Effects of self-assembly on the conformational chirality of block copolymers

Advances in polymer synthesis have led to the development of chiral polymer molecules. When incorporated into a block copolymer architecture, these molecules are capable of exhibiting chirality transfer. That is, chirality at the molecular scale is transferred to the conformational length scale, and ultimately to the mesostructural length scale. Thermodynamic descriptions of the mechanisms of chirality transfer are not fully understood. In this work, we employ particle-based simulations to develop a versatile and tunable model for chiral polymers. A wide range of conformations, ranging from a random-coil to a perfect helix, are obtained for a single chain by tuning suitable interaction parameters. We quantify experimentally measurable conformational characteristics for the single chiral polymer molecule. Subsequently, we incorporate the helical block in a block copolymer and study the self-assembly of a melt of thousands of molecules in the lamellar morphology to examine the impact of the morphology on the conformations of the helical blocks. Surprisingly, we find that the morphological constraints result in quantifiably lower helical nature of the molecules in the melt, compared to the isolated single chain. This suggests a tradeoff occurs, where enthalpic contacts between unlike monomers are reduced, but chain conformations do not minimize their internal energy.