Phase Diagram and Molecular Ordering of Dimer Liquid Crystals Dissolved in a Simple Nematic Solvent

Abe, Akihiro; Shimizu, Renato Norio; Furuya, Hidemine

doi:10.1007/978-3-642-78893-2_12

Cited by 10 publications

(10 citation statements)

References 27 publications

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“…The conformation of the spacer remains almost unaltered with decreasing temperature in agreement with previous results. 5 …”

Section: Resultsmentioning

confidence: 99%

“…5 The l,10-dibromodecane-4,7-13 C 2 was prepared from butanedioic acid-l,4-13 C 2 99atom% 13 C purchased from Nippon Sanso Co., Ltd. First, l,4-dibromobutane-l,4-13C2 was synthesized by standard methods reducing the butanedioic acid-l ,4-13 C 2 with excess lithium aluminium hydride to l,4-butanediol-l,4-13 C 2 and reacting the obtained diol with excess phosphorous tribromide. The obtained dibromide was reacted with 1-butenylmagnesium bromide producing l,1 l-dodecadiene-5,8-13 C 2 .…”

Section: Methodsmentioning

confidence: 99%

“…Following our previous analysis scheme, 5 the long molecular axis (z) of CBA-10 is assumed to be parallel to the line connecting the midpoints of both mesogenes as indicated in Figure 6. In the case of a dimer liquid crystal the relative positions of the molecular axis and principal axis system depend on the conformation of the flexible spacer.…”

Section: The Calculation Of the Order Parametersmentioning

confidence: 99%

“…5 Our goal in this work is to prepare a 13 C-labeled dimer liquid crystal, ll (,w-bis[( 4,4' -cyanobiphenylyl)oxy ]decane (CBA-10) and to analyze its ordering behavior through the observation of the 13 C chemical shift anisotropy, determining the principal values of the 13 C chemical shift tensor for CBA-10 itself. This is the first attempt with a dimer liquid crystal in which the conformation of the spacer must be considered in the analysis of ordering being different from simple monomer liquid crystals.…”

Section: Introductionmentioning

confidence: 99%

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Orientational Ordering of a Dimer Liquid Crystal by High-Resolution Solid-State 13C NMR Spectroscopy

Shimizu

Kurosu

Ando

et al. 1997

Polym J

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ABSTRACT:The ordering of a dimer liquid crystal, IX,w-bis [(4,4'-cyanobiphenylyl)oxy]decane (CBA-10), was studied by variable-temperature high-resolution solid-state 13 C NMR. A large transitional change of the 13 C chemical shift was observed on going from the isotropic to the nematic phase due to uniaxial alignment of the molecule. The principal values of the 13 C chemical shift tensor have been determined by the Herzfeld-Berger method for CBA-10 itself. The molecular axis is assumed to lie parallel to the line connecting the centers of both mesogenic cores, and the evaluation of the order parameters along the molecular axis, (Szz), mesogene axis (S~~ng) and C,-C, axis (S~,;'-c") was attempted here, using the obtained isotropic 13 C chemical shift and principal values of the 13 C chemical shift tensor, and taking into account the conformational behavior of the flexible spacer in the frame of rotational isomeric state (RIS) approach. The order parameter of the molecule S., increased from 0.79 to 0.89 with decrease of I 7.5°C in temperature from nearby the nematic-isotropic transition point. S~~"• increased from 0.74 to 0.80 with decrease of temperature whereas S~,:--c· and the conformation of the spacer was essentially unaltered in the same temperature range.KEY WORDS High-Resolution Solid-State 13 C NMR / 13 C Chemical Shift Tensor/ Conformation/ Rotational Isomeric State / Order Parameter / Dimer Liquid Crystal / Low molecular weight monomer liquid crystals are composed of rod-like molecules which form an uniaxially oriented mesophase. The chemical shift anisotropy of the 13 C nucleus has proved to be a powerful tool for probing the orientational ordering at the molecular level of such compounds 1 · 2 and for a side-chain liquid-crystal polymer. 3 Though the principal values of the chemical shift tensor needed for the analysis are in some cases assumed to be the same for analogous compounds, this may not be true 2 .4 and may lead to error in constructing models of microscopic configurations from the observed data.In the case of dimer liquid crystals consisting of two mesogenic moieties linked by a flexible alkyl chain, as the model of polymer liquid crystals, the molecules align as a whole in the nematic phase, the conformation of the spacer being quite stable in a large temperature range. 5 Our goal in this work is to prepare a 13 C-labeled dimer liquid crystal, ll (,w-bis[( 4,4' -cyanobiphenylyl)oxy ]decane (CBA-10) and to analyze its ordering behavior through the observation of the 13 C chemical shift anisotropy, determining the principal values of the 13 C chemical shift tensor for CBA-10 itself. This is the first attempt with a dimer liquid crystal in which the conformation of the spacer must be considered in the analysis of ordering being different from simple monomer liquid crystals. Spacer conformation is considered in the frame of the rotational isomeric state (RIS) approach.

