Polyethylene glycol assisted micellar, interfacial and phase separation studies of triblock copolymer–nonionic surfactant mixtures

Owing to the relevancy of surfactant–polymer mixtures in several industrial and technological applications, the present work aims to study the aqueous triblock copolymer, Pluronic L64 – nonionic surfactant, Igepal CO 720 mixtures in the presence of various polyethylene glycols viz. PEG 15000, PEG 6000, PEG 2000 and PEG 600. This has been evaluated in terms of micellar, interfacial and phase separation behavior using fluorescence spectroscopy, surface tension, cloud point and dynamic light scattering measurements. The behavior of mixed micelles is seen to be dependent on the solution composition. Increasing the concentrations of Igepal CO 720 in mixtures, the mixed micelles shift from being Pluronic L64 rich to Igepal CO 720 dominated ones. An insight in the behavior of mixtures using PEGs exemplifies this dominance of Igepal CO 720 in the mixed micelles. Results indicate that both the micellization and clouding tendencies of Pluronic L64 are facilitated by the presence of all types of PEGs. However in Igepal CO 720, the micellization gets retarded while clouding behavior is a function of the molecular weight of PEGs. The hydrodynamic diameter of micellar aggregates of pure Pluronic L64, Igepal CO 720 as well as their mixtures is found to increase in the presence of PEGs.