Sound attenuation, shear viscosity, and mutual diffusivity behavior in the nitroethane-cyclohexane critical mixture

Behrends, R.; Iwanowski, Ireneusz; Kosmowska, M.; Szala, A.; Kaatze, U.

doi:10.1063/1.1781614

Cited by 21 publications

(14 citation statements)

References 37 publications

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“…An exception is systems for which the second term on the right-hand side of eq 20 adopts values on the order of the first term. 67 Attempting to estimate the relative importance of both terms in the coupling constant, we used the following data for monolamellar DMPC vesicles: ρ(T m ) = 1.04 g•cm −3 , C p = C p 0 + C p exc with C p 0 = 1.65 kJ/(mol•K) 68 as well as C p exc = 18.4 kJ/(mol•K), 49,62 ∂T m / ∂p = 2.5 × 10 −7 K/Pa, 69 and α p = 9.4 × 10 −2 /K. 70 With those data the thermal expansion coefficient term Tα p in the coupling constant exceeds the term ρC p ∂T m /∂p by a considerable amount.…”

Section: Resultsmentioning

confidence: 99%

“…Parameter g is the adiabatic coupling constant which, within the framework of the BF theory, is given by the slope ∂ T m /∂ p in the pressure dependence of the critical temperature and the thermal expansion coefficient α p at constant pressure: g ( T ) = normalρ ( T m ) C p ( T ) ∂ T normalm / ∂ p − T normalα p ( T ) With critically demixing binary liquids, no pronounced temperature dependence in S BF is normally found. An exception is systems for which the second term on the right-hand side of eq adopts values on the order of the first term . Attempting to estimate the relative importance of both terms in the coupling constant, we used the following data for monolamellar DMPC vesicles: ρ( T m ) = 1.04 g·cm –3 , C p = C p 0 + C p exc with C p 0 = 1.65 kJ/(mol·K) as well as C p exc = 18.4 kJ/(mol·K), , ∂ T m /∂ p = 2.5 × 10 –7 K/Pa, and α p = 9.4 × 10 –2 /K .…”

Section: Discussionmentioning

confidence: 99%

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Cholesterol-Induced Variations in the Domain Structure Fluctuations and Microdynamics of Lipid Membranes

2012

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Broadband ultrasonic attenuation spectra (100 kHz to 2 GHz) of aqueous solutions of vesicles from 1,2-dimyristoyl-l-3-phosphatidylcholine, with different amounts of cholesterol admixed, have been measured at temperatures between 20 and 28 °C. The spectra have been evaluated in terms of suitable relaxation functions. They are discussed in view of the effect of cholesterol on the membrane behavior around the gel-fluid phase transition temperature T(m). In addition to a frequency-independent asymptotic high-frequency term, all spectra reveal a critical term and a Debye-type relaxation term with relaxation time around 0.5 ns. The former is evaluated in the light of the Bhattacharjee-Ferrell dynamic scaling theory. It is assigned to the critical domain structure fluctuations of the membranes. Critical slowing of fluctuations is demonstrated. Also shown are relations of the critical amplitudes to thermodynamic parameters. The Debye term reflects the rotational isomerization of the phospholipid alkyl chains. The relaxation time of isomerization reveals a significant steplike change at T(m). At moderate cholesterol content an additional Debye relaxation term exists. It is assigned to the axial diffusion of the membrane molecules. Because it likewise shows effects of slowing near T(m), the diffusion appears to be coupled to the domain structure fluctuations. A further relaxation term at small cholesterol concentration is assumed to be due to small-range shape fluctuations of vesicles near the phase transition temperature.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Cholesterol-Induced Variations in the Domain Structure Fluctuations and Microdynamics of Lipid Membranes

2012

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“…As indicated by the data for the critical system nitroethanecyclohexane (Fig. 3, inset), the linear range in the α c λ (ν, T )/α c λ (ν, T c ) versus Ω plot becomes noticeably smaller if, at an almost identical low-frequency limit of measurements (160 kHz), the amplitudes of the relaxation time (τ 0 = 6.4 ps [39]) and fluctuation correlation length (ξ 0 = 0.16 nm [39]) are slightly larger than those of the n-pentanol-nitromethane mixture.…”

Section: Scaling Functionmentioning

confidence: 94%

Does the Viscosity Exponent Derive from Ultrasonic Attenuation Spectra?

