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A robust and stretchable cross-linked rubber network with recyclable and self-healable capabilities based on dynamic covalent bonds

Cao, Liming, Fan, Jianfeng, Huang, Jiarong, Chen, Yukun
Journal of materials chemistry A 2019 v.7 no.9 pp. 4922-4933
Fourier transform infrared spectroscopy, cellulose, chemical bonding, crosslinking, electrical conductivity, electronic equipment, epoxides, mechanical stress, moieties, nanocrystals, renewable resources, rubber, temperature, tensile strength, transesterification
Adopting robust, stretchable, recyclable and self-healable elastomers composed of renewable resources is of great importance, but is rarely reported due to the irreversible cross-linked network. Here, we propose a simple and efficient method to prepare a robust and stretchable rubber network with recyclable and self-healable capabilities. TEMPO oxidized cellulose nanocrystals (TOCNs) with a large number of carboxyl groups were used as both the reinforcement phase and covalent cross-linkers for epoxidized natural rubber (ENR). FTIR results indicate that interfacial ester bonds were formed between carboxyl groups and epoxy groups. The covalent rubber network exhibited high tensile stress (>5 MPa) and fracture strain (>600%). Additionally, the network with exchangeable β-hydroxyl ester bonds at the rubber–TOCN interface can alter the network topology via transesterification reactions at evaluated temperatures. Therefore, the samples can achieve up to ∼85% recovery efficiency and ∼80% self-healing efficiency, exhibiting excellent reprocessing and self-healing behaviors. In addition, the samples can also be used as substrates for preparing flexible electronic devices, which exhibited excellent self-healing of electrical conductivity after damage.