Copolymerization of Vinyl Chloride and Ethylene Initiated by Trialkylboron-Peroxide Catalyst Systems

Low-pressure copolymerization was carried out in a water-methanol mixture (1 : 1 by weight) at 0°C. It was found that, when hydroperoxides were used as cocatalysts, triethylboron and tri-rc-butylboron were active as catalysts, while triphenylboron was inactive. As cocatalysts,, hydroperoxides were more active than disubstituted peroxides. The highest catalytic activity was observed when the cocatalyst/catalyst molar ratio was 0.4. The initiating radical has been suggested to be the hydroxy radical, and the initiating mechanism has been discussed briefly. The yield and the reduced specific viscosity of the copolymer decrease rapidly with an increase in the ethylene content of the monomer mixture. The monomer reactivity ratios were: r1(vinyl chloride) = 4.16 and r2(ethylene) = 0.05. This indicates that the copolymerization reaction proceeds via a normal radical mechanism. The resulting copolymer shows characteristic absorption peaks at 750 cm−1 in the infrared spectrum and at 8.37 τ in the NMR spectrum.