Mixed Micellar and Interfacial Studies of Triblock Copolymers with Amphiphilic Drug Ibuprofen in Aqueous Urea Solutions

Mixed micellar and surface properties of non-ionic triblock copolymers (Pluronic (R) P123 and F68) and non-steroidal anti-inflammatory drug Ibuprofen (IBF) have been evaluated in aqueous urea (100 mM) solutions with the help of surface tension and fluorescence measurements at 298.15 K. Various bulk and surface parameters such as critical micelle concentration (CMC) of the mixtures, micellar mole fraction (X), interaction parameter (beta) and free energies were calculated using Clint, Rubingh, Rosen and Maeda models. In aqueous solutions, all the mixtures show synergistic interactions and are more in mixtures of IBF with P123. These interactions decrease in presence aqueous urea solution due to breaking of water structure surrounding the hydrophobic moieties by urea molecules resulting in delayed mixed micellization. Micellar aggregation number (N-agg) obtained from the steady state fluorescence quenching indicate that the participation of triblock copolymer is more than the drug IBF in mixed micelle formation. Stern-Volmer constant (K-SV), dielectric constant (D-exp), and micropolarity (I-1/I-3) have also been evaluated and their contribution in the mixed micellar systems have been discussed.