This work demonstrates a simple process to form insoluble poly(3,4-propylenedioxythiophene) (Poly[ProDOT]) films by defunctionalization of a soluble form, which is useful in the fabrication of multilayer polymer devices. Three new ester disubstituted Poly[ProDOTs], soluble in common organic solvents, including chloroform, methylene chloride, toluene, tetrahydrofuran, and ethyl acetate, have been synthesized by oxidative polymerization using iron(III) chloride. These Poly[ProDOT-diesters] have the expected repeat unit stuctures along with GPC determined number-average molecular weights ranging from 9000 to 12 000 g mol-1. Dilute polymer solutions in toluene exhibited red fluorescence with quantum efficiencies from 0.24 to 0.32. Homogeneous thin films were formed by spray casting polymer solutions onto ITO coated glass slides and compared to films prepared by electropolymerization. These Poly[ProDOT-diesters] are electroactive, switching from a dark blue-purple to a transmissive sky blue when potentials are applied between −0.9 and +0.3 V vs Fc/Fc.+ A thin film saponification method was developed and rendered the spray-cast films insoluble by submersion into 0.1 M KOH in hot methanol for 1 h to remove the solubilizing ester group. In the case of a bis(heptanoate) Poly[ProDOT-diester] (1), spectroelectrochemistry showed minimal change in its electronic spectra after methanolysis and the resulting alcohol-substituted polymer (Poly[ProDOT-diol] (4)) could be repeatably switched between neutral and oxidized states in subsecond times. In contrast, when a more highly functionalized Poly[ProDOT-tetraester] (3) was used, a small change in the electronic spectrum which is associated with a distinct color change from burgundy to blue was observed upon methanolysis to Poly[ProDOT-tetraol] (6). The insoluble alcohol-substituted polymer films were found to be efficient hole transport layers in polymer light-emitting diodes.

This article describes a new electrochromic device (ECD) designed to achieve improved black color and longterm bistability. We achieved these improvements by fabricating a double-layered nanostructure of two different electrochromic materials stacked in layers on a single electrode. The fabricated ECD maintains 90% of the light transmittance of the colored state even after 1 h if powered off in the colored state. To achieve an improved black, green and blue viologens were successively immobilized in the bottom and top layers of materials on an electrode. The green viologens are initially colored at low voltage, and the purple viologens become colored when the voltage increases. This is because the reduction potential of the green viologens is less than that of purple viologens. Finally, an improved black color is obtained through a mixture of the two colors.

Dual polymer absorptive/transmissive electrochromic (EC) window devices have been assembled using the solution-processable and high-EC-contrast polymer PProDOT-(CH(2)OEtHx)(2) as the EC material, along with a non-color-changing electroactive polymer, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), as the counter electrode material. Indium-tin oxide (ITO) and highly transmissive single-walled carbon nanotube (SWNT) film coated glass electrodes are used as electrode substrates. The use of the EC/non-color-changing polymer combination allowed us to construct window devices that rapidly switch between magenta and highly transmissive (>95% T for ITO and approximately 79% T for SWNT) states with large optical modulation (>71% DeltaT for ITO and 66% DeltaT for SWNT). The devices showed effective coloration and bleaching: the lightness parameter (L*) changing from 67 to 95 for ITO (approximately 50-92 for SWNT), essentially reaching a diffuse white upon oxidation. The color modulates from highly pure magenta with a* = 28 (red hue) and b* = -28 (blue chroma) for ITO (a* = 40 and b* = -36 for SWNT) to nearly colorless with a* = 1 and b* = -1 for ITO (a* = -2 and b* = -3 for SWNT) devices. Increasing the switching voltage from 2.55 V up to 3.5 V resulted in faster SWNT-based window device performance.

We report an analytical method which allows the systematic variation of color states of pairs of electrochromic conjugated conducting polymers with simultaneous spectroelectrochemical and colorimetric characterization of the resulting color summation. This method measures colors by transmitting light through two polymer films stacked together in electrolyte and under separate potentiostatic control. The polymers that were used in this work are poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-propylenedioxypyrrole) (PProDOP), and dihexyl-substituted poly(3,4-propylenedioxythiophene) (PProDOT-Hx2). These are all cathodically coloring polymers, PEDOT switching from a transmissive sky blue to a deep blue, PProDOP switching from a highly transmissive gray/blue to a brown and then to an orange, and PProDOT-Hx2 switching from a transmissive sky blue to a purple/magenta color upon reduction. Coupling these polymers logically by the dual-polymer electrochromic film characterization technique led us to obtain new colors which were not observed when these polymers were studied separately. For example, coupling PEDOT and PProDOP films in their neutral state resulted in a new red/brown color (L* = 59, a* = 25, and b* = 50), which is different from the original colors these polymers show in their neutral states, deep blue (L* = 64, a* = −5, and b* = −37) and orange (L* = 76, a* = 31, and b* = 75), respectively. A full palette of colors is accessible by coupling existing electrochromic polymers by this new bipotentiostatic technique.

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