Natural caoutchouc is still a crucial component of high-performance tires, which is mainly ascribed to its perfect cis-1,4 microstructure. It is easy to foresee that this won´t change in the new era of electromobility. Commercial catalytic systems for 1,3-diene polymerization are empirically optimized ternary mixtures of a rare-earth-metal salt, an aluminum component, and an activator. Till date, the actual catalytic process has mostly remained a ‘black box’, while the polymer quality of natural caoutchouc has remained unrivalled. Our initial studies in this field addressed the interplay of the single components in such ternary mixtures, leading to the identification of heterobimetallic alkylaluminates such as Nd(AlR4)3 (R = Me, Et) as pivotal intermediates. Based on these findings, we developed a library of catalyst systems for acquiring a deeper understanding of 1,3-diene polymerization. Our current efforts are directed toward single-component catalysts and, sure, the fabrication of 100% cis-1,4 polyisoprene.
