Bio-based polymyrcene with highly ordered structure via solvent free controlled radical polymerization

• Polymerization of myrcene via RAFT method for the first time.
• Polymerization kinetics follows pseudo first order rates.
• Molar mass is linear function of conversion and dispersities are between 1.1 and 1.4.
• The microstructure of the polymyrcene was uniform around 96% of 1,4 addition.
• Polymyrcene was used in RAFT polymerization of styrene as macro chain transfer agent.

Monomers from renewable resources, such as terpenes, recently came into the focus of interest of polymer chemists. This work describes the first reversible addition fragmentation chain transfer (RAFT) polymerization of myrcene, a simple monoterpene, with 2-ethylsulfanylthiocarbonylsulfanyl-propionic acid ethyl ester chain transfer agent (CTA), in bulk. The polymerizations showed pseudo first order kinetics and the molar masses of the produced polymers increased linearly with the conversion, while the dispersities (Ð) were in the range of 1.1–1.4. Chain extension studies using the preliminary synthesized polymyrcene as macroCTA in the polymerization of styrene resulting in block-copolymer with low Ð. The copolymer formation confirmed the trithiocarbonate chain ends of the used polymer. These results clearly confirm the controlled nature of the polymerization for the selected system. The microstructure of the polymer was also investigated. Low glass transition temperatures of the produced polyterpenes (≈−60 °C) were determined by differential scanning calorimetric measurements that clearly indicate the dominance of the 1,4 polymyrcene structure. The microstructure was quantified by NMR spectroscopy validating a composition of the polymer at least 96% 1,4 units, with the coexistence of cis and trans isomers. These results confirm the controlled nature not only in terms of dispersity, functionality and molar mass, but also of microstructure of the RAFT polymerized monoterpene with the applied CTA.

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