Dielectric and Electrooptic Investigations of B Phases οf Banana Shaped Thioesters

M. Wierzejska Adamowicza, D.M. Ossowska Chruścielb, J. Chruścielb, R. Doualic, Ch. Legrandc, M. Marzeca, A. Mikułkoa, A. Sikorskab, and S. Wróbela a Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland b Institute of Chemistry, University of Podlasie, 3-go Maja 54, 08-110 Siedlce, Poland c LEMCEL, ULCO, 50 rue F. Buisson, B.P. 717, 62228 Calais, France

Full Text PDF

Electrooptic and dielectric measurements were done for B phases of two banana shaped homologues 1,3 phenylene bis{4-[(4 nonylo-xy-benzoyl)sulfanyl]benzoate (9OSOR) and 1,3 phenylene bis{4-[(4 dodecylo-xy-benzoyl)sulfanyl]benzoate (12OSOR). Polarizing microscopy allowed to identify B1 phase for 9OSOR and B2 phase for 12OSOR on the basis of texture observation. Spontaneous polarization measurements were performed using reversal current method. The current response to applied triangular voltage shows that B1 phase is a ferroelectric and B2 phase - antiferroelectric one for which two well separated peaks were observed. Polarization for phase B1 of 9OSOR is rather small and its temperature dependence is unusual for ferroelectric liquid crystals - it increases with temperature. Spontaneous polarization for B2 phase of 12OSOR compound is of about 600 nC/cm2. Dielectric spectra measured with bias field for B2 phase of 12OSOR show two well separated relaxation processes. In the low frequency range the relaxation process is connected with fluctuations of ferroelectric domains. The relaxation process in the high frequency range appearing also without bias field is connected with molecular reorientation. The dielectric spectra measured for B1 phase of 9OSOR with and without bias voltage showed only one dielectric relaxation process connected with molecular reorientation around the short axis.

DOI: 10.12693/APhysPolA.117.557 PACS numbers: 77.84.Nh, 77.84.-s, 78.20.Jq