The intercalated smectic A phase. The liquid crystal properties of the α-(4-cyanobiphenyl-4′-yloxy)-ω)-(4-alkyloxycinnamoate)alkanes

Blatch, A. E.; Fletcher, I. D.; Luckhurst, G. R.

doi:10.1080/02678299508036693

Cited by 100 publications

(46 citation statements)

References 9 publications

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“…Intercalated smectic phases have been widely observed in non-symmetric liquid crystal dimers consisting of two differing mesogenic units, one electron rich and the other electron deficient [58] although it is known that that the nature of the linking group between the spacer and mesogenic units also appears to play a role [59,60]. In these systems, the driving force for the formation of intercalated phases was attributed to a specific interaction between the unlike mesogenic groups thought possibly to be an electrostatic quadrupolar interaction between groups with quadrupole moments which are opposite in sign [61]. Figure 8(a) shows a possible intercalated arrangement for the Chol-n-SS-n-Chol dimers and for this the driving force is presumably the mismatch in the cross sectional areas of the alkyl chains and the cholesteryl-based groups.…”

Section: Resultsmentioning

confidence: 95%

Cholesteryl-based liquid crystal dimers containing a sulfur–sulfur link in the flexible spacer

Lee¹,

Lü²,

Henderson³

et al. 2012

Liquid Crystals

130

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Seven members of the homologous series of the liquid crystal dimers, the bis(ω-(cholesteryloxycarbonyl)alkyl) disulfides, which contain a sulfur−sulfur link in the flexible spacer have been synthesised and their liquid crystal properties characterised. The dimers are referred to using the acronym Chol-n-SS-n-Chol in which n denotes the number of carbon atoms linking the cholesteryl-based groups and the sulfur atoms, and was varied between 3, 5, 6, 8, 10, 11 and 12. All seven homologues exhibit a chiral nematic phase and for the longest three members a smectic A phase was also observed. An odd−even effect is apparent in both the transition temperatures and the values of the entropy change associated with the chiral nematic−isotropic transition, S N * I /R, in which dimers with even values of n show the higher values. This is interpreted in terms of the average molecular shapes in which the C−S−S−C dihedral angle is around 90 • . The values of S N * I /R shown by these dimers are very small for liquid crystal dimers and this is attributed to the increased molecular biaxiality arising from the C−S−S−C dihedral angle. The smectic A phase exhibited by the homologues with n = 10, 11 and 12 is proposed to consist of an intercalated arrangement of the dimers which is driven by the mismatch in cross-sectional areas of the cholesteryl-based groups and alkyl chains.

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Section: Resultsmentioning

confidence: 95%

Cholesteryl-based liquid crystal dimers containing a sulfur–sulfur link in the flexible spacer

Lee¹,

Lü²,

Henderson³

et al. 2012

Liquid Crystals

130

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“…2) that assumes the existence of an intercalated smectic phase. [38,39] The smectic fluctuations were more pronounced for the CD8-MpAz8 mixture (half width of the small-angle peak = 0.289 Å), relative to that of CD8-MpAz12 (half width = 0.383 Å), which led to a sharpening of the small-angle peak (Fig. 4).…”

Section: H Akiyama Et Al/photoresponsive Oligomeric Mesogen Dopantsmentioning

confidence: 99%

Synthesis, Liquid‐Crystalline Properties, and Photo‐optical Studies of Photoresponsive Oligomeric Mesogens as Dopants in a Chiral Glassy Liquid Crystal

Akiyama

Mallia

Tamaoki

2006

Adv Funct Materials

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We have prepared photoresponsive oligomers that have molecular weights of ca. 4500, 8000, and 16 000 g mol–1 via the free‐radical polymerization of 4‐[4‐alkylphenylazo]phenoxyalkyl acrylates. All of the oligomers possess bilayer smectic A (SmA) and smectic B (SmB) phases. Increasing the concentration of these oligomeric dopants in a glass‐forming cholesteric liquid crystal causes a dramatic red‐shift in the reflection wavelength. The pitch shifts are very dependent on the alkyl chain lengths and molecular weights of the dopants. The oligomer that contains octyl chains and an octyl spacer, and that has a molecular weight of 4500 g mol–1 exhibits the largest shift in the reflection wavelength. UV exposure has been used to control the cholesteric reflection pitch of the oligomer‐cholesteric glassy liquid‐crystal mixture over the entire visible region of the electromagnetic spectrum and vitrifies the samples by rapid cooling from their cholesteric temperatures to 0 °C. Extremely stable, even at 70 °C, erasable, full‐color images have been created using this host–guest mixture.

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“…Thus, for the intercalated phases to be observed, the terminal chain must be equal to or shorter in length than the spacer. [49] For UEBA-PD-TFBA and UEBBA-PD-TFBA, the length of the spacer of PD is much shorter than that of the alkyl terminal chain, which is adverse to the formation of intercalated structure. Although the length of trifluoromethyl terminal groups is shorter than that of the spacer (PD), it is plausible for the formation of the intercalated structure, as shown in Figure 10.…”

Section: Lc Properties Analysismentioning

confidence: 99%

1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

Yao

Feng

et al. 2016

Liquid Crystals

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2016): 1,2-Propanediol-linked chiral symmetric and nonsymmetric liquid crystal dimers containing trifluoromethyl, Liquid Crystals, ABSTRACT Four symmetric and non-symmetric chiral liquid crystal dimers containing trifluoromethyl groups, termed as TFBA-PD-TFBA, UEBBA-PD-TFBA, UEBA-PD-TFBA and UEA-PD-TFBA, respectively, have been synthesised and characterised. UEA-PD-TFBA exhibited chiral nematic phase, whereas the other three dimers displayed chiral smectic A phase. X-ray diffraction (XRD) has revealed the structure of the smectic A phase for TFBA-PD-TFBA to be intercalated, whereas that for UEBBA-PD-TFBA and UEBA-PD-TFBA to be monolayer and interdigitated, respectively. In addition, the weaker peak corresponding to a shorter layer spacing was observed for UEBBA-PD-TFBA and UEBA-PD-TFBA. Considering the results of XRD measurements and computer simulations, the structural model corresponding to the shorter layer spacing is assigned as horseshoe-like shape. The absence of smectic behaviour for UEA-PD-TFBA reveals that the weaker aromatic-aromatic interactions cannot stabilise the smectic A phase. ARTICLE HISTORY

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The intercalated smectic A phase. The liquid crystal properties of the α-(4-cyanobiphenyl-4′-yloxy)-ω)-(4-alkyloxycinnamoate)alkanes

Cited by 100 publications

References 9 publications

Cholesteryl-based liquid crystal dimers containing a sulfur–sulfur link in the flexible spacer

Cholesteryl-based liquid crystal dimers containing a sulfur–sulfur link in the flexible spacer

Synthesis, Liquid‐Crystalline Properties, and Photo‐optical Studies of Photoresponsive Oligomeric Mesogens as Dopants in a Chiral Glassy Liquid Crystal

1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

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