In this thesis the primary focus is on polysulfides, a class of oxidation-responsive polymers with potential biomedical applications as 1) polymeric anti-inflammatory/anti-oxidant agents and/or 2) drug delivery vehicles, specifically for inflammation and cancer. Within the Tirelli lab, polysulfides for inflammation targeting drug delivery are a key area of research and as such a comprehensive review of this topic is covered in Chapter 1. Polysulfides are able to target inflammation (and cancer) due to their inherent ability to react with reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) and hypochlorite (ClO-) which are markedly upregulated in inflamed and cancerous milieu; in Chapter 2 we demonstrate the different effects of these two oxidants on poly(propylene sulfide) (PPS) nanoparticles. Using diffusion-ordered NMR spectroscopy (DOSY), both size and spatial characteristics of the oxidation products were probed; specifically, the size of the oxidation products and the spatial location of Pluronic i.e. physically entrapped within the polysulfide core or ‘free’ Pluronic micelles. We additionally showed that these nanoparticles displayed a protective effect on both L929 fibroblasts and J774.2 macrophages when challenged with ClO-. In Chapter 3, micellar PEG-PPS composed of linear- (2-arm) or star-(4, 6 and 8 arm)shaped polymers were synthesised; we found micelles formed of the linear PEG-PPS reacted with H2O2 at a quicker rate than the star PEG-PPS, however, the critical micelle concentration of the stars was significantly lower indicating a marked increase in stability to dilution. Chapter 5 aimed to assess new monomer ethylene sulfide (ES), which was copolymerised with propylene sulfide (PS) and end-capped with PEG vinyl sulfone; the resulting PEG-P(PS-ES) copolymers were found to have a gradient composition due to the greater reactivity of ES. The rate of oxidation with the PEG-P(PS-ES) micelles (1:1 monomer composition) was ~2x faster with respect to PEG-PPS. The effect of primary structure on oxidation and gelation was evaluated using copolymers with various ES/PS gradients; there was little effect on oxidation kinetics, however, high ES gradients displayed significantly lower gel points; we ascribe this to the higher ES-ES association in polymers with longer ES sequences. Chapter 4 investigated the Mitsunobu reaction as a means to functionalize PEG-OH with a variety of commonly used (bio)conjugation groups (thiol, maleimide, azide and amine). This project arose when synthesising PEG-thioacetate as a potential macroinitiator for the polymerisation of PS/ES. Currently, the Mitsunobu reaction is scarcely used for the functionalization of PEG-OH but here we demonstrate its benefits over other commonly used functionalization methods; namely, it being a quantitative and high-yielding one-pot synthesis reaction.

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The limited understanding of the electrochemical mechanism of Na-S battery systems is a barrier to further improve the performance of the Na-S energy storage. The characterization of sodium polysulfides in the Na-S battery systems can offer insightful information to understand the electrochemical reaction mechanism of the Na-S batteries and overcome the "inert" nature of short-chain polysulfides (Na2Sn, 1<n<4) during charge and discharge of the batteries. Up to now, there are limited studies on the sodium polysulfides compound in the Na-S batteries. Meanwhile, although many synthesis methods for sodium polysulfides have been reported, many related studies offer unclear and misleading parameters. This work examines several reported synthesis methods for sodium polysulfide. The results show that the sodium polysulfides cannot be obtained by the reaction of Na2S and S using anhydrous ethanol as the reaction media. In "dry" synthesis method, the pressure will influence the components in the product, and only Na2S4 can be synthesized at atmospheric pressure. This study also revises the synthesis method for Na2S2 and Na2S5, and detailed synthesis parameters are presented. The properties of sodium polysulfides in tetraethylene glycol dimethyl ether TEGDME were studied in this thesis. The solubility of Na2Sn in TEGDME increases with increasing sulfur in sodium polysulfide. The corresponding solution gets to longer-wavelength color and contains more long-chain polysulfides anions. / Master of Science / In recent decades, our society became more and more power-demanding, sodium-sulfur (NaS) energy storage systems attracted researchers’ attention due to their low cost and good performance. However, the limited understanding of the electrochemical mechanism of Na-S battery systems is a barrier to further improve the performance of the Na-S batteries. The characterization of sodium polysulfides in the Na-S battery systems can offer insightful information to understand the working mechanism of the Na-S batteries during charge and discharge of the batteries. Up to now, there are limited studies on the sodium polysulfides compound in the Na-S batteries. Meanwhile, although many synthesis methods for sodium polysulfides have been reported, many related studies offer unclear and misleading parameters. This work examines several reported synthesis methods for sodium polysulfide and offers complete processes with clear parameters for the synthesis of sodium polysulfide. Meanwhile, the sodium polysulfides solution in tetraethylene glycol dimethyl ether (TEGDME), an electrolyte solvent that was widely used in Na-S batteries, were analyzed to study the properties of sodium polysulfides in the Na-S battery system.

