HYPERBRANCHED ALIPHATIC POLYESTERS

Hyperbranched, aliphatic polyesters of theoretically calculated molar masses 1200-44 300 were synthesized in the molten state from 2,2-bis(h ydroxymethyl)propionic acid (repeating unit of AB(x) type) and 2-ethyl -2-(hydroxymethyl)-1,3-propanediol (core molecule) using acid catalysi s. The synthesis procedure was a pseudo-one-step reaction where stoich iometric amounts corresponding to each generation were added successiv ely. The resulting polymers were glassy, slightly yellow solids at roo m temperature with hydroxyl groups as terminal groups. The degree of b ranching of the polyesters was determined with the help of model compo unds using C-13-NMR and was found to be near 80%. The material exhibit ed good thermal stability as analyzed with TGA in a nitrogen atmospher e. Glass transition temperatures were determined using DSC and were fo und to be about 40 degrees C and to be relatively insensitive to varia tions in molar mass.