for the volumetric coefficients there is always a reference diverging 10%, or less, from the proposed model estimations. By including the averages of α and β into the general state of equation the errors increase, being <15%, compared to those based on the Tait equation. Hence, the assumption on the stability of the volumetric coefficients in this working interval is sufficient to make rough estimations of the molar volume of the selected alcohols. Full article

(This article belongs to the Section Chemical Physics of Liquids)

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Open AccessArticle

Thermodynamic Scaling of the Shear Viscosity of Lennard-Jones Chains of Variable Rigidity

Stephanie Delage Santacreu

Hai Hoang

Samy Khennache

and

Guillaume Galliero

Liquids 2021, 1(1), 96-108; https://doi.org/10.3390/liquids1010008 - 09 Dec 2021

Abstract

In this work, the thermodynamic scaling framework has been used to emphasize the limitations of fully flexible coarse grained molecular models to yield shear viscosity of real liquids. In particular, extensive molecular dynamics simulations have confirmed that, while being reasonable to describe the viscosity of short normal alkanes, the fully flexible Lennard-Jones and Mie chains force fields are inadequate to capture the density dependence of shear viscosity of medium to long alkanes. In addition, it is shown that such a weakness in terms of coarse grained molecular models can be readily quantified by using the thermodynamic scaling framework. As a simple alternative to these force fields, it is demonstrated that the insertion of a variable intramolecular rigidity in the Lennard-Jones chains model exhibits promising results to model medium to long chain-like real fluids from both thermodynamic and viscosity points of view. Full article

(This article belongs to the Section Physics of Liquids)

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Open AccessArticle

Isochoric Specific Heat in the Dual Model of Liquids

Fabio Peluso

Liquids 2021, 1(1), 77-95; https://doi.org/10.3390/liquids1010007 - 01 Dec 2021

Abstract

We continue in this paper to illustrate the implications of the dual model of liquids (DML) by deriving the expression for the isochoric specific heat as a function of the collective degree of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks have been accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression has been compared with the analogous one obtained in another theoretical dual model of the liquid state, the phonon theory of liquid thermodynamics. This comparison allows providing interesting insights about the number of collective degrees of freedom available in a liquid and the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework. Full article

(This article belongs to the Section Physics of Liquids)

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Open AccessEditorial

Welcome to Liquids: An Open Access Journal

Enrico Bodo

Liquids 2021, 1(1), 75-76; https://doi.org/10.3390/liquids1010006 - 17 Nov 2021

Abstract

We are thrilled to launch “Liquids” as a peer-reviewed open access journal [...] Full article

Open AccessArticle

LiCoO₂/Graphite Cells with Localized High Concentration Carbonate Electrolytes for Higher Energy Density

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Liquids 2021, 1(1), 60-74; https://doi.org/10.3390/liquids1010005 - 10 Nov 2021

Abstract

Widening the working voltage of lithium-ion batteries is considered as an effective strategy to improve their energy density. However, the decomposition of conventional aprotic electrolytes at high voltage greatly impedes the success until the presence of high concentration electrolytes (HCEs) and the resultant localized HCEs (LHCEs). The unique solvated structure of HCEs/LHCEs endows the involved solvent with enhanced endurance toward high voltage while the LHCEs can simultaneously possess the decent viscosity for sufficient wettability to porous electrodes and separator. Nowadays, most LHCEs use LiFSI/LiTFSI as the salts and β-hydrofluoroethers as the counter solvents due to their good compatibility, yet the LHCE formula of cheap LiPF₆ and high antioxidant α-hydrofluoroethers is seldom investigated. Here, we report a unique formula with 3 mol L⁻¹ LiPF₆ in mixed carbonate solvents and a counter solvent α-substituted fluorine compound (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether). Compared to a conventional electrolyte, this formula enables dramatic improvement in the cycling performance of LiCoO₂//graphite cells from approximately 150 cycles to 1000 cycles within the range of 2.9 to 4.5 V at 0.5 C. This work provides a new choice and scope to design functional LHCEs for high voltage systems. Full article

(This article belongs to the Special Issue Electrolytes for High-Performance Rechargeable Batteries)

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Open AccessArticle

Density, Enthalpy of Vaporization and Local Structure of Neat N-Alkane Liquids

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Liquids 2021, 1(1), 47-59; https://doi.org/10.3390/liquids1010004 - 06 Aug 2021

