Selbstheilende mechanochemische und supramolekulare Polymere

Martin-Luther-Universität Halle-Wittenberg

The current project will address the generation of a self-healing system by combination of two principles of self-healing via encapsulation principles, thus generating self-healing polymers with more than one "self-healing-cycle". Capsules filled with either a multivalent azide/alkyne-polymer will form the "one-healing-cycle" system, whereas a second (supramolecular) healing system will form the basis for multiple healing cycles within the material. The latter principle will be based on two hydrogen bonding systems, one with a relatively long lifetime of association/dissociation (Hamilton-receptor/barbituric acid), the other displaying a short lifetime of association/dissociation (2,6-diaminotriazine/thymine). Both healing principles will rely on liquid polymers bearing multiple (reactive or associative) functional moieties on their chain-ends. Thus multiarm-star-, dendritic- and graft-polymers will be used as encapsulated (polymeric) reagents, with a glass transition-temperature (Tg) significantly below room temperature, so as to retain their liquid flow behavior at room temperature and below. Two main polymers are projected to this purpose: (a) polyisobutylenes (Tg ~ (-70 °C)) and (b) copolymers of (oxy)norbornenes with butadiene (Tg ~ (-90 °C)). Multivalency of all interacting or reactive groups is needed in order to increase the crosslinking density and thus the final mechanical strength of the "healed" material. The presented concept will be extended towards the visualization of crack-formation based on multivalent (alkyne) bearing-polymer and "fluorogenic" dyes that will allow the (visual) detection of the position of mechanical crack-formation via confocal laser microscopy.