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The valorisation of biomass is a key step towards reducing the dependence of chemical production streams on non-renewable sources and for the development of a green economy. Sugar beet pulp (SBP), a secondary biomass product from sugar extraction, can be oxidised with hydrogen peroxide and bleach to produce an industrially valuable, viscous, cellulose-rich material called Curran® which is currently used as a rheology modifier for plastics, paints, and cardboard preparative mixtures. This study investigated the effects these oxidants have on cellulose within the plant cell wall of SBP. The physical and chemical properties of Curran® were influenced by the properties of the cellulose within, and these changes have been measured according to the degree of oxidation and surface accessibility of the cellulose against the monosaccharide composition and viscosity of the oxidised SBP, in comparison with similarly oxidised Whatman paper. This was through methods such as conductometric titrations, novel [3H]oligosaccharide adsorption measurements, and successive ammonium oxalate and sodium hydroxide extractions alongside dynamic viscometric measurements and quantification of cellulase digest products. The viscosity of oxidised SBP suspensions was found to be dependent on the stability of parenchymal cell-ghosts. If these collapsed, then the viscosity was dependent on the properties of cellulose. Rhamnogalacturonan-I was found to be linked to the surface of the cellulose in a manner that was resistant to oxidation. Under the acidic hydrogen peroxide free-radical oxidation and alkaline NaOCl oxidation applied, up to 3.5% of all cellulosic glucose residues in SBP were oxidised. Both oxidation treatments in either order were required to produce carboxylic acid groups preferentially over aldehyde or ketone groups; carboxylic acid groups are preferable for further functionalisation. The (NaOH-soluble) hemicellulose a fraction of the material was found to contain oxidised cellulose, fragmented by the H2O2 oxidation step. The sum of these observations showed that hydrogen peroxide fractured the surface of cellulose during oxidation, solubilising pectin that was non-covalently bound to the cellulose surface and splitting aggregated cells into free-flowing units. This modification of the surface of the microfibrils by hydrogen peroxide would create acidic cellulosic fragments that are still water-insoluble at pH 7, but NaOH-extractable. Bleach oxidation is important for whiteness and viscosity improvement, but this introduces chlorine compounds into the waste stream and its use should be limited. To replace NaOCl oxidation, the esterification of cellulose has been suggested for viscosity improvement of oxidised SBP. Finally, the adsorption of [3H]cellopentaitol and [3H]cellohexaitol onto paper in suspension has been tested as a binding assay to estimate the surface accessibility of the cellulose microfibrils. The binding strength of each probe was measured, and this method successfully showed the accessibility of variously oxidised Whatman paper samples.

A healthy diet is rich in dietary fibre (largely indigestible polysaccharides, most of which derive from plant cell walls). Cellulose is one of the main components of plant cell walls and a major contributor to human dietary fibre intake. It is a natural component of food-plants, and can also be added during commercial preparation of foodstuffs. This project investigates the physico-chemical properties of various commercial sources of cellulose that have been empirically found to differ in palatability, especially 'mouth feel', as additives to confectionery. The aim was to explain why these seemingly similar celluloses behave so differently as food additives. Concurrently, I performed comparable studies on plant cell walls (prepared as alcohol-insoluble residue; AIR), sourced from various plant species and tissues. Potential differences between cellulose preparations could include (a) contaminating non-cellulosic polymers, (b) degree of oxidation, and (c) accessibility of cellulosic surfaces to neighbouring solutes. (a) Contaminating non-cellulosic polymers: I performed various studies for chemical composition - digestion with α-amylase for analysis of starch content; washing with phenol followed by Ba(OH)2 hydrolysis for analysis of covalently bound proteins; assay of acetyl bromide-soluble lignin and hydrolysis with trifluoroacetic acid and H2SO4 (followed by thin-layer chromatography) for analysis of hemicellulose relative to cellulose content. These assays did not reveal major differences between the various commercial cellulose samples - all were relatively pure cellulose. Naturally, the AIR preparations were more diverse in chemical composition, containing all the non-cellulose polymers studied (starch, proteins, lignin, hemicelluloses and pectin).

The self-assembly of nanoscale building blocks offers a scalable route to functional materials, but understanding how the properties of the large-scale structure emerge from the behaviour of individual sub-units is a persistent challenge. A notable example is the self-assembly of cellulose nanocrystals (CNCs) into nanostructured films. CNCs are elongated colloidal particles that spontaneously form a cholesteric liquid crystal phase in aqueous suspension. This helicoidal configuration can be preserved as the suspension dries, resulting in films with vibrant structural colour. Although CNCs have attracted growing interest from different research communities over the past few decades, many fundamental questions about CNC self-assembly remain unanswered. This thesis focuses on two of these questions: First, how does the chirality of the CNC mesophase arise? The chiral crystalline structure of native cellulose is widely believed to play a crucial role, but most CNCs are not strongly twisted and exhibit considerable polydispersity in particle size and shape. A detailed analysis of the morphology of individual CNCs was performed, and related to the ensemble behaviour of CNC suspensions. These results indicated that composite CNC particles are essential for the transfer of chirality across length-scales. Second, how does kinetic arrest influence the visual appearance of CNC films? It is well-known that drying of CNC suspensions traps the systems in a non-equilibrium configuration, but the mechanism of kinetic arrest (whether colloidal gelation or glass transition) is unclear. By tuning the both the suspension formulation and particle morphology, the kinetic arrest transition and its effect on the visual appearance of photonic CNC films was both explained and controlled. These findings deepen our understanding of CNC self-assembly and open up new avenues of enquiry for research on bio-sourced nanomaterials.

Hydroxypropyl cellulose (HPC) is a widely utilised, low environmental impact material. When dissolved at high concentrations it forms structural colours via the formation of a cholesteric, liquid crystalline mesophase, termed photonic HPC. Intrinsically biodegradable, edible and mechanochromic, photonic HPC can be manufactured at scale and low-cost in a simple formulation. A high reflectivity also allows for easy integration with common camera technologies. A rich seam of exploration therefore exists for the photonic application that has already begun with the development of various mechanochromic HPC devices. Currently however, its desirable mechanochromic property has only been reported in the liquid state, and despite a good theoretical understanding, an applied characterisation of aqueous HPC's mechanochromic colour-pressure response is lacking in the literature. In this thesis, a dynamic, structurally coloured HPC-gelatin hydrogel is manufactured using only cost-effective, biocompatible, and widely available raw materials. Combined in a readily scalable formulation process (planetary centrifugal mixing), the mechanochromism of HPC is reported in the viscoelastic solid-like (gel) state for the first time. Mouldable as a continuous unsupported solid, while retaining the shear-thinning non-Newtonian response of HPC, the mechanochromic relaxation time is enhanced over the equivalent HPC-water mesophase via an intrinsic elasticity provided through the addition of gelatin. Then, using soft lithographic techniques, a mechanochromic HPC device is developed to investigate aqueous HPC's mechanochromic sensitivity, response times (rise time, latency, mechanochromic relaxation time constant) and cycling performance as a function of its thickness. A standardised microactuating pixel of fixed size and shape is tested, before various pixel sizes, shapes, spacings and array configurations are explored. Our HPC-gelatin hydrogel is then included. We show that HPC mechanochromism is dependent on the applied strain, with a strain threshold between different compression regimes that dictates the mechanochromic outcome. We conclude that with application of a variety of factors, this outcome can be controlled to provide specific effects, details or colour. With our work, a novel insight into HPC mechanochromism is provided to support a movement towards mechanochromic displays using biocompatible hydroxypropyl cellulose.

As we transition towards a more sustainable society, high-performance bio-based materials are increasingly required. In this context, cellulosic materials hold exceptional promise as they are derived from abundant and bio-sourced feedstock, and they are able to self-assemble into nanoscale architectures. More specifically, several cellulose derivatives exhibit a cholesteric liquid crystalline phase in solution, displaying vibrant structural colours. Amongst them, water-soluble hydroxypropyl cellulose (HPC) is ideal for developing sustainable photonic materials to replace toxic dyes and pigments. The development of photonic HPC materials has been, so far, hindered by the difficulty to retain colouration in solid-state films. In this study, three methods to preserve the colour of HPC-water mesophase in the solid-state were developed, and each of these methods yielded different optical or mechanical behaviour, resulting in materials with a variety of functionalities. Firstly, by combining chemical crosslinking and heat treatment, photonic films across the entire visible spectrum were obtained and instead of the typical metallic iridescence associated with HPC mesophases, these films appeared matte and angular independent. Secondly, a functionalised HPC polymer was exploited as an ink to achieve direct 3D printing of photonic structures, which colour could be tuned by exploiting the lyotropic and thermotropic properties of HPC. Lastly, a strategy to develop HPC gels using supramolecular chemistry was explored, leading to photonic gels crosslinked via host-guest and π-π interactions. Through these studies, a toolbox has been developed to tailor the optical properties of HPC and other cellulosic liquid crystals, paving a path towards sustainable cellulose-based photonic systems.

