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Abstract
Polyhydroxyalkanoates (PHAs) are a promising alternative to traditional petrochemical-based plastics, often compared to polypropylene in their mechanical properties while being fully biodegradable in a variety of environments. An unusual property of native PHA granules is their amorphous structure due to the biological nature of their synthesis. It is critical for the successful commercial production of these polymers that granule crystallization be well controlled during purification; otherwise, the granules coalesce into large masses during centrifugation that are unable to be adequately purified and may damage industrial centrifugal equipment. The research presented in this dissertation elucidates the challenges associated with granule coalescence as well as mechanisms responsible for initiating granule crystallization. Using infrared spectroscopy, the crystallinity of PHA granules in their native environment can be ascertained and various treatments of the granules can be evaluated for their effectiveness to initiate granule crystallization. By ensuring granules are semicrystalline prior to their centrifugation, they are maintained in their native morphology throughout their purification, leading to a higher standard of purity and a polymer that is more stable and suitable for a variety of consumer applications. Additionally, mitigating granule coalescence reduces equipment downtime and material losses. These benefits are relevant to any aqueous PHA purification process and are essential for successful commercialization of these polymers.