Fluorescence of commercial Pluronic F127 samples: Temperature-dependent micellization

We present a novel approach of using the butylated hydroxytoluene (BHT) antioxidant found in commercial Pluronic F127 samples as a marker of polymer aggregation. The BHT marker was compared to the pyrene dye and static light scattering methods as a way to measure the critical micelle concentration (CMC) and critical micelle temperature (CMT). The n ¿ p* transitions of BHT are sensitive to the microenvironment as demonstrated by plotting the fractional intensities of its excitation (¿280 nm) and emission (¿325 nm) peaks. BHT is more sensitive to changes in temperature than concentration. The partition coefficient increases ¿40-fold for pyrene compared to ¿2-fold for BHT when the temperature is increased from 25 to 37 °C. CMT values determined using the BHT fluorescence decrease with increasing F127 concentration. Our results show that BHT can be used as a reliable marker of changes in the microenvironment of Pluronic F127.