Sensing parameters as a function of the chemical structure and thickness of two poly(styrene)-type based composites with carbon black

Abstract

Sensing parameters of polymer composite layers were studied as a function of the polymer matrix structure and the initial resistance of the composite layers. Composites of Poly(styrene) and 4-Chloro-poly(styrene) at the same volume fraction of carbon black (8.7% V/V) were prepared by ultrasonic dispersion. Composite layers with different thicknesses and resistances were deposited by spin coating technique on flexible substrates from commercial cellulose acetate foils. Both kind of composite layers with initial resistances of 10, 50 and 100 kΩ were exposed to Acetone, Tetrahydrofuran, Chloroform and Toluene. Results evidenced that selectivity is very dependent on the chemical structure of the polymer matrix and sensitivity to the initial film electrical resistance. PS-based composite series were selective to Tetrahydrofuran whereas that 4ClPS-based composite series were selective to Acetone as expected due to their solubility parameters. For both composite series sensitivity increased for layers with less than 100 kΩ resistances. For all tested solvents 4ClPS-based composites showed higher sensitivities than PS-based composites. The response times for both series were into the range of 2 to 150 s and recovery times were in the range of 30 to 2000 s.