Chiral emergence in multistep hierarchical assembly of achiral conjugated polymers

TL;DR

This study demonstrates for the first time that achiral conjugated polymers can form hierarchical chiral structures through a multistep assembly process, revealing new complex states of matter with potential applications in chiral optoelectronics.

Contribution

It uncovers the formation of hierarchical chiral microstructures from achiral conjugated polymers via a multistep assembly pathway, combining experimental and simulation approaches.

Findings

Chiral microstructures emerge from achiral polymers at high concentration.

Hierarchical helical structures develop from nano- to micron scale.

Assembly is driven by torsional properties of polymer molecules.

Abstract

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.