Abstract
For the first time the low frequency relaxation process in two smectic phases (smectic A and smectic C) was studied at elevated pressures with the aid of DTA and dielectric spectroscopy. The substance studied, 2-(4-hexyloxyphenyl)-5-octyl-pyrimidine (6OPB8 in short) exhibits the nematic (N) - SA - SC phase sequence. The p-T phase diagram was established with DTA. However, the SA - SC transition was not observed in the DTA, but could be detected by dielectric relaxation measurements. The dielectric relaxation time measured as function of temperature and pressure, τ∥(p,T), enabled us to calculate the activation volume, Δ#V =RT(∂lnτ /∂p)T, and activation enthalpy, Δ#H = R(∂lnτ /∂T−1)p. It was found that Δ#V(SA) > Δ#V(SC) and Δ#H(N) ≫ Δ#H(SA) > Δ#H(SC), indicating that the molecular rotations around the short axes are more feasible in the tilted SC than in the orthogonal SA phase.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
