Abstract
The phase behavior of binary diblock copolymers features a complex interplay between microphase and macrophase separation. Using a combination of self-consistent field-theory (SCFT) and single-chain-in-mean-field (SCMF) simulations, we investigate the self-assembled morphologies of binary blends composed of two linear diblock copolymers, A(1)B(1) and A(2)B(2), both in equilibrium and under processing conditions such as sudden quenching and gradual annealing. We focus on cylinder- and lamella-forming copolymers, where the equilibrium phase diagrams exhibit wide macrophase-separation channels when the length asymmetry between short A(1)B(1) and long A(2)B(2) copolymers becomes sufficiently large. Notably, our particle-based simulations uncover a strong dependence of the resulting morphology on the processing pathway used to reach the same thermodynamic state point within the macrophase-separation channel. Quenching produces a homogeneous mixture of A(1)B(1) and A(2)B(2) copolymers, a narrow cylinder-size distribution, and stronger hexagonal order, whereas annealing induces local demixing of the two copolymers, yielding a bimodal size distribution and weaker hexagonal order. This process-dependent behavior originates from the complex free-energy landscape of the blends. Overall, our study provides insights into the structure-processing-property relationships in block copolymer systems and contributes to the development of rational processing strategies for targeted nanostructures.