Synthesis of Cyclic Oligoesters and Their Rapid Polymerization to High Molecular Weight

We report advances for both synthesizing cyclic oligoesters and tailoring their physical properties to make ring-opening polymerization more practical for polyester manufacturing. Solution and suspension methods provide cyclic oligoesters rapidly with high yield and purity. Both methods can be adapted to continuous process operation using simple, inexpensive raw materials. Synthesis methodology influences the distribution of cyclic ring sizes. Nonequilibrium cyclic oligomer distributions produce variant crystal morphologies. Some kinetic cyclic oligoester mixtures have melting points remarkably reduced from those previously reported for the pure components. New mixed solvent syntheses, cyclic cooligomers, and ring-opening copolymerizations are demonstrated. The kinetics and efficiencies of cyclic oligoester polymerization to high molecular weight for homopolymer and copolymers are characterized. A new approach for a continuous, melt-phase ring-opening polymerization is demonstrated which avoids the high temperatures normally required to melt cyclic oligomers.