Organocatalytic Ring-Opening Polymerization of Trimethylene Carbonate To Yield a Biodegradable Polycarbonate

In this laboratory experiment, students work in pairs to synthesize a simple aliphatic polycarbonate via ring-opening polymerization of trimethylene carbonate using 1,8-diazabicyclo[5.4.0]­undec-7-ene and thiourea as organocatalysts. Following polymer isolation, students cool the material in a dry ice/acetone bath to observe its glass-transition behavior. This experiment is convenient to perform under teaching laboratory conditions and reinforces key concepts learned in second-year undergraduate organic chemistry, for example, nucleophilic acyl substitution, transesterification reactions, and Lewis acidity–basicity. Additionally, the experiment introduces students to polymer chemistry, heterocycles, materials science, and green chemistry. It also covers interesting concepts that are less frequently encountered at the undergraduate level such as biomimetic chemistry, bifunctional catalysis, and polymer–glass transitions.