title: Toughening mystery of natural rubber deciphered by double network incorporating hierarchical structures.
abstract: As an indispensible material for modern society, natural rubber possesses peerless mechanical properties such as strength and toughness over its artificial analogues, which remains a mystery. Intensive experimental and theoretical investigations have revealed the self-enhancement of natural rubber due to strain-induced crystallization. However a rigorous model on the self-enhancement, elucidating natural rubber's extraordinary mechanical properties, is obscured by deficient understanding of the local hierarchical structure under strain. With spatially resolved synchrotron radiation micro-beam scanning X-ray diffraction we discover weak oscillation in distributions of strain-induced crystallinity around crack tip for stretched natural rubber film, demonstrating a soft-hard double network structure. The fracture energy enhancement factor obtained by utilizing the double network model indicates an enhancement of toughness by 3 orders. It's proposed that upon stretching spontaneously developed double network structures integrating hierarchy at multi length-scale in natural rubber play an essential role in its remarkable mechanical performance.
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Weiming
authors.initials: W
authors.lastname: Zhou
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Li
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Ningdong
authors.initials: N
authors.lastname: Huang
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Zeming
authors.initials: Z
authors.lastname: Qi
authors.affiliation: National Synchrotron Radiation Lab and College of Nuclear Science and Technology, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, China.
authors.forename: Liangbin
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Modern Mechanics, University of Science and Technology of China, Hefei, China.
authors.forename: Haiyi
authors.initials: H
authors.lastname: Liang