Local chain configuration dependence of the mechanisms of chemical reactions of PVC. 8. New results from the reductive dechlorination reaction

The reductive dechlorination of poly(vinyl chloride) (PVC) with lithium aluminium hydride, tri-n-butyl tin hydride and lithium triethyl borohydride as reducing agents has been performed in the solution of tetrahydrofuran. A comparative study of the microstructural evolution with conversion using the three different reducing agents was carried out. The quantitative microstructural analysis with conversion has been followed by 13C NMR spectroscopy. From the evolution of the content of isotactic (mm), heterotactic (mr) and syndiotactic (rr) triads, and of mmmm, mmmr and rmmr isotactic pentads in the unmodified parts of the polymer, it is unambiguously inferred that only the central chlorine atoms of isotactic triads in mmr tetrads or heterotactic triads in rmmr pentads are reactive. This conclusion was confirmed on the basis of FTIR results. The results provide valuable information regarding the effect of tacticity and the related local conformations in the chemical reactions of PVC.