Morphing Capabilities and Processing Susceptibility of Vitrimers and Vitrimer Nanocomposites

Polymer research has long taken inspiration from nature in a variety of methods (<i>e.g.,</i> shape morphing as motivated by plants and animals). In addition, recent years have seen a boom in recyclable polymer research with increasing efforts towards sustainability. Particular emphasis is placed on vitrimer materials which behave as either thermosets or thermoplastics at low and high temperatures, respectively. In addition to a traditional glass transition temperature (<i>T_g</i>), vitrimers have a second topology freezing temperature (<i>T_v</i>) above which dynamic covalent bond exchange reactions occur. Herein, we demonstrate the self-healing, shape memory, and shape reconfigurability properties of this unique material with an emphasis on understanding how processing conditions impact their recyclability. For example, we demonstrate that increasing the catalyst concentration and compressive stress increases the application space of vitrimers while also increasing their susceptibility to network rearrangement (<i>i.e.,</i> lowered crosslink density and <i>T_g</i>). In addition, a variety of nanofillers (<i>e.g.,</i> graphene, clay) are introduced to make vitrimer nanocomposites. We demonstrate an increase in the <i>T_v</i> as a function of nanofiller concentration and dispersion, while the impact of nanofiller composition is negligible. Furthermore, we establish that the addition of nanofillers increases the self-healing properties of vitrimers while the shape memory and shape reconfigurability properties are unaffected; however, we note that increasing the filler concentration increases the overall composite modulus resulting in less imbedded strain. These photothermally activated composites allow for shape memory and shape reconfigurable applications such as actuators and self-healing components.