Exploring Divergent Green Reaction Media for the Copolymerization of Biobased Monomers in the Teaching Laboratory

Polymerization reaction media can have a profound effect on the physical properties of the resultant polymer. This phenomenon is showcased in a new experiment for the organic chemistry and polymer science teaching laboratories wherein the radical copolymerization of biobased β-myrcene and dibutyl itaconate is performed using a nonhazardous aqueous emulsion solvent and compared to a bulk reaction. Both procedures demonstrate multiple green chemistry principles and application to sustainable polymer synthesis. The emulsion copolymerization produces a tacky, elastomeric cross-linked material, capable of swelling to many times its original volume in organic solvents, setting the stage for the exploration of the relationship between solvent polarity and swelling capacity. Conversely, the polymerization of β-myrcene and dibutyl itaconate in the bulk yields a viscous non-cross-linked polymer whose 1H NMR spectrum is suitable for student analysis and estimation of polymer number-average molar mass (M n), monomer conversion, and copolymer composition. This inexpensive experiment models the use of renewable feedstocks, the effect of reaction medium on polymer architecture, the unique properties of cross-linked organogels, and the quantitative analysis of polymer structure using 1H NMR spectroscopy.