Issues with the dissolution and diffusion of polysulfides in liquid organic electrolytes hinder the advance of lithium–sulfur (Li-S) batteries for next generation energy storage. To trap and re-utilize the polysulfides, brush-like, zinc oxide (ZnO) nanowires based interlayers were prepared ex-situ using a wet chemistry method and were coupled with a sulfur/multi-walled carbon nanotube (S/MWCNT) composite cathode. The cell with this configuration showed a good cycle life at a high current rate ascribed to (a) a strong interaction between the polysulfides and ZnO nanowires grown on conductive substrates; (b) fast electron transfer and (c) an optimized ion diffusion path from a well-organized nanoarchitecture. A praline-like flexible interlayer consisting of titanium oxide (TiO2) nanoparticles and carbon (C) nanofiber was further prepared in-situ using an electrospinning method, which allows the chemical adsorption of polysulfides throughout a robust conductive film. A significant enhancement in cycle stability and rate capability was achieved by incorporating this interlayer with a composite cathode of S/MWCNT. These results herald a new approach to building functional interlayers by integrating metal oxides with conductive frameworks. The derivatives of the TiO2/C interlayer was synthesized by changing the precursor concentration and carbonization temperature. Finally, a dual-interlayer was fabricated by simply coating titanium nitride (TiN) nanoparticles onto an electro-spun carbon nanofiber mat, which was then sandwiched with a sulfur/assembled Ketjen Black (KB) composite cathode with an ultra-high sulfur loading. The conductive polar TiN nanoparticles not only have a strong chemical affinity to polysulfides through a specific sulfur-nitrogen bond but also improve the reaction kinetics of the cell by catalyzing the conversion of the long-chain polysulfides to lithium sulfide. Besides, carbon nanofiber mat ensures mechanical robustness to TiN layer and acts as a physical barrier to block polysulfides diffusion. The incorporation of dual interlayers with sulfur cathodes offers a commercially feasible approach to improving the performance of Li-S batteries.

The research presented in this thesis focuses on the molecular design of an oxidation-sensitive nanocarrier and its enzyme conjugate with a view of their application in the field of biomaterials. I have polarised our attention on a specific class of polymers, the polysulfides, for their environmental responsiveness (towards oxidising substances, a condition often associated with inflammatory reactions), interesting physico-chemical properties, ease of the preparation and multiple possibilities for further modifications and bioconjugations, which are perfectly suitable for the development as systems for drug delivery applications. In this work we firstly have focused on the synthesis of amphiphilic poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) block copolymers by employing vinyl sulfone as the functional group to link the blocks and modify the end of the PEG. This study was followed by an investigation of the macromolecular interchange and payload exchange of the formed polymeric micelles to understand the 'co-formulation' events, employing fluorophores (dansyl groups) and quenchers (dabsyl groups) either as terminal groups in macroamphiphiles or as encapsulated hydrophobic payloads. In another part of the work, I have developed a micellar system with which simultaneously to two of the most important ROS: superoxide and hydrogen peroxide, for inflammation-responsive drug release. The system is composed of superoxide dismutase (SOD) conjugated to oxidation-sensitive amphiphilic polysulfide/PEG block copolymers; the conjugate combines the SOD reactivity towards superoxide with that of hydrophobic thioethers towards hydrogen peroxide. Specifically, here we have demonstrated how this hybrid system can efficiently convert superoxide into hydrogen peroxide, which is then 'mopped-up' by the polysulfides. This mode of operation is functionally analogous to the SOD/catalase combination, with the advantage of being based on a single and more stable system.

