Torsional Engineering for Asymmetry Amplification in Cyanovinylene-Based Supramolecular Polymers

The "sergeants-and-soldiers" principle in supramolecular copolymerization provides an effective approach to amplify chiroptical signals with minimal chiral component input. However, the structural determinants governing asymmetric amplification remain insufficiently understood. In this study, we elucidate how the torsion angle of π-aromatic units in monomeric structures modulates the "sergeants-and-soldiers" effect by comparing supraocular chiroptical signals in thiophene- versus furan-substituted cyanovinylene systems. Structural analyses demonstrate a striking divergence in the π-aromatic conformation: furan-substituted monomers exhibit a 31.3° dihedral angle, nearly quadruple the 8.6° distortion observed in thiophene analogues. This geometric distinction translates to dramatically different asymmetry amplification efficiencies. The furan system achieves chiroptical signal saturation with merely 10% chiral "sergeant", compared to the 60% threshold required for thiophene derivatives under identical conditions. We attribute this enhanced amplification to torsional engineering, where the pronounced nonplanarity in furan monomers establishes greater rotational offsets between adjacent units, creating a substantial energy barrier against helix inversion. These insights establish molecular torsion as a key design parameter for optimizing asymmetry amplification in chiral supramolecular polymeric systems.