Ignacio Gascón

Anion influence on thermophysical properties of ionic liquids: 1-butylpyridinium tetrafluoroborate and 1-butylpyridinium triflate.

The thermophysical properties of two pyridinium-based ionic liquids, 1-butylpyridinium tetrafluoroborate and 1-butylpyridinium triflate, have been measured. Thus, densities, refractive indices, speeds of sound, viscosities, surface tensions, isobaric molar heat capacities, and thermal properties have been experimentally determined over a wide range of temperatures. The comparison of the properties of the two ionic liquids has allowed us to analyze in detail the anion influence. Moreover, useful derived properties have been calculated from the results. On the other hand, the influence of the lack of a substituent in the cation has been evaluated when properties of 1-butylpyridinium tetrafluoroborate have been contrasted to those of 1-butyl-n-methylpyridinium tetrafluoroborate, (n = 2, 3, or 4). The study has been carried out paying special attention to interactions between ions in order to elucidate the desired relationship between properties and structural characteristics of ionic liquids.

Density and Speed of Sound for Binary Mixtures of a Cyclic Ether with a Butanol Isomer

Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data.

Physicochemical Characterization of n-Butyl-3-methylpyridinium Dicyanamide Ionic Liquid

The room temperature ionic liquid n-butyl-3-methylpyridinium dicyanamide has been characterized. Physicochemical properties such as density, speed of sound, refractive index, surface tension, and kinematic viscosity of the studied liquid have been experimentally measured in a wide range of temperatures. From results, coefficients of thermal expansion, molar refractions, dynamic viscosities and entropies and enthalpies of surface formation per unit surface area at the studied temperatures have been derived. We have analyzed the achieved results for evaluating the effect of the anionic structure in these properties, getting interesting results which lead us to a better understanding of the behavior of the ions in the fluids. Moreover, thermal properties of several pyridinium-based ionic liquids have been investigated. Finally, from both dynamic viscosity values and glass transition temperature of the studied liquids, a detailed analysis of the behavior in fragility terms has been performed.

Viscosities of the ternary mixture (2-butanol+n-hexane+1-butylamine) at 298.15 and 313.15 K

Abstract Viscosities of the ternary mixture (2-butanol+ n -hexane+1-butylamine) and of the binary mixtures (2-butanol+ n -hexane) at 298.15 and 313.15 K, and (2-butanol+1-butylamine) at 313.15 K have been measured at atmospheric pressure. Viscosity deviations and excess Gibbs energy of activation of viscous flow for the binary and ternary systems were fitted to Redlich–Kisters and Cibulkas equations, respectively. To correlate experimental data of ternary system from binary ones, different empirical and semiempirical equations have been used (Nissan and Grunberg, Hind, Frenkel, McAllister, Katti and Chaudhri, Heric and Iulan) and their parameters have been calculated. The “viscosity-thermodynamic” model (UNIMOD) has been applied to correlate experimental data for the binary mixtures and to predict the viscosity for the ternary system. The Group Contribution-Thermodynamic Viscosity model (GC-UNIMOD), and the group contribution method proposed by Wu have been employed to predict the viscosity for the binary and ternary systems.

Excess molar enthalpies of 1,3-dioxolane, or 1,4-dioxane with isomeric butanols

Using a flow-mixing calorimeter, excess molar enthalpies of 1,3-dioxolane, or 1,4-dioxane, with isomeric butanols were determined at the temperatures of 298.15 K and 313.15 K. All the studied systems show positive excess molar enthalpies. The results are compared with calculated values from the UNIFAC model.

Excess properties of the ternary system cyclohexane + 1,3-dioxolane + 1-butanol at 298.15 and 313.15 K

Densities, speeds of sound and heats of mixing for the ternary system cyclohexane + 1,3-dioxolane + 1-butanol have been measured at atmospheric pressure at the temperatures of 298.15 and 313.15 K. Excess molar volumes, excess isentropic compressibilities and excess molar enthalpies have been calculated from experimental data and fitted by Cibulka equation. Excess molar properties were analysed in terms of molecular interactions and structural and packing effects.

