Superhelix Structure in Helical Conjugated Polymers Synthesized in an Asymmetric Reaction Field

The superhelix structure of helical polyacetylene (H-PA) synthesized in a chiral nematic liquid crystal (N*-LC) used as an asymmetric reaction field was mathematically specified and presented as a chemically graspable feature. Fibril and spiral morphologies of H-PA were clarified as forming cylindrical and conical helices, respectively. The torsion of the H-PA main chain as the primary structure induced the formation of higher-order helical structures, such as fibril and spiral morphologies. The formation mechanism of H-PA in N*-LC was investigated in detail from the relationship between the hierarchical helical structure of H-PA and N*-LC. The superhelix structure was also used to rationalize the different formation mechanisms for helical aromatic conjugated polymers, such as helical poly(m-phenylene) (PMP). It was found that the curvature and torsion are essential for distinguishing the helical structures of H-PA and PMP. The present approach, based on conventional mathematical formulas, is useful for describing the helical structures of several types of conjugated polymers.