No abstract

A series of dual polymer electrochromic devices (ECDs) based on 12 complementary pairs of conducting polymer films have been constructed using 3,4-ethylenedioxythiophenecontaining conducting polymers. Poly[3,)-N-methylcarbazole] (PBEDOT-NCH 3 Cz), poly [3,6-bis(2-(3,4-ethylenedioxythiophene))-N-eicosylcarbazole] (PBEDOT-NC 20 H 41 Cz), and poly [4,4′-bis(2-(3,4-ethylenedioxythiophene))biphenyl] (PBEDOT-BP) were utilized as anodically coloring polymers that electrochemically switch between an oxidized deep blue absorptive state and a transmissive (orange or yellow) reduced state. Poly(3,4-ethylenedioxythiophene) (PEDOT) and its alkyl derivatives (PEDOT-C 14 H 29 and PEDOT-C 16 H 33 ) have been used as high-contrast cathodically coloring polymers that switch between a deep blue absorptive state in the reduced form and a sky blue, highly transmissive state in the oxidized form. The dual polymer ECDs were constructed by separating complementary pairs of EC polymer films, deposited on ITO glass, with a gel electrolyte composed of a lithium salt and plasticized poly(methyl methacrylate) (PMMA). Device contrast ratios, measured as ∆%T, ranged from 27% to 63%, and subsecond switching times for full color change were achieved. These devices were found to exhibit extremely high coloration efficiencies of up to 1400 cm 2 /C over narrow (ca. 100 nm) wavelength ranges and to retain up to 60% of their optical response after 10 000 deep, double potential steps, rendering them useful for EC applications.

To date, trial and error strategies guided by intuition have dominated the identification of materials suitable for a specific application. We are entering a data-rich, modelling-driven era where such Edisonian approaches are gradually being replaced by rational strategies, which couple predictions from advanced computational screening with targeted experimental synthesis and validation. Here, consistent with this emerging paradigm, we propose a strategy of hierarchical modelling with successive downselection stages to accelerate the identification of polymer dielectrics that have the potential to surpass 'standard' materials for a given application. Successful synthesis and testing of some of the most promising identified polymers and the measured attractive dielectric properties (which are in quantitative agreement with predictions) strongly supports the proposed approach to material selection.

A series of bis(2-(3,4-ethylenedioxy)thiophene)-based monomers have been synthesized and fully characterized; specifically (E)-1,2-bis(2-(3,4-ethylenedioxy)thienyl)vinylene (BEDOT-V), 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (BEDOT-B), 4,4‘-bis(2-(3,4-ethylenedioxy)thienyl)biphenyl (BEDOT-BP), 2,5-bis(2-(3,4-ethylenedioxy)thienyl)furan (BEDOT-F), 2,5-bis(2-(3,4-ethylenedioxy)thienyl)-thiophene (BEDOT-T), and 2,2‘:5‘,2‘‘-ter(3,4-ethylenedioxy)thiophene, TER-EDOT. The X-ray crystal structures of BEDOT-V and BEDOT-B have been determined. These monomers oxidize and polymerize at low potentials relative to other reported electropolymerizable heterocycles. The electroactive polymers formed exhibit low redox switching potentials and are quite stable in the conducting state. TER-EDOT was found to have the lowest peak oxidation potential of +0.2 V vs Ag/Ag+, making it the most easily oxidized polymerizable thiophene monomer reported. The electronic bandgaps of these EDOT based polymers range from 1.4 to 2.3 eV (measured as the onset of the π−π* transition) offering a diverse range of colors which may prove useful in electrochromic devices. For example, poly(BEDOT-V) is deep purple and opaque in the reduced state and transmissive sky blue in the oxidized state, poly(BEDOT-T) is deep blue opaque in the reduced state and transmissive blue in the oxidized state, while poly(BEDOT-BP) is transmissive orange in the reduced state and opaque purple in the oxidized state. A thin film of poly(BEDOT-V) was found to switch rapidly between redox states (under 2 s) with an initial optical contrast of 43%. This polymer was found to retain 47% of its optical contrast and 48% of its original charge density after 600 double potential steps.