Over the past three decades, the synthesis of new ionic liquids (ILs) and the expansion of their use in newer applications have grown exponentially. From the beginning of this vertiginous period, it ...was known that many of them were hygroscopic, which in some cases limited their use or altered the value of their measured physical properties with all the problems that this entails. In an earlier article, we addressed the hygroscopic grade achieved by the ILs 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium methyl sulfate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methylpyridinium ethyl sulfate, 1-ethyl-3-methylimidazolium tosylate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-1-methylpiperidinium bis(trifluoromethyl sulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluoromethyl sulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl sulfonyl)imide, and methyl trioctyl ammonium bis(trifluoromethyl sulfonyl)imide. The objective was to determine the influence of the chemical nature of the compounds, exposed surface area, sample volume, agitation, and temperature. For this purpose, we exposed the samples to abrupt increases in relative humidity from 15 to 100% for days in an atmosphere chamber and then proceeded with the reverse process in a gentle manner. The results show that the sorption of water from the atmosphere depends on the nature of the IL, especially the anion, with the chloride anion being of particular importance (chloride ≫ alkyl sulfates~bromide > tosylate ≫ tetrafluoroborate). It has also been proven for the EMIM-ES and EMIM-BF
samples that the mechanism of moisture capture is both absorption and adsorption, and that the smaller the exposed surface area, the higher the ratio of the mass of water per unit area.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this work we study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ...ion-electrode interactions in ionic liquids. We compare the interfacial behaviour of Li
+
and K
+
at a charged graphene sheet in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, and its mixtures with lithium and potassium tetrafluoroborate salts. Our results show that there are dense interfacial solvation structures in these electrolytes that lead to the formation of high free energy barriers for these alkali metal cations between the bulk and direct contact with the negatively charged surface. We show that the stronger solvation of Li
+
in the ionic liquid leads to the formation of significantly higher interfacial free energy barriers for Li
+
than for K
+
. The high free energy barriers observed in our simulations can explain the generally high interfacial resistance in electrochemical storage devices that use ionic liquid-based electrolytes. Overcoming these barriers is the rate-limiting step in the interfacial transport of alkali metal ions and, hence, appears to be a major drawback for a generalised application of ionic liquids in electrochemistry. Some plausible strategies for future theoretical and experimental work for tuning them are suggested.
We study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ion-electrode interactions in ionic liquids.
This paper presents a comprehensive study of two alkylammonium nitrate ionic liquids. As part of this family of materials, mainly ethylammonium nitrate (EAN) and also propylammonium nitrate (PAN) ...have attracted a great deal of attention during the last decades due to their potential applications in many fields. Although there have been numerous publications focused on the measurement of their physical properties, a great dispersion can be observed in the results obtained for the same magnitude. One of the critical points to be taken into account in their physical characterization is their water content. Thus, the main objective of this work was to determine the degree of influence of the presence of small quantities of water in EAN and PAN on the measurement of density, viscosity, electrical conductivity, refractive index and surface tension. For this purpose, the first three properties were determined in samples of EAN and PAN with water contents below 30,000 ppm in a wide range of temperatures, between 5 and 95 °C, while the last two were obtained at 25 °C. As a result of this study, it has been concluded that the presence of water is critical in those physical properties that involve mass or charge transport processes, resulting in the finding that the absolute value of the average percentage change in both viscosity and electrical conductivity is above 40%. Meanwhile, refractive index (≤0.3%), density (≤0.5%) and surface tension (≤2%) present much less significant changes.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In this work, we deepen in the characterization of two protic ionic liquids (PILs), ethylammonium nitrate (EAN) and propylammonium nitrate (PAN). With this aim, we determined the influence of ...inorganic nitrate salts addition on their physical properties and their electrochemical potential window (EPW). Thus, experimental measurements of electrical conductivity, density, viscosity, refractive index and surface tension of mixtures of {EAN or PAN + LiNO
, Ca(NO
)
, Mg(NO
)
or Al(NO
)
} at a temperature range between 5 and 95 °C are presented first, except for the last two properties which were measured at 25 °C. In the second part, the corresponding EPWs were determined at 25 °C by linear sweep voltammetry using three different electrochemical cells. Effect of the salt addition was associated mainly with the metal cation characteristics, so, generally, LiNO
showed the lower influence, followed by Ca(NO
)
, Mg(NO
)
or Al(NO
)
. The results obtained for the EAN + LiNO
mixtures, along with those from a previous work, allowed us to develop novel predictive equations for most of the presented physical properties as functions of the lithium salt concentration, the temperature and the water content. Electrochemical results showed that a general order of EPW can be established for both PILs, although exceptions related to measurement conditions and the properties of the mixtures were found.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
En este artículo se realiza un análisis del concepto de libertad social en Honneth, el cual se hace relevante para el tratamiento de la libertad en la filosofía política contemporánea. En ese ...sentido, se aborda la gramática moral del reconocimiento como la base teórica que permite la reflexión sobre la libertad. Desde ahí se presenta la crítica de Honneth a las ideas de libertad negativa y reflexiva como recurso para el desarrollo de la libertad social. Ello conduce al contraste de la libertad social con otras propuestas teóricas de relevancia para la filosofía política contemporánea. Por último, se concluye con una valoración del sentido de libertad social y su aporte a la comprensión contemporánea de la libertad y la justicia social señalando los límites que tiene esta propuesta en Honneth.
