Influence of carbon chain length on physical properties of 3FmHPhF homologues

ABSTRACT

Four compounds from 3FmHPhF homologous series of chiral smectogenic fluorinated compounds (m = 2, 4, 5, 6) were studied by frequency domain dielectric spectroscopy, electro-optic measurements, X-ray diffraction and differential scanning calorimetry. Values of the relaxation time and dielectric increment of relaxation processes versus temperature and bias field were determined. The temperature-dependent tilt angles, spontaneous polarisations, switching times, rotational viscosities, and average intermolecular distances and correlation lengths within smectic layers were obtained. Experimental results were supplemented by density functional theory calculations of isolated 3FmHPhF molecular geometries, and the relationship between the molecular structures and the transverse component of their dipole moments was studied for the mesogens with m = 2, 4, 5, 6, 7. The results are discussed in terms of the length of the C_mH_2m flexible carbon chain of the homologues.

Graphical abstract

KEYWORDS:

• Quantum-mechanical calculations
• dipole moment
• dielectric relaxation
• tilt angle
• glass transition

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 with 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 (DSC 8000 calorimeter). Access to computational resources in the Academic Computer Centre Cyfronet AGH, Kraków, Poland is gratefully acknowledged. A.D. and J.H. acknowledge financial support from the Ministry of Science and Higher Education in Poland (grant no. 7150/E-338/M/2018 to A.D., the ‘Outstanding Young Scientist’ scholarship to J.H.).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Ministerstwo Nauki i Szkolnictwa Wyższego [7150/E-338/M/2018]; European Regional Development Fund [POIG.02.01.00-12-023/08,POIS 13.01.00-00-062/08];