Poly(3,4-alkylenedioxypyrroles): The PXDOPs as Versatile Yet Underutilized Electroactive and Conducting Polymers

Perhaps the most attractive aspect of conjugated and conducting polymers is the ability to fine-tune their optoelectronic properties with straightforward synthetic modifications. Because of this synthetic flexibility, seemingly related properties, such as redox potential and electronic bandgap, can be decoupled and orthogonally modified without drastic adjustment of the fundamental materials synthesis process. Thus, a new material with a desired set of properties can be realized by utilizing the current body of knowledge and logically searching for the correct “puzzle piece”. To date, a large library of polyheterocycles with extremely diverse materials properties has been published. Some of the many interesting properties of polyheterocycles include electrochromism, electroluminescence, and optically transparent conductivity, resulting in their use as photovoltaics, charge dissipators, chemical and biochemical sensors, and drug-delivery systems. Fine-tuning and optimization of the conducting polymer properties for these systems is achieved by modification of the polymer backbone or its pendent groups. One significant discovery was that polythiophene (PTh) could be made soluble while maintaining its high conductivity by the substitution of an alkyl chain onto the polymer repeat unit. In addition to solubility, it has been shown that the variation of the chemical functionality of pendent groups on the PTh backbone has a tremendous effect on the polymer properties and can induce water solubility, hydrogen bonding, and polymer-chain aggregation as just a few examples. When an ethylenedioxy bridge is fused onto the 3and 4-positions of the thiophene ring in 3,4-ethylenedioxythiophene (EDOT), the resulting polymer PEDOT (also called PEDT) possesses a lower bandgap (1.6 versus 2.2 eV), lower R EV EW