In-Situ Transmission Electron Microscopy of the Electrochemical Deposition of Functionalized Poly(thiophenes)

University Of Delaware, Newark DE

Investigators

Abstract

PART 1: NON-TECHNICAL SUMMARY This project will directly monitor the formation of solid electrically conducted polymers (also known as "synthetic metals") from liquid solutions using a special high-resolution electron microscope which allows direct observation of the cyrstallization process as it takes place. These organic materials are used in many advanced applications including flexible batteries, solar cells, and biomedical devices. However, the way their complicated structures actually form at the molecular level is not well understood scientifically. The project will examine the formation and growth of these complex materials during an electrochemical reaction. The experiments will use a special sample stage that will make it possible to watch and monitor within the electron microscope what happens as the materials change from liquid to solid. The research project will teach students in materials science and engineering how to establish a detailed understanding about the relationship between microstructure and properties of electrically active polymers, as well as contribute to their broader interdisciplinary education. PART 2: TECHNICAL SUMMARY This research project will investigate the electrochemical deposition of functionalized poly(thiophenes) using in-situ transmission electron microscopy (TEM). Conjugated poly(thiophenes), including poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT), are of considerable scientific and commercial interest, but the detailed mechanisms of electrochemical deposition are not yet known. An in-situ sample holder will be used to examine the deposition from liquid monomer solution to solid polymer directly in a TEM. These experiments will make it possible to monitor the oxidative polymerization of thiophene monomers in the region of the electrode-electrolyte interface, providing detailed information about the structural evolution of the resulting polymer films as a function of total charge delivered to the electrode. The results will be correlated with measurements of charge transport properties using impedance spectroscopy and cyclic voltammetry. Correlations will also be made with images obtained by complementary imaging techniques including optical and scanning electron microscopy.