Mechanism of enhanced sensitivity of linear poly(ethylenimine)-carbon black composite detectors to carboxylic acid vapors

Enhanced sensitivity towards volatile carboxylic acid vapors is obtained when the basic, amine-containing polymer, linear poly(ethylenimine), l-PEI, is used as the insulating component in a carbon black-polymer composite vapor detector. Specifically, at a partial pressure of analyte corresponding to 1% of its vapor pressure at room temperature, the signal-to-noise ratio for detection of acetic acid is 10³ times larger than that for non-acidic organic vapors. Measurements of the mass uptake, thickness change, and electrical conductivity of such composites have been performed to elucidate the mechanism of this sensitivity enhancement towards volatile carboxylic acid vapors. These data have allowed quantification of the relative contributions of electrical percolation effects, increases in analyte sorption, and charge-induced swelling effects in determining the response characteristics of l-PEI composites.