CONFIGURATIONAL AND CONFORMATIONAL EFFECTS IN THE THERMAL-DEGRADATION OF POLY(VINYL CHLORIDE)

A series of works with the aim of clarifying the mechanisms of thermal and photochemical degradation of PVC are reviewed. They include studies on: i) degradation of PVC samples of various tacticities; ii) degradation of PVC after modification by stereoselective nucleophilic substitution; iii) influence of temperature on both kinetics of degradation and polyene distribution in degraded polymer; iv) changes in the highly resolved C-13 NMR spectrum as the result of thermal degradation to low degrees; and v) degradation of PVC in blends with polymers of various degrees of compatibility. The results, yet partly unpublished, lead to the conclusion that the very labile structures are some normal local conformations, in particular the GTTG- of the isotactic triad, and allow to confirm some earlier approaches to the PVC mechanisms of degradation.