Structural colour arises from the constructive interference of light with a material structured on a lengthscale corresponding to optical wavelengths. This phenomenon is responsible for the appearance of many of the brightest colours in nature and recently the existence of structural colouration in plants has been demonstrated across multiple species. This thesis extends our understanding of the effect specifically in fruit epidermal tissues, it uses the physical principles underlying structural colour to understand biological development and it extracts design ideas from biological tissues to enhance the optical response of biomimetic materials. In more detail, this thesis reports the optical characteristics and architecture of structural colour in several fruits of the genera Pollia and Viburnum. Previous work showed that the external cells of Pollia condensata fruits have extremely thick cell walls which act as photonic crystals to reflect circular polarised light. Here, the spectral and morphological characteristics of photonic cell walls in this and three other Pollia species are reported and it is shown that the unusual right handed circular polarisation reflection is apparent in only P. condensata. It is also shown that the occurrence of right circular polarisation is associated with longer wavelength reflection. This thesis extends this analysis by demonstrating the use of structural colour to observe the development of thickened cell walls in Pollia condensata and Pollia japonica using optical microscopy. It is shown that during development, cell wall material is built up gradually and with a fixed structural periodicity in both species, and that significant cell wall growth occurs in the earliest stages of the long fruit maturation period. In the other genus investigated, structural colour analysis is extended to the fruits of Viburnum tinus and Viburnum davidii and found to arise from layers of globular vesicles in the specialised cell wall. Inspired by these studies, a novel templating technique for reflective self-assembled cellulose nanocrystal films is described, which mimics the morphology of Pollia cells by successfully introducing a curvature in the photonic multilayer whilst maintaining its optical response. Enhancement of the angular independence of light reflected from this curved surface is demonstrated.

Wood from coniferous trees is an important source of renewable biomass. It can contribute to provision of carbon neutral energy, biomaterials and housing for a growing population. Softwood is mainly composed of cellulose, galactoglucomannan, xylan and lignin. This thesis focuses on the biosynthesis and function of Glucuronic acid (GlcA) decorations on softwood xylan. Results demonstrate that this GUX (GlucUronic acid substitution of Xylan)-dependent xylan branching is critical for the maintenance of biomass recalcitrance in a model vascular plant Arabidopsis thaliana. Experiments employing in vitro and in planta activity assays show that conifer transcriptomes encode at least two distinct GUX enzymes which are active glucuronosyltransferases. Interestingly, these enzymes have different specific activities, with one adding evenly spaced GlcA branches and the other one being able to add consecutive decorations. It is possible that these different patterns of xylan branching may have an impact on ability of xylan to interact with cellulose fibrils. To investigate the role for xylan binding to cellulose, Arabidopsis mutant plants in which this interaction is lost were evaluated alongside transgenic mutant lines in which the interaction may be restored. Results of this analysis indicate that the presence of cellulose-bound xylan might have an influence on plant vasculature integrity and thus it may have an effect on plant growth and biomass properties. Moreover, further results indicate that some xylan cellulose interaction is likely to occur in cell wall macrofibrils which can be detected in softwood. Taken together, this thesis provides insights into the process of conifer xylan glucuronidation and the possible role these branches may be playing in the maintenance of softwood recalcitrance and mechanical properties. In addition to identifying potential mutagenesis targets for improving softwood processing, this work is a proof of concept for the use of GUX enzymes for in vivo and in vitro biosynthesis of novel xylan structures with potential industrial application.

Structural colours are produced by constructive interference of light scattered from periodically arranged interfaces within nanostructured materials. A common strategy of plants to achieve structural coloration consists of assembling cellulose microfibrils into helicoidal structures. Examples of these architectures can be found in phylogenetically distant species and in different tissues of plants, such as in the endocarp of the fruit of Margaritaria nobilis, an eudicot, and in the fronds of Microsorum thailandicum, a fern. In this thesis, I studied the optical response and anatomical features of the adaxial and abaxial epidermal layers of cells of M. thailandicum. The optical variation between fronds, between cells, and within cells, both for the adaxial and abaxial surface, were quantified by polarised optical microscopy and microspectroscopy. The adaxial reflection is mainly in the blue range (400-550 nm), with a narrow distribution of reflection peak maxima and peak widths, while the abaxial reflection spans almost the entire visible range (400-650 nm), and spectra are broader and show more varied features. The anatomical structure responsible for this optical behaviour was confirmed by electron microscopy. Numerical modelling based on the microscopy data indicates that there is much more complexity in the helicoidal architecture than just simple local defects. The significant difference between the adaxial and abaxial epidermal cell walls hints at fundamental differences in their biosynthesis. For the endocarp of the fruit of M. nobilis, I correlated the optical response to the ultrastructure of the secondary cell wall, and the morphology and chemical structure of its main components, cellulose and xylan. The composition of the endocarp was characterised as 9% extractives, 36% cellulose, 23% xylan, and 30% lignin. The cellulose microfibrils were isolated in a long series of chemical purifications, and found to be extremely short - around 500 nm - and highly crystalline, as determined via nuclear magnetic resonance spectroscopy and X-ray diffraction. Xylan was found to be the most abundant hemicellulose and its primary structure was characterised via enzyme digestions, gel electrophoresis and mass spectrometry. It has acetyl groups on every other xylose unit, no arabinose and around 4% of glucuronic acid decoration. By combining the information on the xylan with the morphological characteristics of the cellulose microfibrils, I speculate about their assembly into the helicoidal architecture during the cell wall biosynthesis, based on findings from coarsed-grain modelling, and on their interactions in the final tissue, based on small angle X-ray scattering studies.

Structural colours arise from the interaction of visible light with nano-structured materials. The occurrence of such structures in nature has been known for over a century, but it is only in the last few decades that the study of natural photonic structures has fully matured due to the advances in imagining techniques and computational modelling. Even though a plethora of different colour-producing architectures in a variety of species has been investigated, a few significant questions are still open: how do these structures develop in living organisms? Does disorder play a functional role in biological photonics? If so, is it possible to say that the optical response of natural disordered photonics has been optimised under evolutionary pressure? And, finally, can we exploit the well-adapted photonic design principles that we observe in Nature to fabricate functional materials with optimised scattering response? In my thesis I try to answer the questions above: I microscopically investigate $\textit{in vivo}$ the growth of a cuticular multilayer, one of the most common colour-producing strategies in nature, in the green beetles $\textit{Gastrophysa viridula}$ showing how the interplay between different materials varies during the various life stages of the beetles; I further investigate two types of disordered photonic structures and their biological role, the random array of spherical air inclusions in the eggshells of the honeyguide $\textit{Prodotiscus regulus}$, a species under unique evolutionary pressure to produce blue eggs, and the anisotropic chitinous network of fibres in the white beetle $\textit{Cyphochilus}$, the whitest low-refractive index material; finally, inspired by these natural designs, I fabricate and study light transport in biocompatible highly-scattering materials.

Molecular dynamics (MD) simulations have been applied to study the interactions between different carbohydrates and graphene. In cellulose-graphene complexes, the behaviour of hydrophobic and hydrophilic faces of cellulose chains on a single layer of graphene in aqueous solvent have been investigated. The hydrophobic cellulose face forms a stable complex with graphene and the interface remains solvent-excluded over the course of the simulation. Cellulose chains contacting graphene preserved their intra- and inter-chain hydrogen bonds and maintaining a tg orientation of its hydroxymethyl groups that is similar to that found for the sugar in a vacuum environment. The solvent-exposed cellulose chains of the complex showed more flexibility. By contrast, over the course of the 300 ns MD simulation, the hydrophilic face of cellulose exhibits progressive rearrangement as it seeks to present its hydrophobic face, with disrupted intra- and inter-chain hydrogen bonding; sequential residue twisting to form CH-pie interactions with graphene; and permeation then expulsion of interstitial water. This transition is also accompanied by a more favourable cellulose-graphene adhesion energy as predicted at the PM6-DH2 level of theory. The stability of the cellulose-graphene hydrophobic interface in water reflects the amphiphilicity of cellulose and provides insight into favoured interactions within graphene-cellulose nanocomposites. Furthermore, water is observed to permeate cellulose during rearrangement of the hydrophilic face which may have application in addressing cellulose recalcitrance. In addition, the interaction of six different types of monosaccharide (β/alpha-D-Glc, β/alpha-D-Gal and β/alpha-D-Man) on the surface of graphene has been studied, using PM6-DH2 and PMF calculations in both gas phase and explicit water. The parameters studied included anomer, epimer, saccharide face, hydroxymethyl orientation and solvation. Binding of graphene to monosaccharide is more preferred in vacuum than in water; solvation of the complexes leads to reduction in the number of pie-interactions formed with graphene. In almost all studied complexes, β-anomers bind stronger to graphene compared to alpha-anomers in gas phase and water. Each monosaccharide has two unique faces parallel to the plane of the pyranose ring and these surfaces determine the interaction formed with graphene and water. Binding of graphene with different faces significantly influences the value of the computed interaction and binding free energy. We also find that the interactions between graphene and saccharide are mainly controlled by the number of CH-pie and OH-pie interactions formed between saccharides and graphene. The interaction energy and binding energy values suggest that the a-face of β-D-Glc is the most preferred to bind on graphene in vacuum while the b-face of β-D-Glc is preferred in the aqueous phase.

