Design and Preparation of Fully Biobased Poly(diethyl fumarate- <i>co</i> -isoprene) Elastomers with Tailorable Oil Resistance and Damping Performance

In the rubber industry, the development of novel biobased synthetic elastomers derived from renewable biomass resources─which effectively reduces dependence on petroleum resources and mitigates greenhouse gas emissions─provides a strategic pathway toward low-carbon and sustainable development for the sector. In this study, a series of fully biobased poly(diethyl fumarate-co-isoprene) (FPDEFI) elastomers with varying biobased isoprene (B-Ip) contents were synthesized via redox emulsion polymerization, in which the short-side-chain, biobased diethyl fumarate (DEF) and B-Ip served as monomers. The FPDEFI elastomers exhibited a number-average molecular weight (Mn) of 62,000∼90,000 g/mol and a glass transition temperature (Tg) ranging from −25 to −11 °C. The copolymer composition was regulated by adjusting the monomer feed ratio, enabling precise control over macroscopic properties such as thermal and mechanical performance. To achieve enhanced practicality, silica was incorporated into FPDEFI to fabricate high-performance nanocomposites. The FPDEFI/silica nanocomposites exhibit exceptional tensile strength (12.7∼14.7 MPa), elongation at break (347∼537%), thermo-oxidative aging resistance, and a broad damping temperature range (ΔT > 48 °C). Benefiting from the high ester group density of the diethyl fumarate units, they demonstrate oil resistance comparable to that of NBR/silica and superior to that of ESBR/silica. These results demonstrate that FPDEFI exhibits excellent performance and practical application potential. Meanwhile, this study establishes a straightforward, energy-efficient, and environmentally benign synthesis route for preparing fully biobased elastomers in the rubber industry.