Nopadiene: A Pinene-Derived Cyclic Diene as a Styrene Substitute for Fully Biobased Thermoplastic Elastomers

Christoph Hahn; Inigo Göttker-Schnetmann; Ioannis Tzourtzouklis; Manfred Wagner; Axel H E Müller; George Floudas; Stefan Mecking; Holger Frey

doi:10.1021/jacs.3c08130

Nopadiene: A Pinene-Derived Cyclic Diene as a Styrene Substitute for Fully Biobased Thermoplastic Elastomers

J Am Chem Soc. 2023 Dec 13;145(49):26688-26698. doi: 10.1021/jacs.3c08130. Epub 2023 Dec 4.

Authors

Christoph Hahn^{1

2}, Inigo Göttker-Schnetmann³, Ioannis Tzourtzouklis⁴, Manfred Wagner⁵, Axel H E Müller¹, George Floudas^{4

5

6}, Stefan Mecking³, Holger Frey¹

Affiliations

¹ Department of Chemistry, Johannes Gutenberg University, 55128 Mainz, Germany.
² Max-Planck Graduate Center, 55128 Mainz, Germany.
³ Chair Materials Science, Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
⁴ Department of Physics, University of Ioannina, 45110 Ioannina, Greece.
⁵ Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
⁶ Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), 45110 Ioannina, Greece.

PMID: 38048399
DOI: 10.1021/jacs.3c08130

Abstract

The bicyclic 1,2-substituted, 1,3-diene monomer nopadiene (1R,5S)-2-ethenyl-6,6-dimethylbicyclo[3.1.1]hept-2-ene was successfully polymerized by anionic and catalytic polymerization. Nopadiene is produced either through a facile one-step synthesis from myrtenal via Wittig-olefination or via a scalable two-step reaction from nopol (10-hydroxymethylene-2-pinene). Both terpenoids originate from the renewable β-pinene. The living anionic polymerization of nopadiene in apolar and polar solvents at 25 °C using organolithium initiators resulted in homopolymers with well-controlled molar masses in the range of 5.6-103.4 kg·mol^-1 (SEC, PS calibration) and low dispersities (Đ) between 1.06 and 1.18. By means of catalytic polymerization with Me₄CpSi(Me)₂N^tBuTiCl₂ and (Flu)(Pyr)CH₂Lu(CH₂TMS)₂(THF), the 1,4 and 3,4- microstructures of nopadiene are accessible in excellent selectivity. In pronounced contrast to other 1,3-dienes, the rigid polymers of the sterically demanding nopadiene showed an elevated glass temperature, T_g,∞ = 160 °C (in the limit of very high molar mass, M_n). ABA triblock copolymers with a central polymyrcene block and myrcene content of 60-75 mol %, with molar masses of 100-200 kg/mol were prepared by living anionic polymerization of the pinene-derivable monomers nopadiene and myrcene. This diene copolymerization resulted in thermoplastic elastomers displaying nanophase separation at different molar ratios (DSC, SAXS) and an upper service temperature about 30 K higher than that for traditional petroleum-derived styrenic thermoplastic elastomers due to the high glass temperature of polynopadiene. The materials showed good thermal stability at elevated temperatures under nitrogen (TGA), promising tensile strength and ultimate elongation of up to 1600%.