Synthesis and characterization of glycerol-adipic acid hyperbranched polyesters

The structure and molecular weight of the hyperbranched polyesterification of adipic acid and glycerol were characterized by 13C NMR spectroscopy and size-exclusion chromatography as a function of reaction time and reaction stoichiometry. The glycerol substitution patterns and the extent of reaction of both glycerol and adipic acid were determined by NMR. The glycerol species concentrations determined by NMR were used with a Macosko–Miller conditional probability model to predict the hyperbranched polyester weight-average molecular weight. The model accommodated the difference in primary and secondary –OH reactivity and any substituent effects to glycerol –OH reactivity. In all cases, the predicted weight-average molecular weights were in excellent agreement with the absolute molecular weights determined by size-exclusion chromatography with light scattering detection.