Investigation of the Self-Assembly Behavior of Statistical Bottlebrush Copolymers via Self-Consistent Field Theory Simulations

Bottlebrush copolymers, a class of high-density sidechain-grafted copolymers with high molecular weights, have recently attracted extensive research attention due to the dramatic reduction of chain entanglement in these copolymers, unique self-assembly behaviors, and distinctive physical properties. In this study, we employ self-consistent field theory simulations to systemically investigate the phase behavior of statistical bottlebrush copolymers A-stat-B, an intriguing subclass of bottlebrush copolymers with random or alternating sequences of A and B side chains. We find that a broader variety of ordered mesophases can be stabilized in the melts of these copolymers relative to the more extensively studied bottlebrush block copolymers. In particular, we observe that these statistical copolymers can stabilize sphere phases over a larger range of species volume fractions than their diblock and tetrablock counterparts but require much higher segregation strength to achieve this. The sphere and hexagonally packed cylinder phases formed by conformationally symmetric statistical bottlebrush copolymers possess interesting discrete core-shell structures with the backbone and lower volume fraction side-chain species forming shells and cores, respectively. Moreover, we uncover a new strategy of stabilizing the Frank-Kasper phase A15 by introducing conformational asymmetry through different side-chain lengths and also observe deflection of order-order phase boundaries and significant mixing between the backbones and short side chains as conformational asymmetry is introduced.

Automated summary

In this study, the phase behavior of bottlebrush copolymers with different side chain sequences was systematically investigated using self-consistent field theory simulations. It was found that these copolymers can stabilize a wider variety of ordered mesophases compared to bottlebrush block copolymers, and can stabilize sphere phases over a larger range of species volume fractions. Additionally, a new strategy of stabilizing the Frank-Kasper phase A15 was uncovered by introducing conformational asymmetry.