Silver nanoparticles (sub 10 nm), supported on, or in, cellulose, have been demonstrated to be well stabilised and immobilised during application in a model continuous reaction: the reduction of 4-nitrophenol (4-NP) to 4-aminophenol with sodium borohydride. The production of these silver nanoparticles (NP), within the cellulose supports, was carried out by either in situ reduction of silver precursors absorbed into the preformed cellulose supports, or, by inclusion of ex situ synthesised NPs (prepared in DMSO solutions) in the dissolution of cellulose and trapping upon subsequent coagulation of cellulose. The effects of NP synthesis method (affecting particle size and agglomeration) and the cellulose morphology and porous structure were examined with respect to the catalytic activity of the materials. The in situ reduction of a silver salt with aqueous NaBH4 solutions (0.03 to 1.0 wt. %) led to tuneable Ag NP sizes with mean diameters of 5 to 11 nm (TEM) and metal loadings of 0.5-1.0 wt. %. The catalytic activity of these samples in the 4-NP reduction reaction (0.05 mM, 0.167 M NaBH4, 30 °C) was demonstrated to increase upon decreasing NP size: TOF values of 22–356 h-1, consistent with a Langmuir-Hinshelwood mechanism. The porous structure of these Ag-cellulose materials (0.2 to 294 m2 g-1) was demonstrated to be variable and dependent on drying treatments of the regenerated cellulose hydrogel. Thermal drying, freeze-drying and critical point drying resulted in materials with different bulk structure and porosity. In turn the different porosities resulted in extremely different catalyst activities, e.g. Ag-cellulose catalyst (0.3 mm disks) thin film, hydrogel and cryogel phases exhibited TOF values of 2, 12 and 178 h-1, respectively. In addition, the NP synthesis could be carried out in either the cellulose hydrogel or cryogel, which led to different extents of Ag NP catalyst stabilisation against agglomeration during the 4-NP reaction and catalyst recovery and recycling. The Ag NPs synthesised in the cryogel cellulose disks were observed to undergo agglomeration (TEM) after use in 4 repeat batch reductions, whilst those NPs synthesised in the hydrogel cellulose, prior to freeze-drying to the final cryogel catalyst material, did not exhibit any agglomeration upon 4 repeat reduction reactions. The ex situ reduction of Ag and Au NPs was carried out by the reduction of AgOAc and Au(OAc)3 by DMSO and variation of the NP synthesis parameters, such as time (10 min – 1h) and temperature (50 – 80 °C), allowed for control of the NP sizes (3 to 6 nm Ag NPs and 4 to 11 nm Au NPs, TEM). It was demonstrated that the addition of the polysaccharide starch (0.42 wt. % in DMSO) allowed for consistent Ag NP size (ca. 4 nm) to be achieved throughout the 8 h synthesis, the starch acting as both the reducing and capping agent, maintaining the small sizes and narrow particle size distributions of the NPs upon aging (72 h). A kinetic model with a bimolecular nucleation step was developed to describe this reduction of the silver acetate by the starch/DMSO system. However, contact of the NPs with solutions of imidazolium ILs, 1-Ethyl-3-methylimidazolium acetate (EmimOAc) and 1-Butyl-3-methylimidazolium chloride (BmimCl) in DMSO, used in the dissolution of cellulose, led to the oxidation of the Ag(0) and Au(0) NPs. Thus, when these NP solutions were mixed in cellulose solutions regeneration by phase inversion with the aim of preparing cellulose/NP composites led to materials with negligible metal loadings (AAS). This oxidation, of the metal NPS, was partially overcome by stabilisation of the starch capped Ag NPs by pre-treatment with cellulose (1:1 mixture of α and MC cellulose). However, the activity of the resulting Ag-cellulose catalyst (0.5 wt. % AAS, 6.7 nm TEM) was much lower than the Ag-cellulose catalysts prepared by in situ reduction of silver in the cellulose hydrogel, despite the comparable NP sizes. This was presumed to be a result of encapsulation of the Ag NPs by the cellulose, leading to a decrease in the accessible surface of the NPs. Finally, the use of Ag NP / cellulose composites, prepared by in situ reduction of silver in cellulose hydrogel beads (0.19 wt. %, 6.4 nm), were demonstrated in the continuous reduction of 4-NP in a packed bed reactor (τ’ 100 g s dm-3). The activation energies of the reactions of 4-NP catalysed by the Ag-cellulose catalyst materials were determined (3.2 to 9.4 kJ mol-1) from Arrhenius plots, which demonstrated that above 20 °C the reaction was likely subject to diffusion limitations in the cellulose beads. The high degree of stabilisation of the Ag NPs against agglomeration imparted by the cellulose support was demonstrated: the rate of reaction was observed to be constant over 120 h, treating 45 L of 4-NP solution, with the catalyst material after use demonstrating no significant leaching of silver, or agglomeration, of NPs (AAS, TEM).

Simple, reliable and cost-effective methods for detecting pathogens are a vital part of diagnostics inside and outside the clinic, in particular in the developing world. Paper based colorimetric techniques are a promising approach for biosensors and bioassays as they can be used at the point of sampling and require little equipment. This study reports on the development of a colorimetric cellulose bioassay that can detect pathogen DNA with covalently attached single-stranded DNA probes. Chemical activation of cellulose via tosylation and oxidation was investigated. The successful activation of cellulose was characterised by Fourier transform infrared spectroscopy, scanning electron microscopy and elemental analysis. Sulfhydryl and amine functionalised oligonucleotide probes complementary to a segment of IS6110 element in Mycobacterium tuberculosis genome were covalently immobilised on the cellulose strips for recognition of target nucleic acid. The detection of biotinylated target oligonucleotides was achieved with horseradish peroxidase (HRP) linked to streptavidin that binds biotin with high affinity. HRP catalysed the oxdidation of tetramethylbenzidine by hydrogen peroxide. The successful assay was confirmed by the appearance of blue coloured spots on cellulose strips incubated with biotinylated target oligonucleotides complementary to the surface attached probe. The study also showed that tosylated cellulose is more reliable for the detection of targets. Initial experiments have shown sensitivity upto 0.1 µM and considerable specificity. High probe immobilization efficiencies (>90%) have been observed. The assay was also effectively demonstrated with mycobacterial DNA. Additionally, the development of a label free assay based on a dual-probe approach was investigated, but did not yield conclusive results. The developed assay has the potential for use as a simple test for the detection of pathogen DNA in clinical samples since it requires minimal equipment and is cost effective. In addition, it also shows the potential use of tosylated cellulose as a prospective surface for attaching other types of biomolecules in an active conformation.

Abstract: The increasing demand for food containers, along with growing petroplastics concerns and Canada's single-use plastic ban, led to an interest in replacing petroplastics with renewable, biodegradable materials like cellulose. Wheat is one of the main cereal crops produced in Canada, and thus, large amounts of wheat straw, which is mainly composed of cellulose, is produced annually. Recently, cellulose and cellulose-based materials have been demonstrated to have potential as packaging materials. To isolate cellulose, conventional treatments that involve corrosive and toxic solvents have been used. The objectives of this thesis were to study cellulose isolation processes from wheat straw, including pressurized water + ethanol mixtures and alkaline hydrogen peroxide, with further fibrillation using high-intensity ultrasound (HIUS) to develop sustainable materials for potential food packaging applications. Furthermore, the effect of the incorporation of calcium carbonate and glycerol on the materials chemical properties was also studied. The samples treated with subcritical water and pressurized 20% aqueous ethanol (20% EtOH) showed the highest and the lowest contents of cellulose and hemicellulose, respectively. However, the pressurized 20% EtOH treatment removed more lignin. Therefore, the combination of pressurized 20% EtOH and alkaline hydrogen peroxide for 2.5 h resulted in a cellulose-rich solid residue with a cellulose content of 85.48±0.65%. Then, the bleached solid residue was dispersed and subjected to HIUS treatments up to 1200 W for 6, 13, and 20 min, resulting in a wide range of micro/nanofibers. The addition of calcium carbonate in the cellulosic micro/nanopapers produced a significant change in the water interactions with the cellulosic matrix. This research contributed to the understanding of cellulose isolation from wheat straw utilising pressurised water + ethanol mixtures hydrolysis, along with the generation of valuable co-products such as phenolics, carbohydrates, and minerals, hence fostering a circular economy in the wheat production and processing industry.