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“…The conformation of the spacer remains almost unaltered with decreasing temperature in agreement with previous results. 5 …”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: The Calculation Of the Order Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Orientational Ordering of a Dimer Liquid Crystal by High-Resolution Solid-State 13C NMR Spectroscopy

Shimizu

Kurosu

Ando

et al. 1997

Polym J

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“…Although the flexible spacer takes more extended conformation in the LC state, contribution of the spacer to the orientation-dependent intermolecular (attractive) interactions seems to be small [32]. The nematic conformation of the spacer remains nearly invariant over the entire range of the LC state [42]. The conformational analyses of mainchain LCs have been reported from various laboratories.…”

Section: Comparison With the Constant-volume Transition Entropymentioning

confidence: 99%

Nematic Conformation of Chain Molecules Predominating in the Ordered Mesophase

Abe

2013

Hierarchical Macromolecular Structures: 60 Years After the Staudinger Nobel Prize II

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The physical picture of the nematic conformation has been discussed on the basis of the rotational isomeric state analysis for segmented liquid-crystal (LC)-forming molecules, comprising mesogenic units on both sides of a flexible spacer. The disorientation angles (θ) of the two terminal mesogenic units are calculated for given spatial configurations of the spacer. The observed odd-even character of the thermodynamic quantities at the nematic (N)-isotropic (I) phase transition T NI ¼ ΔH NI /ΔS NI has been interpreted in terms of the profiles of the calculated distribution curves P(θ) À θ. Combined use of rotational isomeric state and 2 H NMR techniques has led to an estimate of the conformer fraction in the nematic state. The transition entropies derived on this basis are favorably compared with the constant-volume transition entropies obtained from the pressure-volume-temperature measurement. The observed V-T relation indicates that the expansivity of the nematic LC phase is higher relative to that of the isotropic melt. It has been pointed out that the nematic conformation might possibly gain extra stability from the free volume effect in the LC state. These considerations offer an explanation why amazingly long flexible chain segments can be accommodated in the nematic fluid.

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Conformational analysis of the biphenyl moiety of dimer liquid crystals in the solid state by high-resolution solid-state13C NMR andab initio GIAO-CHF calculations

et al. 1999

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Phase Diagram and Molecular Ordering of Dimer Liquid Crystals Dissolved in a Simple Nematic Solvent

Cited by 10 publications

References 27 publications

Orientational Ordering of a Dimer Liquid Crystal by High-Resolution Solid-State 13C NMR Spectroscopy

Orientational Ordering of a Dimer Liquid Crystal by High-Resolution Solid-State 13C NMR Spectroscopy

Nematic Conformation of Chain Molecules Predominating in the Ordered Mesophase

Conformational analysis of the biphenyl moiety of dimer liquid crystals in the solid state by high-resolution solid-state13C NMR andab initio GIAO-CHF calculations

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