Determining Critical Micelle Concentration

CMC generally reflects the stability of micelles after solution dilution. HS15 (35 mg) and DSPE-PEG2000-L-Val (15 mg) were dissolved in 25 mL of water and diluted to yield concentrations in the range of 0.06–2000 µg/mL. Each polymer solution was transferred to a vial containing pyrene (Macklin, Shanghai, China). The emission spectra were determined by a fluorescence spectrophotometer (F-4500, Hitachi, Tokyo, Japan) at 335 nm excitation wavelength. The scanning range was 350–500 nm, the scanning speed was 240 nm/min, the excitation and emission slits were 5 nm and 2.5 nm, respectively, the voltage of the photomultiplier tube was 700 V, and the response time was 5 s. The intensities of I_373nm and I_384nm vibronic bands were evaluated, and the ratios of these intensities were plotted against the logarithm of the concentration of each sample. The CMC was taken as the intersection of two regression lines calculated from the linear portions of the graphs [27 (link)].