Twisted Grain Boundary Phases in the Binary Mixtures of 3ß-Chloro-5-Cholestene and 4-N-Decyloxybenzoic Acid

Characteristics of electrical properties of wide temperature range TGB phases in liquid crystal dimers

“…For this weak peak, un− certainty in the determination of peak transition tempera− tures is quite large and there has been no regular depend− ence of peak transition temperatures on the scanning rates. The similar observations have also been reported in litera− ture for TGB systems [10,11]. It is important to note that most of the TGB−TGB transitions have been predicted to be second order [2,5] but experimentally they have been found to be weakly first order transitions with transition width of the order of 0.2 to 0.5°C in extremely pure samples as well as in the mixtures [3,4,9].…”

“…Dielectric studies of the phases are still in nascent stage and the data on the dielectric behaviour of TGB phases available in literature is not very comprehensive [10,[12][13][14][15][16][17][18][19][20][21] because most of the TGB phases exist over a very short tem− perature range due to their frustrated nature. Initial fre− quency dependent (dynamic) dielectric studies of the TGBA phase [12][13][14][15] show that electric field induces amplitude fluctuation of tilt angle like those of SmA * phase, leading to excitation of soft mode of dielectric relaxation.…”

Induced twisted-grain-boundary phases in the binary mixtures of a cholesteric and a nematic compound

“…The temperature of the samples for the optical-texture and dielectric studies was controlled with the help of a hot-stage of Instec with an accuracy of AE 3 mK. Other experimental details have been discussed elsewhere (Srivastava and Dhar, 1991;Srivastava et al, 1993;Dhar et al, 2003b).…”

“…In the quest for the phase diagram predicted by Renn (1992), several binary and ternary mixtures in which one component is ester of cholesterol have been investigated by our group (Srivastava et al, 1996;Dhar, 1998, 2001;Dhar et al, 2003b). Our earlier studies were on the binary mixtures of 5-cholesten-3-ol-nonanoate (ChP) with 4-n-nonyloxybenzoic acid (NOBA) (Srivastava et al 1996;Srivastava and Dhar, 1998) and 5-cholesten-3-ol-tetradecanoate (ChM) with 4-n-dodecyloxybenzoic acid (DDOBA) (Srivastava and Dhar, 2001).…”

“…These mixtures have shown TGBA phase in a narrow temperature range, and that too was away from the A-N Ã -C Ã tri-critical point. However, we have recently realised the complete predicted phase diagram of Renn (1992) in the binary system of 3-chloro-5-cholestene (ChCl) and 4-n-decyloxybenzoic acid (DOBA) (Dhar et al, 2003b). In the present work we have investigated the binary system of 5-cholesten-3-ol-octanoate (ChC) and 4-n-nonyloxybenzoic acid (NOBA) by optical texture, thermodynamic and dielectric studies.…”