Related Experiment Video
Updated: Sep 22, 2025
11:17
Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction
Published on: January 19, 2016
22.1K
Mechanochromic Dynamic Covalent Elastomers: Quantitative Stress Evaluation and Autonomous Recovery
Keiichi Imato1,2,3, Takeshi Kanehara1,2,3, Tomoyuki Ohishi1,2,3
1Department of Organic and Polymeric Materials, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
ACS Macro Letters
|May 26, 2022
Summary
Researchers visualized and quantified stress in polyurethane elastomers using dynamic covalent mechanophores. This breakthrough allows for real-time stress monitoring, improving material durability and predicting failure in polymers.
Area of Science:
- Polymer Science
- Materials Science
- Chemical Engineering
Background:
- Stress evaluation in polymers is crucial for preventing failure and understanding degradation mechanisms.
- Improving the lifetime and durability of polymeric materials requires accurate stress assessment.
Purpose of the Study:
- To visualize and quantitatively estimate in situ stress in segmented polyurethane elastomers.
- To utilize diarylbibenzofuranone-based dynamic covalent mechanophores for stress sensing.
Main Methods:
- Incorporation of mechanophores into the soft segments of segmented polyurethane films.
- Activation of mechanophores via mechanical force (uniaxial elongation).
- Quantitative evaluation using in situ electron paramagnetic resonance (EPR) spectroscopy and color change monitoring.
Main Results:
- Successful visualization of stress through color changes in polyurethane elastomers.
- Quantitative estimation of in situ stress during mechanical loading and unloading.
- Demonstration of mechanophore cleavage under stress and recovery upon stress removal.
Conclusions:
- Diarylbibenzofuranone-based dynamic covalent mechanophores effectively report stress in segmented polyurethanes.
- The developed method allows for real-time, in situ stress monitoring, aiding in failure prediction and material design.
- This approach enhances the understanding of polymer degradation and improves material durability.
Related Concept Videos
01:20Elastic Strain Energy for Shearing Stresses
306
As discussed in previous lessons, strain energy in a material is the energy stored when it is elastically deformed, a concept crucial in materials science and mechanical engineering. This energy results from the internal work done against the cohesive forces within the material. When a material undergoes shearing stress and corresponding shearing strain, the strain energy density, which is the energy stored per unit volume, is calculated. Within the elastic limit, where the stress is...
306
01:22Elastic Strain Energy for Normal Stresses
270
Strain energy quantifies the energy stored within a material due to deformation under loading conditions, a fundamental concept in materials science and engineering. The strain energy can be modeled when a material is subjected to axial loading with uniformly distributed stress. In this scenario, the stress experienced by the material is the internal force divided by the cross-sectional area, and the strain induced is directly proportional to this stress through the modulus of elasticity.
If...
If...
270
01:21Plastic Behavior
275
A material's elastic behavior is characterized by the disappearance of stress once the load is removed, allowing the material to return to its original state. However, when stress surpasses the yield point, yielding commences, marking the onset of plastic deformation or permanent set. This change from elastic to plastic behavior is influenced by the peak stress value and the duration before the load is removed. An intriguing observation occurs when a specimen is loaded, unloaded, and...
275
01:18Residual Stresses in Bending
275
In the study of elastoplastic members subjected to bending moments, understanding the loading and unloading phases is crucial for assessing material behavior and structural integrity. During the loading phase, as the bending moment increases, the material initially responds elastically, adhering to Hooke's Law, where stress is directly proportional to strain. When the load exceeds the yield strength, plastic deformation occurs, resulting in permanent strain and deformation that remains even...
275
01:24Stress-Strain Diagram - Ductile Materials
1.0K
The stress-strain relationship in ductile materials such as structural steel or aluminium is intricate and progresses through several stages. When a specimen is loaded, it initially exhibits a linear length increase, depicted by a steep straight line on the stress-strain diagram. It indicates the material is elastically deforming and will return to its original shape once unloaded. However, when a critical stress value is reached, plastic deformation begins. This stage sees substantial...
1.0K
01:16Dynamic Modulus of Elasticity of Concrete
567
The dynamic modulus of elasticity assesses how a concrete structure deforms under impact or dynamic loads. It is typically higher than the static modulus of elasticity, measured under slow, steady loading conditions.
The sonic test is a common method to determine the dynamic modulus. In this test, a concrete beam, sized either 6 x 6 x 30 inches or 4 x 4 x 20 inches, is clamped at its center. Vibrations are initiated at one end of the beam by an electromagnetic exciter unit powered by...
The sonic test is a common method to determine the dynamic modulus. In this test, a concrete beam, sized either 6 x 6 x 30 inches or 4 x 4 x 20 inches, is clamped at its center. Vibrations are initiated at one end of the beam by an electromagnetic exciter unit powered by...
567