In-Situ Studies of the Electrochemical Deposition of Functionalized Poly(thiophene) Copolymers

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PART 1: NON-TECHNICAL SUMMARYCertain organic "plastic" materials known as conjugated polymers are able to conduct electrical charge in a manner similar to traditional metals and semiconductors. These substances are of considerable scientific and commercial interest for a wide variety of applications including energy storage, chemical sensors, and biomedical devices. However, the fundamental mechanisms by which these materials transition from small-molecule liquids to polymer solids are not well understood. This lack of scientific understanding limits the ability to precisely tailor these materials for specific purposes. Specialized electron-microscopic sample stages are now available that allow for detailed local studies of the formation of these materials, revealing previously unknown aspects of this complex process. This project will monitor the local shape and chemistry of the reaction products formed as the material proceeds from precursor liquids, through sticky intermediates, to the final solid conjugated polymer products using a high-resolution electron microscope and related analysis techniques. The work will also enable graduate students in materials science and engineering to obtain specialized advanced education and establish new insights about the formation of polymers from small molecules using an electrochemical reaction. PART 2: TECHNICAL SUMMARYIt has been previously established that in-situ, environmentally-controlled electron-microscopic sample stages can be used to directly monitor the electrochemical transition from a solution of liquid organic monomer 3,4-ethylenedioxythiophene (EDOT) to the final poly(3,4-ethylenedioxythiophene) (PEDOT) conjugated polymer product using low-dose transmission electron microscopy (TEM). However many fundamental questions remain unknown about the process, including the influence of comonomers and introduction of solid nanoparticles in the reaction medium. This research project will quantify the influence of these variations in chemistry and composition on the deposition process, particularly the nucleation, growth, and redissolving of oligomer droplets back into solution when using a more hydrophilic co-monomer (EDOTacid). The TEM experiments will be complemented with methods able to provide additional information about the chemical changes associated with the reaction, including optical microscopy, nanoscale FTIR/AFM, and microfocused Raman spectroscopy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.