Sustainable Materials Based on Dynamic Polymer Networks

Prof. Dr. Volker Abetz, Universität Hamburg

Supramolecular polymer networks based on non-covalent crosslinks such as hydrogen bonding have been known since a long time. Also polymer networks based on reversible covalent crosslinks are known (or used without knowing the details) since a long time (vulcanization of natural rubber with sulfur). With the discovery to use precise reversible chemical reactions, such as transesterification by Leibler’s group more than a decade ago, the concept of so-called vitrimers was introduced and has now been extended to many other types of reactions. Vitrimers belong to the class are associative covalent adaptable networks. They have received an increasing interest in the scientific community, as they offer a broad spectrum of thermal mechanical properties between the properties known from thermoplastics or thermoplastic elastomers on one side and thermosets (duroplasts) on the other side. They are malleable materials, which are characterized by keeping their crosslink density constant due to chemical exchange reactions upon deformation, as the crosslinks are reorganized in an associative way rather than dissociated and rebuilt upon deformation above a temperature characteristic for the chemical exchange reaction. Depending on the glass transition temperature and the so-called topology freezing temperature above which the exchange reaction takes place, these in comparison to thermosets more sustainable materials can display a broad range of features, such as plasticity, shape memory and thermomechanical or chemical reprocessability. Here we present vitrimers using different chemically reversible reactions based on vinylogous urethanes, Schiff bases or dioxaborolane chemistry. The basic components are multifunctional amines, aldehydes, alcohols and acetoacetates, which can be of petrochemical or biogenic origin. Also some vitrimer-based nanocomposites with organic and inorganic fillers will be discussed.