Unusual physical properties in B phase of polar bent-core thioester compound

Abstract

Bent-core compound, 4-chloro-1,3-phenylene bis{4-[(n-undecyloxybenzoyl)-sulfanyl]benzoate}, has been studied by dielectric spectroscopy, DSC calorimetry, and electro-optic methods. As found, the spontaneous polarization of the B phase is by one order of magnitude smaller than for B ₂ phases of nOSOR series studied by us before. Its temperature dependence is characteristic for B ₁ phase, observed for shorter homologues of nOSORs. Measurements of the complex electric permittivity were carried out in the frequency range from 40 to 15 MHz using gold-coated electrodes. Electro-optic studies have been done applying AWAT HG 1.9 µm cells with strongly rubbed polymer layers. Such cells facilitate inhomogeneous planar alignment, which under strong electric field transforms into a mono-domain exhibiting switching behavior. Dielectric and electro-optic data of bent-core compounds will be discussed taking into account molecular structure and phase structure as well.

Keywords:

• bent-core thioester
• ferroelectric phase
• spontaneous polarization
• electro-optic effects
• dielectric relaxation
• molecular and collective processes

Acknowledgments

This research was carried out with the financial support of the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08).