This thesis deals with the preparation and characterization of electrode materials for Li-ion batteries based on elemental sulfur. The theoretical part is focused on the characteristics of Li-ion batteries, electrochemical reactions, the process of electrochemical lithiation of sulfur and solubility properties of intermediate polysulfides. The practical part of the thesis deals with the preparation of cathode materials for Li-ion cells with an active substance in the form of elemental sulfur. The prepared electrodes were investigated using cyclic voltammetry and galvanostatic cycling. Physical characterization by SEM and XRD was provided.

Adsorption is a versatile purification technique to selectively separate different peptide fractions from a mixture using mild operation conditions. Porous carbons are ideally suited to separate ACE-inhibiting dipeptides by combining tailored size exclusion and polarity selectivity. The desired peptide fraction is mostly hydrophobic and very small and should adsorb inside hydrophobic micropores. The second topic of this thesis is linked to energy storage. The lithium-sulfur battery is a promising alternative to common lithium-ion batteries with theoretical capacities of up to 1672 mAh g−1 sulfur. The second aim of this thesis is to conduct an in-depth investigation of polysulfides interacting with selected carbon materials in a simplified battery electrolyte environment. The focus of this study is laid on the impact of surface polarity and pore size distribution of the carbon to develop a quantitative correlation between polysulfide retention and porosity metrics. Both, the enrichment of ACE-inhibitors and the retention of polysulfides rely on liquid phase adsorption in porous materials, linking the above mentioned topics. This thesis not only aims to develop an enrichment process or to find a superior battery cathode but also strives to explore structure-property relationships that are universally valid. Understanding the complex interplay of pore size and polarity leading to selective interactions between pore wall and the adsorbed species is given a high priority.

Les travaux presentés dans ce manuscrit ont été consacrés à l’étude de composés organo-soufrés comme composants d’électrolyte pour systèmes électrochimiques de stockage d’énergie, en particulier dans les batteries lithium-soufre. Des liquides ioniques originaux, basés sur des cations sulfonium fonctionnalisés par des chaînes de type glyme ont été synthétisés et caractérisés, puis testés en tant qu’électrolytes dans des supercondensateurs symétriques avec électrodes en carbone activé. Il est apparu que l’adaptation de la structure des liquides ioniques à la porosité du carbone activé est d’importance fondamentale pour le développement de systèmes plus performants. L’ étude menée sur les batteries lithium-soufre a permis une meilleure compréhension des mécanismes de fonctionnement d’un système redox soufre/diphenyl disulfure dans des solvants glymes. L’influence des solvants sur les équilibres chimiques entre polysulfures organiques et minéraux et sur le fonctionnement du système a été étudiée. D’après les premiers résultats obtenus, cette stratégie semble particulièrement prometteuse pour améliorer les performances des batteries lithium-soufre. / The work presented in this manuscript concentrates on investigating the use of organosulfur compounds as potential electrolyte components for electrochemical energy storage systems, in particular in lithium-sulfur batteries. Novel glyme-functionalised sulfonium-based ionic liquids were synthesised and characterised before being tested as pure electrolytes for symmetrical supercapacitors based on activated carbon electrodes. The adaptation of the structure of the ionic liquids to the porosity of activated carbon was found to be of fundamental importance for the design of more efficient systems. For lithium-sulfur batteries, the study has enabled a better understanding of the mechanisms involved during the operation of the sulfur/diphenyl disulfide redox couple in a range of glyme-based solvents. Similarly, the influence of the glyme-based solvents on the chemical equilibria between organic and mineral polysulfides and on the system operation has been investigated. The initial results demonstrated that this is a particularly promising strategy in order to significantly improve the performances of lithium-sulfur batteries.

