Thermodynamic effects of orientational order in chain-molecule mixtures. Part 2.—Temperature-dependence of heats of mixing of branched and normal alkane mixtures

1974 ◽  
Vol 70 (0) ◽  
pp. 1479-1487 ◽  
Author(s):  
Melvyn D. Croucher ◽  
Donald Patterson
Keyword(s):  
Temperature Dependence ◽  
Orientational Order ◽  
Chain Molecule ◽  
Normal Alkane ◽  
Heats Of Mixing ◽  
Thermodynamic Effects

Interpretation of heats of mixing of 1-butanol, 2-butanol and 2-methyl-2-propanol with cyclohexane in terms of some models of continuously associated solution

1984 ◽  
Vol 49 (6) ◽  
pp. 1334-1341 ◽  
Author(s):  
František Veselý ◽  
Vladimír Dohnal ◽  
Miriam Valentová ◽  
Jiří Pick
Keyword(s):  
Temperature Dependence ◽  
Interaction Parameters ◽  
Heats Of Mixing ◽  
Linear Association ◽  
Two Systems ◽  
Associated Solution

Three models of continuously associated solution complemented by an assumption of polynomial temperature dependence of corresponding interaction parameters were used for simultaneous description of the concentration and temperature dependence of heats of mixing of 1-butanol, 2-butanol and 2-methyl-2-propanol with cyclohexane. Very good results were reached for the first two systems where the Liebermann and Wilhelm model has proved to be the most suitable. With respect to the probable existence of cyclic associates in solutions of 2-methyl-2-propanol, none of the used models which assume only linear association satisfied to the extent required.

Elastic Constants of Nematic Phenylpyrimidines Determined by Two Different Methods

1990 ◽  
Vol 45 (1) ◽  
pp. 37-42 ◽  
Author(s):  
A. Scharkowski ◽  
H. Schmiedel ◽  
R. Stannarius ◽  
E. Weißhuhn
Keyword(s):  
Liquid Crystals ◽  
Temperature Dependence ◽  
Elastic Constants ◽  
Optical Method ◽  
Order Parameter ◽  
Diamagnetic Susceptibility ◽  
Orientational Order ◽  
Orientational Order Parameter ◽  
H Nmr ◽  
Electric And Magnetic Fields

AbstractA survey of various methods to measure the elastic constants Ki of nematic liquid crystals is given. To determine K1, K3 and the anisotropy of the diamagnetic susceptibility Δx of two members of the 5n-hexyl-2-[4n-alkyloxy-phenyl]-pyrimidines and a mixture of both, we used a combined electromagneto- optical method, consisting in independent measurements of the optical phase difference in electric and magnetic fields acting on the same cell. The temperature dependence of the K1- and K3-values for these phenylpyrimidines can be explained by common theories. The Δx data show the same temperature dependence as the values of the orientational order parameter S obtained by 1H-NMR.

Heats of mixing of trialkylamines: disorder and steric hindrance contributions

1978 ◽  
Vol 56 (22) ◽  
pp. 2856-2865 ◽  
Author(s):  
Robert Philippe ◽  
Geneviève Delmas ◽  
Phuong Nguyen Hong
Keyword(s):  
Steric Hindrance ◽  
Significant Contribution ◽  
Orientational Order ◽  
Class A ◽  
Heats Of Mixing ◽  
Class B ◽  
Chain Compounds ◽  
Sterically Hindered ◽  
Long Chain ◽  
Long Chains

Nine trialkylamines, triethyl- to trihexylamine trioctyl-, tridodecyl, tri(methyl-2-butyl)-, and dimethyldodecylamine have been used for heats of mixing of the following systems at 298 K: A, fourteen systems made of all the possible binary mixtures (except one) of the six shorter amines; B, twelve systems made of a long chain amine, trioctyl-, tridodecyl- or dimethyldodecylamine with the four shorter members of the series; C, two systems consisting of the mixture of two long-chain compounds, trioctylamine with tridodecyl- and dimethyldodecylamine. Heats for the class A systems are less than or equal to 40 J/mol, indicating no net effect of the small polarity of the shorter members of the series. The experimental HE of these mixtures are compared with two theories. The Monte Carlo approach gives good predictions but the heats calculated with the Snider–Herrington theory are too negative. Heats of the class B systems are suitable for the investigation of two new contributions to the heats of mixing, the positive heat of disordering of long-chains HE(dis.) and the negative heat found in systems where one of the components is sterically hindered, HE(ster.hindr.). HE(dis.) found with the long-chain amines indicates an orientational order larger than in the case of the n-alkane of the same chain-length but equivalent to that found in the tetraalkyltin compounds of the same length. Recent work has shown that the tetrapropyl and tetraethyltin derivatives when mixed with long-chain alkanes or tin derivatives give rise to a HE(ster.hindr.) contribution. From this work and the present study, the steric hindrance contributions of five sterically hindered compounds tetraethyltin and tetrapropyltin, triethyl- and tripropylamine, and 3,3-diethylpentane mixed with different second components are calculated. The steric hindrance contribution is found proportional to the volume of the second component and increasing in the following order of the sterically hindered component: triethyl- < tripropylamine < tetraethyl- < tetrapropyltin < 3,3-diethylpentane. Heats of the class C systems are small without significant contribution of HE(dis.) due to the fitting of the long-chains in solution.

Thermodynamics of chain-molecule mixtures : heats of mixing of linear methylsiloxanes

1968 ◽  
Vol 64 ◽  
pp. 648 ◽  
Author(s):  
D. Patterson ◽  
S. N. Bhattacharyya ◽  
P. Picker
Keyword(s):  
Chain Molecule ◽  
Heats Of Mixing

Order Parameter Temperature Dependence of Some Nematic Liquids Related to Magnetic and Optical Anisotropies

1976 ◽  
Vol 31 (12) ◽  
pp. 1644-1650 ◽  
Author(s):  
I. H. Ibrahim ◽  
W. Haase
Keyword(s):  
Benzoic Acid ◽  
Single Crystal ◽  
Temperature Dependence ◽  
Order Parameter ◽  
Orientational Order ◽  
Order Parameters ◽  
Optical Data ◽  
Refractive Indices ◽  
Crystal Data ◽  
Parameter Temperature Dependence

Abstract The diamagnetic susceptibilities, refractive indices and densities were measured as a function of temperature for three 4,4'-disubstituted benzoic acid-phenylester compounds. The polarizabilities were calculated using the Vuks formula and Neugebauer's relations. The orientational order parameters obtained from the magnetic and from the optical data as a function of temperature, in the absence of single crystal data, were compared.

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