HYPERBRANCHED AROMATIC POLYESTERS WITH CARBOXYLIC-ACID TERMINAL GROUPS

Melt condensation of 5-acetoxyisophthalic acid (1) and 5-(2-hydroxyeth oxy)isophthalic acid (4) yielded hyperbranched aromatic polyesters wit h carboxylic acid terminal groups. The polymer of 1 has a T(g) of 239- degrees-C and thus required melt acidolysis polymerization temperature s of 240-260-degrees-C to obtain M(w)s in the 20 000 to 80 000 range. The polyester based on 4, with a lower T(g), was obtained at around 19 0-degrees-C using standard polycondensation techniques. Comparisons of Mark-Houwink plots of these polyesters with linear polystyrene were c onsistent with the expected highly branched structures. NMR studies re vealed the degree of branching to be about 50%, similar to what has be en observed in other hyperbranched polyester systems. The hyperbranche d polyesters were easily converted to the ammonium or sodium salts and the viscosity behavior of these water-soluble hyperbranched polyelect rolytes was investigated.