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Sorbent coatings for nitroaromatic vapors: applications with chemical sensors

The solubility properties of a series of nitroaromatic compounds have been determined and utilized with known linear solvation energy relationships to calculate their sorption properties in a series of chemoselective polymers. These measurements and results were used to design a series of novel chemoselective polymers to target polynitroaromatic compounds. The polymers have been evaluated as thin sorbent coatings on surface acoustic wave (SAW) devices for their vapor sorption and selectivity properties. The most promising materials tested, include siloxane polymers functionalized with acidic pendant groups that are complimentary in their solubility properties for nitroaromatic compounds. The most sensitive of the new polymers exhibit SAW sensor detection limits for nitrobenzene and 2,4-dinitrotoluene at 3 parts per billion (ppb) and 235 parts per trillion (ppt) respectively. Optimized polymers exhibit low water vapor sorption, and rapid signal kinetics for nitrobenzene, reaching 90% of signal response in 4 seconds. Studies with an in-situ infra-red spectroscopy technique are used to determine the mechanism of interaction between nitroaromatic compounds and the chemoselective polymer.