Systematic study of the chiral smectic phases of a fluorinated compound

ABSTRACT

Physical properties of the partially fluorinated compound 3F5FPhF, with hockey stick-like molecules, were studied by complementary methods. Apart from the already reported paraelectric SmA*, ferroelectric SmC* and antiferroelectric SmC*_A phases, the presence of the smectic C*_α subphase in the phase sequence was proved by differential scanning calorimetry, polarising optical microscopy, electro-optic and dielectric spectroscopy methods. The temperature dependence of the smectic layer thickness and correlation length of the lateral short-range order was determined by X-ray diffraction. Based on dielectric measurements three relaxation processes were revealed in the antiferroelectric SmC*_A phase (two collective: P_L, P_H and one molecular: s-process), two collective ones (Goldstone and soft modes) were found both in the ferroelectric SmC* phase and SmC*_α subphase while one relaxation process (soft mode) in the paraelectric SmA* phase. The results were compared with that obtained for other structurally similar compounds, and it was shown that even addition of one methylene group to the side chain influences much on the physical properties.

KEYWORDS:

• Antiferroelectric liquid crystal
• electro-optic parameters
• X-ray diffraction
• subphase alpha
• dielectric relaxation

Acknowledgments

The research was carried out with the equipment purchased thanks to the financial support of the European Regional Development Fund 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 (Perkin Elmer DSC8000 calorimeter). A.D. acknowledges the financial support from the Ministry of Science and Higher Education in Poland (grant no. 7150/E–338/M/2018).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Ministry of Science and Higher Education in Poland [7150/E–338/M/2018];European Regional Development Fund Operational Program Infrastructure and Environment [POIS 13.01.00–00–062/08];European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program [POIG.02.01.00–12–023/08];