Polymorphism of Chiral Thioester Studied by Dielectric Spectroscopy
Résumé
(S)-(+)-4′-[(4-(1-methylheptyloxycarbonylphenyl) thiocarbonylphenyl]-decyloxybenzoate (in short
10.OPOSMH) was studied by complementary methods. The substance shows rich polymorphism. In addi-
tion to ferroelectric and antiferroelectric smectic C∗ phases it possesses three ferrielectric sub-phases. Phase
transitions between the phases were revealed by differential scanning calorimetry and static dielectric permittivity
measurements. The aim of this paper was to study phase transitions and differences in dielectric spectra shown
by different phases. Collective and molecular dynamics of all phases shown by 10.OPOSMH will be discussed
in terms of theoretical models. Dielectric spectra of antiferroelectric phase show two characteristic dielectric
relaxation modes: one connected with the molecular process (reorientation around the short axis) and the other
originating from fluctuations of antiferroelectric order parameters.