Synthesis and characterization of A2 + B3-type hyperbranched aromatic polyesters with phenolic end groups

Hyperbranched (hb) aromatic polyesters with phenolic end groups were synthesized according to the A2 + B3 approach both, by solution polymerization and by melt (bulk) polymerization with different monomer ratios (A2:B3). The hb polyesters produced from solution polymerization exhibited higher yields, molar masses and glass transition temperature (Tg) compared to the products prepared in the melt. The resulting hb aromatic polyesters from the A2 + B3 approach were also compared with their properties to hb aromatic polymers produced from the well known AB2 monomer 3,5-bis(trimethylsiloxy)benzoyl chloride. Both types of hb aromatic polyesters possess high Tg, high thermal stability and good solubility in common organic solvents. A typical melt viscosity behavior with shear thinning effect was also observed for both. Thus similar polymer properties compared to melt-condensed products were obtained with the A2 + B3 approach by solution polycondensation possessing the advantage of easy monomer availability and much milder polymerization conditions (at room temperature in solution) compared to the AB2 approach.