The Morphological Evolution and Emergence of Helical Chirality in Electrochemically Synthesized Chiral Polyaniline

Conductive helical polymers play a crucial role in chiral separation and (opto)electronics. Although electropolymerization using chiral camphorsulfonic acid (CSA) as a template has been a well-known method for synthesizing helical chiral polyanilines (PANI), precise control over polymer morphology and underlying mechanisms remains lacking. This research investigates the morphological evolution and emergence of helical chirality of CSA templated PANI using a two-step potential synthesis method. The characterization of the synthesized polymers at different stages revealed that PANI morphology evolves from granules to helices during electropolymerization. Helical chirality emerged at V1 = 1.8 V vs. Ag/AgCl until 1.72 mA/cm2, V2 = 0.8 V vs. Ag/AgCl until 800 mC. Once helical structures formed, X-ray diffraction showed increased crystallinity and a d-spacing typical for π–π stacking interaction; PANI Mw was maintained at ∼100 kDa and CSA doping increased by 1.6-fold. The helix formation mechanism is hypothesized to be driven by cooperative π–π stacking of PANI chains and increased CSA doping due to enhanced crystallinity. Prior to this threshold, the bulkiness of CSA and thermal fluctuations prevent close packing of oligomers, resulting in amorphous, achiral granular structures. Finally, the helical ordering was also proven to be resistant to ion exchange and electrochemical potential stimuli.