Ultratough and ultrastiff elastomers formed by inorganic ionic molecular linkers

Producing both stiff and tough elastomers is crucial in engineering fields. Although diverse cross-linking strategies have been developed to toughen polymers, the co-enhancement of stiffness and toughness is still a contradiction. Here, we developed inorganic ionic molecular linkers (IMLs) by using stable calcium phosphate oligomer as an example for the bottom-up synthesis of butyl acrylate-acrylic acid-based elastomers; these elastomers showed ultrahigh stiffness and toughness compared to elastomers by other cross-linkers. The molecular-size effect of inorganic ionic molecular linkers allows them to connect multiple polymer chains to enhance stiffness, while simultaneously enabling dynamic interchain cross-linking during deformation to achieve high toughness. Furthermore, these inorganic ionic molecular linkers were readily applicable in other commercial elastomers for their co-enhancement of both stiffness and toughness. This strategy produced an alternative molecular cross-linker by interdisciplinary understanding of inorganic and polymer chemistry, pushing forward both theory and technology for the manufacture of high-performance elastomers.