Synthesis of Poly Substituted cis-Hydrindanes

A. Corbella, P. Garibolidi and G. Jommi, J. Chem. Soc., Chem. Commun., 1973, 729 DOI: 10.1039/C39730000729

Spatiotemporal profiles of ensemble subthreshold neuronal oscillation were studied in brainstem slices using high-speed voltage-sensitive dye imaging. After local electrical stimuli, the overall voltage profile demonstrated coherent oscillatory waves that spread over the inferior olive (IO). These oscillations were also observed in concurrently obtained intracellular recordings from IO neurons. Over the first few seconds after the stimuli, the optically recorded oscillations clustered into coherent groups comprising hundreds of neurons. Statistical analysis of the spatial profiles of these clusters revealed size fluctuation around stable core regions that were surrounded by a rim the diameter of which varied in time during the oscillation period. The neuronal ensemble oscillations were calcium derived and had an average frequency range of 1-7 Hz. This rhythmic response demonstrated a different spatiotemporal distribution in the presence of picrotoxin, which induced the merging of neuronal clusters into larger areas of coherent activity. The possibility that such clustering is a consequence of intrinsic oscillations in ensembles of coupled neurons was tested using mathematical modeling.

In curarized dogs under artificial respiration, it was observed that (a) chlorpromazine in high and repeated doses (5 to 20 mg/kg ) can induce marked fall in blood pressure, tachycardia, and increased cerebral blood flow, (b) previous injections of similar high doses of chlorpromazme do not abolish either the pressor responses or cortical stimulation (outbursts) induced by metrazol, and both agents appear rather to lead to enhanced cortical outbursts, (c) chlorpromazme also does not affect the cortical stimulation (E E G changes) following injections of nikethamide, picrotoxin, or amphetamine,but antagonizes the blood pressure responses to these agents, (d) after ganglionic-blockade (ansolysen or hexamethonium) cortical changes induced by chlorpromazme are not prevented, but its depressor response is lessened by ansolysen, but on the contrary enhanced by hexamethonium, (e) after sympathetic blockade (hydergin) both the central stimulation and pressor responses to metrazol are prevented, but the depressor response to chlorpromazme is antagonized and combined hyderginmetrazol treatment appears to prevent the usually observed depressor effects of excessive chlorpromazine injections, and (f) diethazine appears to exert similar actions to those of chlorpromazine, but its effects are less sustained.

This study aims to determine whether or not biosorben synthesized from sea pandanus leaves, the influence of the type of acid used, the optimum adsorption efficiency of Cr and Pb metal ions from various wastes, as well as the synthesis results of biosorben character. The subjects were biosorben of sea pandanus Pandanus tectorius types of Java's southern coast. The objects are adsorptive properties and the character of the pandanus sea biosorben synthesized before and after activation. Purposive sampling is used as the sampling technique. The independent variables are the type of activator (HCl and H 2 SO 4 ) and waste water. The dependent variables are the adsorptive nature and character of the sea pandanus biosorben synthesis results. The study was conducted in three phases, namely the manufacture of biosorben sea pandan leaves, characterization and determination of adsorption efficiency (Ep) biosorben synthesized on metal ions of Cr and Pb in batik waste, leachate, and oil. Qualitative and quantitative analysis are done using Atomic Absorption Spectrophotometer instrument at a wavelength of 357.9 nm for Cr and 217 nm for Pb. Biosorben characterization was conducted on the moisture content, ash content, volatile content, and carbon content compared with SNI 06-3730-1995 and analyzed by FTIR spectra. It is also seen biosorben surface area of synthesized both before and after activation by porosimetry. Biosorben of pandanus sea has to be synthesized. Biosorben synthesized with 5% H 2 SO 4 solution produced optimum Ep for Cr and Pb metal ions from waste leachate obtained are 75.831% and 98.714%. Character biosorben activation results in a solution of 5% HCl and H 2 SO 4 by FTIR have almost similar spectra. Moisture content, ash content, volatile content, and carbon content of biosorben synthesized with 5% HCl and 5% H 2 SO 4 in accordance with SNI 06-3730-1995. Porosimetry characterization of biosorben synthesized before activation is 3.5756 m 2 / g, whereas after activation with HCl 5% to 770.7636 m 2 /g, and after activation with 5% H 2 SO 4 solution become 153.7002 m 2 /g. Keywords: biosorben, sea pandanus, adsorptivity test, chromium, lead

