INTRAMOLECULAR CYCLIZATION IN HYPERBRANCHED POLYESTERS

The effect of monomer structure and catalyst on the synthesis of hyper branched polyesters based on 4,4-(4'-hydroxyphenyl)pentanoic acid has been examined. The nature of the ester group and the catalyst have a s ignificant effect on the molecular weight of the hyperbranched polyest er but do not effect the degree of branching for these materials. The fate of the single ester group at the focal point of these hyperbranch ed macromolecules is probed by the synthesis and polymerization of C-1 3 labeled methyl 4,4-(4'-hydroxyphenyl)pentanoate. Comparison of the m olecular weights determined by H-1- or C-13-NMR spectra with those det ermined by osmometry suggest that intramolecular cyclization does not occur to a significant extent in these systems. (C) 1997 John Wiley & Sons, Inc.