Covalent adaptable network in an anthracenyl functionalised non-olefinic elastomer; a new class of self-healing elastomer coupled with fluorescence switching

Abstract

Fabrication of elastomers with covalent adaptive networks (CANs) leads to easy recyclability and self-healing characteristics leading to extended service life. Herein, a commercially available non-olefinic elastomer, poly(ethylene-co-vinyl acetate-co-glycidyl methacrylate) (EVA-GMA), was functionalised to endow CANs based on thermoreversible Diels-Alder (DA) reaction. For this purpose, the epoxy functionalised elastomer was initially modified with fluorescence active anthracene moieties. Next, the anthracenyl-functionalised elastomer was individually crosslinked with 1,1′-(methylenedi-4,1-phenylene) bismaleimide (BM) and bifunctional 1,2,4-triazoline-3,5-dione (bis-TAD) derivatives to derive the rubbery CANs via DA chemistry. Notably, bis-TAD-derived CANs were obtained much faster (<10 min, r.t.) than maleimide-derived CANs elastomer (96 h at 70 °C). Differential scanning calorimetry (DSC) analysis revealed that functional elastomers with both DA-type CANs are thermoreversible above 130 °C. Noticeably, in the case of the TAD-derived CANs, the (re)processing and healing timings were relatively faster than the maleimide-derived CANs. DA-derived CANs elastomers exhibited a significant healing and recycling efficiency of up to 90 %. The dynamic nature of DA-type CANs elastomers was studied via DMA analysis. Moreover, the fluorescence switching (ON-OFF) behaviour of the anthracenyl functionalised and DA elastomers was studied under UV (λ = 365 nm) light and showed switching behaviour at 140 °C. These functionalised EVA-GMA CANs showed significant self-healing, good recyclability, and well-defined switching properties, indicating their potential applications in speciality rubber products, chemosensors, functional paints, and coatings.