  Intimately connected to the rule of life, chirality remains a long-time
fascination in biology, chemistry, physics and materials science. Chiral
structures, e.g., nucleic acid and cholesteric phase developed from chiral
molecules are common in nature and synthetic soft materials. While it was
recently discovered that achiral but bent core mesogens can also form chiral
helices, the assembly of chiral microstructures from achiral polymers has
rarely been explored. Here, we reveal chiral emergence from achiral conjugated
polymers for the first time, in which hierarchical helical structures are
developed through a multistep assembly pathway. Upon increasing concentration
beyond a threshold volume fraction, pre-aggregated polymer nanofibers form
lyotropic liquid crystalline (LC) mesophases with complex, chiral morphologies.
Combining imaging, X-ray and spectroscopy techniques with molecular
simulations, we demonstrate that this structural evolution arises from
torsional polymer molecules which induce multiscale helical assembly,
progressing from nano- to micron scale helical structures as the solution
concentration increases. This study unveils a previously unknown complex state
of matter for conjugated polymers that can pave way to a new field of chiral
(opto)electronics. We anticipate that hierarchical chiral helical structures
can profoundly impact how conjugated polymers interact with light, transport
charges, and transduce signals from biomolecular interactions and even give
rise to properties unimagined before.
