As opposed to many natural materials (skin, tree bark, etc.), which can autonomously heal after damage, synthetic polymers unavoidably degrade and their original properties decay over time upon long-term exposure to environmental and working conditions. However, society nowadays demands for materials that are reliable, for safety reasons, durable, to offer prolonged service lifetimes, and cost- and energy-efficient, to preserve natural resources and produce minimum waste and environmental impact. In this context, self-healing polymers are “smart” materials with the ability to repair themselves autonomously or to heal on-demand upon exposure to an external stimulus such as heat, light or pressure. One of the most promising directions considers the use of supramolecular polymers, in which polymer chains are endowed with chemical functions that can associate selectively by means of reversible and dynamic noncovalent interactions. However, the broad commercialization and universal application of self-healing polymers is still hampered by a main problem that resides in the balance between self-healing ability and mechanical properties at working conditions.
Along the ERC-StG project PROGRAM-NANO, we found what could be a quite promising solution, by introducing cooperative effects in supramolecular polymers. Such cooperative effects are responsible for the all-or-nothing behaviour found in biological processes like protein folding, DNA duplex formation, or the classical case of O2 uptake by haemoglobin. In the ERC-PoC POLYHEAL project, a team of scientists has been working to demonstrate that self-healable polymer materials with potential applications as thermoplastics can be obtained using our supramolecular approach. We have optimized a production methodology and tested materials properties with the aim to identify possible market niches. The polymer materials obtained so far retain the supramolecular cooperative characteristics of the attached self-assembling units and combine overall good mechanical properties and sufficient chain mobility for self-healing after damage. Furthermore, we see still a lot of room available and promising opportunities for improving the balance between mechanical and self-healing properties, which will be explored in the future in our group and in cooperation with interested companies.
