Is the ODT of diblock copolymers a mean-field transition? Insights from DPD

The order-disorder transition (ODT) in diblock copolymers has fascinated scientists for many decades and has inspired multiple theories to explain its origin. After the pioneering work of Leibler, as well as that of Fredrickson and Helfand, (F-H) it was possible to understand within a mean field theory framework how such phases appeared and what the effect of fluctuations on the ODT transition were. Over the last few years, however, several new theories have emerged trying to incorporate fluctuations in different ways to better match experimentally observed temperatures compared to the F-H results. Here, we revisit this problem by using a coarse-grained computational technique called Dissipative Particle Dynamics and explore the mean field limit within this approximation. Our results suggest that the experimentally observed transition can be well explained by the mean-field limit albeit with a different chain model that correctly captures the physics of the problem, as well as reducing some constraints of the theory which also make physical sense. Molecular insights from the simulations will be provided to show the limitations of previous theories and inform new theories and models in this area.