Catalytic reactivity of organometallic compounds for olefin polymerization. III. Vinyl polymerization by organoboron compounds

Cocatalytic reactivities of molecular oxygen and some oxygen compounds toward the organoboron‐induced vinyl polymerization were examined in detail. The oxygen compounds in an appropriate quantity accelerated the polymerization markedly, but these compounds in excess retarded the polymerization. The reactivity of the organoborm compounds examined decreased in the order: (n‐C 4 H 9 ) 2 BOB(n‐C 4 H 9 ) 2 > B(n‐C 4 H 9 ) 3 > (n‐C 4 H 9 ) 2 B(O‐n‐C 4 H 9 ) > (n‐C 4 H 9 ) 2 BBr > (n‐C 4 H 9 ) 2 BCl. Triphenylboron, which was not inflammable in air, had a much smaller catalytic activity than the aliphatic boron derivatives. Copolymerizations of styrene‐methyl methacrylate and of styrene‐vinyl acetate with boron alkyl as catalyst resulted in the formation of copolymers having the same composition as those the typical radical copolymerization. This suggests a radical mechanism for the present polymerization where redicals arising from the reaction between organoboron and oxygen compound may induce the polymerization. Some features of these polymerizations were described in connection with chain transfer and chain termination with the organoboron compounds.