Thermodynamic properties of discotic mesogens: heat capacities and phase transitions of benzene-hexa-n-alkanoates

Asahina, Shuichi; Sorai, Michio

doi:10.1016/s0021-9614(02)00243-4

Cited by 8 publications

(10 citation statements)

References 46 publications

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“…Such an odd-even effect in DS total has been also observed in normal alkanes, [6] fluoroalkanes, [13] and mesogenic compounds with alkyl chains. [14] The increases observed from 1 a (n = 1) to 1 c (n = 3) and from 1 b (n = 2) to 1 d (n = 4) are comparable (15-20 J K À1 mol À1 ); in each case, the change is due to the addition of four difluoromethylene groups. Compounds 3 ad also exhibited the same tendency.…”

mentioning

confidence: 87%

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Mochida

Funasako

Inagaki

et al. 2013

Chemistry A European J

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Crystal structures and thermal properties of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide (C(n)F2(n+1)SO2)2N anions [n = 0 (1), 1 (1 a), 2 (1 b), 3 (1 c), and 4 (1 d)] and the 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonylamide anion (2) were investigated. In these solids, the cations are surrounded by four anions around their C5 axis, and stacking of these local structures forms two kinds of assembled structures. In the salts with even n (1, 1 b, and 1 d), the cation and anion are arranged alternately to form mixed-stack columns in the crystal. In contrast, in the salts with odd n (1 a and 1 c), the cations and anions independently form segregated-stack columns. An odd-even effect was also observed in the sum of the phase-change entropies from crystal to melt. All of the salts exhibited phase transitions in the solid state. The phase transitions to the lowest-temperature phase in 1, 1 a, and 2 are accompanied by order-disorder of the anions and symmetry lowering of the space group, which results in the formation of an ion pair. Solid-state (13)C NMR measurements on 1 a and 1 b revealed enhanced molecular motions of the cation in the higher-temperature phases.

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confidence: 87%

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Mochida

Funasako

Inagaki

et al. 2013

Chemistry A European J

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“…Only BH(7) and BH(8) enantiotropically manifest a discotic mesophase, while BH(9) monotropically exhibits a discotic mesophase upon cooling. One of the authors (MS) and his collaborators measured their heat capacities by adiabatic calorimetry: BH(5),22 BH(6),23,24 BH(7),24,25 BH(8),26 BH(9),27 and BH(10) 27. Of these, the molar heat capacities of BH(6) are plotted in Figure 2 as a function of temperature.…”

Section: Structural Implication: Peculiar Pairing Of Molar Entropies mentioning

confidence: 99%

“…During the course of our calorimetric investigations, an unexpected aspect related to the molar entropies was found. Figure 3 illustrates the molar entropies of six discotic compounds from BH(5) to BH(10) 27. For convenience, the molar entropies of these compounds are divided by temperature.…”

Section: Structural Implication: Peculiar Pairing Of Molar Entropies mentioning

confidence: 99%

“… Comparison of molar entropies of BH( n ) ( n : 5–10), in which the molar entropies are divided by temperature for convenience, the so‐called “tempered molar entropy.”27 …”

Section: Structural Implication: Peculiar Pairing Of Molar Entropies mentioning

confidence: 99%

“… Tempered molar entropies of n ‐alkanes ( n ‐C m H 2 m + 2 ) from n ‐pentane ( m = 5) to n ‐decane ( m = 10), in which the molar entropies are divided by temperature 27…”

Section: Structural Implication: Peculiar Pairing Of Molar Entropies mentioning

confidence: 99%

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Alkyl chains acting as entropy reservoir in liquid crystalline materials

Sorai

Saito

2003

The Chemical Record

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The roles played by the conformational disordering of alkyl chains in determining the aggregation states of matter are reviewed for liquid crystalline materials from a thermodynamic perspective. Entropy, which is one of the most macroscopic concepts but which has a clear microscopic meaning, provides crucial microscopic information for complex systems for which a microscopic description is hard to establish. Starting from structural implication by absolute (third-law) entropy for crystalline solids, the existence of successive phase transitions caused by the successive conformational melting of alkyl chains in discotic mesogens is explained. An experimental basis is given for the "quasi-binary picture" of thermotropic liquid crystals, i.e., the highly disordered alkyl chains behave like a second component (solvent). A novel entropy transfer between the "components" of a molecule and the resulting "alkyl chains as entropy reservoir" mechanism are explained for cubic mesogens.

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Anomalous Odd–Even Effects in Columnar and Smectic Phases of Discotic Tetraphenylenes

2009

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Rather uncommon but pronounced odd-even effects in the clearing temperatures of liquid crystals are found for three new homologous series of discotic tetraphenylenes [figure: see text]. Detailed similarities to the well-known odd-even effects in calmitic mesogens point towards a more general understanding of odd-even effects in liquid crystals.The phase transition temperatures in many homologous series of liquid crystals show odd-even effects similar to the well-known odd-even effects in non-mesogenic organic compounds like carboxylic acids. For discotic liquid crystals only a few series with a sufficient number of consecutive homologues are available and only a small part of these series show odd-even effects at all. We now synthesized and investigated three series of discotic tetraphenylenes each ranging from the n=7 to the n=16 homologues. For these compounds an anomalous odd-even effect is found: The ascending and descending transition temperatures with increasing number of methylene groups in the side chains exhibit an inversion of this alternation which is always found between the n=12 and n=14 homologues. An overview of odd-even effects in liquid crystals is presented and we discuss the nature and the origin of odd-even effect in discotic mesogens.

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Thermodynamic properties of discotic mesogens: heat capacities and phase transitions of benzene-hexa-n-alkanoates

Cited by 8 publications

References 46 publications

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Alkyl chains acting as entropy reservoir in liquid crystalline materials

Anomalous Odd–Even Effects in Columnar and Smectic Phases of Discotic Tetraphenylenes

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