Ultra-Tough, Strong, and Defect-Tolerant Elastomers with Self-Healing and Intelligent-Responsive Abilities

Abstract

Mechanical strength, toughness, and defect tolerance are usually exclusive in most artificial materials. Herein, inspired by many biomaterials that overcome this tradeoff by integrating soft and hard ingredients through elaborate structural designs, we report a facile latex-assembly method to fabricate ultra-tough, strong, and defect-tolerant elastomers. The elastomers are featured by a microscopic inverse opal-mimetic rigid skeleton of dynamically cross-linked chitosan and a continuous soft matrix of vulcanized natural rubber. Such structural design enables the load-bearing capability, sacrificial property, and self-healing ability of the skeleton, the stress redistribution and extensibility of the matrix, and the stiffness variation between hard and soft ingredients, thereby imparting the elastomers with outstanding mechanical strength and defect tolerance, as well as extremely high toughness of 122 KJ m^-2, which is even higher than that of the current state-of-the-art titanium alloys. Moreover, the elastomers show prominent humidity sensitivity due to the hydrophilic nature of the chitosan skeleton. Harnessing these advantages, we fabricate a walking robot triggered by humidity variation and shoes that are able to regulate temperature and humidity. The concept of designing a rigid sacrificial skeleton within a soft continuous matrix on the microscale is quite general, enabling the development of high-performance and intelligent materials for emerging applications.