Alternating Copolymerization of Butadiene and Acrylic Compounds

Abstract

A kinetic investigation on the alternating copolymerization of butadiene (BD) and methyl methacrylate (MMA) was undertaken by using EtAlCl2 (Al) and VOCl3 (V) as catalysts. The rate orders with respect to both components were the same as those for the butadiene (BD)–acrylonitrile (AN) system as reported previously; the rate of polymerization, Rp,o, is proportional to [Al]3/2 and [V]1/2, and the concentration of active species seems to be proportional to [Al]1/2 and [V]1/2.These relations are interpreted in terms of the mechanism involving a rapid initiation followed by stepwise propagation through a BD–MMA–Al complexed monomer. The formation of a benzene–MMA–Al complex as well as a MMA–Al complex is supposed. The rate order with respect to BD and acrylic monomer (A) was found to be complicated, i.e., in the BD–AN system Rp,o is proportional to [BD][AN]2, whereas in the BD–MMA system Rp,o depends on neither [BD] nor [MMA]. This fact may be accounted for in terms of the equilibrium of the BD–A–Al complex and the (A)n–Al complex. It is assumed that in a BD–AN–Al system the equilibrium constant for the (AN)n–Al complex is very large, whereas in a MMA–BD–Al system the equilibrium constant for the (MMA)n–Al complex is smaller than that of the BD–MMA–Al complex.