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The increasing interest in antimicrobial materials (e.g. wound dressings, food preservatives and health care products) to mitigate antibiotic overuse, drives the objectives of this project to examine the use of cellulose as a sustainable and biocompatible support for antimicrobial enzymes. Cellulose self-assembly can be modulated using chemical surface modifications and/or exposure to different environmental conditions (solvents, pH, temperature, salt concentration, etc.). The use of specific advanced solvents such as ionic liquids allows the dissolution of native cellulose. Such solutions can be precipitated in the form of a hydrated polymer network known as a RCH. In this work, the interactions between cellulose hydrogels and H2O2-producing enzymes were studied. Different cellulose chemical modifications were carried out in order to optimise the enzyme/cellulose interactions and the antimicrobial performance (H2O2 production as well as MDR bacteria growth inhibition). In particular, maximisation of interactions between the enzymes and the cellulose support is crucial for avoiding the loss of expensive enzymes during the manufacturing process. Different fabrication routes were followed in order to assess the feasibility of cellulose/enzymes hybrids as antimicrobial materials. For instance, the use of cationic cellulose nanofibrils (CCNF) as main component for the formation of novel core-shell hydrogel spheroids functionalised with glucose oxidase is described in Chapter 3. The electrostatic interactions between CCNF (positively charged) and the enzyme (negatively charged) allowed an efficient incorporation of enzyme into the spheroid hydrogel core where it was secured by the presence of a polyacrylic acid (PAA) semi-permeable membrane shell. The PAA spheroid shell (pore size ~ 12.6 kDa) allowed the exchange of the enzyme substrate (glucose) and products (H2O2 and gluconic acid) and prevented the enzyme from leaching (Chapter 3). A successful entrapment and preservation of the antimicrobial enzyme activity (for at least 8 days) in CCNF/PAA core-shell spheroids was achieved. Nonetheless, the semi-permeable nature of the spheroids makes them vulnerable to osmotic pressure changes which may lead to shrinkage or bursting (Chapter 3). For this reason, the use of more robust RCH was also examined. The development of a periodate oxidised RCH able to covalently bind enzymes and, at the same time, retain its antimicrobial activity is explored in Chapter 4. As result of cellulose periodate oxidation, DAC hydrogels with different degree of oxidation (DO) were obtained and used as structural supports for the covalent binding of glucose oxidase. This study aims to identify the best parameters (i.e., pH and DO) for an efficient functionalisation of DAC beads to be used as antimicrobial materials. Covalent binding of the enzyme in the beads is achieved by reacting aldehyde groups present on DAC with non-protonated primary amines on the enzyme (Schiff base formation). The optimised enzyme-functionalised beads were found to produce antimicrobial levels of H2O2 able to inhibit the growth of pathogenic antibiotic resistance bacteria such as S. aureus, P. aeruginosa and MRSA (Chapter 4). However, the covalent cellulose/enzyme cross-linking may cause deleterious conformational changes of the enzyme, thus, a decrease in the activity. Moreover, all chemical modification routes may be harmful for the environment because of the intrinsic toxicity of the reagents used (GTMAC and periodate). In view of making enzyme functionalised cellulose materials more sustainable, an antimicrobial cellulose/enzyme system which exploits naturally present cellulose binding modules (CBM) in the enzyme was designed (Chapter 5). Some enzymes extracted from fungi, involved in environmental cellulose degradation, such as cellobiohydrolase and cellobiose dehydrogenase naturally possess CBM. The presence of CBM on the antimicrobial enzymes (for example cellobiose dehydrogenase) allows a nondenaturing and thermodynamically stable adhesion on the RCH supports. In particular, the work on CBM-possessing enzymes (Chapter 5) describes the design of a self-degrading material that exploits the cellulose as structural support for the enzymes and at the same time uses it as substrate for the production of H2O2 (Chapter 5). Despite the high binding affinity towards cellulose, naturally sourced CBM-possessing enzymes display a lower specific activity and higher production costs compared to other commercially available oxidative enzymes (i.e., GOx). Genetic recombination can be used to combine the high binding affinity of natural CBM-possessing enzymes with the high specific activity and low cost of commercial enzymes. In chapter 6, we describe the design and the synthesis of a chimeric enzyme consisting of a GOx catalytic domain and a CBM sourced from Trichoderma reseei cellobiohydrolase (TrCel7). The generation of such a chimeric GOxCBM aims to reduce enzyme production costs while maximising H2O2 release and binding efficiency towards cellulose. The creation of a functional chimeric GOx-CBM would allow the design of more environmentally and economically sustainable cellulose/enzymes hybrid materials.In conclusion, this PhD project aims to achieve a broad and comprehensive understanding of design rules for an efficient fabrication of cellulose/enzyme hybrids to be used as antimicrobial materials.

