Mesomorphic phase transitions of 3F7HPhF studied by complementary methods

ABSTRACT

Physical properties and the phase sequence of (S)-4′-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-2-fluorobenzoate exhibiting the liquid crystalline paraelectric smectic A*, ferroelectric smectic C* and antiferroelectric smectic C_A* phases were studied by complementary methods in the temperature range from −125 to 120 °C. Differential scanning calorimetry measurements together with polarizing optical microscopy provided the phase sequence, including the glass transition and a cold crystallization. X-ray diffraction was used to obtain the unit-cell parameters of the crystal phase, as well as the layer thickness and correlation length in the liquid crystalline smectic phases. The tilt angle was found to reach 45°, as determined from the measurements of the layer thickness and molecular modeling. Relaxation processes in the smectic phases and the fragility parameter were studied using frequency-domain dielectric spectroscopy.

KEYWORDS:

• Ferroelectric liquid crystal
• antiferroelectric liquid crystal
• tilt angle
• orthoconic smectic
• glass transition
• cold crystallization

Acknowledgments

The research was carried out with the equipment purchased, thanks to the financial support of the European Regional Development Found Operational Program Infrastructure and Environment (contract no. POIS 13.01.00-00-062/08) (X-ray diffractometer Empyrean 2 equipped with the Cryostream 700 Plus) and the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08) (Diamond 8000 DSC calorimeter). Financial support of Ministry of Science and Higher Education [grant number 7150/E-338/M/2017] is acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

European Regional Development Found Operational Program Infrastructure and Environment (contract no. POIS 13.01.00-00-062/08), European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08), Ministry of Science and Higher Education [grant number 7150/E-338/M/2017]