Influence of Molecular Rotation on the Viscosity of Liquids

Davies, David B.; Matheson, A. J.

doi:10.1063/1.1727649

Cited by 45 publications

(10 citation statements)

References 22 publications

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“…This assumption is consistent with the viscosity theories [22,23,24] which will be disc ussed below. The fractional number of molecules which relaxes with relaxation time Ti between In Ti-1f2 dIn T and In Tj+ 1f2 dIn T is (9) where gE(Ei) dE is the fractional number of molecules with activation free energy between Ei -1f2dE and Ei + IhdE.…”

Section: I Lsupporting

confidence: 68%

“…We have found in Ge02 supporting evidence that the departure from th e Arrhenius c urve for viscosity is caused by the app earance of a distribution of relaxation time s, and , furth er , that the associa ted distribution of activation e nergies has not only higher activation energies but also lowe r. The present theories which predict non-Arrhenius behavior are ty pified by the work of Ree, Ree, and Eyring [22] , Ada m and Gibbs [23], and Davies and Matheson [24]. These theories picture the molecules as being relati vely free at high te mperatures in the Arrhenius region, and / connect the appearance of non-Arrhenius behavior with some increase in cooperation between molecules , ' or a loss in certain degrees of freedom as the temperature is lowered.…”

Section: I Lsupporting

confidence: 49%

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Spectrum of relaxation times in GeO2 glass

Napolitano¹,

Macedo²

1968

J. RES. NATL. BUR. STAN. SECT. A.

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Index-of· re fra ction ve rs us time iso th e rm s ha ve bee n esta bli shed for ge rmania glass. Us in g th e c rosso ve r te c hniqu e with air-q ue nc hed sampl es and app lyin g th e two relaxatio n tim e mod el pre viou s ly reported for borosilicate glass, it was found that th e width of th e spec tr~m of re laxatlO~ lim es f or "ermania «lass was te mp e rature depe nd e nt. Upo n ana lyzlI1 g thi s 111 term s of a di strIbutIOn of a c t~vatlOn ~n e rgi es, Dle res ults showed that, s il:-ularly to B20 3 , activation energies small e r than the activatIOn e ne rgy present in th e Arrhenius regio n appear at low te mperatures.Extens ive viscos ity meas ure me nts DY th e fib e r elon gation me thod we re mad e from 10" to 6 X 10 14 poi ses. Fro m thi s data a lower and more precise value of th e activation e ne rgy (E" = 72 .3 kcal/mo l) was obtained in th e annealin g ran ge.Key Word s: Activation e ne rgy ; annea lin g; german ia glass; index of refra ction ; re laxat ion tim es; th e rm al expan sion; two relaxation model ; vi scosity.

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Section: I Lsupporting

confidence: 68%

Section: I Lsupporting

confidence: 49%

Spectrum of relaxation times in GeO2 glass

Napolitano¹,

Macedo²

1968

J. RES. NATL. BUR. STAN. SECT. A.

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“…The physical model treated by Davies and Matheson (41,43) involves restriction of rotational modes of freedom as the amount of free volume is reduced. In the Arrhenius region the molecules have sufficient rotational freedom to reorientate several times between translational jumps.…”

Section: Energies Of Activation For Conductivity At Constant Volume Amentioning

confidence: 99%

Electrical conductivities of quaternary ammonium salts in acetone.: Part II. The mechanisms of transport

Adams¹,

Laidler²

1968

Can. J. Chem.

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The limiting equivalent conductivities of tetramethylammonium iodide, tetraethylammonium iodide, and tetra-12-propylammonium iodide in acetone solution have been interpreted in terms of activatedcomplex theory; the energies of activation for conductivity at constant pressure and at constant volume, and the volumes of activation for conductivity, were calculated.The hole free-volume theory of liquids has been discussed and found to give a satisfictory explanation for the observed pressure and temperature coefficients of conductivity, viscosity, and self-diffusion in several solvents. The magnitude of the limiting ionic equivalent conductivity has been shown to depend in a critical way on the ionic radius and on the relative strengths of the ion-solvent and the solventsolvent interactions.

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“…The slip limit is not unexpected since it has been found to apply to a variety of neat non-associative dense liquids [39], in addition to several other glass forming fluids, such as glycerol [40], O-terphenyl [7] and phenyl-o-cresol [5]. It seems that if rotational motions occurred only as a result of translational jumps below Tk, as proposed [17], stick boundary conditions would be applicable. However, we need to emphasize the approximate nature of our conclusions regarding the validity of the Debye equation because of the possible presence of cooperative motions and of the anisotropic nature of reorientations in the supercooled state.…”

Section: Temperature Effects On Ring Motionsmentioning

confidence: 91%

“…Ubbelholde et al [15] and Rao et al [16] attributed the anomalous behaviour to cluster formation. Davies and Matheson [17] explained the viscosity anomaly in terms of the free volume theory originally proposed by Doolittle [12], Williams, Landel and Ferry [18] and Cohen and Turnbull [11]. They concluded that at temperatures above Tk, the molecules can fully reorient about at most one symmetry axis during the time between translational jumps.…”

Section: Downloaded By [University Of Arizona] At 22:51 05 February 2015mentioning

confidence: 97%

N.M.R. study of the dynamic structure of isopropylbenzene

Artaki

Jonáš

1985

Molecular Physics

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The dynamic molecular behaviour of isopropylbenzene, IPB, in the liquid and supercooled state has been investigated by N.M.R. The proton, deuterium and 1~C relaxation times were measured in selectively deuterated IPB, over the temperature range 125 to 200K and the pressure range 1 bar to 5 kbar. The viscosity range extended from 1 cP to 10 P. The most significant result of the study is that although at ambient pressures the modified DebyeStokes-Einstein relation adequately describes the microscopic dynamics of IPB in the slip limit, at high pressures the reorientational correlation times are no longer linear in ~I/T. The rotational-translational coupling parameter was found to be strongly density dependent, but insensitive to kinetic energy changes. An isotopic dilution study was employed to separate the intermolecular and intramolecular contributions to Tip. It was shown that the viscosity anomaly at T k is related to a change in the type of translational rather than rotational motions. The intramolecular interactions were interpreted in terms of a Cole-Davidson distribution of correlation times. Torrey's isotropic jump diffusion model was used in the analysis of the intermolecular interactions.Two different relaxation mechanisms, indicated by minima in the temperature dependence of Tip were detected in both the chain and the ring motions of IPB and were associated with the dielectric loss peaks, 0t and ft.

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Influence of Molecular Rotation on the Viscosity of Liquids

Cited by 45 publications

References 22 publications

Spectrum of relaxation times in GeO2 glass

Spectrum of relaxation times in GeO2 glass

Electrical conductivities of quaternary ammonium salts in acetone.: Part II. The mechanisms of transport

N.M.R. study of the dynamic structure of isopropylbenzene

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