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.

Healable, Recyclable, and Mechanically Tough Polyurethane Elastomers with Exceptional Damage Tolerance

“…Because of their high entropy-elasticity, elastomers can dissipate mechanical energy and restore their original shape and mechanical properties after undergoing repeated shape deformations. [1][2][3][4][5][6][7][8][9] Elastomers have a wide range of applications such as in tires, seals, actuators, and shock absorbers, and are one of the most consumed materials in daily life. [10][11][12][13][14][15][16][17][18][19] For instance, the annual global rubber consumption in 2019 was However, these elastomers cannot heal physical damage.…”

“…The damage tolerance of elastomers or other kinds of polymer materials requires efficiently dissipating energy concentrated in the damaged regions. [9,38,39] Damage-tolerant polymer composites with high mechanical strength can be fabricated by embedding stiffer fibers or particles within relatively soft matrices. [9,36,38] Damagetolerant elastomers with fracture energies ranging from several tens to a maximum value of ≈120 kJ m −2 have been fabricated.…”

“…[9,38,39] Damage-tolerant polymer composites with high mechanical strength can be fabricated by embedding stiffer fibers or particles within relatively soft matrices. [9,36,38] Damagetolerant elastomers with fracture energies ranging from several tens to a maximum value of ≈120 kJ m −2 have been fabricated. [9] There is a huge requirement of elastomers for use in tires, seals, and shock absorbers every year worldwide.…”

“…[9,36,38] Damagetolerant elastomers with fracture energies ranging from several tens to a maximum value of ≈120 kJ m −2 have been fabricated. [9] There is a huge requirement of elastomers for use in tires, seals, and shock absorbers every year worldwide. In view of a sustainable society, the next generation of elastomers is expected to combine outstanding healing, recycling, and damage-tolerant capacities with high strength, elasticity, and toughness.…”

Evolution of self-healing elastomers, from extrinsic to combined intrinsic mechanisms: a review

“…On the contrary, these strategies are largely under development and are under study for both traditional and advanced applications. For example, the use of extrinsic mechanisms has shown a notable increase in coatings, 39 instrument panels, 42 and sponges, 43 while intrinsic ones have turned out to be more versatile for general purpose elastomers in innovative applications such as nanogenerators, 44 sensors, 45 conductive elastomers, 46 and even tires. 20 Table 1 summarizes some examples of the published work in the last five years in self-healing rubbers based on the first three generations.…”