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

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 bio-based 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.