CHAPTER 2: Polyacetylenes

Polyacetylene (PA) is the simplest linear conjugated macromolecule and is representative of conducting polymers. The insolubility and infusibility of PA first seemed to be obstacles in the way of controlling the morphology of polyacetylene. However, these properties are useful from the viewpoint of maintaining morphology after acetylene polymerization. Once the morphology is formed during polymerization, it can be held stable when faced with elevated temperatures or solvents. Since highly aligned PA films were synthesized in a N-LC reaction field with the Ziegler–Natta catalyst, the LC reaction field has been attracting interest for controlling the morphology of conjugated polymers during polymerization. This chapter deals with the synthesis of several types of PAs with profound electrical and mechanical properties and also that of helical PA (H-PA) using a chiral nematic liquid crystal (N*-LC) reaction field as an asymmetric polymerization solvent. We outline the approaches on how to control the hierarchical structure of conjugated polymers during polymerization with a LC reaction field. We focus on the hierarchical helical structures involving the screwed PA chain, fibril bundle, and spiral morphology of H-PA synthesized in a N*-LC reaction field.