Binary vs. ternary reactivity ratios: Appropriate estimation procedures with terpolymerization data

Abstract

There is a widely accepted analogy between copolymerization and terpolymerization mechanisms that has allowed researchers to use reactivity ratios obtained for binary pairs (from copolymerization experiments) in models dealing with terpolymerizations. However, binary reactivity ratios are not always applicable to terpolymerization systems; using the binary-ternary analogy (even as an approximation) requires making considerable assumptions about the system. When binary reactivity ratios are used to describe ternary systems, the consequences may include substantial differences in reactivity ratio estimates, poor composition prediction performance, and incorrect determination of product (terpolymer) characteristics. Experimental results and reactivity ratio estimation (via the error-in-variables-model) for the terpolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AAm) and acrylic acid (AAc) (and associated copolymers) are compared, all other conditions being equal.