At present, the production of polymers is mainly based on fossil feedstocks, which are unsustainable due to high greenhouse gas emissions and feedstock depletion. The need to transition to bio-based feedstocks for polymer synthesis is therefore widely acknowledged, but bio-based polymers currently face limitations, such as high costs, inferior properties and limited availability. Terpenes, which can be found in various plants, are a renewable, yet underutilised, feedstock, providing potential for use in polymer synthesis. Traditionally, terpenes can be extracted from plants in small quantities or can be obtained from waste resources, however, recent progress in biotechnological routes also allows for the synthesis of terpenes from fermentation of sugars on a multitonne scale at reasonable costs. In this project two sesquiterpenes, ß-elemene and ß-farnesene, which can be obtained via fermentation routes, are investigated for use as building blocks and monomers in the synthesis of various bio-based polymers. Polythioethers, polyesters, polyamides and nonisocyanate polyurethanes were synthesised and comprehensive analysis of both thermal and mechanical properties of these polymers was carried out to identify potential industrial applications. Synthesis of polythioether thermosets by reaction of ß-elemene and/or ß-farnesene with different multifunctional thiols is described. Thiol-ene photocuring was utilised as a sustainable, cheap and scalable synthesis method for these polymers. Polymer properties were found to be tuneable by choice of monomer and post-curing treatment, and ranged from rubbery materials with low glass transition temperatures to stiff and hard polymers with high Young's moduli, which could find potential application as coatings, adhesives or sealants. Thiol-ene addition was also employed to generate novel ß-elemene monomers with dimethyl ester, diol or diamine groups. These were investigated in polyester and polyamide synthesis via polycondensation reaction. Different co-monomers, reaction conditions and catalysts were studied and formation of insoluble polymers, or soluble polymers with low to moderate molecular weights, was achieved. ß-Elemene epoxide derivatives were investigated as monomers in ring-opening copolymerisation with phthalic anhydride. Semi-aromatic polyesters with low molecular weights or insoluble materials could be obtained and post-polymerisation functionalisation or cross-linking was explored to alter the polymer properties. Furthermore, carbonation of a ß-elemene trisepoxide derivative led to a cyclic dicarbonate monomer, which was used in the formation of non-isocyanate polyurethanes with various diamines. This led to brittle, insoluble polymers with high glass transition temperatures.

