Entropically Driven Ring-Opening Polymerization of Strainless Organic Macrocycles

Entropically driven ring-opening polymerization (ED-ROPs) are a relatively new approach to the synthesis of condensation polymers. Carrying out ED-ROPs simply involves taking macrocyclic oligomers (MCOs) at high concentration and using reaction conditions that favor the establishment of the ring-chain equilibria (RCE). Attractive features of ED-ROPs include the facts that little or no heat is evolved during polymerization and no small molecules are emitted. The reactions are easily carried out on a small scale. By restricting the availability of end groups, unusually high molecular weights can be obtained. In many cases, without specifically seeking to obtain unusually high molecular weights, Mw's of up to 250000 with dispersities < 2.8 have been obtained. ED-ROPs are beginning to find applications as a green method of polymerization, for high-throughput syntheses, and for polymer processing, such as reactive molding and in the synthesis of composites. The relatively low melt viscosity of the MCOs facilitates some methods of processing.