Effects of Skewness on the Formation of Complex Spherical Phases in Disperse Diblock Copolymers

One of the most captivating features of block copolymers is their ability to self-assemble into a plethora of ordered structures. In the simplest case of monodisperse linear diblock copolymers, the phase behavior is governed by the strength of the interactions between the two chemically distinct blocks and their molecular weights. For disperse systems, the self-assembly can also be influenced by the molecular weight distribution (MWD). The most widely used quantity to characterize the MWD is the dispersity index that characterize the width of the MWD. However, recent experiments have begun to reveal the importance of skewness of the MWD in the self-assembly process. Therefore, the MWD shape matters, such that different self-assembled structures could be observed in samples with similar dispersity index and different skewness. In our study, we examine the effect of skewness on the formation of the complex spherical packing phases in disperse diblock copolymers using the self-consistent field theory. We find that the MWD skewness is a key parameter regulating the selection of accessible spherical packing phases, demonstrating the importance of the MWD shape.