Sustainable polymers in the organic chemistry laboratory: Synthesis and characterization of a renewable polymer from δ-decalactone and l-lactide

The importance of green syntheses and sustainable polymers is highlighted in a new experiment developed for incorporation into the introductory organic chemistry laboratory curriculum. δ-Decalactone, a naturally occurring cyclic ester used by the food and flavor industry for its coconut fragrance and taste, is polymerized under acidic conditions with a diol initiator. The solvent-free, room-temperature reaction conditions result in a viscous homopolymer from which the catalyst is easily removed. Subsequent chain extension of this homopolymer with the renewable monomer l-lactide, followed by purification, isolation, and annealing in an aluminum pan, affords a block copolymer product as a transparent, flexible film. Well-resolved resonances in the ¹H NMR spectrum of the individual polymer repeat units facilitate quantitative analysis of polymer composition and molecular weight determination. This experiment introduces students to structures and fundamental concepts of polymer chemistry and exemplifies modern advances in sustainable materials.