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Title: Preparation and Characterisation of Novel Lyotropic Liquid Crystalline Colloidal Systems
Authors: Shukla, Ravi Kumar
Supervisor: Raina, K. K.
Keywords: Lyotropic liquid crystals;non-aqueous lyotropic liquid crystalline systems;dielectric spectroscopy of LLC.
Issue Date: 2-Nov-2012
Abstract: Lyotropic liquid crystals (LLC) constitute almost half the area in soft matter science. The key areas in the lyotropes like binary and ternary mesophases transition metal based mesophases and the lyotropic colloidal systems gain considerable interest and facilitate applications in diverse fields (biology, cosmetics, pharmaceutical) as a soft template, drug delivery vehicles and active components of optical, capacitive and electrical devices The present study deals with the synthesis, structural, thermal, dielectric and electro-optical characterizations of binary, ternary and colloidal LLC systems. The prepared mixtures were studied in as prepared and quenched conditions at 303K and elevated temperatures (303-400K).The entire work is presented in the six chapters. Chapter 1 deals with background of LLC systems, their diverse classes and physiochemical parameters which play vital role to engineer LLC materials for diverse applications. The importance and need of binary non-aqueous, transition metal salt (TMS) based ternary and colloidal LLC mixtures under different conditions have been discussed. This section also summarize the detailed description of the milestones and fundamental aspects achieved in the concerned research area so far including their future applications considering fundamental and technological view points. Chapter 2 gives the detailed description of experimental route implemented for the synthesis of binary, ternary and colloidal LLC mixtures. Fundamental techniques like X-ray diffraction (XRD) and Polarization optical microscopy (POM) were used to explicate the structural behaviour of the as prepared and quenched mixtures. Thermal, thermo-optical, dielectric and optical behaviour have been studied using differential scanning calorimetry (DSC), LCR meter and Abbe refractrometer. Chapter 3 demonstrates the structural and morphological analysis of aqueous and non-aqueous binary LLC mixtures obtained from ionic and non-ionic amphiphiles in the higher and lower concentration regime of varying polarity solvents. The origin of diverse lyotropic crystalline phases and phase transitions have been explored and discussed for non-aqueous and aqueous LLC mixtures in as prepared and quenched conditions on the basis of XRD and textural analysis. In addition thermal, dielectric and thermo-optical behaviour of these binary LLC mixtures are described in this chapter. Thermal parameters and order of the transitions have also been discussed inferring about the melting and nucleation of new phases at elevated temperature. Frequency and temperature dependent dielectric dynamics of these LLC mixtures were explored and correlated with structural analysis. The higher dielectric constant observed for these systems is one of the key finding of the thesis. The optical behaviour was also discussed for all the mixtures at 303K and higher temperature. Chapter 4 represents the fabrication, structural, textural, thermal and optical investigations of transition metal salts [(ZnCl2 and CuCl2): cetyl pyridinium chloride: ethylene glycol] based ternary mixtures at room and higher temperature in as prepared and quenched conditions. XRD and POM characterizations demonstrate the growth of new phases and structural phase transition with TMS addition at lower and higher content. Interestingly dispersion of CuCl2 gives rise to the growth of cubic rods at lower concentration is one of the important finding of this work. Thermal and thermo-optical analysis of these systems were done to examine the various phase transitions and the nucleation of new phases. Some hypothetical models have been applied to describe the solute-solvent interactions in these systems. The optical properties of these systems were also examined and correlated with the structural and thermal analysis. Chapter 5 gives insight about the preparation, structural, morphological, thermal, dielectric and optical behaviours of colloidal systems derived from ionic and non-ionic surfactant systems (at very low concentration 10:90 wt%) via dispersion of Zinc oxide (ZnO) particles at varying concentrations(0.05,0.1 and 0.5wt%). XRD and POM analysis were employed to examine the various structural changes and phase transition with the addition of these particles. DSC profiles of these systems were explained to ascertain the thermal stability of the observed phases and phase transitions. A dielectric measurement reveals the enhancement in permittivity in the mesophases derived from cationic amphiphiles and decrease in other two. Such behaviour of these colloidal mixtures infers that physical properties of these systems not only depend upon the colloidal particles but also on the nature of the basic building blocks and the structure of mesophase. Chapter 6 includes the conclusion and significance of the systems prepared along with the future scope.
Description: Ph.D. (SPMS)
Appears in Collections:Doctoral Theses@SPMS

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