THE TRUE MOLECULAR-WEIGHT DISTRIBUTIONS OF ACRYLATE POLYMERS FORMED IN PROPAGATING FRONTS

We have analyzed fractionated samples of poly(methacrylic acid) produc ed in a propagating front for the amount of anhydride that formed and determined that a large percentage of acid groups exist as anhydrides (> 20%). By analyzing the samples after cleavage, we found that the mo lecular weight dropped significantly (from M(n) = 1.4 X 10(5) to M(n) = 1.0 X 10(4)). We conclude that the high molecular weights observed p reviously were the result of intermolecular anhydride formation. Poly( butyl acrylate), which cannot form anhydride bonds, produced in fronts had broad (M(w)/M(n) = 1.7-2.0) but unimodal molecular weight distrib utions with M(w) < 10(5). The average molecular weight decreased with increasing initiator concentrations. (C) 1996 John Wiley & Sons, Inc.