Phenomenon of micellization of block copolymers in nine different selective solvents is studied. For this purpose the purpose the viscosity of the micelles in different concentrations and at different (278.16-333.16oK) temperatures is determined. By considering the change of Huggins constant and intrinsic viscosity with the change in temperature, it is concluded that the micelles are more compact at lower temperatures. They expand as the temperature is raised. At higher temperatures the solvent can not hold the molecules together and these micelles change to unimers. One maxima is observed, when the intrinsic viscosity was plotted against temperature. This may be due to the phenomenon stated above.