Grainger College of Engineering Seminars & Speakers

Spontaneous chiral symmetry breaking remains a fascination in chemistry, biology, materials science and even astronomy. Chiral symmetry breaking usually requires intrinsic molecular chirality or extrinsic chiral sources but remains rare in non-chiral systems. Here, we reveal a ubiquitous, entropy-driven chiral symmetry breaking mechanism observed in state-of-the-art conjugated polymers in absence of chiral sources – a phenomenon overlooked for decades. Chiral assemblies spontaneously occur through liquid-liquid phase separation of lyotropic mesophases from isotropic solutions upon concentration increase. Machine learning identifies underpinning molecular features validated by further molecular design. We further show that such hierarchical helical structures can be largely modulated by non-equilibrium processing during solution printing as to achieve exceptional homochirality over large area. With the ability to widely tune helical structures, helical sense and homochirality, we set out to demonstrate the promise of chiral assemblies of conjugated polymers in organic solar cells, doped conductors, and spintronic devices.