The surface active and association properties of commercial diblock B9E16 and triblock E43B14E43 copolymers from Dow Chemical Company were measured from surface tension, dynamic light scattering, and viscosity data. The values of critical micelle concentrations, surface active properties, and the micellar size and its temperature dependence have been found to be distinct in both the copolymers which differ in the ratio of hydrophobic to hydrophilic block lengths. The noted increase in the micellar size and distortion in the shape of the micelles of diblock copolymer with temperature rise have been explained considering the dehydration of micelles at elevated temperatures. An attempt has also been made to relate the distinct differences in the dilute solution phase diagrams to the changes in micellar dimensions.