Copolymerization

Abstract

In addition to forming polymers with molecules of their own kind, many monomers can form copolymers with other monomers. The scale of possibilities is thus widely extended. In free radical polymerization, for example, styrene is converted to poly(styrene), methyl methacrylate to poly(methyl methacrylate), and vinyl acetate to poly(vinyl acetate). A mixture of styrene and methyl methacrylate gives poly(styrene-co-methyl methacrylate) even at the lowest conversions. From a mixture of styrene and vinyl acetate, on the other hand, practically pure poly(styrene) is first formed, and then, when the styrene is exhausted, almost pure poly(vinyl acetate). This is therefore a mixture (blend) and not a copolymer. Whereas stilbene, free-radically initiated, does not give a unipolymer, and maleic anhydride gives one of only low molecular weight, a mixture of both monomers leads to a copolymer of the composition 1:1.