Preparation, Degradation, Cyclopentadienylation, and Grafting of PVC's Containing Relatively High Levels of Allylic Chlorines

Easily modifiable colorless PVC's containing relatively high levels of short internal polyene sequences and allylic chlorines, PVC(A)'s, have been prepared by controlled chemical dehydrochlorination. The thermal and thermooxidative stability of PVC(A)'s decreases significantly in comparison to the original resin. The initial dehydrochlorination rate of PVC(A)'s has been found to be linear with allylic chlorine concentration. Results indicate that nonallylic irregularities, chain-end defect sites, and/or initiation of HCl zip-elimination at regular repeat units may also play a nonnegligible role in PVC instability. Treatment of PVC(A)'s with dim ethylcyclopentadienylaluminum (Me2CpAl) led to cyclopentadienylated PVC's (PVC-Cp) which gelled on drying, and the gel could be solubilized by treatment with strong dienophiles. This indicates Diels-Alder addition between cyclopentadienyl groups and/or polyene sequences of PVC(A). The PVC(A)/BCl3/i-C4H8 system provided efficient grafting of isobutylene and resulted in poly(vinyl chloride-g-isobutylene) in which polyisobutylene branches carry tertiary chlorine termini. The latter could in turn be cyclopentadienylated by treatment with Me2CpAl and led to networks which could be broken by strong dienophiles.