Micelle dimerization in melts of asymmetric diblock copolymer chains

Experiments on asymmetric diblock copolymer melts have reported the formation of metastable Frank-Kasper and Laves phases, which are presumed to emerge as a consequence of arrested dynamics upon rapidly cooling a disordered micellar system. Although these reports have generated a renewed interest in the disordered micellar regime, a definitive understanding is still lacking. In this work, we perform coarse-grained molecular dynamics simulations on asymmetric diblock copolymer chains having a minority block volume fraction of 0.125. Analysis of the aggregation numbers and the shape anisotropies of clusters reveals frequent formation and breaking of bridges between two or more micelles in both the ordered and disordered states. Due to the rapid formation and breaking of bridges, we expect this phenomenon to complicate the identification of micelle fusion and fission in molecular simulations. These provocative results may be difficult to verify experimentally, yet will play an important role in the dynamics associated with the formation and transformation of disordered and ordered morphologies.