Progress in Conjugated Polyindoles: Synthesis, Polymerization Mechanisms, Properties, and Applications

Similarly to polyanilines, polypyrroles, and polythiophenes, polyindoles belonging to the fused-ring family have emerged in the past several decades as promising materials due to their unique physical and electrochemical properties. To date, polyindoles have been studied in over 200 scientific publications. These studies revealed that the materials based on polyindoles could have an important influence on electrochromic devices, sensors, catalysis and electro-catalysis, anticorrosion, diodes, supercapacitors, batteries, and biology-related applications. The aim of this review is to provide an overview of the development of polyindoles with regard to synthesis, polymerization mechanisms, copolymers, composites, properties, and applications, and reflect on the related existing challenges and make notes on future perspectives.