Investigation of Polybenzoxazine Vitrimers Based on Dynamic Transesterification Exchange

With the ever-increasing issue of plastic waste production, a greener approach to synthetic processes and increased sustainability in plastic materials is still a high demand. Thermosets, which find uses in applications such as coatings, adhesives, and aerospace composites account for 15% of global plastics production, are particularly problematic in this context, as covalent crosslinks within the material serve both as a source of high-performance stability during use and as a barrier to conventional recycling after use. Therefore, our efforts focus on the incorporation of dynamic transesterification exchange chemistry into polybenzoxazine thermosets, which allows these materials to undergo reprocessing. This investigation highlights the synthesis of novel benzoxazine monomers capable of forming vitrimeric networks and the structure property relationships based on monomer design flexibility. A series of benzoxazine monomer libraries were synthesized to evaluate the structure property relationships based on key factors such as amine selection, ester concentration, and dynamic and non-dynamic functionalities. The thermomechanical and mechanical properties of the resulting networks were evaluated and correlated to the monomer structure. The dynamic behavior of the polybenzoxazine networks was assessed with respect to the topological rearrangement temperature, activation energy, and relaxation times. Reprocessability of the networks were highlighted in Chapter III, revealing retention of thermomechanical properties and reusability of the materials. Flexibility in properties are shown in the networks in Chapter IV, highlighting materials with dynamic capabilities, variable mechanical strengths, and flame resistance. Finally, novel polybenzoxazine vitrimer networks are synthesized in Chapter V, revealing the use of variation in monomer design to further tune and understand dynamic exchange