Polymerization-Induced Helicity Inversion Driven by Stacking Modes and Self-Assembly Pathway Differentiation

Regulating the mutual stacking arrangements is of great interest for understanding the origin of chirality at different hierarchical levels in nature. Different from molecular level chirality, the control and manipulation of hierarchical chirality in polymer systems is limited to the use of external factors as the energetically demanding switching stimulus. Herein, the first self-assembly strategy of polymerization-induced helicity inversion (PIHI), in which the controlled packing and dynamic stereomutation of azobenzene (Azo) building blocks are realized by in situ polymerization without any external stimulus, is reported. A multiple helicity inversion and intriguing helix-helix transition of polymeric supramolecular nanofibers occurs during polymerization, which is collectively confirmed to be mediated by the transition between functionality-oriented pi-pi stacking, H-, and J-aggregation. The studies further reveal that helicity inversion proceeds through a delicate interplay of the thermodynamically and kinetically controlled, pathway-dependent interconversion process, which should provide new insight into the origin and handedness control of helical nanostructures with desired chirality.