The Effect on Mesomorphic Properties of Substituting a Sulfur for the Ether Oxygen Atom in the Ester Linkage of 4-Alkylphenyl-4′-Alkyl or Alkoxybenzoates

Neubert, Mary E.; Cline, Robert E.; Zawaski, M. J.; Wildman, Patricia J.; Ekachai, Arun

doi:10.1080/00268948108074675

Cited by 48 publications

(5 citation statements)

References 21 publications

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“…The 8S5 was synthesized at Kent State University and the transition temperatures were observed to be close to those previously recorded for the bulk material [8,9]. The aerosil particles (hydrophilic type-300) were provided by Degussa and were dried prior to sample preparation.…”

Section: Experimental Techniquesmentioning

confidence: 99%

High-resolution x-ray study of the nematic–smectic-Aand smectic-A–smectic-Ctransitions in liquid-crystal–aerosil gels

et al. 2003

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The effects of dispersed aerosil nanoparticles on two of the phase transitions of the thermotropic liquid crystal material 4-n-pentylphenylthiol-4'-n-octyloxybenzoate (8S5) have been studied using high-resolution x-ray diffraction techniques. The aerosils hydrogen bond together to form a gel which imposes a weak quenched disorder on the liquid crystal. The smectic-A fluctuations are well characterized by a two-component line shape representing thermal and random-field contributions. An elaboration on this line shape is required to describe the fluctuations in the smectic-C phase; specifically the effect of the tilt on the wave-vector dependence of the thermal fluctuations must be explicitly taken into account. Both the magnitude and the temperature dependence of the smectic-C tilt order parameter are observed to be unaffected by the disorder. This may be a consequence of the large bare smectic correlation length in the direction of modulation for this transition. These results show that the understanding developed for the nematic to smectic-A transition for octylcyanobiphenyl (8CB) and octyloxycyanobiphenyl (8OCB) liquid crystals with quenched disorder can be extended to quite different materials and transitions.

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Section: Experimental Techniquesmentioning

confidence: 99%

High-resolution x-ray study of the nematic–smectic-Aand smectic-A–smectic-Ctransitions in liquid-crystal–aerosil gels

et al. 2003

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“…The crystals formed on cooling (Cr 2 ) had a lower melting temperature than the virgin crystals (Cr 1 ) but converted to Cr 1 on standing at room temperature for several days. d Data are from reference [27]. e The first crystals formed at 20.2uC and then changed to another form on cooling to 17.4uC; on reheating these crystals (Cr 2 ) melted to the N phase.…”

Section: Discussionmentioning

confidence: 99%

The effect on mesomorphic properties of a triple bond in a terminal chain of 4,4′‐disubstituted phenyl benzoates and phenyl thiobenzoates

et al. 2005

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2005) The effect on mesomorphic properties of a triple bond in a terminal chain of 4,4′-disubstituted phenyl benzoates and phenyl thiobenzoates, Liquid Crystals, 32:2, 247-266,The effect of a triple bond in a terminal chain on the mesomorphic properties of rod-like mesogens was studied by replacing a straight alkyl chain with a terminal 1,2-alkynyl chain in some esters and thioesters of the type: or by incorporating the triple bond into an alkyl ester chain in esters and thioesters of the types:The triple bond should provide increased rigidity to the triple bond region but increased flexibility at the adjacent single bond. These should have opposite effects on the mesomorphic properties. The first compounds were synthesized by esterification of the appropriate alkynylbenzoic acids with various phenols or thiols using the carbodiimide method. Detailed syntheses are provided for the alkynylbenzoic acids. Preparation of the alkynyl ester compounds was by acylation of the precursor hydroxyl esters or thioesters using either the acid chloride or carbodiimide method. The synthesis of the phenolic or thiolic ester intermediates, usually using a protection group, is described. Mesomorphic properties of these new esters and thioesters were determined using hot stage polarizing microscopy and DSC and compared with those for the known parent compounds. Fewer mesophases having shorter temperature ranges and lower transition temperatures were usually observed. Some of the intermediate phenols or benzyl ethers were also studied. Long chain benzyloxy esters showed a nematic phase as did some of the hydroxy thioesters but no mesophases were observed in the hydroxy esters.

