Poly(3,4-alkylenedioxyselenophene)s: Past, Present, and Future

Because of their optical and electronic properties, polythiophenes and their derivatives, especially poly(3,4-alkylenedioxythiophene)s, are among the most promising materials in the field of electrochromic polymers. The properties of these polymers can be tuned by replacing the sulfur atom of the thiophene moiety with a selenium atom, because selenium has a lower electronegativity, a higher metallic character, a larger atomic size, and greater polarizability than sulfur. This approach has opened the door to a new and vibrant class of conjugated polymers. Today 3,4-alkylenedioxyselenophenes are thought as powerful competitors to 3,4-alkylenedioxythiophenes. Here, an overview is presented of poly(3,4-alkylenedioxyselenophene)s, as one of the most attractive groups of conjugated polymers. The design, synthesis, and applications of poly(3,4-alkylenedioxyselenophene)s and their derivatives are discussed in detail and compared with the corresponding features of their thiophene analogues. The electrochemical and electrochromic properties and band gaps of poly(3,4-alkylenedioxyselenophene) s are also discussed in relation to their chemical structures.