Dielectric study of three homologous Schiff base ferroelectric liquid crystals with the variations of temperature and frequency  

作　　者：Vijayshree Patil N. B.N.Veerabhadraswamy Susanta Chakraborty S.M.Khened R.D.Mathad C.V.Yelamaggad 

机构地区：[1]Department of Physics,Gulbarga University Kalaburagi 585106,Karnataka,India [2]Centre for Nano and Soft Matter Sciences,Prof.U.R.Rao Road Jalahalli Bengaluru 560013,Karnataka,India [3]Department of Physics,Laxmi Venkatesh Desai College Raichur 584101,Karnataka,India [4]Department of Physics,North Bengal University,Siliguri Darjeeling 734013,West Bengal,India

出　　处：《Journal of Advanced Dielectrics》2020年第5期11-24,共14页先进电介质学报（英文）

摘　　要：In this investigation,the dielectric behaviors of three ferroelectric liquid crystals(FLCs)belonging to a homologous series have been revealed in the frequency range of 10 Hz-10 MHz.FLCs used in this study are three-ring calamitic LCs,namely(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-octyloxy)benzoate,(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-decyloxy)benzoate and(S)-4-(((4-(octan-2-yloxy)phenyl)imino)methyl)phenyl 4-(n-undecyloxy)benzoate.The polarizing optical microscopic and differential scanning calorimetric results confirm that these compounds,synthesized as per the known synthetic steps,show not only a ferroelectrically switchable chiral smectic C(SmC*)phase over a wide thermal range,but also other mesophases such as blue phase-I/II(BP-I/II),chiral nematic(N*)and unknown smectic(SmX)phases.Several essential dielectric parameters of the FLC phase have been measured at different temperatures.The relative permittivity has been measured with the variations of temperature and frequency.Besides,the dielectric loss and tanδhave been measured.Different dielectric relaxations have been calculated and explained at the molecular level.The systematic measurements revealed a strong anomaly,and crossover of relative permittivity values for the FLCs has been determined at selective frequencies between 1 kHz and 20 kHz.Strong dielectric anomaly/fall for the response function infers the involvement of collective response of dipolar assembly confined to ferroelectric Weiss domains.

关 键 词：Liquid crystal TANΔ relative permittivity Maxwell-Wagner mode Goldstone mode smectic C*phase 

分 类 号：O62[理学—有机化学]