USE OF POLY(AMIDOAMINES) AS CO2-SENSITIVE AND SI-2-SENSITIVE MATERIALFOR GRAVIMETRIC SENSORS

A novel polymeric material of poly(amidoamine) [PAA] structure was use d as sensor-coating for the detection of CO2 and SO2 in gaseous mixtur es by means of gravimetric sensors. The PAA utilized for this work was an amorphous rubber-like material, purposely selected for the flexibi lity of its macromolecular structure, which favours the diffusion of a nalyte molecules through the polymeric layer. It was prepared and char acterized in our laboratory by means of IR and NMR spectroscopy, DSC a nalysis, viscometric measurements and potentiometric titration with st andard acids. The polymeric films were prepared by casting from dilute methanol solutions and their average thickness ranged between 0.40 an d 0.80 mu m. The morphology of the films was studied by means of SEM. Sorption experiments in the presence of CO2 and SO2( )alternately were carried out in environments at controlled temperature and relative hu midity (RH) levels. The response towards both CO2 and SO2 approached l inearity. The limits of sensitivity towards both gaseous analytes were determined, and the dependence of the PAA sorption on RH was investig ated. The long-term stability of the material in normal atmospheric co nditions was also considered. The sorption phenomenon was completely r eversible in the case of CO2, while hysteresis was detected in the cas e of SO2. The response times were on the order of 5 min for CO2 and 7 min for SO2.