Summarized here are the results of research by the author and his associates on several aspects of the chemistry of poly(vinyl chloride) (PVC), one of the world's most widely used and extensively studied synthetic polymers. The principal topics covered are the molecular microstructure of PVC and its elucidation, the mechanism for the thermal dehydrochlorination of PVC and its autocatalysis by HCl, and the thermal stabilization of PVC by ester thiols, a patented technology that has been licensed for commercialization both domestically and overseas. Special attention is given to the role of free radicals in PVC thermolysis. This article is an invited contribution based on the author's AIC Chemical Pioneer Award address delivered on May 9, 2019. [ABSTRACT FROM AUTHOR]