Alkoxy-functionalized polythiophenes such as poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT) have become promising materials for a variety of applications including bioelectronic devices due to their high conductivity, relatively soft mechanical response, good chemical stability and excellent biocompatibility. However the long-term applications of PEDOT and PProDOT coatings are still limited by their relatively poor electrochemical stability on various inorganic substrates. Here, we report the synthesis of an octa-ProDOT-functionalized polyhedral oligomeric silsesquioxane (POSS) derivative (POSS-ProDOT) and its copolymerization with EDOT to improve the stability of PEDOT coatings. The POSS-ProDOT crosslinker was synthesized via thiol–ene “click” chemistry, and its structure was confirmed by both Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopies. PEDOT copolymer films were then electrochemically deposited with various concentrations of the crosslinker. The resulting PEDOT- co -POSS-ProDOT copolymer films were characterized by cyclic voltammetry, Electrochemical Impedance Spectroscopy, Ultraviolet-Visible spectroscopy and Scanning Electron Microscopy. The optical, morphological and electrochemical properties of the copolymer films could be systematically tuned with the incorporation of POSS-ProDOT. Significantly enhanced electrochemical stability of the copolymers was observed at intermediate levels of POSS-ProDOT content (3.1 wt%). It is expected that these highly stable PEDOT- co -POSS-ProDOT materials will be excellent candidates for use in bioelectronics devices such as neural electrodes.
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Direct Observation of Liquid-to-Solid Phase Transformations during the Electrochemical Deposition of Poly(3,4-ethylenedioxythiophene) (PEDOT) by Liquid-Phase Transmission Electron Microscopy (LPTEM)
We have used Liquid-Phase Transmission Electron Microscopy (LPTEM) to directly image the fundamental processes occurring at the electrode-solution interface during electrochemical deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) from an isotropic 3,4-ethylenedioxythiophene (EDOT) monomer solution. We clearly observed the various stages of the electrodeposition process including the initial nucleation of liquid-like EDOT oligomer droplets onto the glassy carbon working electrode and then the merging, coalesce and growth in size and thickness of these droplets into solid, stable, and dark PEDOT conjugated polymer films. We also used correlative transmitted light optical microscopy to study this process, revealing the change in color of the translucent clusters to the dark polymer film caused by the increase in conjugation length. From our studies we have been able to correlate specific observations of local structure and dynamics to the liquid-like (EDOT oligomer) droplets and solid-like (PEDOT polymer) films including their mobility, mass thickness, edge roughness, size, circularity, and optical absorption.
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- Award ID(s):
- 1808048
- NSF-PAR ID:
- 10273539
- Date Published:
- Journal Name:
- Macromolecules
- ISSN:
- 0024-9297
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.macromol.1c00404
