Fast switching redox processes in aqueous media can be obtained in poly(3,4‐ethylenedioxythiophene)/poly(allylamine hydrochloride) (see Figure for chemical structure) multilayer films. Due to the intense near‐infrared charge carrier transition of the oxidized form tailing through the visible region, these films provide two color states, which are voltage‐controllable.

4]dioxin-2-yl-methoxy)-1-butanesulfonic acid (PEDOT-S) has been synthesized both chemically and electrochemically, and the properties of the resultant films have been examined and compared. In particular, it was found that PEDOT-S, deposited in conjunction with poly(allylamine hyrochloride) PAH in the form of polyelectrolyte multilayer (L-B-L) films of PEDOTS/PAH, possesses highly advantageous properties that allow for applications involving aqueousbased electrolytes. Electrochemically prepared films of PEDOT-S and L-B-L prepared films of PEDOT-S/PAH were characterized by electrochemical, spectroelectrochemical, and colorimetric methods illustrating reversible redox states at -0.2 and +0.2 V, respectively (vs Ag/Ag + in organic media), which resulted in distinctive color changes between light blue (oxidized) and purple/pink (neutral). The change in color states was evident by a change in the electronic absorbance in the 500 nm region (neutral state) which was transferred to the near-IR absorption >800 nm (oxidized state). The phenomena of "acid doping" in aqueous and organic media was also investigated spectroscopically and found to result in a reversible color change accompanied by a relatively small changes in conductivity between 2 × 10 -4 S/cm (oxidized) and 7.1 × 10 -5 S/cm (neutral) when films were deposited on glass. In all cases, PEDOT-S/PAH exhibited superior and more reproducible electrochemical properties relative to electrochemically formed films that were tested for possible application in electrochromic devices and as the hole transport layer of OLEDs. It was found that PEDOT-S/PAH displays comparable properties to spin-coated PEDOT:PSS as a hole injecting layer in NIR emitting PLEDs.

Electrochemical polymerization in the strong Lewis acid, boron trifluoride ethylether (BFEE), has been used to prepare electrochromic polythiophene (PTh) and its derivatives: poly(3‐methylthiophene) (PMeTh), poly(3‐bromothiophene) (PBrTh), and poly(3,4‐dibromothiophene) (PDBrTh). The polymerization processes and properties of the resultant films are compared, where possible, to those carried out in traditional organic electrochemical solvents. The polymerization of these high oxidation potential thiophene monomers in BFEE yielded good‐quality, homogenous, and smooth electroactive and electrochromic films that could be repeatedly switched in common electrochemical solvents up to 240, 1380, 560, and 420 cycles for PTh, PMeTh, PBrTh, and PDBrTh, respectively, for 50 % retention of electroactivity. A colorimetric study of these films showed distinctive color changes between red and blue as they were switched between reduced and oxidized states. These findings allow the use of commercially available high oxidation potential thiophene monomers to provide electrochromic polymers, avoiding the use of other custom‐synthesized monomers.

No abstract

No abstract