Thermodynamics of Adsorption and Micellization of Triblock Copolymers of Oxyethylene and Oxybutylene in Aqueous Medium Using Surface Tensiometry

Abstract

The aqueous solutions of three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type EmB10Em have been analyzed by surface tension measurements. Surface activity of these triblock copolymers was studied by measuring surface parameters, like surface excess concentration, Γ2, area per molecule of polymer and standard Gibb's free energy of adsorption, ΔoGads, at various temperatures in the range of 20 to 50°C. The Effect of block length of hydrophilic portion of triblock copolymers on surface activity was investigated in this work. Miceller behavior of these triblock copolymers was also investigated using above technique. Critical micelle concentration (CMC) was determined from the plot of surface tension versus log of concentration in the range of temperature of 20–50°C. Thermodynamic parameters, standard free energy of micellization, ΔoGmic, standard enthalpy of micellization, ΔoHmic, and standard entropy of micellization, ΔoSmic were calculated from CMC value using closed association model in this range of temperature. Self assembly behavior of triblock copolymer E20B10E20 was compared with E30B10E30 and E48B10E48 triblock copolymer. Effect of temperature on surface and miceller properties of the triblock copolymers was also studied.