This thesis explores new synthetic methodology for the construction of multiporphyrin arrays. The formation of new carbon-carbon bonds is a unifying theme in all of the syntheses presented as part of this work. Suzuki cross-coupling chemistry and olefin metathesis were explored in the context of synthetic porphyrin chemistry leading to large, multichromophoric systems. Subsequent analysis of the host-guest chemistry of these systems gave insight into cooperative processes and the association kinetics in supramolecular complexes held together by metal-ligand and π-π interactions. Initial work focused on template-directed strategies for the synthesis of cyclic porphyrin arrays. The unusually high affinity of fullerenes for porphyrins inspired the application of C60 and C70 to the templated synthesis of two different types of cyclic porphyrin trimer. Olefin metathesis was selected as the method of reversibly linking the porphyrinic monomers during synthesis, resulting in a product distribution that is largely under thermodynamic control. The fullerene is also believed to have a secondary, kinetic role in the stabilisation of a 3-porphyrin transition state prior to covalent linkage. Varying the solvent composition during the synthesis of the hexa-linked trimer showed that the product yield varied quadratically with the percentage of toluene in dichloromethane/toluene mixtures. This result illustrated the complex and synergistic relationship between solvation, desolvation and cooperative processes in a templated synthesis driven by π-π interactions. Solvent-related differences in the initiation rate of Grubbs’ catalyst were also considered in light of this result. The second component of this thesis describes the design of an artificial light harvesting device based on a supramolecular cucurbit[7]uril-methyl viologen inclusion complex with porphyrin units appended to the periphery. Although the synthetic chemistry leading to a covalently-linked cucurbituril-porphyrin conjugate was unsuccessful, several broadly applicable porphyrinic building blocks were developed as part of this work. Recognition processes in multivalent metalloporphyrin hosts were studied using a binding motif based on a biphenyl-linked bisporphyrin. The synthesis of these porphyrin dimers and dyads proceeded via a stepwise approach in which sequential amide and Suzuki couplings gave rise to both homo- and heteroporphyrin dyads in reasonable yields and without the need for extensive purification. The complexation of the Zn(II)/Zn(II) dimer with 4,4’-dipyridyl, 1,2-bis(4-pyridyl)ethane and DABCO was examined, revealing that a ‘cyclic’ 1:1 complex forms initially and is eventually degraded to the 1:2 complex in the presence of excess ligand. The calculated microscopic binding constants were self-consistent with the Ka values derived from titration of this host with the monotopic ligands pyridine, 4-methylpyridine and quinuclidine. Secondly, the elaboration of this core binding motif with a derivative of C60 was achieved using similar synthetic methodology. Intended as a tunable system where the efficiency of photoinduced electron transfer could be studied as a function of donor-acceptor orientation, the host-guest chemistry of this complex was also explored. The K1 values for the formation of a supramolecular tetrad with the bipyridyl ligands were 30-40% lower cf. the model zinc(II) dimer, reflecting competition from the C60 moiety. The binding stoichiometry of the bisporphyrin-C60 triad-DABCO complex was determined by a combined global non-linear regression analysis of UV-vis and fluorescence spectroscopic titration data, revealing the unusual self-assembly of a 2:2 complex.

