SO2 gas sorption properties were examined for poly(styrene-co-chloromethyl styrene) functionalized with N,N-dimethyl-1,3-propanediamine (DMPDA). The DMPDA-functional copolymers were prepared under various reaction conditions. Two types of SO2 sorption behaviors were observed for these DMPDA-functional copolymers: SO2 sorption capacity was very high irrespective of slow sorption/desorption rates (type I), and the sorption/desorption rates were very fast while SO2 sorption capacity was small (type II). Fourier transform infrared analysis and dielectric loss measurement revealed that the type II sorption behavior was obtained for the highly crosslinked DMPDA-functional copolymers. The degree of cross-linking was affected by both the solvent used to react DMPDA with the copolymer and the percent conversion of the chloromethyl styrene group. It was confirmed that DMPDA-functional copolymers having a highly crosslinked structure are suitable materials in quartz crystal microbalance (QCM)type polymeric SO2 gas sensors. (C) 2003 Wiley Periodicals, Inc.