Triad Concentrations (P12P23P31andP13P32P21) as a Guide to Monomer Reactivity in Copolymers and Terpolymers

Abstract

Abstract A simple procedure using triangular coordinates for representing triad concentrations as a function of terpolymer compositions (and monomer proportions) is presented. Equal triad concentrations are represented by concentric closed loops or rings of equal triad concentrations converging to a unique point of highest triad concentration. The technique is illustrated with several common terpolymer systems. Alternation in terpolymer systems is assessed by determination of heterotriad concentrations. These results are compared with alternation in component binary systems. An equation is derived for calculating P 12 P MAX 21, maximum 1,2-dyad concentration (maximum mol fraction alternation) from r 1 r 2 product at equimolar copolymer. Alternatively, an equation is proposed for calculating P 12 P MAX 21 from Q-e values. Uses and limitations of r 1 r 2 product in assessing alternation in binary copolymers are discussed.