Linear PCHD and polyisoprenes with different microstructures and molecular weights are synthesized and chemically modified to improve their thermal and chemical stability by forming a three-membered ring structure containing two C–F bonds. Pyrolysis of these fluorinated polydienes proceeds through a two-stage decomposition involving chain scission, crosslinking, dehydrogenation, and dehalogenation. The pyrolysis leads to graphite-like residues, whereas their polydiene precursors decompose completely under the same conditions. The fluorination of PCHD enhances its thermal stability. The stronger C–F bond along with high strain of the three-membered ring structure and formation of relatively stable free radicals play an important role in the thermal stability of fluorinated polydienes.