Doctor of Philosophy
Dr. Oleg Semenikhin
Electronically conducting polymers (ECPs) have been growing in interest as important materials for a variety of different applications such as charge storage devices and photovoltaics. However, in all of these applications, the performance of conducting polymers are strongly dependent upon their local properties such as morphology, local conductivity and carrier mobility, local chemical composition, etc. All polymer materials feature a distribution of these parameters and therefore, they are considered heterogeneous. In this work, we use atomic force microscopy (AFM) and its related techniques such as current-sensing AFM (CS-AFM), Kelvin probe force microscopy (KFM) and phase imaging (PI-AFM) to directly investigate the heterogeneity of ECPs, specifically poly[2,2’-bithiophene] (PBT), in order to determine how their performance depends on their local properties and their distribution.
Chapter 4 will address the correlation between topography, local conductivity and local surface potential/work function of various conducting polymers such as PBT and poly[2-methoxy-5-(2 -ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). To explain this correlation, a model has been proposed which relates these properties to the molecular weight distribution during electropolymerization of conducting polymers. Chapter 5 will investigate further into this model by studying the nucleation and growth of conducting polymers. It will utilize phase imaging to determine how the distribution of molecular weight, and therefore, crystallinity can directly affect the overall properties such as conductivity and surface potential in these materials. Chapter 6 will focus on the effect of common electrochemical techniques used to prepare these materials and their influence on the local properties of conducting polymers, specifically morphology and crystallinity, in both thin and think conducting polymer films. Chapter 7 and chapter 8 will add to the previous chapters by investigating the charge/discharge (doping/undoping) efficiencies of these materials as charge storage devices in relation to the local properties of these conducting polymer films in order to effectively prepare these materials to increase efficiency for use in electronic devices.
O'Neil, Kevin D., "Scanning Probe Microscopy Studies of the Properties of Conducting Polymers" (2012). Electronic Thesis and Dissertation Repository. 432.