A convenient room temperature polycondensation toward hyperbranched AB2-type all-aromatic polyesters with phenol terminal groups

As a convenient alternative to the classical melt polycondensation the one‐pot solution polycondensation of suitable AB2 monomers under mild conditions has been successfully adapted to hyperbranched all‐aromatic polyester with phenol terminal groups. The polymerization was performed in solution at room temperature directly using commercially available 3,5‐dihydroxybenzoic acid as monomer and 4‐(dimethylamino) pyridinium 4‐tosylate as catalyst to suppress the formation of N‐acylurea. Different carbodiimides as coupling agents were investigated to find the optimal esterification conditions. The polymers have been characterized extensively and were compared with their well‐known analogs synthesized in melt. The characterization was carried out by NMR spectroscopy, size exclusion chromatography, and asymmetric flow‐field flow fractionation as an alternative separation technique for multifunctional polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5158–5168, 2009 A simple way for synthesis of hyperbranched all‐aromatic polyesters with phenol terminal groups under very mild conditions directly from the commercially available 3,5‐bishydroxybenzoic acid was developed. The advantages of this method compared with the classical melt polycondensation are that no pretreated monomers are required and the degree of polymerization can be simply controlled by the reaction time. Excellent thermal properties at a degree of branching of 60% were found. Comprehensive molecular weight analysis by size exclusion chromatography and asymmetric flow‐field flow fractionation techniques is demonstrated. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]