Turning aminated polyolefin into a more sustainable polymer via physical and chemical approaches

Aminated polyolefins (APOs) represent a unique class of specialty polymers, due to the amine functionalities on polyolefin backbones. The pendant amines enable self-healing and adhesive behaviour, through dynamic non-covalent interactions. The dynamic non-covalent interactions within APOs enhance cohesive strength, while the amines increase the polymer surface energy and improve the adhesion to a wide range of surfaces. APOs exhibit potential as specialized adhesives for niche applications, however, the dynamic non-covalent interactions promote amine aggregation over time. Aggregation results in reduced adhesion and insolubility that shortens product lifetime. This thesis presents two approaches to improve the sustainability of APOs using process-level and molecular-level strategies, with the goal to extend the functional lifetime of APOs. First, a physical recycling method was developed and optimized to recover APO from a polymer blend. Next, the molecular structure of APO was modified to incorporate cleavable aminal linkages to form a recyclable network. The first approach establishes a process for selective APO extraction from an APO/EVA-40 polymer blend using minimal organic solvents. A solvent/anti-solvent system was identified to recover APO under mild conditions. Solvents were reused to improve the sustainability of the process. The recycled APO maintains its molecular weight, thermal stability, surface topography, and dynamic behaviour, with slight changes in thermal and viscoelastic properties. In contrast, the recycled EVA-40 exhibited reduced thermal stability and crystallinity due to residual APO. Nevertheless, the recycling process was efficient and effective to recover APO with minimal aging, demonstrating the potential for future process scale-up. The second approach introduces dynamic aminal linkages to convert linear thermoplastic APO into recyclable thermosets. The crosslinker, N,N′-diphenyl-N,N′-bis(4-cyclooctene-1-methyl)methylenediamine (a3), was synthesized via CO₂ reductive functionalization. Highly crosslinked APO were rigid and brittle, whereas low crosslinked APO retained dynamic behaviour. A post-polymerization modification of APO with CH₂I₂ crosslinkers afforded para-para methylene linkage with controllable crosslinking density and tunable thermal and rheological properties. Overall, this thesis demonstrates that physical recycling methods and dynamic covalent networks offer viable pathways for enhancing APO sustainability. These findings lay the groundwork for the development of recyclable aminated thermosets.