A universal strategy for decoupling stiffness and extensibility of polymer networks

Stiffness and extensibility are two fundamental mechanical properties of polymer networks. However, they are intrinsically coupled: stiffer networks are less extensible. Here, we design and synthesize networks by crosslinking foldable bottlebrush polymers, which feature a collapsed backbone grafted with many linear side chains. During stretching, the collapsed backbone unfolds, releasing stored length and enabling remarkable extensibility. Simultaneously, the network stiffness is determined by the side chains. We create polymer networks with nearly constant stiffness while increasing the tensile breaking strain by ~100 times from 0.23±0.04 to 23.62±3.64. Furthermore, we demonstrate that this concept applies to polymers of different chemical species. Our discovery provides a universal strategy for decoupling the stiffness and extensibility of polymer networks, opening an avenue for developing polymers with extraordinary mechanical properties.