Intramolecular cyclization in hyperbranched polyesters

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