Metal nanoparticles have attracted considerable interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Among different metal nanoparticles, Copper and Nickel nanoparticles have attracted great attention. Grinding method is used to synthesize Copper and Nickel nanoparticles. In this paper, the new cationic Thiol polyurethane surfactants with different alkyl chain length were synthesized (PQ8, PQ10 and PQ12). The chemical structure of the synthesized surfactants was confirmed using infra-red spectroscopy (IR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). The nanostructure of the synthesized surfactant with Copper and Nickel nanoparticles with diameters ranging from 10 to 55 nm was prepared and characterized using ultra violet spectrophotometer (UV), infra-red spectroscopy (IR) and transmission electron microscope (TEM). The results declare formation and stabilization of Copper and Nickel nanoparticle using synthesized cationic surfactants. Antimicrobial activity of the synthesized cationic surfactants and their nanostructure with Copper and Nickel nanoparticles were evaluated against pathogenic bacteria and fungi. The antimicrobial activity showed the enhancement in the antimicrobial activity of the synthesized cationic surfactants in the nanostructures form.

The aim of the present study is to demonstrate how mesoporous nanostructures of Zinc Sulfide (ZnS) will precipitate in an ethanol media in spite of negligible solubility of Sodium Nitrate (Na2S), which is role-played as sulfur precursor. On the following, the role of such synthesizing method on the photocatalytic behavior of ZnS mesoporous nanostructures has been investigated. Characterization of the synthesized samples was carried out through X-ray diffraction patterns (XRD), Furrier Transformation Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Diffuse Reflectance Spectroscopy (DRS), Field Emission Scanning Electron Microscopy (FESEM) and N2 adsorption – desorption analysis. Formation of NaNO3 in assistance with negligible solubility of Na2S in ethanol enhances the stability of ZnS nanoparticles. Besides, formation of NaNO3 as well as sonication process can induce mesopores in the ZnS nanoparticles. Changes in the critical micelle concentrations (CMCs) of CTAB had impacts either in the lattice properties or in the textural structure of the mesopores of the synthesized samples. An attempt was made to explain how enhancement of CMCs values made crystallite size decreased and subsequently lattice strain increased. The photocatalytic behavior and the adsorption capacity of the ZnS mesoporous structures were studied through methylene blue degradation from aqueous solution. It was found that adsorption capacity and photocatalytic efficiency of synthesized samples were improved by modification of CMC values of CTAB. Findings were in compatibility with the band gap energy values and water droplet contact angle measurements. This study is finalized with explaining how the synthesized photocatalysts remove contaminations under ultraviolet irradiation.

