The ability to process conjugated polymers from environmentally benign solvents is essential for making organic electronics commercially viable by reducing costs and enhancing safety in the printing and processing environment. To enhance the solubility of typically alkyl-functionalized redox-active and electrochromic polymers, poly(3,4-propylenedioxythiophenes) with ester-functionalized side chains were synthesized via direct arylation polymerization, resulting in polymers that are processable from 2-methyltetrahydrofuran, ethyl acetate, and propyl acetate. Optical and atomic force microscopy results of spray-processed films indicate that topological features, such as film roughness, can be manipulated via the vapor pressure of the processing solvent. The solvent choice affects the resulting onset of absorbance and relative intensities of vibronic features, which translates into distinctly observable and quantifiable color differences. While the color is sensitive to the casting solvent, the redox properties and onset of oxidation are fairly independent of the processing medium. Most notably, electrochromic properties, such as contrast and switching times, are not drastically affected by the casting solvent or underlying morphologies. Independent of casting solvent, each polymer exhibited a transmittance change greater than 70% at λ max in the oxidized state with switching speeds of ∼2 s for 2 cm 2 films in organic electrolytes. This work highlights the synthetic tailorability of the poly(3,4-propylenedioxythiophene) family of materials to introduce functional groups that improve processability without sacrificing electrochromic performance.
An adenine-functionalized polythiophene is synthesized via direct arylation polymerization using Boc-protection to overcome catalyst deactivation. The resulting copolymer is highly soluble and shows reversible fluorescence quenching.
Developing aqueous
electrolyte compatible, redox-active polymers
that can be processed from environmentally sustainable solvents is
desirable because these traits will effectively reduce environmental
impact and human health hazards during processing procedures and in
the final device architecture. To achieve organic solvent solubility
and aqueous compatibility, a poly(3,4-propylenedioxythiophene) containing
four ester functionalities was synthesized via direct arylation polymerization.
The resulting polymer was spray-cast into a thin film from the environmentally
sustainable solvent 2-methyltetrahydrofuran, and the presence of multiple
polar functionalities rendered the film aqueous electrolyte compatible.
The multiester-functionalized polymer exhibits a relatively low onset
of oxidation (∼0.4 V vs Ag/AgCl) and electrochromic character
by transitioning from a colored neutral state to a colorless oxidized
state with increasing potential in 0.1 M NaCl aqueous electrolyte.
Additionally, the ester-functionalized polymer exhibits similar electrochromic
properties in aqueous electrolytes when compared to traditional alkyl-substituted
poly(3,4-propylenedioxythiophenes) in organic electrolytes, as evidenced
by contrast values of ∼70% and switching speeds of ∼2
s. This work highlights the use of multipolar functionalities as a
design strategy for synthesizing organic solvent processable, aqueous
electrolyte compatible redox-active polymers without postpolymerization
modifications or the sacrifice of electrochromic properties.
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