(658b) Design and Synthesis of Poly(triarylamine-thiophene) Derivatives for Supercapacitor Electrodes

Supercapacitors are electrical energy storage devices combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high-energy density of a battery. Power sources based on supercapacitors are emerging as a preferred option for applications requiring short power pulses, particularly when combined with conventional batteries. In order to maximize capacitance, switching speed, and power, materials for supercapacitors need to incorporate conductive and redox-active materials into high surface area structures. Conducting polymer are well-suited to address these challenges owing to the myriad of synthetic and processing methods which result a in a variety of nanostructures and electrical behaviors. One approach to increasing the energy and power density of electrode materials is incorporating efficient, reversible redox couples. In this research, we evaluate the influence of molecular structural variations on the electrochemical properties of polythiophene electrodes containing triphenylamine redox centers. Polymer electrodes are electrochemically synthesized using monomers with varying thiophene compositions, which controls the length of the thiophene chain between triarylamine centers. We show that the energy density of the polymer electrodes is strongly correlated to the triphenylamine composition and arrangement. The regularity of the polymer is controlled by incorporating methyl side-groups into the monomer, which influences the electrical and energy storage properties. When methyl groups are incorporated to direct the polymerization of the terminal thiophene moieties at the favorable 2,5-positions, the energy and power density of the polymer electrodes is significantly improved. Finally, we demonstrate that electrochemical copolymerization of bithiophene and the triarylamine can be used to vary the electrode composition and results increased capacity compared to the homopolymers. The design criteria demonstrated for triarylamine-thiophene polymers is used to improve the energy storage properties of these materials and provide insight into the development of new polymer electrode systems.