Nitroxide-Mediated Polymerization of Bio-Based Farnesene with a Functionalized Methacrylate

Farnesene (Far) is a bio-based terpene monomer that is similar in structure to commercially used dienes like butadiene and isoprene. Nitroxide-mediated polymerization (NMP) is adept for the polymerization of dienes, but not particularly effective at controlling the polymerization of methacrylates using commercial nitroxides. In this study, Far is statistically copolymerized with a functional methacrylate, glycidyl methacrylate (GMA), by NMP using N-succinimidyl modified commercial BlocBuilder (NHS-BB) initiator. Reactivity ratios are determined to be r(Far) = 0.54 +/- 0.04 and r(GMA) = 0.24 +/- 0.02. The ability of the poly(Far-stat-GMA) chains to reinitiate for chain extension with styrene showed a clear shift in molecular weight and monomodal distribution. Copolymerizations using a new alkoxyamine, Dispolreg 007 (D7), is explored as it is shown to homopolymerize methacrylates, but not yet reported for statistical copolymerizations. Bimodal molecular weight distributions are observed when an equimolar ratio of Far and GMA is copolymerized with D7 due to slow decomposition of the initiator, but chain ends are active as shown by successful chain extension with styrene. Both NHS-BB and D7 initiators are used to synthesize poly[Far-b-(GMA-stat-Far)] and poly(Far-b-GMA) diblock copolymers. While the NHS-BB initiated polymer chains have lower dispersity, D7 exhibits more linear polymerization kinetics and maintains more active chain ends.