Copolymerization with depropagation: A study of alpha-methyl styrene/methyl methacrylate in bulk at elevated temperatures

Previously published material on the alpha-methyl styrene/methyl methacryla te (alpha-MS/MMA) copolymer system at temperatures above the ceiling temper ature of alpha-MS has focused on low-conversion results. Several attempts h ave been made to estimate copolymer reactivity ratios from experimental dat a, but in most cases errors are present in the determination of copolymer c omposition variables. In this article, the results of rigorous parameter es timations, as applied to two sets of equations developed independently by P . Wittmer (Adv Chem 1971, 99, 140-174) and H. Kruger, J. Bauer, and J. Rubn er (Makromol Chem 1987, 188, 2163-2175), are discussed. Experimental data f or the copolymer system at low conversions, as well as over the full conver sion range, are presented, covering a temperature range of 60-140 degrees C . A comparison of the data trends with traditional copolymer systems indica tes that the reversibility of both MMA and alpha-MS must be considered when composition, polymerization rate, or molecular weight equations are being developed. (C) 2000 John Wiley & Sons, Inc.