Cellulose ethers are valuable matrices for drug-delivery systems (DDS), namely amorphous solid dispersions (ASD). ASD are efficient vehicles that can solubilize and stabilize poorly soluble drugs by increasing the time that it takes for drugs to crystallize, thereby allowing higher drug concentrations and providing increased bioavailability. However, most commercially available cellulose derivatives were not specifically designed for this application, leading to gaps in understanding the key mechanisms by which ASD operate. This creates the need for polysaccharide derivatives specifically conceptualized for ASD and for elucidating structure-property relationships. In this dissertation, I successfully demonstrated regioselective and chemoselective techniques to functionalize cellulose to prepare new ASD as well as smart tracking devices. I efficiently and successfully create complex structures via appending bile salt substituents using olefin cross-metathesis. I ascertained that high performance crystallization inhibitors can be achieved with enhanced hydrophilicity by the marriage of two classes crystallization inhibitors (cellulose and bile salts), as illustrated with the commercial, fast crystallizing prostate cancer drug, enzalutamide. I obtained ketone-functionalized cellulose derivatives using oxidation chemistry to produce fluorescent poly- and oligosaccharides (hydroxypropyl cellulose, hydroxypropyl methylcellulose, and hydroxypropyl beta cyclodextrin). Schiff-base chemistry was then explored to append a commercially available fluorescent label, Nile Blue. Due to the dynamic nature and hydrolytic lability of Schiff-bases, I applied reductive-amination chemistry with either one pot, or two-step techniques and evaluated the efficiency of these approaches. I characterized the new fluorescent polymers, and with the objective of elucidating ASD mechanisms, I investigated their response in solvents of different polarities to probe environment-sensitivity. Flavonoids are interesting drug candidates; they have been explored for many biomedical applications, including as inducers of apoptosis and functioning as antioxidants by radical scavenging. I prepared high-performance ASD polymer candidates, then prepared and characterized ASDs with different loadings of the flavonoids, genistein and quercetin. I explored the performance of polymers with different functionalities, hydrophilicity/hydrophobicity, and carboxylic acid content (cellulose acetate glutarate, 5-carboxypentyl hydroxypropyl cellulose, and hydroxypropyl methyl cellulose acetate succinate as positive control) by using in vitro dissolution studies. In this screening process, I determined that cellulose acetate glutarate provides the most advantageous enhancement, possessing the appropriate amphiphilicity to increase drug concentration in this study, supported by the similarity of the polymer and drug solubility parameters. I was further able to confirm via polarized light microscopy that advantageous nanodroplet formation occurs during the drug-release process.

This project investigated the potential for the regeneration of fibres from cotton-based waste garments. The project focused on the preparation of the cotton waste pulps and assessed the suitability of the prepared material for regeneration of ReCell fibres. Mechanical processes have been developed to degrade the fabrics into a fibrous pulp potentially allowing easier fibre dissolution and purification in the fibre regeneration processes. Wet degradation and dry degradation methods were evaluated and the optimal method identified. It was established that the wet deconstruction method could produce fibres with longer length and lesser degradation of the cellulose than the dry deconstruction method. The pulp produced by wet deconstruction methods could be formed into sheets which were stronger than the pulp produced by the dry deconstruction methods. Although the cotton pulp reclaimed by the wet deconstruction methods requires extra energy to dry, it is still the most attractive processing route since the pulp will be transported to the fibre spinning plant in the form of dry cellulosic sheets. Methods for stripping off the easy care finishes in order to increase dissolution of the cellulosic garments were optimised. The stripping performance was assessed by fibre degradation, contents of the easy care finishes, and solubility of the stripped fibres in selected solvents. It was established that a combination of acidic and alkaline treatment can effect the removal of all easy care finishes and enable efficient dissolution of the pulps for fibre making. ReCell fibres were produced from 100% reclaimed material and a blend of reclaimed cotton pulp and wood pulp and structural and mechanical properties were characterised and compared to the existing Lyocell fibres. It was established that for easy separation of non-cellulosic material from the cellulose-based waste garment pulp the fibres must be modified to avoid formation of tufts. Fibre enrichment by gravity separation was recommended as a pre-requisite process prior to wet cyclone separation and the optimisation of the process was recommended for future work. ReCell processing of dyed waste garments, fibre spinning, fabric construction and wet processing of ReCell fibres have been recommended for future work. The results from this project will be used for pilot tests and later commercial production of ReCell fibres by Lenzing Company. Commercial production of ReCell fibres will contribute to the reduction of economic and environmental challenges caused by textile wastes. Moreover, the findings have identified a potential reduction of pressure on raw material for fibre production by providing an alternative source of material for regeneration of cellulosic fibres.

The enzymatic deconstruction of lignocellulosic plant biomass is performed by specialist microbial species. It is a ubiquitous process within nature and central to the global recycling of carbon and energy. Lignocellulose is a complex heteropolymer, highly recalcitrant and resistant to hydrolysis due to the major polysaccharide cellulose existing as a crystalline lattice, intimately associated with a disordered sheath of hemicellulosic polysaccharides and lignin. In this thesis I aim to transfer the highly efficient cellulolytic mechanism of the bacterium Cellulomonas fimi, to that of a suitably amenable and genetically tractable expression host, in the hopes of better understanding the enzymatic hydrolysis of lignocellulose. Using tools and concepts from molecular biology and synthetic biology, I constructed a library of standardised genetic parts derived from C. fimi, each encoding a known enzymatic activity involved in the hydrolysis of cellulose, mannan or xylan; three of the major polysaccharides present in lignocellulose. Characterization assays were performed on individual parts to confirm enzymatic activity and compare efficiencies against a range of substrates. Results then informed the rational design and construction of parts into modular devices. The resultant genetic devices were introduced into the expression hosts Escherichia coli and Citrobacter freundii, and transformed strains were assayed for the ability to utilize various forms of xylan, mannan and cellulose as a sole carbon source. Results identified devices which when expressed by either host showed growth on the respective carbon sources. Notably, devices with improved activity against amorphous cellulose, crystalline cellulose, mannan and xylan were determined. Recombinant cellulase expressing strains of E. coli and C. freundii were shown capable of both deconstruction and utilization of pure cellulose paper as a sole carbon source. Moreover, this capacity was shown to be entirely unhindered when C. freundii strains were cultured in saline media. These findings show promise in developing C. freundii for bioprocessing of biomass in sea water, so as to reduce the use of fresh water resources and improve sustainability as well as process economics. Work presented in this thesis contributes towards understanding the complementarities and synergies of the enzymes responsible for lignocellulose hydrolysis. Moreover, the research emphasizes the merits of standardizing genetic parts used within metabolic engineering projects and how adopting such design principles can expedite the research process.

Macromolecular structures, such as lignin and cellulose, are important components of soil organic carbon, the major terrestrial global carbon pool. The degradation of these macromolecules, including lignin and cellulose, in plant-derived soil organic matter, is important to the global carbon cycle. In grasslands, saprotrophic (decomposer) fungi are major decomposers of such organic material. Some of these compounds, such as lignin are relatively resistant to decay by the microbial community if compared with other compound classes such as cellulose. In this work we investigate the involvement of fungi in the decomposition of both lignin and cellulose and look to link the decomposition processes observed in the field to those observed in a laboratory-controlled environment. The key findings of this work are:- Field based experiments in both tropical and temperate environments indicated that lignin can be degraded completely, most likely by white-rot fungi, as shown by the shifts in the [Ac/Al]S, [Ac/Al]G and [S/G] relative lignin decomposition state proxies. The results confirm that even in a very low carbon environment, fungi are able to completely degrade lignin over time. However, lignin is degraded much faster in tropical environments. Culturing experiments showed that it was possible to isolate a number of fungi present on the degraded wheat straw collected in the field, especially soft-rot fungi. When used in microcosm experiments using a range of organic substrates, the relative lignin decomposition state proxies indicated that Absidia cylindrospora and Trichoderma koningii are not able to completely degrade lignin but preferentially degrade cellulose. Cellulose degradation rates are much higher than those of lignin in degraded field samples over time, confirming previous work.

Plant cell walls play a central role in cell growth and morphogenesis. All plant cells have a primary wall. The formation of a secondary cell wall is restricted to particular cell types, such as the xylem cells, highly lignified cells that provide support and transport functions to the plant. The mechanisms regulating secondary cell wall biogenesis remain largely unknown. To identify genes involved in such mechanisms, a genetic screen for mutants with altered xylem development in the primary root of Arabidopsis thaliana has been conducted. Three different classes of mutants were identified. They are characterised by increased number of xylem strands (m"), altered timing of protoxylem differentiation (tpx) and ectopic lignification (eh). Initial characterisation of the mutant phenotypes, establishment of different complementation groups and their map position in the Arabidopsis genome has been determined. Mutations in the EL [I locus have been characterised in further detail. The eli l mutants exhibited ectopic lignification of cells throughout the plant that never normally lignify. Xylem cells in elil were misshapen and failed to differentiate into continuous strands, causing a disorganised xylem. elil mutants also exhibited altered cell expansion resulting in a stunted phenotype. Abnormal distribution of cellulose and lignin was observed in elil cell walls. Ultrastructural analysis of elil cell walls using an anti-lignin antibody has revealed that that the ectopic deposition of lignin-like compounds occurs within an altered secondary wall. Furthermore, other previously described cell expansion mutants, such as lit, rswl (at the conditional temperature) and det3, exhibited lignification patterns reminiscent to that of elil mutants. Analysis of the genetic interactions of elil with the lit mutant revealed that ELlI and LIT genes act in independent pathways to control cell expansion. These results, together with the double mutant analysis of eli l with other cell expansion mutants suggested a link between cell growth and differentiation of secondary thickened walls. Map-based cloning placed the ELJ1 gene in a 140-Kb interval on the top arm of Arabidopsis chromosome V. A candidate gene approach was used that identified a gene encoding a cellulose synthase catalytic subunit (CesA), AthCesA-3 as a candidate. Sequence analysis revealed that the AthCesA-3 gene is mutated in two elil alleles sequenced, both mutations leading to amino acid substitutions. Initial complementation experiments of elil plants with the wild type AthCesA-3 gene appeared to restore the wild type phenotype, suggesting that mutations in the AthCesA-3 gene gave rise to the elil phenotypes. These studies represent an important contribution to our understanding of the molecular mechanism of cellulose deposition during cell expansion and secondary cell wall deposition during plant morphogenesis.

