One-step Synthesis of Fully Biobased Two-Sided Tapered ABA-type Thermoplastic Elastomers
Moritz Meier‐Merziger, Nikolaos Fotaras, Ioannis Tzourtzouklis, Chaymaa Allouch, Manfred Wagner, Axel H. E. Müller, George Floudas, Holger Frey
Abstract
The synthesis of a fully biobased thermoplastic elastomer (TPE) is presented as an alternative to classical styrene/isoprene-derived TPEs. Limitations of classical systems, e.g., the microstructure of dienes or elaborate multistep addition pathways can be overcome by the combination of bifunctional initiation in the scarcely used, moderately polar solvent methyl tert -butyl ether (MTBE) and by using the monomers β-farnesene and nopadiene. The monomers can be derived from renewable sugar cane and pine tree feedstocks. Excellent control of carbanionic copolymerization is confirmed by in situ NMR kinetics. The study reveals that two-sided tapered ABA triblock copolymers are accessible in a one-step approach, capitalizing on a difunctional initiator in MTBE. The material properties can be tuned in a broad range─highly elastic materials with elongation exceeding 1300% as well as tough materials with Young’s modulus exceeding 500 MPa were obtained. Small-angle Χ-ray scattering, temperature-modulated differential scanning calorimetry, rheology, and dielectric spectroscopy were employed to relate the material properties to the phase state. They revealed local phase segregation accompanied by respective glass temperatures, albeit in the absence of long-range order.