CoopHeal · Enhancing Self-healing Properties in Polymer Materials through Cooperative Supramolecular Interactions

Enhancing Self-healing Properties in Polymer Materials through Cooperative Supramolecular Interactions

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. Modern society 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. The polymer chains in these materials form a network that is crosslinked through weak, transient, physical bonds, able to connect and reconnect multiple times, which leads to properties that are actually associated with bulk covalent polymers of much higher molecular weight. After damage, these noncovalent bonds are dissociated and separated apart. The generated new fractured interface contains now multiple unbound bonds, which remain “sticky” at the surface for a period of time. Thus, recombination of the two fragments leads to reformation of the bonds closing the gap and healing the damaged site. 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. CoopHeal is focused on giving solutions and alternatives to this problem by introducing cooperative ‘all-or-nothing’ interactions in supramolecular polymers. Hence, our strategy is the synthesis of polymers that combine supramolecular motifs able to strongly bind through multiple and cooperative non-covalent interactions, with polymer chains that are flexible enough to facilitate recombination after damage. This type of materials is able to emulate traditional resins, where their main feature is a high degree of crosslinking (necessary for applications where hardness and rigidity play an important role) by means of hydrogen bonding located at the chain ends, easy to unreticulate by an external stimulus –heat or light- for reprocessing.

Data: CORDIS, © European Union