Effect of temperature, cosolvent, and added drug on Pluronic-flurbiprofen micellization

Structural changes in the micellization of Pluronics P103 and P123, as a function of temperature, cosolvent (ethanol, 10 v/v %), and the addition of the hydrophobic drug flurbiprofen, were investigated by SANS and tensiometry. Addition of ethanol increases the critical micellization concentration of the Pluronics (making the polymer more soluble), while increasing the repulsive interactions between the flurbiprofen-Pluronic spherical complexes. However, increasing temperature and addition of drug increases both the aggregation number and core radius and leads to a more dehydrated core. The addition of flurbiprofen to Pluronic P103 was also found to reduce the critical micellization temperature from between 15 and 20 °C to below 10 °C and at higher drug concentrations leads to an attractive interaction between micelles and eventually phase separation.