Light-Responsive Conductive Surface Coatings on the Basis of Azidomethyl-PEDOT Electropolymer Films

Abstract

The design of responsive coatings has gained increasing attention recently, with light-responsive interfaces receiving particular appreciation, as their surface properties can be modulated with excellent spatiotemporal control. In this article, we present light-responsive conductive coatings acquired through a copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction between electropolymerized azide-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT-N 3 ) and arylazopyrazole (AAP)-bearing alkynes. The UV/vis and X-ray photoelectron spectroscopy (XPS) data indicate a successful post-modification, supporting a covalent attachment of AAP moieties to PEDOT-N 3 . The thickness and degree of PEDOT-N 3 modification are accessible by varying the amount of passed charge during electropolymerization and time of reaction, respectively, providing a degree of synthetic control over the physicochemical material properties. The produced substrates demonstrate a reversible and stable light-driven switching of photochromic properties in both “dry” and swelled states, as well as efficient electrocatalytic Z → E switching. The AAP-modified polymer substrates exhibit a light-controlled wetting behavior, demonstrating a consistently reversible switching of the static water contact angle with a difference up to 10.0° for CF 3 -AAP@PEDOT-N 3 . The results highlight the application of conducting PEDOT-N 3 for the covalent immobilization of molecular switches while preserving their stimuli-responsive features.

Multi‐responsive Electropolymer Surface Coatings Based on Azo Molecular Switches and Carbazoles: Light, pH, and Electrochemical Control of Z→E Isomerization in Thin Films

“…Either a potentiostatic hold at 1.00 V (vs. Ag|AgCl) or cyclovoltammetric cycling in a potential range of 0.00 V–1.00 V (vs. Ag|AgCl) of a polymer film preliminary treated with UV light resulted in an increase of the optical density at 320–400 nm in accordance with Z → E azo bond isomerization (Figure 5a; S18a,d, red lines). The consistently higher absorbance at 350 nm (Figure 5a, red line) in comparison with PSS 520 nm indicates a higher amount of E‐ isomer associated with an electrocatalytic stationary state (ECS; Figure 5b) being in line with previous observations of quantitative isomerization of azobenzenes upon oxidation [32] and our previous study of electrocatalytic Z → E isomerization of AAP units within modified PEDOT polymer films [51] . We note that the step with visible light irradiation can also be easily omitted, confirming complete mutual independence of stimuli as the switching efficiency of the electrocatalysis remains unchanged (Figure S18c,f; Figure S19).…”

“…The consistently higher absorbance at 350 nm (Figure 5a, red line) in comparison with PSS 520 nm indicates a higher amount of E-isomer associated with an electrocatalytic stationary state (ECS; Figure 5b) being in line with previous observations of quantitative isomerization of azobenzenes upon oxidation [32] and our previous study of electrocatalytic Z!E isomerization of AAP units within modified PEDOT polymer films. [51] We note that the step with visible light irradiation can also be easily omitted, confirming complete mutual independence of stimuli as the switching efficiency of the electrocatalysis remains unchanged (Figure S18c,f; Figure S19). The studied polymer films demonstrated little degradation upon multiple cycles of electrochemical treatment.…”

“…[49,50] Recently, we demonstrated the application of electropolymerization for the creation of lightresponsive polymer films by chemical post-modification of PEDOT-azide. [51] Herein we present a novel type of stimuli-responsive polymer coatings formed from monomers featuring both an electropolymerizable bis-carbazole backbone and an azo-based photoswitch; azobenzene, arylazopyrazole, and arylazoisoxasole (Figure 1). The chemical design enables facile and rapid production of confined films at electrodes through electropolymerization, with high retention of polymerization efficiency owing to the substantial conductivity of the polycarbazole electropolymer backbone.…”

“…Moreover, electropolymerization has already successfully yielded functional coatings with incorporated photochromic moieties, such as azobenzenes [45,46] diarylethenes, [47] spiropyrans [48,49] and various other chromophores, [46] although full retention of photochemical properties in immobilized polymer films can prove challenging due to spatial restrictions [49,50] . Recently, we demonstrated the application of electropolymerization for the creation of light‐responsive polymer films by chemical post‐modification of PEDOT‐azide [51] …”

Azoheteroarene und Diazocine als Molekulare Photoschalter: Selbstassemblierung, Responsive Materialien und Photopharmakologie

“…Das photoresponsive Benetzungsverhalten dieser Monoschichten wurde eingehend untersucht [57] . Kürzlich untersuchte unsere Gruppe das elektrokatalytische Z ‐zu‐ E ‐Schaltverhalten von AAP in Verbindung mit der Photoisomerisierung, um lichtempfindliche leitfähige Beschichtungen auf einer ITO‐Oberfläche zu erzielen [58] …”