%0 Journal Article
%T Image Analysis Studies for Phase Transitions of Ferroelectric Liquid Crystals
%A S. Sreehari Sastry
%A B. Gowri Sankara Rao
%A K. B. Mahalakshmi
%A K. Mallika
%A C. Nageswara Rao
%A Ha Sie Tiong
%J ISRN Condensed Matter Physics
%D 2012
%R 10.5402/2012/423650
%X Phase transition temperatures of ferroelectric liquid crystals ((S)-(-)-2-methylbutyl 4¡ä-(4¡å-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (where and 18)) are studied through two techniques of image analysis. One is a statistical method, applied to compute the statistical parameters from the textures of each sample and the other, computation of Legendre moments being applied as image moment analysis, both of which are considered as a function of temperature. The textures of the samples are recorded with the polarizing optical microscope (POM) attached to the hot stage and high resolution camera. The phase transition temperatures of samples are inferred by the abrupt changes in the computed parameter values. The results obtained from the present methodology are in good agreement with those published in earlier literature done by the different techniques, like differential scanning calorimetry (DSC). 1. Introduction The studies on phase transitions in thermotropic liquid crystal have seen considerable progress since 1980 [1]. With the availability of high resolution and sensitive experimental techniques, it could be made easy to record precisely the transformations that occur during mesophase changes. Identification of transition phases and transition temperatures is the vital aspect to characterize the properties of liquid crystal compounds. Besides, the ordering in phase transitions, namely, first-order/second-order phases, is crucial in current liquid crystal field studies [2¨C4]. With its wide applications in the use of optical switches, light valves, display and storage devices, and other electrooptic devices, in particular the study on the ferroelectric liquid crystals (FLCs) has generated much interest for synthesizing and characterizing the new FLCs [5¨C9]. Having these objectives, the present attempt is aimed to study the transition temperatures of the two synthesized ferroelectric liquid crystals ((S)-(-)-2-methylbutyl 4¡ä-(4¡ä¡ä-n -alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (where and 18)) through the image analysis techniques, statistical and image moments approaches applied to the microscopic textures of FLCs. The results of the study are compared with those of published earlier studies [10]. Also this kind of work was done for room temperature liquid crystals, cholesteric liquid crystals, and for discotic liquid crystals [11¨C15]. 2. Experimental The liquid crystals of chiral esters (S)-(-)-2-methylbutyl 4¡ä-(4¡ä¡ä-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates where and 18 having different alkyl chain lengths are synthesized [10] and used.
%U http://www.hindawi.com/journals/isrn.cmp/2012/423650/