p,T dependence of the hydrophobic interaction in a model solution

Has, Michael; Lüdemann, H.‐D.

doi:10.1007/bfb0115985

Cited by 1 publication

(2 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Interestingly, the hydrophobic interaction that drives the aggregation of small nonpolar solutes and amphiphilic molecules in dilute aqueous solutions − has been found to increase with increasing temperature. ,,,− Recent small-angle neutron scattering (SANS) experiments with 0.04 mol fraction TBA solution in water have indicated that the TBA clustering reaches the maximum at ∼353 K. The increase in clustering with temperature is believed to originate from the increase in entropy as a few water molecules are released in the bulk when two hydrophobic surfaces come into contact . Therefore, the clustering process is entropy-driven where the water structure is disrupted and the subsequent dehydration lowers the free energy of the solution.…”

Section: Introductionmentioning

confidence: 99%

“…17,18,[20][21][22] Interestingly, the hydrophobic interaction that drives the aggregation of small nonpolar solutes and amphiphilic molecules in dilute aqueous solutions [23][24][25][26][27][28] has been found to increase with increasing temperature. 8,9,22,[29][30][31][32][33][34][35][36] Recent small-angle neutron scattering (SANS) experiments with 0.04 mol fraction TBA solution in water 17 have indicated that the TBA clustering reaches the maximum at ∼353 K. The increase in clustering ABSTRACT: The temperature dependence of solution heterogeneity in binary mixtures of water and tertiary butanol (TBA) and its effects on a chemical reaction have been investigated by using steady-state and time-resolved spectroscopic experiments within the temperature range of 278 e T/K e 373. Eleven different mole fractions of TBA, covering extremely low TBA mole fractions to pure TBA, have been considered.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Heterogeneity in Binary Mixtures of (Water + Tertiary Butanol): Temperature Dependence Across Mixture Composition

Gazi

Biswas

2011

J. Phys. Chem. A

View full text Add to dashboard Cite

The temperature dependence of solution heterogeneity in binary mixtures of water and tertiary butanol (TBA) and its effects on a chemical reaction have been investigated by using steady-state and time-resolved spectroscopic experiments within the temperature range of 278 ≤ T/K ≤ 373. Eleven different mole fractions of TBA, covering extremely low TBA mole fractions to pure TBA, have been considered. An organic chromophore that undergoes a photoexcited intramolecular charge-transfer reaction is employed to reveal the signature of the solution heterogeneity. Upon increasing the solution temperature, the absorption spectrum of the dissolved chromophore exhibits a red shift at very low TBA concentrations but shifts toward higher energy (blue shift) at higher alcohol concentrations. This is a reflection of temperature-assisted aggregation of TBA molecules in very dilute aqueous solutions. The magnitude of the temperature-induced red shift is the largest at around 0.04 mol fraction of TBA, and a larger variation of the spectral line width across the temperature suggests enhanced solution heterogeneity. Reaction time constants measured at various mixture compositions are found to follow an Arrhenius-type temperature dependence. The average activation energy, when plotted as a function of mixture composition, steeply rises with TBA concentration in the limit of the very low TBA mole fraction and then suddenly levels off to a plateau upon further addition of TBA. The alcohol concentration-dependent activation energy abruptly changes its slope at a TBA mole fraction ∼0.1, at which a transition from the three-dimensional water-type network to the zigzag alcohol chain structure is known to occur. The plateau value of the activation energy is ∼6k B T and agrees well with the earlier estimate for the same chromophore from the pure solvent data at room temperature. The observed increase in the spectral red shift with temperature at low TBA mole fractions is in general agreement with the existing experimental results which support the view that temperature assists the aggregation of TBA molecules in dilute aqueous solutions of TBA. However, unlike in the small-angle neutron scattering study [ Bowron D. T. Finney J. L. J. Phys. Chem. B20071119838], which finds clustering of TBA molecules reaching a maximum at ∼353 K, the present data do not indicate any such temperature maximum within the temperature range of 278 ≤ T/K ≤ 373.

show abstract