Polydiacetylene-based periodic mesoporous organosilicas with colorimetric reversibility under multiple stimuli

Abstract Polydiacetylene-based periodic mesoporous organosilica (PDAPMO) films with different molar fractions of diacetylene-bridged silsesquioxane (DASi) were synthesized through the evaporation-induced self-assembly followed by the topochemical polymerization via 254 nm ultraviolet radiation. Specifically, the as-polymerized blue PDAPMO films could undergo a multi-step thermochromic process, turning purple, red and yellow successively over a wide range from room temperature to above 150 °C. Importantly, the high temperature triggered multi-step color transition process could be divided into two stages: the first reversible blue-to-purple-to-red transition and the second irreversible red-to-yellow transition. In particular, the purple-to-red transition in the first stage was rapidly and completely reversible, and the reversibility could be repeated for many heating-cooling cycles. To study the mechanism of the thermochromic response, Raman and temperature-dependent FT-IR spectra, the results of which successfully highlighted the close relationship between chromatic transitions and the conformational changes of PDA backbone, were recorded. Furthermore, the PDAPMO films could also respond chromatically to mechanical stress and organic solvents, expanding their application in portable sensors.