Xyloglucans are an important class of plant hemicellulosic polysaccharide and fulfil two roles in plants. They are major components of the specialised storage cell walls of some seeds, functioning as energy reserves. They are also present in primary cell walls where they are associated with cellulose in the cellulose/xyloglucan network This network is considered to play a role in the maintenance of structural integrity and the regulation of cell growth. To examine the way in which the structural features of xyloglucan affect the xyloglucan/cellulose interaction an in vitro system modelling the network has been developed (Whitney SEC, Brigham JE, Darke AH, Reid JSG, Gidley MJ, The Plant Journal, 8, 1995). This involves extrusion of cellulose by a Gram negative bacterium Acetobacter xylinus (formerly Acetobacter acetii ssp. xylinum ATCC 53524) into a medium containing xyloglucan resulting in a xyloglucan/cellulose matrix. This thesis examines the interaction between enzymatically tailored tamarind seed xyloglucan and in vitro produced cellulose. Four xyloglucan-specific hydrolases were purified from nasturtium cotyledons. Three of these enzymes, p-galactosidase, nasturtium xyloglucan endoglucanase / endotransglycosylase (NXET), and a-xylosidase, were then used to obtain structurally modified xyloglucans. The performance of these tailored xyloglucans in the Acetobacter model system was then investigated using biochemical techniques, '^C-NMR, Uniaxial Tensile Testing and Deep-Etch Freeze-Fracture Transmission Electron Microscopy. The p-galactosidase was used to produce xyloglucans with 30% and 60% galactose depletion and characterisation of the resulting composites methods showed that increased removal of galactose from xyloglucan reduced its solubility and caused it to self-aggregate, rendering it unavailable for association with cellulose. Several approaches to the selective removal of xylose were explored. Xylose-depleted xyloglucan was obtained by the concerted action of a-xylosidase and NXET. Characterisation of the resulting cellulose/xyloglucan composites showed very little association with cellulose due to the lowered molecular weight of the tailored xyloglucan.

This thesis examines the interaction of xyloglucan, the major hemicellulosic component of type I primary plant cell walls, with cellulose. Initial attempts to form xyloglucan-cellulose complexes by in vitro association methods are described, which gave low levels of interaction, with features not similar to those found in primary wall networks. The majority of the work focusses on the use of the bacterium Acetobacter aceti ssp. xylinum (ATCC 53524), which synthesise highly pure, crystalline cellulose as an extracellular polysaccharide. Addition of xyloglucan to a cellulose-synthesising bacterial culture results in the formation of cellulose-xyloglucan networks with ultrastructural and molecular features similar to those of the networks of higher plants. Applicatioon of the bacterial fermentation system is extended to incorporate the polysaccharides glucomannan, galactomannan, xylan, mixed-linkage glucan, pectin and carboxymethylcellulose, all of which impart unique architectural and molecular effects on the composistes formed. Preliminary data on the mechanical properties of composite structures under large and small deformation conditions are also described.

Responsive and functional microcapsules have many envisioned applications, spanning uses as diverse as drug delivery, cell protection, pollution mitigation, and cosmetics. The vastmajority of capsules are made from rigid cross-linked polymers ormetals that are strong but inflexible, restricting their applications in some sectors. There is then a strong need to develop flexible but robust structures using sustainable materials as a basis for new multifunctional capsules. Bacterial cellulose microcapsules have been developed with a highly flexible but strong fiber mesh structure that will enable engineering of new multifunctional capsule forms. The strong but sparse capsule structures possess key length scales from nanometers to millimeters and can be used as substrate for various surface modifications while still acting as flexible enclosures for chemical cargo. This work demonstrates three newuses of the particles: First, the low-density cellulose capsules are functionalized with metal organic framework (MOF)-enzyme groups that convert them into active particle motors, propelled by reaction with dissolved hydrogen peroxide. Unlike solid micromotors, the capsules can compress in response to confinement, using their surface reaction to navigate through narrow passages without damage. A second modification of the capsules by grafted poly-NIPAM makes the capsules temperature-responsive as well as tuning their permeability and elasticity. The highly elastic capsules can absorb and expel liquid during temperature-induced contraction and swelling, providing active uptake, release, and mixing of the liquid cargo. Finally, drying of the native bacterial cellulose microcapsules is studied to assess their ability to undergo extreme compression, store elastic energy, and mimic pollen’s self-sealing capabilities. In the course of the drying process, capillary forces induce stress leading to cellulose fiber alignment and pore closure and permanent deformation of the cellulose microcapsule. However, adding a negligible amount of biodegradable polymer like carboxymethyl cellulose prevents permanent bundling of the cellulose fibers. As a result, the millimeter-scale capsule converts to a nano-scale thin disk during drying but then recovers to its initial dimension by re-hydration, experiencing 1000 times change in volume. The modified bacterial cellulose microcapsule is proposed as a new class of soft and flexible multifunctional material capable of active motion, response, and deformation to supplement conventional microcapsules.

With a globally increasing population and largely unchecked consumption of raw materials, human society is on track for devastating consequences. Two industries responsible for utilizing massive amounts of raw materials and generating equally gargantuan quantities of waste are the packaging and infrastructure sectors. In 2017 in Europe, for example, packaging reached a record 173 kg of packaging waste per capita. One of the largest packaging consumers is the food industry, in which 40% of packaging is made of petroleum-derived single-use plastic, leading to a massive carbon imbalance. “The Built Environment,” on the other hand, is responsible for about 50% of all extracted raw material from the earth. In the EU the construction industry accounts for more than 35% of all waste that is generated while also being responsible for 5–12% of greenhouse gas emissions. Unfortunately, society’s reliance on packaging and infrastructure is only forecast to increase, and at a staggering rate. It is currently estimated that global materials consumption will double in the next forty years with an attendant 70% increase in waste generation. This situation demands a restructuring of globally packaging and infrastructure strategies. An important part of this restructuring will be the development of novel technologies wherein products are designed to be degraded or recycled — a concept referred to as the circular economy. A centerpiece for creating a circular economy is the use of biopolymers rather than petroleum-derived polymers. As opposed to petroleum-derived polymers, biopolymers are readily recycled by various microorganisms. Like synthetic polymers, however, biopolymers and their composites are capable of remarkable strength and resilience. This dissertation focuses on strategies that can be employed to valorize biopolymers to reduce the consumption of raw materials in support of a more circular economy. Chapter 1 focuses on the recent advances that have been made to develop starch-based films towards food packaging applications. Included in this analysis are the various strategies and additives that can be utilized to endow films with enhanced mechanical or functional applications as well as discussing how up-and-coming technologies can be used concomitantly to accelerate this basic-research field towards real industrial applications. The remaining chapters contribute to an overarching approach employing synthetic manipulation of biopolymers or biomass in order to endow them with functional groups capable of reacting with sulfur (a waste product of petroleum refining) through an inverse vulcanization pathway. The impact of the biopolymer/biomass source as well as attributes like degree of modification and biopolymer crystallinity on the resultant morphological and mechanical properties of biopolymer/biomass-sulfur composites is explored. Chapters 2–3 more specifically focus on the synthesis and characterization of various starch derivatives and their subsequent reactions with elemental sulfur in order to develop strong thermoplastic materials. In Chapter 4 a novel method for the modification of cellulose with 3-bromo-2-methylpropene is discussed. The resultant cellulose derivative is characterized and reacted with sulfur in order to develop the first polysaccharide-sulfur composites. The morphology and mechanical properties of these composites are thoroughly characterized. Chapter 5 discusses the green synthesis of a terpinol-cellulose derivative. Similarities in the degree of modification of these terpinol-cellulose derivatives to cellulose derivatives in Chapters 4 and 5 allow the importance of biopolymer crystallinity as well as the type and quantity sulfur-reactive functional groups is highlighted. In Chapter 6 raw waste material from peanut processing (peanut shell powder) is modified and reacted with sulfur to generate composites with up to twice the compressive strength required for residential Portland cement. Chapter 7 aims to determine the impact of each component of the complex peanut shell waste material by utilizing more basic model systems for comparison. This work displays the impact of residual peanut oil, the importance of cellulose-lignin crosslinking/inclusion, and the importance of feed ratio in determining structure-property relationships of prepared composites. Chapter 8 focuses on determining how the particle size of peanut shell powder impacts the resultant mechanical properties of biomass-sulfur composites. This is done by preparing fractions having narrowly-defined particle sizes and reacting each fraction with sulfur to yield a series of composites. Various prescient trends are revealed that inform on properties required to affect improved particle-reinforced sulfur composites in next-generation materials.

Flexible packaging is an integral part of the food supply chain due to its unique thermal, mechanical, and barrier properties. The many advantages (e.g., lightweight, product protection, reduction in food waste, communication medium, etc.) come with certain drawbacks (low recyclability rate, pollution of ecosystems, etc.). Still, the heavy reliance of the food industry on these products, many of them being non-sustainable polyolefins, is unlikely to diminish in the foreseeable future. Thus, more sustainable alternatives that do not sacrifice performance (machinability, shelf-life, etc.) are needed before pollution becomes irreversible and public outcry insurmountable. Nanocellulose, especially in the form of cellulose nanocrystals (CNCs), can be incorporated into sustainable polymer matrices to enhance mechanical, thermal, and barrier properties. Cellulose is the most abundant polymer (polysaccharide) found in nature. More research to find novel biomasses for CNC extraction would be welcome to the industry. One potential biomass source for the extraction of nanocellulose is the invasive deciduous perennial: kudzu (peuraria montana var. lobata). This legume is predominantly an agricultural nuisance. However, an industrial benefit may exist that would increase raw material supply for the degradable packaging market. However, no formal research exists for this application of kudzu. The purpose of this research is to: (1) identify a CNC extraction methodology for kudzu, and (2) physiochemically characterize the product to evaluate its efficacy as a possible nanofiller in degradable packaging solutions.

