Etude par résonance magnétique nucléaire des polychlorures de vinyle polymérisés par les systémes titanate de butyle–alcoyles-aluminium

TLDR: In this article, NMR analysis of the chain ends of poly(vinyl chloride) prepared using a Ti(OBu)4-alkylaluminum system in CCl4 reveals that the mechanism of the formation of free radicals depends on whether the alkylaluminum used is chlorinated or not.

Abstract: NMR analysis of the chain ends of samples of poly(vinyl chloride) prepared using a Ti(OBu)4–alkylaluminum system in CCl4 reveals that the mechanism of the formation of free radicals depends on whether the alkylaluminum used is chlorinated or not. In the first case, some of the radicals are reactive in the initiation step of the polymerization, while in the latter case theses radicals first undergo transfer to CCl4, then the CCl3· formed initiates the polymerization of vinyl chloride. The poly(vinyl chloride) radicals are chiefly stopped by transfer to CCl4 (chlorine abstraction) or to alkylaluminum (hydrogen abstraction). In transfer reactions between growing radicals and alkylaluminum, the radicals formed have to react with CCl4 before reinitiating the polymerization of vinyl chloride.