Mechanically Robust, Self-Repairable, Shape Memory and Recyclable Ionomeric Elastomer Composites with Renewable Lignin via Interfacial Metal–Ligand Interactions

Abstract

Lignin, the most abundant aromatic polymer in nature, is one of the most promising renewable feedstocks for value-added polymer products. However, it is challenging to prepare high-performance and multifunctional polymer materials with renewable lignin because of its poor compatibility with the elastomer matrix. In fact, lignin often requires solvent fractionation, chemical modification, or prohibitively expensive additives. This work develops a cost-effective strategy to prepare ionomeric elastomer composites based on a commercial carboxyl elastomer and a high content of lignin without purification or chemical modification. The compatibility between the elastomer and lignin is improved by the incorporation of zinc oxide which creates metal−ligand coordination at the interfaces between the carboxyl groups of the elastomer and the oxygen-bearing groups of the lignin. This results in fine dispersion of the lignin in the elastomer matrix, even when its content reaches 50 wt %. The lignin/elastomer composites show excellent mechanical properties, which are attributed to the reinforcing effect of the lignin domains and the presence of abundant sacrificial coordination bonds. Moreover, ionic bonds and ionic aggregates created by the neutralization of the zinc ions with the carboxyl groups of the elastomer behave as physical crosslinks which endow the composites with excellent recyclability; namely, their mechanical properties are retained or even improved after multiple reprocessing cycles. They also show good self-repairability and shape memory. Hence, this work may open up new avenues to utilize lignin as a renewable alternative to petroleum derivatives for designing and fabricating high-performance and multifunctional elastomer materials.

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

“…The lignin/VPR compounds were prepared through a Haake mixer, and the process was conducted according to the previously reported method. 9 For the various lignin/VPR compounds, the weight ratio of lignin to ZnCl 2 remains at 10 : 1. To ease the description, all samples are named L x Zn y , where L and Zn represent lignin and ZnCl 2 , respectively, and x , y represent their content, respectively.…”

“…Recently, bio-derived materials, such as cellulose nanocrystals (CNCs), 6,7 lignin, 8,9 chitosan, 10,11 starch, 12,13 etc. , have been placed in substitute reinforcing fillers of rubbers.…”

“…To achieve high-performance lignin-based rubber composites with high-volume utilization of lignin, our previous work developed a cost-effective method to prepare mechanically robust, self-repairable, and recyclable lignin-based composites based on the commercial carboxylated nitrile rubber (XNBR) and high content (reaching up to 50 wt%) of enzymatic hydrolysis lignin without purification or chemical modification. 9 Based on the construction of Zn–ligand coordination bonds, lignin could achieve fine dispersion in the XNBR matrix and excellent interfacial interactions.…”

Recent Advances of Lignin Functionalization for High-Performance and Advanced Functional Rubber Composites

“…(b) Preparation of XNBR/lignin composites with ionic cross-links . Adapted with permission from ref . Copyright 2022 ACS.…”

High-Performance Stimulus-Healable Sustainable Multiblock Copolymer Elastomers with Magnetothermal and Photothermal Properties

“…Natural resources, such as cellulose, lignin, starch, chitin, plant oils, and terpenes, have been utilized as promising candidates to fabricate novel biobased elastomers. − Lignin, the most abundant aromatic biopolymer, has been considered an ideal filler to design composite elastomers with improved properties . Alternatively, various aromatic-containing platform chemicals can be obtained by the depolymerization of lignin, and these lignin-derived aromatic compounds have been reported to produce high-value sustainable plastics, thermosets, and elastomers in order to fully substitute or partially replace the fossil-based polymers. − Vanillin, which can be transformed from lignin, is a representative lignin-based derivative that can be utilized to synthesize biobased polymer materials with high glass transition temperatures ( T g s) through controlled radical polymerization techniques. − The major challenge for biobased elastomers is their limited mechanical performance compared to those of fossil-based elastomeric materials.…”