Liquid Polybutadienes (LPBDs) are low molecular weight, unsaturated oligomers in liquid form that offer numerous processing, performance, and environmental benefits across various rubber and elastomer applications. Conventional LPBDs undergo an irreversible curing reaction, making them non-recyclable waste at the end of their lifecycle. Additionally, reinforcing fillers are typically added to LPBDs to produce rubber composites with improved properties and stability. Enhancing the sustainability of these elastomeric materials can be achieved through two key strategies: modifying elastomers to enable reversible crosslinking,¹,² and developing fillers derived from biomass.³
This study modifies LPBDs and cellulosic bio-fillers to develop renewable, recyclable, and reprocessable composites using dynamic covalent Diels-Alder networks. Selected LPBDs varied in molecular weight and architecture (1,4-cis, 1,4-trans, 1,2 unsaturations). The modification process involved epoxidation via the Prilezhaev reaction, followed by furfuryl alcohol addition. Different bis-maleimides, varying in molecular structure and weight, were synthesized by reacting diamines with maleic anhydride to serve as the dienophile. Cellulose nanocrystals (CNCs) were extracted from hemp pulp via acidic hydrolysis and selected as a bio-filler. The extracted material was then modified through periodate oxidation followed by reductive amination with furfurylamine to introduce furan groups onto the CNC surface, ensuring filler-matrix compatibility and facilitating interfacial reactions during composite cross-linking.
Preliminary rubber composite films were prepared by Diels-Alder reaction using different furan/maleimide molar ratios, to optimize their cross-linking density and mechanical properties.
This study was carried out within the MadABio project – funded by European Union – Next Generation EU within the PRIN 2022 PNRR program.
References:
[1] N. Zheng et al. Chem. Rev. 121, 1716 (2021)
[2] P. Chakma et al. Angew. Chem. Int. Ed. 58, 9682 (2019)
[3] Z. Wang, L. Yuan, C.Tang Acc. Chem. Res. 50, 1762 (2017)