This thesis reports on the synthesis of a hydrogel made from oxidized tannic acid (OTA) nanoparticles and TEMPO-oxidized cellulose nanofibers ((TOCN). We prepared the OTA nanoparticles by oxidizing tannic acid (TA) under slightly alkaline conditions. Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) were used to probe the chemical and structural changes of the OTA nanoparticles during the oxidation. The morphology of OTA particles was observed using a Scanning Electron Microscopy (SEM). OTA nanoparticles were added into a TOCN suspension to form TOCN/OTA hydrogels at 60 ℃ for 28 hours. In addition to hydrogels, TOCN/OTA aerogels were also prepared through freeze-drying. We noted that the hydroxyl groups on the surface of TOCN and OTA could form intra- and interchain hydrogen bonds, while the flexible cellulose nanofibers could form high physical entanglements. TGA spectra verified the improved thermal stability of the cellulose aerogel when OTA nanoparticles were incorporated. We also investigated the effect of the weight ratio of TOCN/OTA on the thermal and viscoelastic properties of the hydrogels and aerogels. Samples prepared at higher TOCN/OTA weight ratios exhibited higher thermal stability. Rheological tests indicate that TOCN/OTA hydrogels act as elastic solids under cyclical deformation. An optimal weight ratio of TOCN/OTA was determined. TOCN/OTA hydrogels were prepared from natural resources, and through ‘green’ methods, and it is expected that these new materials could find applications in medical and hygienic products as well as in environmental remediation processes.

Understanding plant adaptation mechanisms to prolonged water immersion provides options for genetic modification of existing crops to create cultivars more tolerant of periodic flooding. An important advancement in understanding flooding adaptation would be to elucidate the mechanism of aerenchyma air-space formation induced by prolonged immersion. Lysigenous aerenchyma formation occurs through programmed cell death (PCD), which entails the chemical modification of polysaccharides in root tissue cell walls. I investigated if a relationship exists between modification of pectic polysaccharides through de-methyl-esterification, xyloglucan through fucosylation, and the formation of root aerenchyma in select Fabaceae species. To explore this objective, I first characterized the progression of aerenchyma formation within the vascular stele of three different legumes - Pisum sativum, Cicer arietinum, and Phaseolus coccineus – through traditional light microscopy histological staining and scanning electron microscopy. I assessed alterations in stele morphology, cavity dimensions, and cell wall chemistry. Then I conducted an immunolabeling protocol to detect cellulose, hemicellulose (xylan, fucosylated and non-fucosylated xyloglucan), and specific degrees of de-methyl-esterified (DME) homogalacturonan (HG) among species during a 48-hour flooding time series. Additionally, I performed an enzymatic pretreatment to remove select cell wall polymers prior to immunolabeling for cellulose, hemicellulose and DME HG. I was able to determine that all species possessed similar aerenchyma formation mechanisms that begin with degradation of root vascular stele metaxylem cells. Immunolabeling results suggest de-methyl-esterification of HG, and degradation of xyloglucan, occurs prior or concurrent with aerenchyma formation in root vascular tissues. Furthermore, enzymatic pretreatment demonstrated that removal of cellulose and select hemicellulosic carbohydrates unmasks additional antigen binding sites for DMEpectin antibodies, while removal of cellulose and HG unmasks additional antigen binding sites for xyloglucan. These results suggest that additional carbohydrate modification may occur alongside HG de-methyl-esterification and xyloglucan fucosylation in select cells bordering developing aerenchyma. By providing a greater understanding of cell wall pectin remodeling among legume species, I encourage further investigation into the mechanism of carbohydrate modifications during aerenchyma formation and possible avenues for flood-tolerance improvement of legume crops.

The thesis is divided into two parts, which in turn are subdivided as follows: Account of the various methods for the preparation of glucosan. Proof of the constitution of glucosan, together with the general problem of its relationship to starch and cellulose. An investigation of the acid products obtained during the methylation of glucosan by means of silver oxide and methyl iodide. And: An investigation of the conditions necessary for the polymerisation of glucosan, and of the properties and constitution of the products.

Cellulose nanomaterials (CNMs) are derived from plant matter and are comprised of nanoscopic cellulose crystals and fibers. They have a diverse set of applications, from cosmetics to oil recovery. This study focuses on the properties of Oxone® mediated TEMPO-oxidized cellulose nanomaterials (OTO-CNMs) and their use in controlling the transport properties of polymeric substrates. Synthesis and characterization of cellulosic nanoparticles have resulted in the creation of OTO-CNMs with properties that increase hydrophilicity. With added hydrophilicity, OTO-CNMs possess lower fouling propensity, making them ideal membrane additive for transport limited separations such as hemodialysis. To utilize the material and unique properties thereof, this study then explores three possible areas of application development for the OTO-CNMs produced. The three areas explored are nanomaterial characterization, OTO-CNM cellulose triacetate mixed matrix ultrafiltration membrane production, as well as innovative methodology to apply OTO-CNMs as a composite gas barrier coating. This work will lead to the advancement of natural fiber-based nanomaterials and applications thereof.

Cellulose is the most abundant polymer on earth. Its use within the bioenergy and bio-materials sector to provide raw feedstock molecules is critical to supplant petrochemical-derived resources. The alkaline carbohydrate fuel cell has recently been of growing interest as it has been shown to produce power directly from monosaccharides without further breakdown and combustion steps that introduce substantial energetic losses. The development of the direct alkaline carbohydrate fuel cell is currently in its infancy, with developments needed to refine understandings of cell geometry, charge mediation and industrial application pathways. The findings of this thesis represent contributions to these areas, demonstrating greater mechanistic understanding of these devices and new pathways forward. Mechanistic insights were gained through examining simple geometric design considerations that proved capable of significantly improving fuel cell performance. Decreasing the distance between electrodes from 20 to 6 mm increased power outputs by ~35 % and increasing the density of the nickel foam anode from 250 mg cm3 to 1000 mg cm3 increased power outputs by ~30 %. Further, indigo carmine was found to be unstable in highly alkaline solutions. Breakdown of the dye produced significant amounts of current without any carbohydrate present, calling into question the previously reported relationship between the indigo carmine concentration and power generation within an alkaline carbohydrate fuel cell. As pure carbohydrate fuels may raise ethical concerns about food security, new organic fuels were proposed and new cellulose to energy pathways examined. III A novel low-temperature hydrothermal cellulose degradation process was developed to create new cellulose-derived alternatives. The process converted over 61 % of microcrystalline cellulose to soluble aldaric acids whilst simultaneously producing value-added magnetic nanoparticles. Finally, a new novel fuelling approach was reported in which the selected fuel was reverse-engineered from the desired oxidation products. Within the fuel cell, the oxidation pathway between 5-HMF and FDCA was exploited to generate 6.5 x the power of the equivalent glucose fuel cell, whilst synthesising high-value molecules known to be useful for bioplastics. As the scale of bio-molecule production increases, this passive energy generation scheme presents an opportunity to produce significant power from an otherwise untapped chemical process, increasing the green chemical industry’s energy efficiency. Overall, this thesis entails optimisations towards enhancing energy production within the alkaline organic fuel cell and explores new novel applications which broaden the scope of these green electricity-generating devices.

Lignocellulosic biomass is composed of lignin, cellulose, and hemicellulose. Lignin is naturally formed renewable aromatic biopolymer; the cellulose and hemicellulose are polysaccharides. By far, the “second generation” biorefineries mainly use the value of cellulose pulp in paper industries or in making low-value chemicals such as ethanol while more than 98% of lignin is discarded into direct combustion. The valorizations of lignin and polysaccharides are still under development. Herein, we have studied the heterogeneous catalytic conversion of lignin monomers and polysaccharides with Ru/C catalyst with different metal oxides for making a variety of value-added chemicals. For instance, we developed a Ru/C and Nb2O5 co-catalyst system to funnel different lignin monomers into C9 hydrocarbons which could potentially be used as drop-in fuels. We also investigated the Ru/C and WOx co-catalysts to convert the polysaccharides into diols and polyols. By performing the isotopic reactions and time programmed sampling, our study disclosed the mechanisms and kinetics of the catalytic reactions. To achieve the goal of biomass valorization, we also developed a purification method to avoid catalyst poisoning by the contaminations from raw biomass and thus facilitated the sustainable utilization of native lignin into valuable chemicals.

