SO2 gas sensors using polymers with different amino groups

The QCM-type SO2 gas sensors were fabricated using amino-functional poly(styrene-co-chloromethyl styrene) derivatives. Three kinds of diamine compounds, DMEDA, DMPDA and DPEDA, were comparatively used to introduce amino groups into the copolymer. The response time was the shortest for the sensor using the DPEDA functional copolymer, though the sensitivity was the smallest at the same measuring temperature. Sensing characteristics were affected by the measuring temperature and by the mole fraction of chloromethylstyrene in the copolymers. Further, a small addition of organically modified siloxane oligomer was effective for further reduction of the response time. The sensor using the DPEDA functional copolymer containing 5 wt.% of siloxane oligomer had the fastest response time (t1 0 0=11 min) and complete reversibility even at 50°C.