Abstract: The orders of C—Cl bond in three different types of poly(vinyl chloride) (PVC) were simulated by a B3LYP/631 method using a GAUSSIAN 09 software according to the Wiberg Bond Index theory. The results indicated that the isotactic isomers in PVC macromolecule were more stable than syndiotactic ones on the basis of the molecular orbital theory. Chemical structures of PVC samples were characterized by 13CNMR, suggesting that the PVC macromolecules containing more isotactic isomers were more stable. The thermal degradation behaviors were also investigated by thermogravimetricinfrared combination analysis, which indicated that the first degradation of PVC was mainly derived from the dehydrochlorination. Dynamic thermal stabilities of PVC samples were investigated with a torque reheometer. The results indicated that the PVC macromolecules with a fewer isotactic isomers were more thermally unstable. These results were in good agreement with the structural characterizations.

Key words: poly(vinyl chloride), computer simulation, chemical structure, thermal stability