Giant liposomes, or giant unilamellar vesicles (GUVs), are thin, semi-permeable,man-made compartments that often serve as models of the cell plasma membrane due to their sizes (1−100 ?m) and molecular composition (composed of lipids). GUVs have proven useful for understanding a variety of different biophysical phenomena such as lipid membrane organization, membrane protein function, and cytoskeletal mechanics. A variety of different formation methods have been developed to try to optimize the populations of GUVs produced. However, information that allows for the direct comparison of the sizes and yields of the GUVs obtained from the different methods is lacking. In my dissertation, I describe my work on the development of a novel confocal microscopy-based technique that allows for the characterization of the populations of GUVs produced from the most commonly employed surface-assisted assembly methods. Through the development and standardization of careful protocols that allow for the quantification of ?(100,000) vesicles per sample, I characterize the surface-assembled populations of GUVs in comprehensive sets of experiments. From this work, I show novel discoveries including i) the use of nanocellulose paper as a surface to obtain GUVs, ii) the effect of substrate properties on the formation of GUVs, iii) the modulations of ionic strength technique to allow high yields of GUVS to be obtained using physiological salts, and iv) the effect of osmolytes on the formation of GUVs. The results from these quantitative experiments has led to the development of the budding and merging thermodynamic model which describes the mechanism of GUV formation. Overall, the discoveries pave the way for the largescale production of GUVs for biophysical studies as well as towards more practical applications of GUVs such as for compartments for targeted drug delivery or synthetic cells.

The focus of my thesis is the development of an advanced methodology to create 3D nanostructures by design, and to demonstrate the control over geometry and chemical functionalities of the nanostructures produced. The driving motive behind this are the pressing need for 3D nanostructures in biomaterials development, modern nanodevices and biomedical applications. My approach is scanning probe microscopy-based nanolithography in combination with advanced surface chemistry. This thesis clearly demonstrated the concept and feasibility of the approach. While the power of 3D printing has proven to be a powerful tool in additive manufacture, extending the spatial precision to nanometer scale would lay the foundation for the next science and technology revolutions. Specific applications impacted by this work include surface science, catalysis, modern sensors, nanophotonics, and nanoelectronics.Three significant goalposts are reported in this thesis followed by future prospective research. First focuses on mechanically sensitive molecules known as mechanophores, which have recently attracted much interest due to the need for mechanoresponsive materials. Maleimide−anthracene mechanophores located at the interface between poly- (glycidyl methacrylate) (PGMA) polymer brushes and Si wafer surfaces were activated locally using atomic force microscopy (AFM) probes to deliver mechanical stimulation. Each individual maleimide−anthracene mechanophore exhibits binary behavior: undergoing a retro-[4 + 2] cycloaddition reaction under high load to form a surface-bound anthracene moiety and free PGMA or remaining unchanged if the load falls below the activation threshold. In the context of nanolithography, this behavior allows the high spatial selectivity required for the design and production of complex and hierarchical patterns with nanometer precision. The high spatial precision and control reported in this work brings us closer to molecular level programming of surface chemistry, with promising applications such as 3D nanoprinting, production of coatings, and composite materials that require nanopatterning or texture control as well as nanodevices and sensors for measuring mechanical stress and damage in situ.Following our success with creating structures by design using nanolithography and mechanophore chemistry, we set out to fabricate organizational chirality on surfaces, which has been an interest in chemistry and materials science due to the need for enantioselective catalysis, separation, and reactions. Current methods for production of organizational chirality are primarily based upon self-assembly of molecules. While powerful, the chiral structures produced are restricted to those dictated by reaction thermodynamics. This work introduces a method to create organizational chirality by design. Using atomic force microscopy in conjunction with our chosen surface chemistry, various chiral structures were designed and produced with nanometer precision, from simple chiral spirals to arrays of chiral nanofeatures to hierarchical chiral structures. The size, geometry, and organizational chirality faithfully follow the designs with a high degree of spatial control. The concept and methodology reported here provides researchers a new means to carry out organizational chiral chemistry, with the intrinsic advantages of chiral structures by design. The results open new and promising applications including organizational chiral sensors, 3D nanoprinting of chiral structures, enantiomeric separation, and enantiomeric heterogeneous catalysis.Building upon the theme of controlled fabrication of nanostructures, we utilized controlled assembly to create structures by design. Our prior work has demonstrated the concept of controlled assembly of macromolecules such as star polymers [molecular weight (Mw) ∼383 kDa,hydrodynamic radius R ∼ 13.8 nm] in droplets. This work extends this concept to smaller molecules, in this case, poly(ethylene glycol) bis-tetrazine (PEGbisTz, Mw 8.1 kDa, R ∼1.5 nm). The key to controlled molecular assembly is to first deliver ultrasmall volumes (sub-fL) of solution containing PEG-bisTz to a substrate. The solvent evaporates rapidly due to the minute volume, thus forcing the assembly of solute, whose overall size and dimension are dictated by the initial liquid geometry and size. Using prepatterned surfaces, this work revealed that the initial liquid shape can be further tuned, and we could control the final assembly of solute such as PEGbisTz molecules. The degree of control was demonstrated by varying the micropatterns and delivery conditions. This work demonstrated the validity of controlled assembly for PEG-bisTz and enables three-dimensional (3D) nanoprinting of functional materials. The technology has promising applications in nanophotonics, nanoelectronics, nanocomposite materials, and tissue engineering.These investigations into fabrication of a variety of nanostructures demonstrated the success in creating, complex, hierarchical, and chiral structures with nanometer precision. This success lays the foundation for utilization of scanning probe lithography to create functional nanostructures out of new and exciting materials. Future investigations of this technology will focus on incorporating materials such as mithrene, a unique 3D material that possesses 2D properties, and anthraquinone modified cellulose nanocrystals. Combined with the methodology presented here, the development of these structures will be useful in future applications such as modern sensors, nanodevices, nanophotonics, and nanoelectronics.

Filamentous fungi such as Neurospora crassa use G protein coupled receptors (GPCRs) and associated heterotrimeric G proteins to respond to sensory cues from the environment. A fundamental challenge in G protein signaling is to identify the specific subunits of the heterotrimer (Gα, Gβ, Gγ) that interact in cases where multiple versions of subunits are present. Relevant to downstream signaling by heterotrimeric G proteins, fungi differentially regulate secreted enzymes for catabolism of cellulose, but the connection between cellulose metabolism and any signal transduction pathway is lacking in N. crassa. The primary objectives of this thesis are to 1. Determine genetic relationships between the putative Gβ subunit CPC-2 and the three Gα protein subunits in N. crassa, 2. Investigate the extent of G protein involvement in the cellulose response in N. crassa, and 3. Determine the role of N. crassa G proteins on the global transcriptional response to cellulose as a carbon source. In Chapter 2, we characterized the relationships between the Gβ subunit CPC-2 and the other known G protein subunits in N. crassa on minimal medium containing sucrose. We illustrated that CPC-2 is cytoplasmic. We also demonstrated that cpc-2 is epistatic to gna-2 with regards to basal hyphae growth rate and aerial hyphae height. Strains lacking both Gβ subunits possessed more severe defects for all phenotypic traits except for production of macroconidia, supporting a synergistic relationship between GNB-1 and CPC-2 in N. crassa. In Chapter 3, I examined the relationship that G protein signaling has with cellulose metabolism. Loss of the Gα subunits gna-1 and gna-3, the Gβ subunits gnb-1 and cpc-2, the Gγ gng-1, or adenylyl cyclase (cr-1) resulted in loss of detectable cellulase activity. The expression patterns for five cellulase genes revealed that Δgna-1, Δgnb-1, and Δgna-3 mutants produce less cellulase mRNA than wild type, consistent with transcriptional regulation. Δcpc-2 and Δcr-1 mutants had wild-type levels of the cellulase transcripts. These results suggest that CPC-2 and CR-1 affect cellulase production in a post-transcriptional manner. Moreover, cAMP addition only partially corrected cellulase activity defects in Δgna-1 and Δgnb-1 mutants, indicating that GNA-1 and GNB-1 target cAMP-independent pathways to control cellulase activity. In Chapter 4, I analyzed the transcriptomes and exoproteomes from cellulose grown cultures of the mutants for the Gα subunits gna-1 and gna-3, as well as the adenylate cyclase cr-1 via RNAseq and LC/MS-MS protein identification. 20 of the 22 highly expressed cellulases found in wild type cultures were transcriptionally downregulated in Δgna-1 mutants, and 6 of these 20 were also down-regulated in Δgna-3 mutants. Δcr-1 mutants were not transcriptionally downregulated for any cellulase enzymes. Our transcriptional data suggests that gna-1 and gna-3 control the response to cellulose in N. crassa, while cr-1 affects cellulases in a post-transcriptional manner.

Linear Elastic Fracture Mechanics (LEFM) has been modified to account for the role of inherent fracture processing zone in failure of fibrous materials. The presented study further validates the theory using both prepared handsheets with different pressing conditions and literature reported handsheet tensile strength data under different notch size. The analysis shows that modified LEFM can capture the trend of tensile strength as functions of notch size. To further expand the application of the model, we used a simple shifting manipulation coupled with a fitting procedure to indirectly determine characteristic fracture processing zone length. After the treatment, all the tensile strength data were fitted into a unified fracture model. The results show that increasing porosity or decreasing density leads to increase of fracture processing zone length. Lastly, we evaluated the role of tensile strength in affecting the tear strength. We found that tear strength reaches a maximum value as tensile strength increases but drops dramatically once tensile strength or breaking length reaches a critical value for softwood based handsheets. The implication of this results suggests that one should consider the nature of the fibers when preparing high tensile strength and tear strength fibrous materials.

