Novel nanocomposite film developed via screen-printing of viologen polymer for anti-counterfeiting applications: Photochromism, thermochromism and vapochromic

Abstract

Novel photochromic, thermochromic and gaseous ammonia sensing paper sheets were developed via screen-printing with a viologen-based covalent polymer, resulting in multi-stimuli responsive chromogenic paper substrates. The viologen-based covalent polymer was synthesized from the polymerization of a hydroxyl-substituted aryl-dihydrazide with a viologen-dialdehyde in an acidic aqueous medium. Translucent viologen/resin nanocomposite films prepared on the surface of the paper sheets were developed by the well-dispersion of the covalent organic viologen polymer as a chromogenic agent in a resin-based binder solution without aggregation. As shown by CIE coloration measurements, the translucent film immobilized on cellulose paper surface became green when exposed to UV light. Organic nanocomposite-containing a covalent organic polymer of viologen and a resin binder was used to make a new photochromic film for anti-counterfeiting papers. The photochromic impact was explored at various concentrations of the covalent organic viologen polymer. When exposed to ammonia gas, the viologen-coated paper strips changed color from yellow to green very rapidly. It recovered to yellow immediately after being removed away from the ammonia stimulus. The present paper strip demonstrated a detection limit for aqueous ammonia ranging between 15 and 350 ppm. In addition, heat (95 °C) was able to reversibly trigger the color transformation process. The thermal properties of the synthesized viologen-based covalent polymer were also investigated. Under UV irradiation, the screen-printed documents exhibited a reversible photochromism with high photostability. In addition to examining the rheologies of the generated nanocomposites, the screen-printed papers mechanical and morphological properties were also explored.