Metallopolymers self-healing

Metallopolymers as an Emerging Class of Self-Healing Materials... 

Furthermore, the supply of thermal energy could also be used to influence the properties of a metallopolymer and to yield the desired effects. For this purpose, Zhou and coworkers utilized phase-separated ruthenium-containing polymers with two glass transition temperatures [71]. The transitions induced the a kind of mobility that is required for the self-healing process [72]. 

This all-embracing example shows that many different stimuli can affect a metallopolymer to result in the desired properties. In particular, the reversibility of the metal-Ugand interaction and the mobility of a metallopolymer are key factors for the implementation of self-healing properties [76, 77]. Additionally, the addressability by other stimuli allows the possibility of triggering healing processes in metallopolymers. 

The above-mentioned properties of metallopolymers are the basic requirements for the generation of self-healing behavior. As a consequence, it is possible to generate a reversible system and to introduce self-healing mechanisms, which is the principle of intrinsic self-healing systems [78-81]. 

Furthermore, Terech et al. presented a self-healing metallopolymer gel that was based on the diterpyridyl moiety polymerized by the addition of nickel irais [99]. The resulting linear polymer exhibited very poor mechanical properties and showed a good healing efficiency due to high flexibility of the polymer itself. 

In 2011, Rowan and Weder et al. described the self-healing properties of a linear metallopolymer. fii order to obtain self-healing behavior, the authors used UV light [44], For this purpose, poly (ethylene-co-butylene) was functionalized with two 2,6-fi/s(l -methylbenzimidazolyl)pyridine moieties at the termini and the subsequent addition of zinc di[Z>/s(trifluoromethylsulfonyl)imide] or lanthanum tri[6/s(trifluoromethylsulfonyl)imide] led to a linear metallopolymer. 

Fig. 6 Demonstration of the self-healing ability of a linear metallopolymer (Copyright 2013 Nature Publishing Group) [44]...

Recently, the basic concept of self-healing metallopolymer networks was improved. For this purpose, the Schubert group utilized cadmium(ll)-bis-terpyridine complexes [101]. A metallopolymer network based on these complexes was synthesized by the addition of cadmium acetate. The authors could show that these materials behave completely different due to a different coordination of the metal center. Presumably, the acetate moiety also coordinates to the cadmium, but this metal-ligand interaction is much weaker, which results in an improved self-healing behavior (Fig. 7). 

---