Mapping the structure evolution and mechanical properties of elastic polymers or biomaterials during bulk deformation has been difficult, yet this information has long been thought to be key for understanding the structure-mechanical property relationship necessary to guide the design of new materials. Here we use a nanomechanical mapping to assess the structural evolution and mechanical properties of a deformed isoprene rubber (IR) to elucidate a self-reinforcement mechanism in this material. A hierarchical nanofibrillar structure, ranging from several to a hundred nanometers in size, comprised of fibers oriented parallel to the stretching direction was found. The nanofibers, connected by oriented amorphous tie chains, form a network structure that is responsible for significantly enhanced stress, a key factor giving rise to the self-reinforcement of IR and, more than likely, most elastomers that undergo strained-induced crystallization.
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