An environmentally friendly fabrication technology to synthesize β-dicarbonyl polymers is developed with tailored properties of fluorescence and ammonia sensing. It is achieved by utilizing the miniemulsion polymerization technique, with functional monomer 2-(acetoacetoxy) ethyl methacrylate (AAEMA), and an innocuous polymeric costablilizer of poly (2-(acetoacetoxy) ethyl methacrylate) (PAAEMA). The advantages of the miniemulsion polymerization technique lie in the use of less surfactant and the prevention of polymer particles from coagulation with particles diameter around 100 nm. The latex particles so prepared have β-dicarbonyl moiety possessing high fluorescence emission capacity due to the enol-keto tautomerism of β-dicarbonyl and intermolecular proton transfer. Furthermore, introd...[ Read more ]

An environmentally friendly fabrication technology to synthesize β-dicarbonyl polymers is developed with tailored properties of fluorescence and ammonia sensing. It is achieved by utilizing the miniemulsion polymerization technique, with functional monomer 2-(acetoacetoxy) ethyl methacrylate (AAEMA), and an innocuous polymeric costablilizer of poly (2-(acetoacetoxy) ethyl methacrylate) (PAAEMA). The advantages of the miniemulsion polymerization technique lie in the use of less surfactant and the prevention of polymer particles from coagulation with particles diameter around 100 nm. The latex particles so prepared have β-dicarbonyl moiety possessing high fluorescence emission capacity due to the enol-keto tautomerism of β-dicarbonyl and intermolecular proton transfer. Furthermore, introducing amine group compounds like ammonia into the latex enhances the emission capability of the faint β-dicarbonyl flurophores because of the formation of the fluorescent complex between β-dicarbonyl aggregates and ammonia. The results of 3-D EEM (three-dimensional excitation emission matrix) spectroscopy indicate that the complex is a better fluorophore than β-dicarbonyl and its aggregates.

The PAAEMA thin film is very sensitive for ammonia sensing. When ammonia existed, morphology study by SEM and AFM all indicates PAAEMA tended to be clustered and became small grains. The supramolecular complex is also formed when solid PAAEMA films expose to ammonia. Its characteristic absorption in UV-Vis spectra around 275 nm has been explored and its high capability of sensing ammonia was demonstrated in air, with competitive air pollutants such as CO, NOx, SO₂ showing no response. The response time of the thin films to ammonia gas is in the order of few seconds depending on ammonia concentration. Ammonia concentration response model of β-dicarbonyl polymers has been built up with the form of Freundlich isotherm. PAAEMA sensing films can be regenerated rapidly under UVC irradiation, which can be attributed to the ring open reaction of β-dicarbonyl aggregates and its ammonia complex inside the PAAEMA layer.