Responsive Thin-Film Interference Colors from Polaronic Conjugated Block Copolymers

Colors responsive to the chemical environment can form the basis for simple and highly accessible diagnostic tools. Herein, the charge modulation of conjugated polymers is demonstrated as a new mechanism for chemically responsive structural colors based on thin-film interference. A liquid-liquid interfacial self-assembly is employed to create a conjugated block copolymer film that is flexible, transferable, and highly homogeneous in thickness over a large area. Gold (Au) complexes are introduced in the self-assembly process for in situ oxidation of conjugated polymers into a hole-polaronic state that renders the polymer film responsive to the chemical environment. When transferred onto a reflective substrate, the film shows thickness-dependent tunable reflective colors due to the optical interference. Furthermore, it experiences drastic changes in its dielectric behavior upon switching of the polaronic state, thereby enabling large modulations to the interferometric colors. Such responsive thin-film colors, in turn, can be used as a simple and intuitive multicolor readout for the recognition of reductive vapors including biological decomposition products.

Automated summary

In this study, a new mechanism for chemically responsive structural colors based on thin-film interference was demonstrated through the charge modulation of conjugated polymers. A liquid-liquid interfacial self-assembly method was utilized to create a flexible, transferable, and highly homogeneous conjugated block copolymer film. The introduction of gold (Au) complexes in the self-assembly process enabled in situ oxidation of conjugated polymers into a hole-polaronic state, rendering the polymer film responsive to the chemical environment. The responsive thin-film colors showed thickness-dependent tunable reflective colors and experienced drastic changes in dielectric behavior upon switching of the polaronic state, allowing for large modulations to the interferometric colors.