Conjugated Polymer Nanostructures and Supercapacitors

Controlling the nanostructure of conjugated polymers is essential for their application to functional materials. In Part 1 of this work, I present two novel methods for controlling conjugated polymer nanostructure using electrochemical polymerization in hard templates. First, we report the synthesis and characterization of a series of nanostructures and propose a mechanism whereby morphology changes as a function of building block. We show how side-chain hydrophobicity can be used to prepare nanostructures with a geometry that is different from the shape of the template. Hydrophobic side-chains result in collapsed, nonlinear, and nonrigid shapes, while hydrophilic side-chains lead to linear nanostructures. Second, I present a study of the morphology of polythiophene nanostructures synthesized in different solvent/electrolyte systems. We find that the wall thickness of such nanostructures is greatly influenced by the choice of solvent/electrolyte, which affects the rate of polymerization. Solvent/electrolyte systems that increase the rate of thiophene polymerization yield solid nanowires, whereas systems that decrease the rate of polymerization yield thin-wall nanotubes. A solvent/electrolyte system that leads to an intermediate polymerization rate yields thick wall nanotubes. The results in Part 1 open new opportunities for preparing nanostructures with greater complexity, functionality, and distinct optical properties. Conjugated polymers that can store both a positive and negative charge can function as both the positive and negative charge storage material in a supercapacitor device, however few have been explored for this application. In part 2, I describe the synthesis of several monomers and their electrodeposited polymer electrodes. First, using different donor-acceptor molecular structures we examine the effect of electron acceptor concentration and show that device stability is improved significantly by increasing the acceptor concentration. Supercapacitors with specific energy and power of 11 Wh/kg (at 0.5 A/g) and 20 kW/kg (at 50 A/g with an energy of 3.6 Wh/kg) are reported. Further, we provide computational insight into the important chemical requirements for achieving even better performing supercapacitors. Working from these experimental and computational results, we selected thieno[3,4-b]pyrazines as a class of molecule to explore. Thieno[3,4-b]pyrazines form narrow band gap homopolymers, storing both positive and negative charge. Initial investigations into four poly(thieno[3,4-b]pyrazine)s as charge storage electrodes is presented.Ph.D.2017-06-08 00:00:0