Evaluation of the terpolymer composition equation

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Abstract
The equations describing the relationships between polymer composition and feed composition in a three‐monomer polymerization have been experimentally verified at high monomer conversions for the first time. In this paper, a three‐component system involving vinyl acetate‐octyl fumarate‐N‐vinyl pyrrolidone was analyzed. The six reactivity ratios, or relative reaction rate constants, were either taken from previous literature or determined from two‐component systems. The differential terpolymerization equations could be integrated analytically in special cases, owing to the negligibility of some of the terms, but a more precise technique was to integrate numerically with a digital computer. Two feed compositions were polymerized to various levels of fumarate conversion covering the entire range. The extent of conversion was determined polarographically. Average terpolymer compositions, determined by elemental analysis, checked with values predicted by the mathematical model well within experimental error. The calculations also showed that the instantaneous terpolymer composition can vary considerably during a batch polymerization and give rise to a spectrum of polymer properties.