Self-healing polymers are synthetic or artificially-created substances that have the built-in ability to automatically repair damages to themselves without any external diagnosis of the problem or human intervention. Generally, materials will degrade over time due to damage incurred during operation, environmental conditions or fatigue. Cracks and other types of damage on macro- and microscopic levels have been shown to change acoustical, electrical and thermal properties of polymers, and the propagation of cracks can lead to the eventual failure of the material. In general, cracks are hard to detect at an early stage, and manual intervention is required for periodic repairs and inspections. In contrast, self-healing polymers counter degradation through the initiation of a repair mechanism that responds to the microdamage. Some self-healing polymers are classed as smart structures and can adapt to various environmental conditions according to their sensing and actuation properties. Although the most common types of self-healing materials are elastomers or polymers, self-healing covers all classes of materials, including cementitious substances, ceramics and metals. Healing mechanisms vary from an intrinsic repair of the polymer to the addition of a repair agent contained in a microscopic vessel. For a polymer to be strictly defined as autonomously self-healing, it is necessary that the healing process occurs without human intervention. Self-healing polymers may, however, activate in response to an external stimulus (e.g., pressure, temperature, light) to initiate the healing processes. A polymer that can intrinsically correct damage caused by normal usage could prevent costs incurred by material failure and lower the costs of a number of different industrial processes through the longer lifetime of parts and the reduction of inefficiency caused by degradation over time. The field of self-healing polymers is related to biomimetic materials as well as to other novel materials and surfaces with the embedded capacity for self-organization, such as self-cleaning and self-lubricating materials.
The following modern directions in the development of self-healing polymers are noted: cross-linked polymers, polymerization of multifunctional monomers, thiol-based polymers, poly(urea-urethane), vitrimers, microcapsule healing, 1D, 2D and 3D vascular-based polymeric systems, hollow tube polymers, discrete channels and interconnected networks in polymers, carbon nanotube networks, sacrificial thread stitching, self-healing coatings, self-healing cementitious materials, self-healing ceramics, self-healing metals, self-healing organic dyes, the self-healing of ice and bio-based healing.
The aim of this Special Issue is to highlight and overview modern trends and attract the attention of the scientific community to the problem of self-healing polymers. All types of papers (reviews, mini-reviews, full papers, short communications, technical notes, highlights, etc.) are welcome for consideration.
Acknowledgments
This editorial note has been supported by the RUDN University Strategic Academic Leadership Program.
Funding Statement
This research received no external funding.
Conflicts of Interest
The author declares no conflict of interest.
Footnotes
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
FAQs
These materials were able to close cracks, to heal damage, and to restore their (mechanical) properties almost like the big role model: nature.
Are self-healing polymers sustainable? ›
It is evidenced that the concept of self-healing materials has the potential to contribute greatly towards the sustainability of all classes of materials by limiting waste formation and avoiding the need to produce new products.
What is the basic description of self-healing polymers? ›
Self-healing polymers are synthetic or artificially-created substances that have the built-in ability to automatically repair damages to themselves without any external diagnosis of the problem or human intervention.
Do self-healing materials exist? ›
Self-healing cementitious materials
Cementitious materials have existed since the Roman era. These materials have a natural ability to self-heal, which was first reported by the French Academy of Science in 1836. This ability can be improved by the integration of chemical and biochemical strategies.
What is the main problem with polymers? ›
Most polymers, including poly(ethene) and poly(propene) are not biodegradable close biodegradableMaterial that can be broken down in the environment by microorganisms.. This means that microorganisms. cannot break them down, so they: cause a litter problem if disposed of carelessly.
How will self-healing polymer change the future? ›
Self-healing polymers have emerged as a groundbreaking area of research in materials science and engineering, owing to their ability to repair damage thereby extending the life cycle of products and reducing plastic waste and costs.
What are the downsides of using self-healing polymers? ›
Catastrophic failure of the materials may occur due to the growth and merging of the microcracks, which results in the reduction of the service life of the materials. To avoid these problems and increase the service life, early detection and mending of the microcracks are extremely important.
Are polymers good or bad for the environment? ›
Synthetic polymers mainly obtained from petroleum are a major environmental concern. The drilling of petroleum can cause major disruptions to wildlands and habitats, along with potential pollution (such as leakage of toxic substances) from active wells and processing plants.
What is the most sustainable polymer? ›
The most commercially available sustainable polymer is PLA. This cannot currently be recycled, and should be separated in the recycling stream. See below for information on composting of PLA.
Why do we need self-healing materials? ›
Self-healing materials can recover their mechanical properties after fracture. The self-healing materials can save environment and resources by expanding lifetime of the materials.
Microcapsule-based self-healing process. The self-healing ability of polymers can be obtained in two ways. In autonomous self-healing processes, the polymer is encapsulated with small microcapsules that contain the healing agent that is released into the polymer when the capsule shell is damaged.
How do self-healing materials work? ›
When a crack runs through the cured material, it breaks open the micro- capsules. Capillary action draws the monomer into the crack where it is exposed to the catalyst and thus polymerises. The polymerised material binds the two faces of the crack together. The material thus heals itself in response to damage.
What is the fastest self healing material? ›
This suggests that, in terms of healing efficiency, Poly(BCOE-r-UPy1) is one of the fastest H-bonding facilitated autonomous self-healable polymers. We also compared the healing properties of Poly(BCOE-r-UPy)s with other healable polymers in a log–log plot with over 90 % of mechanical recovery [16].
What triggers self-healing materials to react? ›
Reversible covalent bonds in a self-healable polymer enable structural changes and bond arrangement via reversible reactions that are triggered by an external stimulus such as pH, heat, or light.
How do I activate self-healing? ›
This is what natural self healing can and should look like now:
- Deciding to create successful new routines and activating them.
- Exercising healthfully, sleeping more regularly, reducing stress, going out in nature and developing mind-body skills.
Self-healing materials are those smart materials that, after suffering damage, damage, cut or fracture, can return to their original state causing their own repair. These materials have been developed, like many others, based on nature, and more specifically, on the regenerative system of living beings.
What are the advantages of self-healing materials? ›
The key potential benefits of self-healing materials are as follows:
- Minimizing the production cost of various industrial processes required for repairing damage.
- Prolonging the service life of the materials.
- Reducing the inefficiency of the materials due to degradation.
Self-healing hydrogel is an intrinsic polymer, and this special healing ability of hydrogel either comes from the reversible physical or chemical bonds or a combination of those bonds [31]. Other properties of SHH are conductivity, fast adhesion, and stimuli-responsiveness [32,33,34].
Why do we need self-healing? ›
It allows us to address any underlying issues that may be affecting us emotionally, mentally, and physically. When we prioritize our own healing, we can let go of negative patterns and behaviours, develop a more positive mindset, and cultivate healthier relationships with ourselves and others.