Abstract

The properties of alkanes are consequential for understanding many chemical processes in nature and industry. We use molecular dynamics simulations with the Amber force field GAFF2 to examine the structure of pure liquids at each respective normal boiling point, spanning the 15 n-alkanes from methane to pentadecane. The densities predicted from the simulations are found to agree well with reported experimental values, with an average deviation of 1.9%. The enthalpies of vaporization have an average absolute deviation from experiment of 10.4%. Radial distribution functions show that short alkanes have distinct local structures that are found to converge with each other with increasing chain length. This provides a unique perspective on trends in the n-alkane series and will be useful for interpreting similarities and differences in the n-alkane series as well as the breakdown of ideal solution behavior in mixtures of these molecules. Full article

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Open AccessArticle

Investigation of Binary Liquids in Unstable States—An Experimental Approach

Alexander Igolnikov

Sergey Rutin

and

Pavel Skripov

Liquids 2021, 1(1), 36-46; https://doi.org/10.3390/liquids1010003 - 28 May 2021

Cited by 2

Abstract

In this article, we present a methodology for conducting measurements based on pulse heating of a wire probe in partially soluble binary liquids. These liquids, which can be rapidly transferred to the region of unstable states above the diffusional spinodal, are novel research objects for the thermophysics of extreme states. Using the example of aqueous solutions of polypropylene glycol and glycol monobutyl ether having a lower critical solution temperature, the key hypothesis of the study on the general measurability of the properties of unstable solutions has been confirmed. The characteristic heating times from 1 to 15 milliseconds corresponded to the thickness of the heated layer comprising a few micrometers. The pressure was varied from units of MPa to 100 MPa. The conditions for the transition from measurements on pure components to those on solutions are formulated. The characteristic thermal patterns of the decay of unstable states depending on pressure and heating rate are revealed. The general possibility of using partially soluble binary liquids as a promising coolant in processes involving powerful local heat release is demonstrated. Full article

(This article belongs to the Section Physics of Liquids)

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Open AccessArticle

Information Entropy of Regular Dendrimer Aggregates and Irregular Intermediate Structures

Denis Sabirov

Alina Tukhbatullina

and

Igor Shepelevich

Liquids 2021, 1(1), 25-35; https://doi.org/10.3390/liquids1010002 - 05 Mar 2021

Cited by 3

Abstract

Dendrimer molecules and aggregates are chemical structures with regular branching that underlies their physicochemical properties. Regular dendrimers have been studied both theoretically and experimentally, but the irregular intermediate structures between the dendrimers of neighboring generations have not. In the present work, dendrimer aggregates, both regular and intermediate, are investigated in terms of the information entropy approach. As found, the information entropy of the regular dendrimer asymptotically increases with the generation number; herewith, its maximal value equals 2. The intermediate structures have been studied for the growing dendrimer G1 → G2 → G3 → G4 with the tricoordinated building block. The plot of the information entropy of the growing dendrimer on the size has the frontier consisting of the lowest values that correspond to the regular and irregular structures described with the symmetrical graphs. Other intermediate structures have information entropies higher than the regular dendrimers. Thus, to move the system from one informationally stable state to another, its information capacity must be temporarily increased. Full article

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Open AccessArticle

Protolytic Equilibria in Organized Solutions: Ionization and Tautomerism of Fluorescein Dyes and Related Indicators in Cetyltrimethylammonium Chloride Micellar Solutions at High Ionic Strength of the Bulk Phase

Nikolay O. Mchedlov-Petrossyan

and

Natalya A. Vodolazkaya

Liquids 2021, 1(1), 1-24; https://doi.org/10.3390/liquids1010001 - 20 Feb 2021

Cited by 3

Abstract

Ionic equilibrium of 22 hydroxyxanthenes, including halogen and nitro derivatives of fluorescein, and their thio- and aza analogues, were studied spectrophotometrically in micellar solutions of cetyltrimethylammonium chloride at ionic strength of the bulk phase 4.0 M KCl. This micellar pseudophase is characterized by [...] Read more.

E_{T}^{N}

value of 0.623. In the case of dyes bearing the COOH group, colorless lactone is the predominant tautomer of the molecular form H₂R. A new classification of fluoresceins is developed. The dyes were divided into four groups based on the nature of tautomerism of the anions. In the case of the fluorescein type, the monoanions HR⁻ exist predominantly as “carboxylate” tautomers, with ionized carboxylic and non–ionized hydroxylic group. For the dyes of the eosin type, the situation is opposite, while for the intervening type of compounds, the concentrations of the two tautomers are comparable. Dyes capable of forming lactone anions HR⁻ were classified as the fourth type. For some of them, even the dianion R²⁻ exists as a lactone. The relationship between the stepwise ionization constants,