Penultimate unit effects in terpolymerization

Although the effects of penultimate units in binary copolymerization have been extensively treated, the investigation of these effects in terpolymerization has been neglected. Undoubtedly, this neglect is attributable to the fact that possible effects arising from twenty‐seven different propagation possibilities must be considered. Fortunately, for practical purposes, it often occurs that only a few of the penultimate possibilities are important in determining copolymer composition, and that most of the propagating steps can be treated with regard to terminal unit effects alone. Simplified equations are presented which allow for such restrictions. These equations are applied to several experimental examples. In addition, simplified terpolymer equations are derived which allow for the circumstances where one or two homopropagation rate constants approach zero. Furthermore, methods are introduced for assessing K32/K31 where K33 approaches zero. These methods lead, in turn, to more precise assessments of Q and e for 1,2‐disubstituted olefins.