REVISITING THE DESIGN OF EXPERIMENTS FOR COPOLYMER REACTIVITY RATIO ESTIMATION

Tidwell and Mortimer used the D-optimal criterion to design terminal m odel reactivity ratio estimation experiments. In this paper, two probl ems are investigated which were not addressed by Tidwell and Mortimer. The first problem is the design of reactivity ratio estimation experi ments subject to composition constraints. It is shown that all the key information contained in the D-optimal criterion can be summarized in two equations: one which is a function of r1, and one which in a func tion of r2. These two equations can be used to design reactivity ratio estimation experiments under composition constraints which are within 3 mol % of the D-optimal feed compositions. The second problem is the design of penultimate reactivity ratio estimation experiments. The D- optimal criterion for the penultimate model was derived and optimized for two existing systems as well as a large number of hypothetical sys tems. The D-optimal criterion for the penultimate model was found to b e much more complicated than the terminal model criterion. For this re ason, the optimal penultimate reactivity ratio estimation experiments can not be approximated by simple equations. Anyone interested in desi gning such experiments must derive and optimize the D-optimal criterio n. (C) 1993 John Wiley & Sons, Inc.