A facile strategy to achieve vitrimer-like elastomer composites with lignin as a renewable bio-filler toward excellent reinforcement and recyclability

Abstract

Reinforcement and cross-linking are two critical issues in the rubber industry. However, carbon black (CB) as the most dominant reinforcing filler is derived from fossil resource-derived chemicals. And currently adopted cross-linking strategies would result in difficulties in the recycling of end-of-life rubbers. Herein, lignin, the most abundant renewable aromatic polymer, was developed as an effective reinforcing filler of rubber. The butadiene–styrene–vinylpyridine rubber (VPR) was selected as the rubber matrix, and a facile and cost-effective strategy was provided to improve the compatibility and interfacial interaction between lignin and the non-polar rubber matrix. Based on the Zn²⁺–pyridine coordination between the pyridine groups in the VPR chains and phenoxy groups in the lignin molecules, the lignin particles could obtain fine dispersion in the rubber matrix, exhibiting an excellent reinforcing effect. Moreover, the pyridine groups in the VPR chains were developed as cross-linking points, and the VPR could be effectively cross-linked based on the chemical reaction between the pyridine group and alkyl halide, producing quaternized pyridine groups. Due to the existence of the exchange reaction via the C–N transalkylation of the quaternized pyridine groups, the lignin/VPR composites could show vitrimer-like properties and are endowed with good reprocessability at high temperatures. Additionally, due to the photothermal conversion capability of lignin, the lignin/VPR composites could exhibit good photothermal performance triggered by 808 nm near-infrared light, and further possess light-driven shape memory properties. Hence, we envisage that this work can provide an avenue to design and fabricate green, sustainable, and recyclable elastomer materials with lignin as a renewable bio-filler.