Abstract: Surface-enhanced Raman scattering (SERS) has evolved into a powerful analytical measurement technique with the potential for single molecule detection. The technological advancement of handheld Raman instrumentation is powering the development of SERS applications in a variety of industries. Moreover, it is driving the movement from laboratory-based analyses to on-site/remote analyses. As a result, a main research component from this movement is to develop compatible SERS substrates. While the market is dominated by solid-based substrates, solution-based substrates do offer some benefits. These could include low production costs, high scalability, competitive reproducibility and shorter analysis times. The primary focus of the work in this thesis is to develop solution-based SERS substrates and explore their usage for in-solution measurements. This work highlights the development of three different types of solution-based substrates. The first substrate involves the synthesis and optimization of gold nanostars as a colloidal SERS substrate. The SERS performance is investigated and optimized using different Good’s buffers, examining the buffer to gold salt concentration ratio and the use of an aggregating agent. In short, the results indicated that gold nanostars with smaller branches provided larger enhancement than those with larger branches, and this has been attributed to the Raman probe surface coverage on the nanostars rather than an electromagnetic effect. A SERS assay is also developed to quantitate methimazole in urine using a handheld Raman spectrometer. The second and third solution-based substrates are metal decorated cellulose nanofibers, also known as plasmonic cellulose nanofibers. These chapters focus on the growth of silver and gold nanoparticles onto oxidized cellulose nanofibers, and are used as a water dispersible substrate. In the development of plasmonic cellulose nanofibers, the cellulose nanofibers have two important roles: (1) to act as a dispersant in water and (2) act as a support for metallic nanoparticles. For both substrates, centrifugation played a key role in producing significant signal enhancement. Cellulose nanofibers decorated with silver nanoparticles were used for in-solution measurements of malachite green, while cellulose nanofibers decorated with gold nanoparticles were used for in-solution measurements of methimazole. Moreover, an assay is developed to quantitate methimazole in synthetic urine with cellulose nanofibers decorated with gold nanoparticles. Measurements using plasmonic cellulose nanofibers are taken with a Raman microscope, however, examples are shown to highlight the capability of remote analysis by coupling the substrates with a handheld Raman spectrometer. This work concludes with a comparative study between solid- and solution-based substrates. Using cellulose nanofibers decorated with gold nanoparticles, membrane- and glass- based SERS substrate are developed. This work discusses the benefits and challenges of solid- and solution-based substrates in terms of substrate development, measurement versatility and reproducibility. The primary contribution of this work is the development of multiple solution-based SERS substrates for in-solution measurements.

Structure and processing of polymer composites are essential for not only optimizing materials properties for high performance applications, but also making materials more environmentally sustainable. In the aerospace and automobile industries, the need for lightweight materials to increase fuel efficiency, while still boasting impressive mechanical properties drives innovation towards the manufacturing and use of more eco-friendly materials. In this dissertation, we concentrate on the processing and characterization of polymers reinforced with bio-based cellulose nanoparticles at an industrial scale. The successful incorporation of cellulose nanocrystals (CNCs) in polyamides, specifically polyamide 11 (PA 11) and polyamide 6 (PA 6), can result in a more sustainable material. However, unless polyamide nanocellulose composites can be produced at an industry scale, the use of traditional fillers like glass fibers will continue to be the industry standard despite their lack of being bio-based or providing comparable mechanical enhancement. Challenges of thermal stability, homogeneous dispersion, and moisture uptake have long served as the bottleneck to industrial-scale processing of these cellulose nanocomposites. To overcome these challenges, various industrially viable pre-mixing techniques, such as planetary ball milling, roller blade mixing, and master batching, are developed herein to fabricate these materials for melt processing while retaining the thermal and mechanical integrity of the nanocomposites. In this dissertation, successful high-temperature processing of these nanocellulose composites is shown with resultant nucleated materials showing up to approximately 75 % reinforcement of PA 6 and up to 180 % of PA 11. The efficacy of cellulose nanocrystals as a nucleating agent and the respective crystallization kinetics of the nanocomposite at process-relevant conditions were explored using fast scanning calorimetry. It was found that the PA 11 composite would need at least 0.5 s above 100 °C in order to crystallize via heterogeneous nucleation and that in the heterogeneous regime, the nucleated samples exhibited much quicker peak crystallization times. This successful development and optimization of these processing methods and parameters taps into the immense potential cellulose nanomaterials have in creating high performance, environmentally sustainable materials. Additionally, the use of these cellulose nanomaterials as templates for graphene oxide nanotubes is explored in this dissertation as well. Utilizing an inverting thermal degradation (iTD) method, the combustion kinetics of nanocellulose fibers were altered through surface hydrophobization and salt saturation to influence ignition propagation rate and ignition nucleating points. Samples were ignited at both slow and rapid rates, with flash burning of these nanofibers producing graphene oxide nanotubes through ignition of the bulk material and leaving behind the chemically altered surface structure of the nanofibers. Fiber aspect ratio, crystallinity, salt occlusion, ignition rate, and local oxygen availability proved influential in the resulting nanostructures, characterized through electron microscopy coupled with focused ion beam, solid state NMR, and XPS. Using this facile process and utilizing nanocellulose, the world's most abundant natural polymer, as the starting material, the work presented herein could have profound implications for the future production of environmentally sustainable carbon nanotubes. In the biomedical industry, new materials and processing techniques are required to match the increasing demand for personalized treatment. Furthermore, bone implants that promote osseointegration and long-term retention has instigated the search for materials to replace the traditional metal or ceramic implants that typically come with a high risk of immune rejection. In this dissertation, a novel processing technique to fabricate porous poly(ether ether ketone) (PEEK) is developed and studied for its potential application as a bone replacement material. A PEEK composite was created with the addition of nano hydroxyapatite (nHA), which has shown to improve the biocompatibility of the material. While hydroxyapatite-PEEK composites have previously been investigated for use in bone replacement, they have faced challenges with dispersion and ultimate mechanical tensile and compressive strength. The ethanol solvent-exchange based novel process presented herein produces a material with porous structuration that mimics the transition of cortical (compact) to cancellous (porous) bone while also having a homogeneous dispersion of hydroxyapatite throughout the material. With a density of 0.84 g cm−3 ± 0.18, this nanocomposite material exhibited compressive strength of up to 180 ± 15 MPa, which compares well to that of natural human cortical bone ranging from 100-230 MPa. This PEEK nanocomposite could provide a treatment alternative that displays a longer lifespan, lowers risk of immune rejection, and eliminates damage to surrounding tissue. The advancements in processing of nanocomposites presented in this work can greatly impact various industries from providing better medical care to reducing the carbon footprint of plastics.

Abstract: Agricultural straw is an abundant lignocellulosic biomass mainly composed of cellulose (33-75%), hemicellulose (13-37%) and lignin (3-31%) that offers great potential as a feed material for a biorefinery. Emerging technologies such as pressurized fluid fractionation and high-intensity ultrasound are promising alternatives to be employed for straw biomass refining towards bioactive compounds like phenolic compounds, and nanofiber production. Specifically, cellulose nanofibers have been considered as potential scaffold for tissue engineering applications. Therefore, the objective of this thesis was to employ pressurized fluids such as subcritical water and pressurized aqueous ethanol to fractionate canola straw biomass, and then nanofibrillate the treated fiber via high-intensity ultrasound to produce self-assembled scaffolds, and investigate their cytocompatibility for human gingival fibroblast cells. First, the straw biomass was treated using pressurized fluids at 140-220 °C, 50-200 bar, 0-100% v/v ethanol, with a constant flow rate of 5 mL/min for 40 min. Pressurized aqueous ethanol (20% v/v) at 180 °C and 50 bar, resulted in a hydrolysate with maximum total carbohydrates (443-528 mg GE/g straw) and phenolics (45-53 mg GAE/g straw) contents, and a solid residue mainly composed of 63% cellulose, 9% hemicellulose and 20% lignin. Then, the obtained enriched cellulose fiber was nanofibrillated using high-intensity ultrasound at specific energies of 4-20 kJ/g to obtain lignocellulosic nanofibers with maximum fibrillation yield of 36 wt.%, and an average diameter of 21 nm. Further bleaching of the enriched cellulose fiber (at 75 °C for 2-6 h) removed large amount of lignin and resulted in a bleached cellulose fiber mainly composed of 71-82% cellulose, 4-5% hemicellulose and 8-18% lignin. The nanofibrillation process of bleached fibers using high-intensity ultrasound at specific energies of 4-20 kJ/g led to nanofibers with maximum fibrillation yield of 46 wt.% and an average diameter of 14 nm, which were self-assembled into a three-dimensional hydrogel structure. Cytocompatibility test performed using the dried hydrogel scaffolds showed no cytotoxicity of the residual lignin of up to 18%, and an increased cell proliferation compared to the control (glass slip) up to day 11. Finally, clove essential oil up to 0.5 wt.%, and cellulose nanofiber hydrogel were used as an emulsion-filled gel system for tissue engineering scaffolds with no cytotoxicity and cell viability of 74-101%. The results suggested that pressurized fluid fractionation followed by high-intensity ultrasound is a promising strategy for biorefinering of straw biomass towards nanofiber and tissue engineering scaffold production. Furthermore, the emulsion-filled gel using clove essential oil and cellulose nanofiber hydrogel could provide scaffolds with unique antimicrobial properties, suggesting its potential use in the biomedical field.