The Polymerization of β-Ocimene by Using the Borohydrido–Neodymium as Pre-catalyst

Abstract

β-ocimene (3,7-dimethyl-1,3,6-octatriene), a dimer of isoprene, which can be found in various essential oils such as ocimium plant genus, holds the potential to serve as a source material for creating elastomers entirely derived from bio-based sources. Due to its structural similarity to myrcene (C₁₀H₁₆), this conjugated diene, offers the possibility of undergoing polymerization using the same method employed for myrcene. This involves the utilization of neodymium trisborohydride as a pre-catalyst activated by boron derivatives in the presence of triisobutyl aluminum. This innovative approach has led to the successful production of 1,4-cis polyocimene, a significant achievement in the field of polymer chemistry. Detailed analysis through the application of ¹³C NMR and DEPT 135 spectroscopy has shed light on the microstructure of the resulting polyocimene. It has been revealed that the polymer exhibits a predominant microstructure of 1,4‑cis (comprising up to 83.38% of the structure) along with the presence of 1,2-trans isomer (constituting 16.62%). The findings also highlight that the molecular weight distributions of the polymer are relatively broader (PDI > 2). This catalytic system enables the production of polymers that can be used as promising starting materials for bio-based thermoplastic elastomers.