Influence of the tacticity on thermal degradation of PVC. IV. Degradation in solution in comparison with degradation at solid state

Four fractions of PVC were obtained by successive extractions with appropriate solvents from PVC samples prepared in bulk at 60, 40, 0, and −50°C. Then they were carefully characterized, especially as far as stereoregularity is concerned. The samples were submitted to thermal degradation both at solid state and as solutions in dioctyl phthalate. The type of the polyene sequence distribution in degraded samples was determined by both the UV‐visible spectroscopy and the number of chain scissions resulting from the ozonization reaction. The degradation rate was proved to rise together with the syndiotactic sequence content in agreement with results in Parts I–III, obtained only with degradation at solid state. On the other hand, The content of the long polyenes relative to that of the short polyenes in the degraded polymers was found to be higher, and the number of chain scissions through ozonization reaction lower, when the syndiotactic sequence content is high. These results enable us to conclude that the actual mechanism of the PVC thermal degradation depends markedly on the tacticity distribution regardless of whether the degradation occurs either at solid state or in solution.