Reflective and absorptive/transmissive polymer electrochromic devices (ECDs) composed of spray-coated films of poly(3,3-bis(octadecyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT(CH₂OC₁₈H₃₇)₂) and poly(3,3-bis(2-ethylhexyloxymethyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT(CH₂OEtHx)₂) layers as cathodically coloring polymers and poly(3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-methyl-9H-carbazole) (PBEDOT-NMeCz) as the anodically coloring polymer have been constructed and evaluated. These devices exhibit low switching voltages (±1.2 V), high visible contrast values, sub-second switching times, and high switching stability in atmospheric conditions. The reflective ECD comprising PProDOT(CH₂OEtHx)₂ as the active layer demonstrates an unusual electrochromic behavior. By regulating the applied voltage, a high reflectance contrast of greater than 70% ΔT was achieved in the NIR region (2 µm) without any noticeable color change of the device.

A new, well-defined diblock copolymer (P3HT-b-C₆₀) based on regioregular poly(3-hexylthiophene) (P3HT) and fullerene was synthesized. First, regioregular P3HT was synthesized through Grignard metathesis polymerization, and then methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) were copolymerized by using an end-functionalized P3HT as a macroinitiator for the atom transfer radical polymerization to yield a diblock copolymer (P3HT-b-P(MMA-r-HEMA)). A fullerene derivative functionalized with carboxylic acid, [6,6]-phenyl-C₆₁-butyric acid (PCBA), was then chemically linked to the HEMA unit in the second block (P(MMA-r-HEMA)) to produce a diblock copolymer with the second block containing fullerenes. Annealing thin films of the copolymer revealed nanometer-scale phase separation, a more suitable morphology for enabling excitons generated in the P3HT domain to more efficiently reach the donor–acceptor interface, relative to simple blends of P3HT and C₆₀. As a result, photoluminescence of the P3HT-b-C₆₀diblock copolymer in the films showed a complete quenching of photoluminescence of P3HT, which is indicative of charge transfer between P3HT and fullerene.