Then the sample solutions were sonicated for 30 min at room temper-ature to equilibrate pyrene. The emission spectra of the solutionswere recorded from 360 to 550 nm with an excitation wavelengthof 339 nm. Peak height intensity ratio (I1/I3) of the first peak (I1at375 nm) to the third peak (I3at 386 nm) was plotted against the log-arithm of polymer concentration. The CMC value was taken fromthe intersection of the tangent to the curve at the inflection withthe horizontal tangent through the points at low concentrations.