The Ring-Opening Polymerization-Polycondensation (ROPPOC) Approach to Cyclic Polymers

A new concept called ring-opening polymerization-polycondensation (ROPPOC) is presented and discussed. This synthetic strategy is based on the intermediate formation of chains having two end groups that can react with each other. The ROPPOC syntheses are subdivided into three groups according to the nature of the chain ends: two ionic end groups, one ionic and one covalent chain end, and a combination of two reactive covalent end groups may be involved, depending on the catalyst. The usefulness for the preparation of cyclic polymers is discussed with a review of numerous previously published examples. These examples concern the following classes of cyclic polymers: polypeptides, polyamides, and polyesters, including polycarbonates and cyclic polysiloxanes. It is demonstrated that the results of certain ROPPOC syntheses are in contradiction to the Jacobson-Stockmayer theory. Finally, the usefulness of ROPPOCs for the detection of polydisperse catenanes is discussed.