Metal-Free Ring-Opening Polymerization of Propylene Oxide: Synthesis and Characterization of Polyether in the Undergraduate Organic Chemistry Laboratory

Ring-opening polymerization (ROP) of propylene oxide (PO) is an essential reaction for polymer synthesis. The product of poly(propylene oxide) (PPO) is widely used for the manufacture of foams and elastomers. The recent innovation of organocatalytic polymerization methods has greatly improved the efficiency and controllability of this polymerization. This article describes the laboratory experiment where students synthesize PPO by the ROP of PO using triethylboron combined with a phosphazene base as a binary organocatalyst system. Students also use NMR spectroscopy and gel-permeation chromatography for the characterization of monomer conversion, polymer structure, and polymer molecular weight. The laboratory experiment is sought to be incorporated into the second-year undergraduate organic chemistry laboratory curriculum. The experiment is performed at room temperature, is solvent-free, and is completed within 3 h, which is easy for second-year undergraduate students to operate. The experiment also introduces students to several fundamental concepts of organic chemistry and polymer chemistry.