La enseñanza de la filosofía en tiempos de pandemia ha sido un desafío para la labor docente en perspectiva de pedagogía, con miras a superar la brecha digital por parte de quienes intervienen en el ...proceso de enseñanza. Quedaría, entonces, como se interpreta desde De Sousa Santos: mirar las enseñanzas que ha dejado el virus, siendo lo que, en tal sentido, se propone este escrito. Por tanto, se reflexiona en torno a cómo se desarrolla la interacción de la gamificación en la enseñanza de filosofía como elemento pedagógico en el contexto de la Universidad de Pamplona, Colombia. Así las cosas, se argumenta que el principal desafío de la enseñanza de la filosofía en medio de la crisis sanitaria generada por el SARS-CoV-2 es de carácter didáctico y pedagógico en sus procesos de enseñanza. Dicho proceso apunta al desarrollo de la interactividad y la instrucción de las diferentes asignaturas del pénsum de Filosofía en modalidad sincrónica, mediada por una plataforma online de enseñanza. El siguiente desafío se enfoca en la inclusión de la gamificación en la educación virtual en procesos didácticos de enseñanza y evaluación. Se concluye que en la Universidad de Pamplona la educación remota sincrónica y asincrónica se está desarrollando en el entorno virtual de aprendizaje para promover el aprender a conocer, a hacer, a vivir juntos para llegar a aprender a ser.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The present study describes an ambulatory, free skin micrograft technique with cyanoacrylate as a coadjuvant venous leg ulcer (VLU) healing strategy and its outcomes after one month.
This prospective ...study involved Comprehensive Classification System for Chronic Venous Disorders (CEAP) stage C6 patients with good granulation tissue and negative culture results, consecutively recruited in January 2017 in the Hospital Clinico San Carlos. A skin micrograft was harvested from the anterior surface of the patient's thigh with a 0.4cm punch (0.12cm
). The graft was adhered to the ulcer bed with cyanoacrylate. Anti-adherent dressing and double-layer bandaging was applied, with weekly replacements. Measurements were obtained of the surface of the VLU and graft progression (in cm
) using a photographic grid.
A total of 12 VLUs in 12 patients were included, with a mean treated surface of 20.32±13.9cm
. A total of 18 grafts were placed and all were found to be viable after one week. Average graft growth was not noticeable after one week but was found to be 0.25±0.08cm
after week two, 0.41±0.98cm
after week three, and 0.70±0.15cm
after week four (p<0.001). There were no complications in the donor zone.
The findings of this study show that free skin micrografting with cyanoacrylate as outpatient treatment for VLUs was simple, rapid and without complication in this study, and may contribute to its wider application in clinical use.
Molecular dynamics simulations of mixtures of the protic ionic liquid ethylammonium nitrate (EAN) and the aprotic 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF
4
) are reported and the ...results are compared with experimental density and electrical conductivity measurements. Essentially ideal mixing of the ionic liquids is seen to take place by means of experimental and simulated excess molar volumes, whose very low values suggest a gradual transition between the structures of the two end constituents of the mixture. A weak dominance of the structure of the protic ionic liquid is nevertheless registered, due to a slight preferential formation of the network of hydrogen bonds, as reflected in the coordination number and the number of hydrogen bonds in the mixture. A novel conductivity curve showing pronounced deviations from the simple ideal mixing rule is reported, with three different regions defined by a local maximum - reflecting enhanced translational dynamics relative to ideal mixture behaviour - and a global minimum at intermediate concentrations. The physical origin of this behaviour is discussed along with the structure and single-particle dynamics of the mixture, and it is seen that these regions are defined by the onset of the formation of the EAN hydrogen bonded network (
x
EAN
= 0.2) and the virtual disappearance of the structure of the aprotic ionic liquid at
x
EAN
= 0.7. It is concluded that the delicate interplay between both networks has a deep effect on the placement and mobility of EMIM
+
cations in the mixture all throughout the different stages of the structural transition, which seems to be the driving force behind the reported transport properties of the mixture at intermediate to high EAN concentrations.
Molecular dynamics simulations of mixtures of the protic ionic liquid EAN and the aprotic EMIMBF
4
are reported and the results are compared with experimental density and electrical conductivity measurements.
Dynamic viscosity and specific electrical conductivity on three binary systems of 1-alkyl-3-methyl imidazolium tetrafluoroborate CnMIMBF4 with water covering all ranges of concentrations are ...presented. Viscosity was measured at 15.0 °C, 25.0 °C, 35.0 °C, and 45.0 °C, while conductivity was measured at those four temperatures for equimolar mixtures only and at 25 °C over the whole composition range. The alkyl chains of the ILs used were ethyl EMIMBF4, butyl BMIMBF4, and hexyl HMIMBF4. Note that HMIMBF4 is only partially miscible in water at the studied temperatures and atmospheric pressure. Viscosity deviations and molar conductivity were derived from experimental data and fitted to suitable equations. Experimental data were also compared with those previously published, and a good agreement was observed. Transport properties were discussed in terms of Walden’s rule, which is partially correct. This paper complements one recently published by us, where density and surface tension at 25 °C for exactly the same systems are presented. The goal of this work is to study the effect on the transport magnitudes of the alkyl chain length in the n-alkyl methyl imidazolium cation and to compare the two main transport magnitudes.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
PDF