Developing next generation secondary batteries has attracted much attention in recent years due to the increasing demand of high energy and high power density energy storage for portable electronics, electric vehicles and renewable sources of energy. This dissertation investigates sulfur based advanced electrode materials in Lithium/Sodium batteries. The electrochemical performances of the electrode materials have been enhanced due to their unique nano structures as well as the formation of novel composites. First, a nitrogen-doped graphene nanosheets/sulfur (NGNSs/S) composite was synthesized via a facile chemical reaction deposition. In this composite, NGNSs were employed as a conductive host to entrap S/polysulfides in the cathode part. The NGNSs/S composite delivered an initial discharge capacity of 856.7 mAh g-1 and a reversible capacity of 319.3 mAh g-1 at 0.1C with good recoverable rate capability. Second, NGNS/S nanocomposites, synthesized using chemical reaction-deposition method and low temperature heat treatment, were further studied as active cathode materials for room temperature Na-S batteries. Both high loading composite with 86% gamma-S8 and low loading composite with 25% gamma-S8 have been electrochemically evaluated and compared with both NGNS and S control electrodes. It was found that low loading NGNS/S composite exhibited better electrochemical performance with specific capacity of 110 and 48 mAh g-1 at 0.1C at the 1st and 300th cycle, respectively. The Coulombic efficiency of 100% was obtained at the 300th cycle. Third, high purity rock-salt (RS), zinc-blende (ZB) and wurtzite (WZ) MnS nanocrystals with different morphologies were successfully synthesized via a facile solvothermal method. RS-, ZB- and WZ-MnS electrodes showed the capacities of 232.5 mAh g-1, 287.9 mAh g-1 and 79.8 mAh g-1 at the 600th cycle, respectively. ZB-MnS displayed the best performance in terms of specific capacity and cyclability. Interestingly, MnS electrodes exhibited an unusual phenomenon of capacity increase upon cycling which was ascribed to the decreased cell resistance and enhanced interfacial charge storage. In summary, this dissertation provides investigation of sulfur based electrode materials with sulfur/N-doped graphene composites and MnS nanocrystals. Their electrochemical performances have been evaluated and discussed. The understanding of their reaction mechanisms and electrochemical enhancement could make progress on development of secondary batteries.

Adsorption is a versatile purification technique to selectively separate different peptide fractions from a mixture using mild operation conditions. Porous carbons are ideally suited to separate ACE-inhibiting dipeptides by combining tailored size exclusion and polarity selectivity. The desired peptide fraction is mostly hydrophobic and very small and should adsorb inside hydrophobic micropores. The second topic of this thesis is linked to energy storage. The lithium-sulfur battery is a promising alternative to common lithium-ion batteries with theoretical capacities of up to 1672 mAh g−1 sulfur. The second aim of this thesis is to conduct an in-depth investigation of polysulfides interacting with selected carbon materials in a simplified battery electrolyte environment. The focus of this study is laid on the impact of surface polarity and pore size distribution of the carbon to develop a quantitative correlation between polysulfide retention and porosity metrics. Both, the enrichment of ACE-inhibitors and the retention of polysulfides rely on liquid phase adsorption in porous materials, linking the above mentioned topics. This thesis not only aims to develop an enrichment process or to find a superior battery cathode but also strives to explore structure-property relationships that are universally valid. Understanding the complex interplay of pore size and polarity leading to selective interactions between pore wall and the adsorbed species is given a high priority.