Polymer materials are ubiquitous in everyday life and are used in various applications (medical, automobile, electronics, structural, etc.). These materials experience stress through normal use, which can lead to damage and failure of the product. Having the ability to detect damage and locate areas under high stress in situ is essential to eliminating failure of the material. Our invention incorporates a chemical into the polymer backbone that signals an area under stress by causing a visible color change in the material.
This invention will allow for damage detection via a color change of the material and thus early repair before failure, ultimately extending the lifetime of the product.
For this invention, the chemical incorporated into the polymer backbone is a stress-responsive spiropyran mechanophore. One spiropyran molecule is placed in the center of the polymer backbone and undergoes a structural change in response to stress. This change causes a visible color change of the polymer material.
There are several advantages to this method of stress/damage detection. The damage sensing mechanophore is chemically incorporated into the polymer backbone and hence is distributed evenly throughout the material. Since the spiropyran is chemically incorporated, no extra processing steps are required post-polymerization and the mechanophore cannot be eliminated by everyday wear.
Finally, damage can be detected visually without removing parts or using expensive detection equipment such as UV of x-ray monitors.