Green Synthesis of Farnesene, Dibutyl Itaconate, Styrene, and Recycled Styrene-Based Liquid Rubbers and Their Physical Properties

Abstract

Liquid rubbers have recently emerged as essential processing aids, acting as processing oils that preserve the mechanical properties of the base rubber while supporting long-term sustainability. These rubbers are primarily low molecular weight materials with significant viscous flow at room temperature. Notably, during vulcanization, they form crosslinks with the primary rubber chains, enhancing or maintaining the performance of the final compounds. In light of cost, product longevity, energy efficiency, and environmental concerns, liquid rubber-based processing oils show potential as an alternative to the highly aromatic oils commonly used in the rubber industry, offering long-term functionality through environmentally safer processes. In this study, for the first time, we developed a bio-based liquid rubber using farnesene (FA) and dibutyl itaconate (DBI), styrene (Sty), and recycled styrene (rSty) via a straightforward and eco-friendly Diels-Alder (DA) reaction. The successful preparation of a homopolymer of FA and its copolymer with DBI, Sty, and rSty was examined by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy. Additionally, gel permeation chromatography (GPC) was employed to determine the molecular weight and polydispersity index of the synthesized liquid rubbers. Thus, the results indicated that the produced liquid rubbers have notable properties, stating their applicability for industrial purposes.