HYPERBRANCHED AROMATIC POLYESTERS WITH CARBOXYLIC-ACID TERMINAL GROUPS

Melt condensation of 5-acetoxyisophthalic acid (1) and 5-(2-hydroxyethoxy)isophthalic acid (4) yielded hyperbranched aromatic polyesters with carboxylic acid terminal groups. The polymer of 1 has a T(g) of 239-degrees-C and thus required melt acidolysis polymerization temperatures 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 190-degrees-C using standard polycondensation techniques. Comparisons of Mark-Houwink plots of these polyesters with linear polystyrene were consistent with the expected highly branched structures. NMR studies revealed the degree of branching to be about 50%, similar to what has been observed in other hyperbranched polyester systems. The hyperbranched polyesters were easily converted to the ammonium or sodium salts and the viscosity behavior of these water-soluble hyperbranched polyelectrolytes was investigated.