Investigation of the Interactions Between Fillers and Dynamic Non-covalent and Covalent Bonds in Self-healing Nanocomposites

Work on self-healing materials has drastically grown over the years as researchers have hoped to improve device lifetime. While first beginning as embedded capsules with self-healing reagents to provide a one-time self-healing event, self-healing research has also expanded into imparting intrinsic self-healing properties by incorporating dynamic bonds into commonly used polymers to achieve repeatable self-healing properties and maintaining original polymer properties. The subsequent dispersion of functional fillers into these self-healing polymers was a logical next step to create self-healing sensors, soft robots, etc. However, like non-self-healing filled elastomers, fillers cannot be arbitrarily added to dynamic elastomers without encountering a loss in self-healing polymers. Often, this limits functional and structural enhancement. While research in self-healing composites has been heavily done, direct insight into the key factors dictating maximum filler content is not fully understood. The overarching goal of this dissertation is to elucidate some of the key interactions that dictate self-healing efficiency in polymer composites. Different systems of self-healing bond time and functional filler time are combined and explored. Specifically, this work explores the different interactions of rigid (carbon nanotubes) and soft (liquid metal) fillers on room temperature self-healing networks, the effect of rigid fillers on on-demand self-healing networks, and the exploration of networks with both room temperature and on-demand dynamic bonds. Via a variety of static and mechanical experiments, this work provides experimental insight on how self-healing networks are affected by filler properties and state. Additionally, we explore how combining two different self-healing bond types can impact self-healing properties. In a larger scope, this work provides insight on the key factors that dictate dynamic properties in self-healing nanocomposites when designing functionalized self-healing composites that demonstrate high functionality and high self-healing efficiency.