Achieving Smart Photochromics Using Water-Processable, High-Contrast, Oxygen-Sensing, and Photoactuating Thiazolothiazole-Embedded Polymer Films
Tyler J. Adams, Naz F. Tumpa, Maithili Acharya, Quy H. Nguyen, Nuren Shuchi, Mia Baliukonis, Sarah E. Starnes, Tino Hofmann, Michael G. Walter
Abstract
High Resolution Image Download MS PowerPoint Slide Water-soluble dipyridinium thiazolo[5,4- d ]thiazole (TTz) compounds are incorporated into inexpensive poly(vinyl alcohol) (PVA)/borax films and exhibit fast (<1 s), high-contrast photochromism, photofluorochromism, and oxygen sensing. Under illumination, the films change from clear/yellow TTz 2+ to purple TTz •+ and then blue TTz 0 . The contrast and speed of the photochromism are dependent on the polymer matrix redox properties and the concentration of TTz 2+ . The photoreduced films exhibit strong, near-infrared light (1000–1500 nm) absorbances in addition to visible color changes. Spectroscopic ellipsometry was used to establish the complex dielectric function for the TTz 2+ and TTz 0 states. Incorporating non-photochromic dyes yields yellow-to-green and pink-to-purple photochromism. Additionally, when illuminated, reversible photoactuation occurs, causing mechanical contraction in the TTz-embedded films. The blue film returns to its colorless state via exposure to O 2, making the films able to sense oxygen and leak direction for smart packaging. These films show potential for use in self-tinting smart windows, eyeglasses, displays, erasable memory devices, fiber optic communication, and oxygen sensing.