Terpolymerization of Methacrylonitrile, Styrene, and α-Methylstyrene

The free radical copolymerization of methacrylonitrile, styrene, and α-methylstyrene was studied at 60 °C in toluene solution. Copolymer composition was calculated from the composition of the unreacted monomers, as measured by g.l.c. Reactivity ratios measured previously for the three monomer pairs involved were used with the simple terpolymerization equation to predict polymer composition. Agreement between predicted and experimental polymer compositions was satisfactory. The behavior of α-methylstyrene can be described by a simple model without reference to ceiling temperature or penultimate effects because sequence lengths of this monomer in the terpolymers are short.A true azeotropic feed composition was not investigated, but several monomer mixtures produced copolymers with compositions which varied so little from that of the feed that the systems could be considered to be azeotropic for practical synthetic purposes. This behavior is in accord with expectations.Analytical accuracy of the gas chromatographic techniques was examined and means are suggested to make the best use of this method in copolymerization studies.