Radical and ionic polymerization of vinyl chloride with tert‐butylmagnesium chloride

The earlier results concerning the kinetics of polymerization and initiator consumption, molecular weight distribution, and the nature of the chain ends in the polymerization of vinyl chloride initiated by tert‐butylmagnesium chloride (tBuMgCl) in tetrahydrofuran and other solvents are rediscussed in terms of the simultaneous participation of an ionic mechanism and a radical mechanism. The former is operative mainly at the beginning of the process and gives very low molecular weight products. The latter is responsible for the formation of the high polymer. The radicals are generated from the organomagnesium compound giving a tert‐butyl group as a chain end for every macromolecule. New experiments support the radical mechanism: comparison with radical polymerizations in the same conditions of temperature and solvent medium, inhibition by NO, copolymerization with vinylidene chloride. Also the high polymer is not obtained if the ionic mechanism is exalted by introduction of a powerful solvating agent, the dimethoxyethane.