Study on Aggregation Behavior and Thermodynamics of Micellization of Some Cationic Gemini Surfactants Using Fluorescence and Conductometric Methods

Abstract

In the present thesis work the micellization properties of synthesized gemini surfactants have been studied using fluorescence and conductometric techniques The probe molecules showing Twisted Intramolecular Charge Transfer TICT fluorescence have been utilized to study the different systems such as micelles mixed micelles and nanoparticles NPs The solvation dynamics and rotational relaxation of a fluorescence dye Coumarin 480 C480 have been studied in the micelles of gemini surfactants In the introduction part of the thesis an overview of above mentioned systems fluorescence properties of TICT probes and Coumarin dyes are explained The scope of the present study is briefed by stating the research gap and the work done in this thesis The materials methods and instruments used in the present study are also explained newlineThe aggregation behavior of two gemini surfactants ie 123OH122Br and 124OH2122Br with hydroxyl substituted spacer groups have been studied in aqueous medium using a TICT fluorescence probe trans24dimethylaminostyrylbenzothiazole DMASBT A higher critical micellar concentration cmc is observed for 124OH2122Br than that of 123OH122Br Formations of a number of premicellar aggregates have been demonstrated in addition to the description of the microenvironment around DMASBT The hydroxyl group of the spacer group induces the formation of premicellar aggregates The micropolarity of environment around DMASBT increases on going from premicellar to micellar aggregates and found to be lower for 124OH2122Br than that of 123OH122Br The microviscocity of premicellar and micellar aggregates of 124OH2122Br are higher than that of 123OH122Br Further the aggregation behavior of 123OH122Br and 124OH2122Br are investigated in presence of water and waterorganic solvents 14dioxane DO and ethylene glycol EG mixed media by conductivity measurements at four different temperatures Higher cmc values are observed for studied geminis in presence of organic cosolvents than that in pure water Various thermodynamic properties such as