The production and use of plastics is expected to double in the next 20 years from the current 407 million tons per year. Almost 99% of these plastics are produced from non-renewable fossil-based feedstocks. The anticipated volume growth in plastic production and increasing world population and urbanisation will place severe burden on these unsustainable resources. The net emission of greenhouse gases into the atmosphere and challenges associated with the disposal of these materials are other factors that is driving the research in this area towards more sustainably sourced materials. 2,5-furandicarboxylic acid (FDCA) has been termed as a "sleeping giant" due to its unexplored potential as a renewable monomer and a platform chemical. Chapter 1 of this thesis introduces the subject area of research with focus on furanic monomers and polymeric material produced from them. Literature related to polyamides in general and furan-based polyamides (FPAs) in particular has been reviewed and presented in this chapter. In Chapter 2, preliminary investigations into the synthesis of a model furan-based polyamide PA6F, were carried out using an eco-friendly and solvent-free melt polymerisation approach. A two-step synthesis, combining oligomerisation and polycondensation steps, was developed and tested in a small scale thin-film reactor. A range of catalysts were screened to facilitate the amidation of FDCA. Titanium(IV) isopropoxide (TIPT) and titanium(IV) citrate (TIC) were found to be active catalysts for PA6F production. The reaction conditions were optimised in order to produce a reasonably high molecular weight polymer. PA6F produced after optimisation, demonstrated significantly higher molecular weights (Mw ~ 46 kg/mol) and better thermal properties (Tg ~ 130 ᵒC) compared to those synthesised using conventional method. Chapter 3 explores the up-scaling potential of PA6F by synthesis in a 250 mL glass reactor using the conditions and best performing catalysts identified in Chapter 2. The effect of catalyst loadings, polycondensation temperature and reaction stoichiometry was assessed. PA6F structure and properties were also investigated in more detail using a range of analytical techniques. The resulting polymers again showed consistently better molecular weights. The incorporation of HMDA in slight excess showed positive impact on the molecular weights. On the other hand, DSC, DMA and WAXD revealed a predominantly amorphous nature of PA6F. The scope of catalytic melt polymerisation technique was further extended in Chapter 4 by employing some common aliphatic diamines used in the polyamide production. In addition to PA6F synthesised earlier, four other FPAs (PA4F, PA8F, PA10F and PA6MF) were produced using TIPT catalyst. The polymer structures and thermomechanical properties were investigated. Depending on the methylene chain length, the Mw of the obtained polymers ranged between 23 - 36 kg/mol, while the glass transition temperatures were in the range of 97-140 ᵒC. All polymers showed exceptional thermal stability during TGA. PA10F, a 100% bio-based polyamide, displayed the highest thermal stability (Td-max = 446 ᵒC) among tested FPAs. However, all FPAs were found to be mainly amorphous, as confirmed with DSC, DMA and WAXD analysis. To address the FPA's lower tendency to crystallise, copolymerisation of two other aromatic diesters, i.e. DMTPA and DMTDC, was explored in Chapter 5. Again, the analogous catalytic melt polymerisation technique was employed to synthesise PA6F/6T and PA6F/6S type copolymers containing different ratios of DMTPA and DMTD. DMTPA was found to be more effective monomer to induce some degree of crystallisation when 50 mol% of DMFDC was replaced by DMTPA in the copolymer. The semi-crystalline nature of the 50/50 sample was confirmed with help of DSC, DMA and WAXD analysis. Furthermore, taking the advantage of renewable nature of C10 diamine, PA10F/10T random and block copolymers were also produced. It was validated that block copolymers displayed semi-crystalline behaviour at a significantly lower proportion of non-renewable DMTPA compared to random copolymers.

Ionic current rectification describes the unique electrochemical behaviour for devices based on microporous materials to conduct ions only in one direction under applied potential bias. The mechanism of ionic current rectification for all types of microporous materials are similar and based on electrolyte accumulation (open diode) and depletion (closed diode) within the region of a microhole in the substrate. The ionic current rectification phenomenon has been investigated for different types of ion conducting microporous materials with applications linked to future water desalination technology. In general, there are three types of microporous materials studied in the thesis that have been investigated based on (i) one-dimensional, (ii) two-dimensional, and (iii) three-dimensional pore systems. All of these microporous materials show good performance as long as semi-permeability can be achieved and maintained. In this thesis, ionic current rectification phenomena have been studied and investigated for different types of microporous materials such as, bacteriophage M13 (one-dimensional), graphene oxide and titanate nanosheets (two-dimensional), and Nafion and PIM-EA-TB “heterojunction” (three-dimensional). Each of these microporous materials gives unique electrochemical characteristics (ionic current rectification phenomena) when deposited as a film onto a poly-ethylene-terephthalate (PET) susbtrate with 20 μm diameter microhole. In the final chapter of this thesis, it is demonstrated a water desalination prototype based on ionic current rectification in microporous materials. It can be concluded that ionic diode devices based on different types of microporous materials provide a new avenue of fundamental electrochemical study with effects based on materials, device geometry, and electrolyte media. In the future, there is a possibility to develop ionic circuits and a wider range of ionic devices to provide new types of interfaces between artificial electronic systems and biological ionic systems.

