(505i) Chiral Conformations in Block Copolymers Affect the Thermodynamics of Self-Assembly

Conformations exhibited by block copolymers have long been known to affect the thermodynamics of self-assembly, where asymmetry in Kuhn length or stiffness shifts boundaries in the phase diagram. More recently, with the development of novel chiral block copolymers, the conformations tend to be stiffer than the non-chiral counterparts and can be described by additional features such as pitch of the helical turns. In recent experimental studies, the location of the order-disorder transition appears to be shifted towards higher or lower temperatures, depending on the type of the specific chemistry. The underlying physics of the upward or downward trend is unresolved. Using particle-based simulations and free energy calculations, the goal of this study is to decouple the entropic and enthalpic contributions during the thermodynamics of self-assembly. In this model, the ideal conformations can be tuned by changing intramolecular interaction parameters. We focused on two regions in the phase diagrams: one above and the other below the order-disorder transition temperature. In the disordered region, a clear entropic loss is measured as the chains adopt more helical conformations. In the ordered region, the domain spacing appear to dictate the conformations, where the helicity in the self-assembled state is lower than under ideal conditions that would minimize intramolecular energy. These insights have implications on the hierarchical transfer of chirality across length scales through self-assembly, otherwise known as chirality transfer.