ABSTRACT
The binary liquid mixtures of glycol ethers (glymes) + 1-alkanol were characterized from the microscopic and macroscopic viewpoints through a combined experimental and theoretical study. Structuring, dynamics, and intermolecular forces were determined using density functional theory and classical molecular dynamics methods. The macroscopic behavior was studied though the measurement of relevant physicochemical properties and Raman IR studies. The changes in intermolecular forces with mixture composition, temperature, and the effects from the types of glymes as well as 1-alkanols were considered. Hydrogen bonding in the mixed fluids, its changes upon mixing, and mixture composition showed a large effect on fluids' structure and determined most of the fluids' properties together with the presence of hydrophobic domains from long 1-alkanols.
ABSTRACT
Macroscopic properties and structuring at the molecular level of dialkylcarbonate + 1-alkanol mixed fluids have been studied as a function of alkyl chain lengths in 1-alkanol and dialkylcarbonate, mixture composition, and temperature. A combined experimental and computational approach was considered for studying the relationships between the nanoscopic structure of the mixed fluids; nature, extension, and organization of hydrogen bonding; and physicochemical properties. Thermodynamics characterization, using excess and mixing properties, are related with the strength and characteristics of intermolecular forces. Classic molecular dynamics simulations and quantum chemistry calculations provide a detailed picture of the mixed fluids' structuring and dynamic behavior.
ABSTRACT
The properties of formamide + 1,2-alkanediol binary liquid systems were studied both at the macro- and microscopic levels using a combined experimental and computational methodology. Physicochemical properties, infrared spectroscopy, and solvatochromic studies together with classic molecular dynamics and quantum chemistry calculations allowed the main characteristics of these binary fluids to be inferred with regard to the variations of hydrogen bonding with formamide and 1,2-alkanediol molecular structures, mixture composition, and temperature. The complexity of these liquid systems arising from the presence of three different functional groups, which may act as hydrogen bond donors and acceptors, is analyzed, allowing a detailed picture to be inferred of the studied systems which is of relevance both for basic liquid state theory and for industrial purposes.
ABSTRACT
The unusual properties of poly(ethyleneoxide) + alcohol mixtures were analyzed using a poly(ethylene oxide) monomer (1,2-dimethoxyethane) in ethanol solutions as a model. A collection of thermophysical measurements and computational studies, using density functional theory and classical molecular dynamics approaches, provide valuable information about the molecular-level structure of this mixture and on the interaction between 1,2-dimethoxyethane and ethanol molecules. Thermophysical measurements show remarkable deviations from ideality, which are related to the development of intermolecular hydrogen bonding between both molecules upon mixing and to the balance of homo- and heteroassociations. Density functional theory allows better characterization from energetic and structural viewpoints. In this work, the characteristics for the different 1,2-dimethoxyethane/ethanol hydrogen-bonding complexes are analyzed via atoms in a molecule and natural bond orbital methods. Classical molecular dynamics simulations are carried out for pure 1,2-dimethoxyethane and for mixtures in the whole composition range. Force field validation is done by comparison of predicted thermophysical properties with measured ones and through the analysis of 1,2-dimethoxyethane conformers. Structural features are inferred from the analysis of radial and distribution functions and their evolution with composition, together with the study of molecular distribution in the mixed fluids (microheterogeneities). Dynamic aspects of the mixtures' behavior are inferred from the calculated self-diffusion constants and mean square displacements. The whole study points to a highly structured fluid, whose structure is determined by the balance of the 1,2-dimethoxyethane disrupting effect on the ethanol hydrogen-bonding network and the appearance of microheterogeneities.