2012

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Based on a representation of the sound velocity of critical liquids in terms of a frequency-dependent complex specific heat at constant pressure, a simple relation between the low-frequency normalized sonic attenuation coefficient and the correlation length of fluctuations is derived. This relation provides a promising alternative for the determination of the dynamics exponent and thus the critical exponent of the shear viscosity. Sonic attenuation data from the literature, measured at frequencies down to 50 kHz, are re-evaluated with a view of the viscosity exponent determination. It is found that only in a small temperature range, the major requirement of the approach is fulfilled with the available data. Close to the critical temperature, the frequencies of measurement are still insufficiently small as compared to the inverse relaxation time of order parameter fluctuations. Criteria for future experiments are discussed briefly.

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“…At temperatures far from a critical solution temperature a two-exponential decay function has been observed recently in the dynamic light scattering of critical composition mixtures, 31 reflecting two hydrodynamic relaxation modes with their own relaxation times. 33 All mixtures were prepared gravimetrically. 31 The specific heat anomaly of the ternary system triethylamine-water-heavy water did not show any indications of a critical exponent different from that of binary systems.…”

Section: ͑7͒mentioning

confidence: 99%

Relaxation rate and scaling function of the critical system 3-methylpentane-nitroethane-cyclohexane

Iwanowski

Mirzaev

Kaatze

2008

The Journal of Chemical Physics

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The critical system 3-methylpentane-nitroethane-cyclohexane (3-MP-NE-CH) has been investigated and compared to the limiting binary systems 3-MP-NE as well as NE-CH in order to study the degree of renormalization in the critical exponents of the ternary system. The solubility curves of the 3-MP-NE-CH system have been determined at various molar ratios of the nonpolar constituents in order to obtain the plait points as a function of mixture composition. At the col point (the mixture with the lowest transition temperature) and two further plait point compositions shear viscosity, dynamic light scattering, and frequency-dependent ultrasonic attenuation coefficient measurements have been performed as a function of temperature near the critical temperatures. The fluctuation correlation length and the relaxation rate of fluctuations display power law behavior as a function of reduced temperature, with universal critical exponents nu = 0.63 and nuZ(0) = 1.928, respectively, as characteristic for binary critical mixtures. In conformity with the 3-MP-NE and NE-CH critical mixtures the scaling function in the ultrasonic spectra nicely agrees with the empirical scaling function of the Bhattacharjee-Ferrell dynamic scaling theory. Hence with respect to power laws and scaling the 3-MP-NE-CH system behaves like a quasibinary mixture. The individual amplitudes of the relaxation rate show a minimum at the col point composition, corresponding with a maximum in the background viscosity of the liquids. The amount of the adiabatic coupling constant g, derived from the amplitudes in the ultrasonic spectra, increases monotonously when going from NE-CH (/g/ = 0.1) to 3-MP-NE (/g/ = 0.26).

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Sound attenuation, shear viscosity, and mutual diffusivity behavior in the nitroethane-cyclohexane critical mixture

Cited by 21 publications

References 37 publications

Cholesterol-Induced Variations in the Domain Structure Fluctuations and Microdynamics of Lipid Membranes

Cholesterol-Induced Variations in the Domain Structure Fluctuations and Microdynamics of Lipid Membranes

Does the Viscosity Exponent Derive from Ultrasonic Attenuation Spectra?

Relaxation rate and scaling function of the critical system 3-methylpentane-nitroethane-cyclohexane

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