X‐ray studies on the crystalline E phase of the 4‐n‐alkyl‐4′‐isothiocyanatobiphenyl homologous series (nBT,n = 2–10)

Jasiurkowska, M.; Budziak, A.; Czub, J.; Massalska-Arodź, Maria; Urban, S.

doi:10.1080/02678290801989975

Cited by 38 publications

(50 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the crystal-like phases (smectic B, E,...), the distances between mass centers of the parallel layered molecules are considerably shorter than the molecular lengths; thus, rotational jumps can be realized only when fluctuations of the surrounding molecules create sufficient free space. 4,5 A similar situation is expected to prevail in the nematic (N) phase. Measurement of τ | as functions of temperature T, pressure P, and specific volume V (inverse of mass density) is essential to understanding the nature of the molecular interactions in LC phases.…”

Section: Introductionmentioning

confidence: 72%

Interaction Potential in Nematogenic 6CHBT

et al. 2008

Self Cite

View full text Add to dashboard Cite

Pressure-volume-temperature (PVT) measurements were carried out on the nematic liquid crystal 4(trans-4′-n-hexylcyclohexyl)isothiocyanatobenzene (6CHBT). In combination with previous dielectric relaxation measurements at elevated pressure and new measurements extending to GHz frequencies, the characteristics of the anisotropic interaction potential were determined. The thermodynamic potential parameter, Γ, which measures the variation of the interaction energy with volume, equals 5.03 ( 0.06, with a barrier height equal to ∼7 kJ/mol. Thus, there is a low potential barrier to reorientations of the 6CHBT molecule about its short axis; however, the retarding potential is strongly volume-dependent. The longitudinal reorientational times determined for various thermodynamic conditions superpose using a scaling exponent equal to Γ within the experimental error. It then follows, as found recently for other liquid crystals, that this relaxation time must be constant along the pressure-dependent clearing line. Thus, the control parameter (e.g., Gibbs free energy) governing the competition between the anisotropic energy and the entropy must also govern the rotational dynamics in the ordered phase of this liquid crystal.

show abstract

Section: Introductionmentioning

confidence: 72%

Interaction Potential in Nematogenic 6CHBT

et al. 2008

Self Cite

View full text Add to dashboard Cite

show abstract

“…[26] or calculated using crystallographic data [23,24] and for n-alkyl--isothiocyanato-biphenyls (nTCB) using packing coeffi cients from Ref. [27]. It can be seen that for all nOCB in crystal phase, the values predicted from Eq.…”

Section: Positron Annihilation In Liquid Crystalsmentioning

confidence: 93%

“…As it was mentioned, this phase has a layer structure. The molecules exhibit spatial periodicity in three dimensions with orthorhombic symmetry and exhibit no fl uidity within the layer [27]. They form herringbone array in layers with highly disordered vertical orientation of molecules (head-to-tail disorder).…”

Section: Positron Annihilation In Liquid Crystalsmentioning

confidence: 99%

See 1 more Smart Citation

Positron annihilation in liquid crystals

Dryzek

Juszyńska-Gałązka

2015

Nukleonika

View full text Add to dashboard Cite

Abstract. Positron annihilation studies of liquid crystals are reviewed with particular reference to thermotropic liquid crystals with rod-like molecules. The studies of compounds exhibiting smectic A or smectic E phases indicate that local arrangement of dipole molecules play an important role because high electron density at the end group of molecules can infl uence substantially formation and annihilation of positronium. The obtained ortho-positronium lifetimes in these phases can be explained by antiparallel pairing of molecules in case of the smectic A phase or a structure with a nanosegregation of alkyl chains and others parts of molecules into sublayers and liquid-like state of alkyl chains in case of the smectic E phase.

show abstract

“…X-Ray diffraction patterns, obtained by the method in [29,30], are displayed in Figure 7. In the SmC phase a sharp peak (001) close to the incident beam and a broad maximum around 2θ ≈ 20…”

Section: Identification Of the Smx Phasementioning

confidence: 99%

Volumetric, dielectric, calorimetric and X-ray studies of smectogenic 10PBO8 at atmospheric and elevated pressures

et al. 2012

Self Cite

View full text Add to dashboard Cite

The synthesis and pressure-volume-temperature (PVT), differential thermal analysis (DTA), dielectric and X-ray diffraction data of 2-(4-octylcarbonyloxyphenyl)-5-decylpyrimidine (10PBO8) are presented. The substance exhibits two crystalline and smectic C (SmC) phases on heating and a SmC-monotropic crystalline smectic B (SmB cr ) SmB cr -crystal sequence of phase transitions on cooling. Above ca. 15 MPa, the SmB cr phase becomes enantiotropic (reversible polymorphism). The phase behaviour and molecular dynamics in the liquid crystalline phases are analysed and discussed, with the conformational component of the total entropy for the SmC-isotropic liquid transition estimated. We also calculate from the PVT results the potential parameter characterising the steepness of the interaction potential.

show abstract

X‐ray studies on the crystalline E phase of the 4‐n‐alkyl‐4′‐isothiocyanatobiphenyl homologous series (nBT,n = 2–10)

Cited by 38 publications

References 23 publications

Interaction Potential in Nematogenic 6CHBT

Interaction Potential in Nematogenic 6CHBT

Positron annihilation in liquid crystals

Volumetric, dielectric, calorimetric and X-ray studies of smectogenic 10PBO8 at atmospheric and elevated pressures

Contact Info

Product

Resources

About