Preparation of nascent molecular electronic devices from gold nanoparticles and terminal alkyne functionalised monolayer films

A metal–molecule–GNP assembly has been fabricated using an acetylene-terminated phenylene–ethynylene molecular monolayer, namely 4-((4-((4-ethynylphenyl)ethynyl)phenyl)ethynyl)benzoic acid (HOPEA), sandwiched between a gold substrate bottom electrode and gold nanoparticle (GNP) top contact electrode. In the first stage of the fabrication process, a monolayer of directionally oriented (carboxylate-to-gold) HOPEA was formed onto the bottom electrode using the Langmuir–Blodgett (LB) technique. In the second stage, the gold-substrate supported monolayer was incubated in a solution of gold nanoparticles (GNPs), which resulted in covalent attachment of the GNPs on top of the film via an alkynyl carbon–Au σ-bond thereby creating the metallic top electrode. Adsorption of the GNPs to the organic LB film was confirmed by both UV-vis absorption spectroscopy and X-ray photoemission spectroscopy (XPS), whilst the contact angle showed changes in the physical properties of the film surface as a result of top-coating of the LB film with the GNPs. Importantly, surface-enhanced Raman scattering (SERS) confirmed the covalent attachment of the metal particles to the LB film by formation of Au–C σ-bonds via a heterolytic cleavage of the alkyne C–H bond. Electrical properties of these nascent metal–molecule–GNP assemblies were determined from I–V curves recorded with a conductive-AFM in the Peak Force Tunneling AFM (PF-TUNA™) mode. The I–V curves obtained from these structures rule out the formation of any significant number of short-circuits due to GNP penetration through the monolayer, suggesting that this strategy of self-assembly of GNPs to alkyne-terminated monolayers is an effective ‘soft’ procedure for the fabrication of molecular junctions without damaging the organic layer.

Viscosities of the ternary mixture (cyclohexane + tetrahydrofuran + chlorocyclohexane) at 298.15 and 313.15 K

Abstract Viscosities of the ternary mixture (cyclohexane+tetrahydrofuran+chlorocyclohexane) and the binary mixtures (cyclohexane+tetrahydrofuran and cyclohexane+chlorocyclohexane) have been measured at normal pressure at the temperatures of 298.15 and 313.15 K. The viscosity data for the binary and ternary mixtures were fitted to a McAllister-type equation [R.A. McAllister, AIChE J. 6 (1960) 427–431]. Viscosity deviations for the binary and ternary mixtures were fitted to Redlich–Kisters and Cibulkas equations [I. Cibulka, Coll. Czech. Chem. Commun. 47 (1982) 1414–1419]. The group contribution method proposed by Wu [D.T. Wu, Fluid Phase Equilib. 30 (1986) 149–156] has been used to predict the viscosity of the binary and ternary systems.

Experimental data of isobaric vapour–liquid equilibrium for binary mixtures containing tetrahydrofuran and isomeric chlorobutanes

Isobaric vapour–liquid equilibrium (VLE) measurements for mixtures formed by tetrahydrofuran and isomeric chlorobutanes at 40.0 kPa (except for the mixture containing 2-methyl-2-chloropropane) and 101.3 kPa are reported. The activity coefficients were calculated from experimental data. The mixture containing 2-chlorobutane at 40.0 kPa presents an azeotrope. The VLE measurements have been found thermodynamically consistent according to Van Ness test. Wilson, NRTL, and UNIQUAC equations have been used to correlate the activity coefficients and we have obtained satisfactory results.

Molecular Arrangement in Langmuir and Langmuir―Blodgett Films of a Mesogenic Bent-Core Carboxylic Acid

A different alternative to previous research on Langmuir and Langmuir-Blodgett (LB) films of bent-core liquid crystals is reported in this work. A bent-shaped molecule wearing a terminal carboxylic group has been used to obtain monomolecular films with their long molecular axis almost perpendicular to the aqueous surface. Langmuir films at the air-liquid interface (pH=9) have been characterized by a combination of surface pressure and surface potential versus area per molecule isotherms, Brewster angle microscopy, and ultraviolet reflection spectroscopy. A condensed phase is reached at surface pressures up to 20 mN x m-1. In this condensed phase, molecules are packed forming H-aggregates with a well-defined molecular orientation. Langmuir films have been transferred onto quartz and silicon substrates and characterized by means of UV-vis spectroscopy and XRR. The transference is Z-type, with a constant deposition of the monolayers. The total LB monolayer film thickness is evaluated to be about 5.8 nm, which is in good agreement with the deduced orientation at the air-liquid interface as well as with the lamellar order observed within the solid obtained by cooling the sample from the mesophase.