Current demand for donor organs and tissues for transplantation vastly surpasses availability. To address this, tissue engineering is a rapidly advancing field, with much research directed towards the production of new biomaterial scaffolds, from sustainable and economically viable sources, with tailored properties to generate functional tissue for specific applications. Herein, a family of diverse cellulose scaffolds, with novel decorated surfaces, were developed through simple, robust and scalable chemical modifications, with the aim to facilitate cellular attachment and further tune, or regulate, cell response in tissue culture applications. Two-component systems (cell and scaffold) were achieved using 2D cellulose films derivitised with glycidyl trimethylammonium chloride, introducing a positive surface charge, which facilitated cellular attachment comparable to tissue culture plastic, without the addition of foetal bovine serum or other ligands. Surface properties were characterised and scaffold-cell interactions revealed that initial attachment was governed by electrostatic interactions between cellulose bearing a positive charge and the negatively charge phospholipid bilayer of the cell membrane. Micropatterned surfaces with cationic cellulose 'islands' were produced using reactive inkjet printing and cells shown to preferentially attach to these islands, thus demonstrating directed cell attachment. Crosslinking with glyoxal had the dual effect of enhancing cellular response, by increasing the cell microenvironment stiffness, and scaffold robustness, enabling more complex 3D structures to be produced. Applying this chemical modification to cellulose fibres resulted in dispersible cationic cellulose nanofibrils (CCNF), which led to the formation of hydrogels. The fundamental form and dimensions of the CCNF were probed and interfibrillar interactions, leading to gelation, investigated. Directionally freezing these hydrogels, followed by lyophilisation, produced 3D porous foams. Internal architectures were produced ranging from aligned smooth walled micro-channels, mimicking vascularised tissue, to pumice-like wall textures, reminiscent of porous bone. These exquisitely structured, yet robust foams, could provide biomaterial scaffolds suitable for industrial applications that require 3D cell culturing.

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).

The work contained within this thesis presents a multidisciplinary method for the integrated reaction and separation of a liquid-liquid biphasic system. The area of multiphase liquid reactions is traditionally addressed through use of a solvent system to achieved mutual dissolution. However, the removal of such solvents in downstream processing often entails a high energy cost. This research investigated the potential to perform these reactions, specifically between oil and aqueous phases, without a solvent, thereby negating the downstream removal cost. The method presented in this thesis proposes the rate limiting step of the liquid-liquid reaction be determined, specifically the relationship between interfacial surface area and rate of reaction. The use of high shear homogenisation, microfluidic and capillary based droplet creation methods enabled a range (3.9 – 9.6x10-4 m2.g-1) of oil-aqueous interfacial areas to be formulated. The rate limiting step of a model reaction, the epoxidation of sunflower seed oil with an aqueous solution of hydrogen peroxide, sodium tungstate and a carboxylic acid, was dependent on the interfacial surface area, but only when less than 0.25 m2.g-1. At oil-aqueous areas in excess of this the reaction system was rate limited by the aqueous phase formation of active catalyst species, a peroxotungstate. The design and construction of a continuous membrane reactor based on the rate of reaction information was carried out. By operating under conditions such that an interfacial surface area in excess of 0.25 m2g-1 was maintained, the biphasic system was successfully reacted on large scale (5 L), and critically the inherent immiscibility of the oil-aqueous system allowed for the facile downstream separation of phases. Therefore this research presents an approach to achieve the non-mass transfer limited reaction and downstream separation of a liquid-liquid biphasic system without the use of solvents.