An anomaly in the heat capacity and a structural phase transformation of the ordering type in an aqueous solution of t-butanol

Анисимов, М. А.; Esipov, V. S.; Zaprudskii, V. M.; Zaugol'Nikova, N. S.; Ovodov, G. I.; Ovodova, T. M.; Seifer, A. L.

doi:10.1007/bf00746104

Cited by 21 publications

(17 citation statements)

References 3 publications

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“…Molecular dynamics studies show that the clusters of hydrotrope molecules, hydrogen-bonded with the aqueous surrounding, are short-ranged (order of 1 nm in size) and short-lived with a lifetime of tens or hundreds picoseconds [10][11][12]. This molecular clustering, usually involving hydrogen bonds with water molecules, can cause distinct thermodynamic anomalies, such as those observed in aqueous alcohol solutions in water-rich region [11,[14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Mesoscale solubilization and critical phenomena in binary and quasi-binary solutions of hydrotropes

Robertson

Phan

Macaluso

et al. 2016

Fluid Phase Equilibria

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A B S T R A C THydrotropes are substances consisting of amphiphilic molecules that are too small to self-assemble in equilibrium structures in aqueous solutions, but can form dynamic molecular clusters H-bonded with water molecules. Some hydrotropes, such as low-molecular-weight alcohols and amines, can solubilize hydrophobic compounds in aqueous solutions at a mesoscopic scale ($100 nm) with formation of longlived mesoscale droplets. In this work, we report on the studies of near-critical and phase behavior of binary (2,6-lutidine-H 2 O) and quasibinary (2,6-lutidine-H 2 O/D 2 O and tert-butanol/2-butanol-H 2 O) solutions in the presence of a solubilized hydrophobic impurity (cyclohexane). In additional to visual observation of fluid-phase equilibria, two experimental techniques were used: light scattering and smallangle neutron scattering. It was found that the increase of the tert-butanol/2-butanol ratio affects the liquid-liquid equilibria in the quasi-binary system at ambient pressure in the same way as the increase of pressure modifies the phase behavior of binary 2-butanol-H 2 O solutions. The correlation length of critical fluctuations near the liquid-liquid separation and the size of mesoscale droplets of solubilized cyclohexane were obtained by dynamic light scattering and by small-angle neutron scattering. It is shown that the effect of the presence of small amounts of cyclohexane on the near-critical phase behavior is twofold: (1) the transition temperature changes toward increasing the two-phase domain; (2) longlived mesoscopic inhomogeneities emerge in the macroscopically homogeneous domain. These homogeneities remain unchanged upon approach to the critical point of macroscopic phase separation and do not alter the universal nature of criticality. However, a larger amount of cyclohexane generates additional liquid-liquid phase separation at lower temperatures.

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Section: Introductionmentioning

confidence: 99%

Mesoscale solubilization and critical phenomena in binary and quasi-binary solutions of hydrotropes

Robertson

Phan

Macaluso

et al. 2016

Fluid Phase Equilibria

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show abstract

“…Examples of such non-ideal behavior in the binary mixture of water and amphiphilic solutes are varied and well-studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Sometimes the anomaly is strongest at surprisingly low solute concentrations.…”

Section: Introductionmentioning

confidence: 99%

Fluctuating micro-heterogeneity in water–tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies

Banerjee

Furtado

Bagchi

2014

The Journal of Chemical Physics

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Water-tert-butyl alcohol (TBA) binary mixture exhibits a large number of thermodynamic and dynamic anomalies. These anomalies are observed at surprisingly low TBA mole fraction, with xTBA ≈ 0.03 − 0.07. We demonstrate here that the origin of the anomalies lies in the local structural changes that occur due to self-aggregation of TBA molecules. We observe a percolation transition of the TBA molecules at xTBA ≈ 0.05. We note that "islands" of TBA clusters form even below this mole fraction, while a large spanning cluster emerges above that mole fraction. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Alongside, the structure of water is also perturbed, albeit weakly, by the aggregation of TBA molecules. There is a monotonic decrease in the tetrahedral order parameter of water, while the dipole moment correlation shows a weak non-linearity. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration, xTBA ≈ 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of largest water cluster. This second transition gives rise to another set of anomalies around. Both the percolation transitions can be regarded as manifestations of Janus effect at small molecular level.

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“…The change of the water-alcohol structure near the peculiar line is also manifest in the behavior of the adiabatic compressibility [16,17], the heat capacity [18,19], diffusion of components [20] and other phenomena. However, all these manifestations were only fragmentarily investigated.…”

Section: Introductionmentioning

confidence: 99%

Peculiar points in the phase diagram of the water-alcohol solutions

Chechko¹,

Gotsulsky²,

Malomuzh³

2013

Condens. Matter Phys.

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The work is devoted to the investigation of nontrivial behavior of dilute water-alcohol solutions. The temperature and concentration dependencies of the contraction for aqueous solutions of ethanol and methanol are analyzed. The existence of a specific point, the so-called peculiar point, was established. It is shown that wateralcohol solutions of different types obey the principle of corresponding states if temperature and volume fraction are used as principal coordinates. In this case, the concentration of the peculiar point for different solutions is close to x ν = 0.28. Several predictions are made.

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An anomaly in the heat capacity and a structural phase transformation of the ordering type in an aqueous solution of t-butanol

Cited by 21 publications

References 3 publications

Mesoscale solubilization and critical phenomena in binary and quasi-binary solutions of hydrotropes

Mesoscale solubilization and critical phenomena in binary and quasi-binary solutions of hydrotropes

Fluctuating micro-heterogeneity in water–tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies

Peculiar points in the phase diagram of the water-alcohol solutions

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