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

Roland, C. M.; Fragiadakis, D.; Bogoslovov, R. B.; Urban, S.; Dąbrowski, R.; Tykarska, Marzena; Osiecka, Natalia; Czub, J.

doi:10.1080/02678292.2012.689867

Cited by 11 publications

(13 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For many nematic and smectic liquid crystals it has been shown that this dynamic scaling exponent γ bears a close approximation to , 6,7,13,14 a result corroborated by recent simulations. 15 We have pointed out that the equivalence = γ implies that the relaxation time τ must be constant at a phase transition, 16 although Satoh 15 avers that an order parameter that is invariant at a liquid crystal transition 2 gives the same result.…”

Section: Introductionsupporting

confidence: 74%

Phase behavior and dynamics of a cholesteric liquid crystal

Roy

Fragiadakis

Roland

et al. 2014

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

The synthesis, equation of state, phase diagram, and dielectric relaxation properties are reported for a new liquid crystal, 4(')-butyl-4-(2-methylbutoxy)azoxybenzene (4ABO5*), which exhibits a cholesteric phase at ambient temperature. The steepness of the intermolecular potential was characterized from the thermodynamic potential parameter, Γ = 4.3 ± 0.1 and the dynamic scaling exponent, γ = 3.5 ± 0.2. The difference between them is similar to that seen previously for nematic and smectic liquid crystals, with the near equivalence of Γ and γ consistent with the near constancy of the relaxation time of 4ABO5* at the cholesteric to isotropic phase transition (i.e., the clearing line). Thus, chirality does not cause deviations from the general relationship between thermodynamics and dynamics in the ordered phase of liquid crystals. The ionic conductivity of 4ABO5* shows strong coupling to the reorientational dynamics.

show abstract

Section: Introductionsupporting

confidence: 74%

Phase behavior and dynamics of a cholesteric liquid crystal

Roy

Fragiadakis

Roland

et al. 2014

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…Although the potential parameters obtained herein for the nematic phase of 8OCB, γ and Γ , have magnitudes similar to those for other LC compounds [6,7,34], the value extracted from scaling of the dynamics, γ * = 4.4, is significantly larger than the thermodynamic potential parameter, Γ = 3.15 ( Figure 3). In the context of Maier-Saupe theory of the nematic state [35] (2)); γ * corresponds to the reduced relaxation times (Equation (6)).…”

Section: Discussionmentioning

confidence: 93%

Volumetric study ofn-octyloxy-cyanobiphenyl (8OCB)

et al. 2013

View full text Add to dashboard Cite

Volumetric measurements were carried out on n-octyloxy-cyanobiphenyl (8OCB) over temperatures from ambient to 150• C at pressures up to 200 MPa, encompassing the liquid, nematic and smectic liquid crystalline, and crystal states. From the step changes in volume at the transitions, the phase boundaries and the associated activation enthalpies and energies were determined. The results are consistent with prior studies that were limited to a narrower range of thermodynamic conditions. The thermodynamic potential parameter, Γ , found for the isotropic-nematic transition, =3.15, is significantly smaller than the scaling exponent γ (=4.4) that superposes the longitudinal relaxation times in the nematic state. From this non-equivalence, we conclude that the order parameter must vary with pressure along the clearing line. By comparing the phase behaviour of the nematic state for isochoric and isobaric conditions, the relative contribution of volume was determined to be less that the effect of thermal energy on the thermodynamic stability.

show abstract

“…Thermally induced phase transitions in liquid crystals studied with DRS appear as frequency independent changes in ε ′ . For these measurements, the capacitor was heated up to 170°C, then cooled down to −150°C and subsequently heated up to 170°C while the dielectric response was recorded continuously at 1 ΜHz, 100, 10, and 1 kHz (isochronal measurements).…”

Section: Methodsmentioning

confidence: 99%

Thermal transitions and molecular dynamics in main‐chain liquid crystalline polyester/fullerene nanocomposites

et al. 2016

View full text Add to dashboard Cite

Molecular dynamics and liquid crystalline (LC) transitions in nanocomposites with main-chain liquid crystalline alkylene-aromatic polyester as a matrix and fullerene C 60 as a filler, with filler content varying from 0.3 up to 5 wt% were studied. Measurements by differential scanning calorimetry (DSC) and temperature modulated DSC techniques were performed in order to study glass transition and LC transitions. Dielectric relaxation spectroscopy (DRS) was used both to record LC transitions through isochronal measurements at four different frequencies during cooling/ heating at constant rate and to study molecular mobility through isothermal measurements in a wide temperature and frequency range, 21508C to 1908C and 10 21 to 10 6 Hz, respectively. Glass transition and LC transitions were followed for the neat matrix as well as for the nanocomposites. A moderate increase of glass transition temperature in nanocomposites was found, while the LC transitions were shifted to lower temperatures with increasing filler content. A good correlation between DSC and DRS results was found. For all the samples under study four dielectric relaxations were followed by DRS, in order of increasing temperature: two secondary relaxations, b and c, the a-relaxation related to the amorphous phase glass transition and an interfacial relaxation (Maxwell-Wagner-Sillars, MWS) due to charge accumulation at the amorphouscrystalline interface. The experimental data were analyzed in detail and the results revealed rather weak effects of fullerenes on molecular dynamics. POLYM. COMPOS., 38:E331-E341, 2017.

show abstract

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

Cited by 11 publications

References 30 publications

Phase behavior and dynamics of a cholesteric liquid crystal

Phase behavior and dynamics of a cholesteric liquid crystal

Volumetric study ofn-octyloxy-cyanobiphenyl (8OCB)

Thermal transitions and molecular dynamics in main‐chain liquid crystalline polyester/fullerene nanocomposites

Contact Info

Product

Resources

About