Carbon Nanodots as High-Functionality Cross-Linkers for Bioinspired Engineering of Multiple Sacrificial Units toward Strong yet Tough Elastomers

It is still a huge challenge to implement multiple energy dissipation mechanisms into polymers toward strong yet tough elastomers. Here, we describe a biomimetic design for diene-rubber by incorporating carbon nanodots (CDs) into a chemically cross-linked network. The high-functionality CDs serve as both physical and chemical cross-linkers, which give rise to a covalent network that interlinks multiple chains with nonuniform lengths, and interfacial hydrogen bonds. Upon stretching, the hydrogen bonds preferentially detach, leading to the orientation of short covalent bridging, which contributes the forward onset of strain-induced crystallization. The subsequent rupture of short covalent bridging, together with the successive detachment of hydrogen bonds result in further orientation of hidden length, which enhances the crystallinity. Consequently, the samples exhibit an integrated improvement of strength and toughness, and intact stretchability. We envisage that this strategy may provide a new avenue to implement biomimetic design for high-performance elastomers through multiple energy dissipation mechanisms.