Polypropylene: Now Available without Chain Ends

Summary Polyolefin manufacturing eclipsed 170 million tons in 2016, but the cyclic versions of these important materials are only synthesized in small quantities or are simply synthetically inaccessible. In this work, we describe the synthesis of "atactic" cyclic polypropylene. Cyclic polypropyne is first synthesized via catalytic ring expansion polymerization of propyne and then hydrogenation of the unsaturated polymer provides cyclic polypropylene. Evidence for a cyclic topology comes from both solution and solid-state characterization. Importantly, we report the rheological differences between linear and cyclic polypropylene.