Synthesis, structure, and properties of core-terminated hyperbranched polyesters based on dimethyl 5-(2-hydroxyethoxy)isophthalate

The molecular weight of hyperbranched polyesters, prepared by condensation polymerization of the AB₂ monomer dimethyl 5-(2-hydroxyethoxy)isophthalate in the presence of either a B₃ core (trimethyl 1,3,5-benzenetriearboxylate) or a B₂ core (dimethyl isophthalate), was controlled by varying the core-to-monomer ratio. During polymerization polycondensation, cyelization and core-termination reactions occurred in competition. The polyester's weight-average molecular weight continued to increase even after complete consumption of the A groups by cyclization and core termination, which is postulated to result from a redistribution of polymer chains by ester-ester interchange reactions. The polymers are soluble in common organic solvents, and solutions have characteristically low intrinsic viscosities. The physical characterization of these polymers is reported.