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“…A comparison of both melting ( Figure 2) and clearing ( Figure 3) temperatures for the BC esters with X = RO, 6 with those for the analogous 5 and 6 SC esters with R > 7 indicates that these temperatures are always lower for the BC compounds than for the SC ones. Generally, in homologous series plots of melting …”

Section: Mesomorphic Propertiesmentioning

confidence: 94%

“…Although the analogous straight chain (SC) phenylbenzoates show more smectic phases when both chains are longer, these also are often mon~tropic.~-' However, the SC thiobenzoates 4 show more smectic phases at shorter chain lengths, many of which are enantiotropic. 6 Thus, these thioesters would be better for studying the effect of methyl FERROELECT'RIC LIQUID CRYSTALS 229 branching on mesomorphic properties. Since studies were already started in the esters, we were interested in studying the effect of branching in both series so a comparison could be made.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Methyl Group Position in Branched Alkyl Chains on the Phenolic End of 4,4′-Disubstituted Phenylbenzoates on Mesomorphic Properties and Some Optically Active Analogs as Ferroelectric Liquid Crystals

Neubert

Leonhardt

Sabol-keast

1989

Molecular Crystals and Liquid Crystals Incorporating Nonlinear

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A select number of homologs of the branched chain (BC) Cs ester series: n in which m = 0-3 and n = 0-2, and X = R, RO, and &C02 have been synthesized to study the effect of branching and the position of the branching methyl group on mesomorphic properties. This effect was also determined for the BC cyclohexane diesters: Me to test the generality of any trends observed in a different structural series. Mesomorphic properties of the esters were determined by hot-stage polarizing microscopy. Nematic, S,, S,, and S(,?, phases in various combinations were observed. Both clearing and melting temperatures for the BC phenylbenzoates, when X = RO and C&O, were always lower than for the analogous straight chain (SC) esters containing the same number of carbon atoms, as were in the backbone of the BC.Comparisons of the effect of the BC on the mesomorphic properties of these esters are made with the effect observed in a variety of other thioesters, substituted phenylbenzoates, and the analogous biphenyl compounds. Often Sc phases are enhanced at the expense of the SA phase, and N phases seem most preferred when the methyl group is in the 2-position on the chain of the phenol/thiol. Clearing temperatures are always lower than in the analogous SC compounds and melting temperatures are usually lower. However, enough discrepancies occur to make the melting trend a less general one. The effect of location of the methyl group on transition temperatures in C5 BC phenylbenzoates is similar to that observed previously for the C4 BC esters, i.e. they tend to increase as the methyl group is moved further from the benzene ring. This trend, however, does not always occur in other systems such as the thioesters.Mesophase ranges were good among the BC phenylbenzoates with X = RO and room temperature SA-Sc combinations were found in this series when rn = n = 2. Therefore, several homologs were prepared with an optical isomer of this chain to determine their usefulness in mixtures as ferroelectric materials.

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The Effect on Mesomorphic Properties of Substituting a Sulfur for the Ether Oxygen Atom in the Ester Linkage of 4-Alkylphenyl-4′-Alkyl or Alkoxybenzoates

Cited by 48 publications

References 21 publications

High-resolution x-ray study of the nematic–smectic-Aand smectic-A–smectic-Ctransitions in liquid-crystal–aerosil gels

High-resolution x-ray study of the nematic–smectic-Aand smectic-A–smectic-Ctransitions in liquid-crystal–aerosil gels

The effect on mesomorphic properties of a triple bond in a terminal chain of 4,4′‐disubstituted phenyl benzoates and phenyl thiobenzoates

The Effect of Methyl Group Position in Branched Alkyl Chains on the Phenolic End of 4,4′-Disubstituted Phenylbenzoates on Mesomorphic Properties and Some Optically Active Analogs as Ferroelectric Liquid Crystals

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