Bifunctional carbanionic synthesis of fully bio-based triblock structures derived from β-farnesene and LL-dilactide : thermoplastic elastomers

Abstract

Current environmental challenges and the shrinking fossil-fuel feedstock are important criteria for the next generation of polymer materials. In this context, we present a fully bio-based material, which shows promise as thermoplastic elastomer (TPE). Due to the use of β-farnesene and L-lactide as monomers, bio-based feedstocks, namely sugar cane and corn can be used. A bifunctional initiator for the carbanionic polymerization was employed, to permit an efficient synthesis of ABA-type block structures. In addition, the “green” solvent MTBE (methyl tert-butyl ether) was used. This afforded low dispersity (Đ = 1.07 to 1.10) and telechelic polyfarnesene macro­initiators. These were employed for lactide polymerization to obtain H-shaped triblock copolymers. TEM and SAXS revealed clearly phase-separated morphologies and tensile tests revealed elastic mechanical properties. The materials featured two glass transition temperatures, at - 66 °C and 51 °C as well as gyroid or cylindrical morphologies, resulting in soft elastic materials at room temperature.