Toward Bio-Sourced Elastomers with Reactive/Polar Groups. Myrcene - Glycidyl Methacrylate Copolymerization: Reactivity Ratios, Properties, and Preliminary RAFT Emulsion Polymerization

There is a pronounced need of replacing fossil-origin materials with sustainable ones. Myrcene (Myr) is a biobased terpene-type monomer derived from diverse plants that is a potential substitute for diene monomers (e.g., butadiene), in the manufacture of elastomers. Here, the copolymerization of Myr with glycidyl methacrylate (GMA) is studied as a candidate route for producing functional/polar elastomers. Reactivity ratios (RR) for this system are estimated using the error-in-variables method resulting in r(Myr) = 0.519 +/- 0.062 and r(GMA) = 0.301 +/- 0.014, indicating an alternating tendency. The copolymers obtained exhibit number-average molecular weights (M-n) in the range 42-674 kDa that markedly increase with the GMA content and dispersities in the range 1.49-1.90. The addition of Myr units predominantly results (H-1-NMR) in the 1,4 cis microstructure (94-97%) that increases with the GMA content. Differential scanning calorimetry analysis is performed in some of the copolymer samples. Additionally, preliminary emulsion copolymerizations of Myr-GMA are carried out at 70 degrees C, 15% solids, with potassium persulfate as initiator and 4-cyano-4-[(dodecyl sulfanylthiocarbonyl)sulfanyl] pentanoic acid as RAFT agent, yielding conversions of 74-85% in 24 h and gel contents of 17-78% that increase with increasing GMA (0-21%) fed. The GMA presence in the copolymer is demonstrated by fourier transform infrared spectroscopy (FTIR) analysis.