Design and Characterization of Double Dynamic Networks Based on Boronic Ester and Imine Dynamic Covalent Bonds

Dual dynamic networks (DDNs) are polymeric materials that combine two (or more) distinct crosslinkers in one system. By coupling different crosslinking strategies, precisely tailored materials can be designed. This thesis explores the implementation of the vitrimer concept into DDNs. Elastomeric vitrimers consisting of two interpenetrated dynamic networks that rely on boronic ester metathesis and on imine-aldehyde exchange, respectively, were designed to this aim. Both reactions proceed via a degenerate mechanism and are orthogonal to each other. By the engagement of two types of dynamic covalent crosslinks, two distinct dynamics are established in each subnetwork. To obtain and evaluate the final DDN, the respective subnetworks were synthesized beforehand, and characterized as single networks. The characteristics of the single networks were tailored individually to fulfill their specific needs in terms of dynamic behavior, processability and dimensional stability. These properties were adjusted by changing the molar mass of the thermoplastic precursors, their degree of functionality, their crosslinking density, or the lifetime of the dynamic bonds. The two networks were successfully united into a DDN. In a comparative study, insights were obtained how the individual subnetworks contribute to the DDN’s properties, and whether synergetic effects arise. In fact, the interpenetrated nature of the vitrimer DDN allows increasing at the time creep resistance and elongation at break, which is really challenging to achieve, yet highly desirable for most elastomers. Over and beyond, the obtained materials show great potential for mechanical and chemical recycling.