We synthesized the alternating copolymers of 1,3-diene monomers with Sulfur dioxide (SO2) as a new class of thermally stable polymers by the radical copolymerization process and the subsequent hydrogenation. the copolymerizations of 2,4-hexadiene (HD), 1,3-butadiene (BD), and isoprene (IP) with SO2 were carried out at -78 to 0 degrees C in toluene in the presence of tert-butyl hydroperoxide, which acts as one component in the redox initiating system in combination with SO2. The resulting poly(diene-alt-SO2)s were found to consist of highly controlled repeating units, that is, an alternating and 1,4-regiospecific repeating structure. Poly(HD-alt-SO2) was soluble in several organic solvents, such as chloroform, nitromethane, tetrahydrofuran, acetone, and dimethyl sulfoxide. In contrast, poly(IP-alt-SO2) was Soluble only in dimethyl sulfoxide, whereas poly(BD-alt-SO2) was insoluble in all of the solvents. the poly(diene-alt-SO2)s readily degraded upon heating because of the expected fast depolymerization. We have demonstrated that the thermal stability of the poly(diene-alt-SO2)s is modified by the hydrogenation of the double bond in the polymer main chain. the hydrogenation of poly(HD-alt-SO2) resulted in a drastic increase in the 5% weight-loss temperature from 135 to 317 degrees C.