Anionic Polymerization of Terpene Monomers: New Options for Bio-Based Thermoplastic Elastomers

Abstract

Biomass-derived materials possess vast potential for material science and industry in the next decades. Dwindling fossil resources and an increasing environmental awareness increase the demand for sustainable feedstock-based alternatives. In addition to natural rubber (cis-1,4-polyisoprene), the class of terpenes offers a large variety of renewable monomers, like the 1,3-diene monomers β-myrcene and β-farnesene. Living anionic polymerization of biobased 1,3-diene monomers enables the synthesis of well-defined, high molecular weight block-and statistical copolymers with unique control over molecular weights, polymer architecture, and polydiene microstructure. The resulting materials can be used for a variety of applications. For instance, polyfarnesene has been introduced as an additive in tire mixtures and replaces fossil resource-based rubbery building blocks in styrenic thermoplastic elastomers. In addition, the unsaturated nature of polymyrcene and polyfarnesene renders them accessible for functionalization by a variety of postmodification reactions, which results, for example, in improved interaction with functional fillers. (End-)functionalized polyterpenes are promising candidates as precursors for the synthesis of fully bio-based thermoplastic elastomers. In this Perspective we provide an overview of recent developments regarding the anionic polymerization of terpenes and the considerable potential the resulting polymer architectures offer for material science and a more sustainable future.

Reversible addition fragmentation chain transfer copolymerization of functional myrcene with styrene

“…Under the conditions developed for homo-polymerization of functional dienes, 41 the copolymerizations were implemented at various monomer feedings and terminated at a low polymer recovery yield (<10%) to minimize monomer ratio drift. 7,31 The consumption of monomer with evolution of polymerization time was measured by 1 H NMR spectroscopy by comparing the Me group of My-OH integration versus the Ph of styrene. The polymerization reactivity ratios r My-OH and r St were determined to be 1.28 ± 0.02 and 0.81 ± 0.02, respectively (Fig.…”

“…Reactivity ratios between pairs of monomers, which is a central concern for copolymerization, were estimated. Under the conditions developed for homo‐polymerization of functional dienes, 41 the copolymerizations were implemented at various monomer feedings and terminated at a low polymer recovery yield (<10%) to minimize monomer ratio drift 7,31 . The consumption of monomer with evolution of polymerization time was measured by 1 H NMR spectroscopy by comparing the Me group of My‐OH integration versus the Ph of styrene.…”

“…7-Methyl-3-methylene-octa-1,6-diene (myrcene, My), a mimic to conjugated diene, is an important renewable feedstock derived from terpene. 15 Direct utilization of myrcene as a monomer source in polymer synthesis has been accomplished via coordination-insertion, [16][17][18][19][20] anionic, 21,22 cationic 23,24 and free radical mechanisms, [25][26][27][28][29] mostly with styrene, [10][11][12]30,31 ester [32][33][34][35][36] and conjugated diene. 16,18,37,38 Use of myrcene as a feedstock for a functional monomer and subsequent fabricating for advanced materials can be found in a handful of research papers 17,[39][40][41] but is still a less explored field.…”

Bioelastomers: current state of development

“…68 For further information on this topic, the authors recommend that readers consult the review by Wahlen and Frey, where they specifically described the anionic polymerization of terpenes. 69…”

Fully biobased triblock copolymers generated using an unconventional oscillatory plug flow reactor

“…Poly(β-farnesene) is hydrophobic polymer derived from terpenes, a class of highly promising renewable monomers that have wide ranging properties. [38][39][40][41] Telechelic poly(farnesene) diol (PFD) has already been used in the context of hydrolysis resistant biobased polyurethane precursors. 42 Likewise, a related telechelic terpene derivative, poly (myrcene) has been shown to be effective as a midblock by polymerizing LA monomer, exhibiting the utility of structurally similar building blocks in generating triblock copolymers.…”