The behavior of symmetric diblock copolymer chains of two different lengths at different concentrations is simulated by means of the bond fluctuation model. Two alternative sets of energies between interacting neighbors are proposed. In one of the sets, attractions between monomers of the same type are considered. In the other set, repulsions between monomers of different types are considered. The collective scattering of the simulation boxes is computed for different values of the reduced energy interaction parameter and the total polymer volume fraction. The analysis of this property is used to locate the transition associated with the formation of mesophases (lamellae) as a function of these two variables. A comparison between the results corresponding to the two different models is performed. When the significant excluded volume corrections are introduced in the model with repulsive interactions, both sets of data agree, except for the most dilute samples. The agreement with the self‐consistent field theory is only fair, and important differences are observed in the intermediate concentration regime. These differences were expected, since the theoretical treatment is only rigorously valid for very long chains.
Comparison of the simulation data for the transition points with the prediction of the self‐consistent field theory (solid line).
