Influence of Molecular Architecture on the Dynamics of Block Copolymer Chains at Equilibrium

Block copolymers (BCPs) self-assemble into well-defined nanoscale morphologies, driven by chemical incompatibility between the constituent blocks and enabled by sufficient molecular mobility. The chemical incompatibility is determined by the choice of polymers while molecular mobility is typically induced through annealing. Once the desired equilibrium morphology is formed, further molecular mobility is typically considered unnecessary. Consequently, the annealing process is halted, causing the morphology to become fixed, or "frozen," with very little subsequent molecular motion. In this study, we investigate the behavior of BCP chains at their equilibrium state when molecular mobility is maintained. Using molecular dynamics simulations, we observe that the dynamic behavior of BCP chains is highly dependent on their molecular architecture. Asymmetric, cylinder-forming BCP chains are more mobile and show larger displacements than symmetric, lamellar-forming BCP chains. In addition to these observations, we employ the thermodynamic integration method to quantify the energetic favorability of these motions.