Monte Carlo simulations of self-assembling star-block copolymers in dilute solutions

Computer simulations have been performed to analyze the aggregation behavior in dilute solutions of star-block copolymers of the type ( A B ) n in a selective solvent for the B block. We found spontaneous aggregation of single stars and formation of roughly spherical aggregates. By changing the solvophobic/solvophilic length ratio of the two blocks, and keeping the total arm length constant, we observed significant changes in the resulting micellar properties, such as the critical micellar concentration (CMC) and aggregation number. More specifically, by increasing the length of the solvophobic A block, we observe micellization at higher temperatures; whereas by increasing the length of the solvophilic B block, we observe micellization at very low temperatures. We also found a dependence of the CMC on the temperature which is in very good agreement with a recent theoretical description based on a simple thermodynamic framework. We compare our results with this theory and predict the enthalpy and entropy of micellization as a function of the temperature.