PhD Defense, Faculty of Science - Matthew J. Dunlop

“Towards the Scalable Isolation and Utilization of Cellulose Nanocrystals from Tunicates”

FULL ABSTRACT

Prince Edward Island (PEI) has a vibrant aquaculture community and is currently the largest producer of blue mussels in Canada. However, PEI aquaculture is threatened by the growing problems associated with tunicates, an invasive marine animal. To address invasive tunicates mitigation and containment strategies have been employed, but a long- term solution remains elusive. This work demonstrates a direct solution to the problem: treat the tunicates as a resource rather than as a nuisance, harvest them, and convert them to value added products. The value-added products which are the focus of this work are cellulose nanocrystals (CNCs), which are sustainable, highly crystalline, rod-like nanomaterials with a plethora of potential applications. The only CNCs currently available commercially in kilogram scale quantities are obtained from wood pulp (W- CNCs). While these W-CNCs have captured the interest of researchers, industries, and governments alike, they have a limited aspect ratio (AR = length/diameter) which is usually in the range of 10-20. Tunicate derived CNCs (T-CNCs) are a high aspect ratio CNC usually in the range of 50-100, which can complement commercially available W- CNCs in the growing global CNC market. This work demonstrates the isolation of T- CNC at three scales; the initial processing utilized 20 grams of tunicate input, this was then scaled up to 25 kilograms of tunicate input, and finally the largest scale demonstration used 100 kilograms of invasive tunicate as a process input. Various techniques were developed to facilitate the increasing scale of tunicate to T-CNC processing which are described herein. This work represents, to our best knowledge, the largest scale tunicate to CNC processing ever reported, and it moves us closer to directly addressing invasive tunicates on PEI. In addition, this work also utilizes the T-CNC isolated from these tunicates in novel ways. First the differences between W-CNC and T- CNC when dispersed within a polymer matrix were elucidated by preparing and characterizing polymeric nanocomposite materials. Additionally, dispersions of T-CNC and W-CNC are combined to form what are designated as ‘hybrid’ nanocomposites, where multiple CNC sources are combined in a common polymer matrix. These nanocomposites were prepared by laboratory scale techniques such as solution mixing and film casting, but also industrial processes such as twin-screw extrusion. In this work the novel area of hybrid CNC nanocomposites is explored and is documented for the first time in both hydrophilic and hydrophobic polymer matrices. In the case of the hydrophobic polymer, the W-CNC and T-CNC were surface modified to induce hydrophobicity, which was the first time that the particular CNC surface modification had been used in nanocomposites of any kind. In all cases, as expected, T-CNC reinforces the polymer matrix at lower loading levels than W-CNC does. In the case of hybrid nanocomposites, unique mechanical reinforcement trends were documented and are further assessed herein. Also assessed here are the various findings developed throughout the iterative process of scaling up the isolation of tunicate CNC from 20 gram to 100 kilogram tunicate batches. In totality this work represents a significant step towards directly utilizing invasive tunicates for the benefit of local aquaculture, and also describes hybrid polymeric CNC nanocomposite materials, their unique properties, and their promising implications for the first time.

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