Versatile Ketene Polymers

A new class of polymers based on the seldom-used ketene group (–C=C=O) could help meet the demand for materials in which a single chemical moiety performs multiple roles, such as facilitating cross-linking, light harvesting, and ligation (Nat. Chem., DOI: 10.1038/nchem.538). To create the ketene-based polymers, a team led by Bongjin Moon of South Korea’s Sogang University and Craig. J. Hawker of the University of California, Santa Barbara, used Meldrum’s acid as both a monomer building block and a precursor to the reactive ketene group. When a polymer prepared from a monomer containing Meldrum’s acid is heated, the dioxodione ring of the Meldrum’s acid moeity loses acetone and carbon dioxide to form a ketene. The ketene provides a means to cross-link polymers by dimerization and acts as a reactive handle to attach functional molecules—both actions can occur at the same time to make copolymers, such as the one shown below. To demonstrate the versatility of the polymers, the researchers patterned a fluorescent dye on the surface of a polymer film by microcontact printing; heating the film generated the ketene, which covalently attached the dye to the polymer. Hawker believes the ketene-based chemistry could become a useful addition to the growing list of functionalization strategies for polymer chemistry.