Galectins are β-galactoside binding proteins that are found in all type of living organisms, and involved in many physiological functions such as inflammation, immune responses, cell adhesion, growth and migration, apoptosis, etc. Due to their association with the progression of several metabolic and disease conditions, galectins are recognised as important targets for the drug development. Galectin-8 is involved in several biological functions such as cell adhesion and growth, immune responses, inflammation, new blood vessel formation, osteoblast and osteoclast differentiation, cancer growth and metastasis, platelet aggregation. Structurally, galectin-8 is a tandem-repeat type galectin, comprising an N-terminal and (galectin-8N) C-terminal (galectin-8C) CRD domain connected by a peptide linker. Superimposition of both the CRDs reveals structural differences between their carbohydrate binding sites. The individual N- and C-CRD domain shows similar functional roles which are observed with full length galectin-8, however, their potency is less compared to full length galectin-8. Several structural investigations showed that the N-terminal domain preferentially binds to the anionic sialylated, sulphated oligosaccharides due to the presence of the unique Arg59, which is only present in galectin-8N and hence is unique amongst all galectins. The main body of research presented in this thesis is about design, synthesis of selective and potent galectin-8N antagonists by utilising a structure-based drug design approach. Our previous structural investigation revealed unique amino acids of the galectin-8N binding site such as Arg59, Gln47, Tyr141. The structure-based ligand design campaign was further continued by targeting these unique amino acids of the N-terminal carbohydrate binding site. The novel compounds have been successfully designed and chemically synthesized. Galectin-8 protein expression (in E. coli) and affinity-based purification (using Lactosyl-Sepharose column) were performed to obtain the purified protein. The binding affinity of the synthesized compounds against galectin-8N were evaluated by ITC. X-ray crystallography was carried out to determine the binding interactions of compounds with the galectin-8N carbohydrate binding site. These compounds were further evaluated in cell culture studies to determine their ability to inhibit cancer promoting gene expression during my visit to our collaborator Prof. Yehiel Zick’s research laboratory, at the Weizmann Institute of Science, Israel. It was reported that disaccharide lactose has stronger binding affinity than the monosaccharide galactose due to significantly more interactions with the galectin-8N binding site. However, we chose to work with monosaccharide galactose as a pharmacophore at the beginning of the drug design campaign. For the design of galactose 3-OH substitution, the initial thought was to design an inhibitor which can cross-link two arginines (Arg45, Arg59) that are located across the binding site and thus holding the inhibitor from both sides. The primary aim was to design unique scaffolds which can cross link these arginines. After deciding the scaffold, we successfully designed, synthesized a library of galactomalonic acid derivatives and determined their in vitro binding affinity against galectin-8N. This structure-based ligand design approach led to the development of a monosaccharide based compound 42 which shows almost 7 times stronger binding affinity than the disaccharide lactose. The X-ray crystallographic structural investigation of the galectin-8N-compound 45 complex revealed the binding interactions which are responsible for the strong binding affinity of these compounds. Considering these novel research findings, the galactose-coumarin ester complexes were subsequently designed, synthesized and analysed to determine their in vitro binding affinity. The binding affinity results demonstrated that the galactose-coumarin ester complex 70 shows 5 times stronger binding affinity than disaccharide lactose. Compound 70 was further analysed in SUM159 cell culture and a mice osteoblast study. The cell culture results demonstrated that compound 70 could be a potential candidate for anti-cancer drug discovery. Our structure-based drug design campaign was further continued to design even more stronger binding affinity compound. Bis(methyl-β-D-galactopyranoside)-3-O-malonate was designed, synthesized and analysed for determining its in vitro binding affinity. The binding affinity results demonstrated that it shows almost 6 times stronger binding affinity than disaccharide lactose. Our collaborator Prof. Yehiel Zick and colleagues recently reported that galectin-8 upregulates proinflammatory cytokine and chemokine gene expression in several cell types including mice osteoblast. It was also observed that these cytokine and chemokine promotes the migration of cancer cells toward cells expressing this lectin. Based on these results, the synthesized novel compounds were analysed in cell culture and osteoblast studies during my research visit to Prof. Yehiel Zick’s research laboratory, at the Weizmann Institute of Science, Israel. The cell culture results demonstrated that the biological inhibition of these compounds follows the order of in vitro binding affinity of these compounds. Overall, the research presented in this thesis, demonstrates the successful rational medicinal chemistry application to design and development of potent galectin-8N antagonists to tackle galectin-8 associated diseases.

In this paper, we study the problem of rule synthesizing from multiple related databases where items representing the databases may be different, and the databases may not be relevant, or similar to each other We argue that, for such multi-related databases, simple rule synthesizing without a detailed understanding of the databases is not able to reveal meaningful patterns inside the data collections Consequently, we propose a two-step clustering on the databases at both item and rule levels such that the databases in the final clusters contain both similar items and similar rules A weighted rule synthesizing method is then applied on each such cluster to generate final rules Experimental results demonstrate that the new rule synthesizing method is able to discover important rules which can not be synthesized by other methods.

Driven by the concern about the future petro-chemical feedstock availability, as well as the need for a green and sustainable society, renewable and bio-based materials have become the natural candidates for alternatives to petro-chemicals. As the most abundant biomass feedstock, carbohydrates are attracting significant attention from both academia and industry for the production of chemicals, fuels and energy. However, one major drawback of directly using carbohydrates in industrial processes is their limited thermal stability caused by the existence of multiple functional groups, for instance hydroxyl groups. Consequently, simplified or bi-functional carbohydrate-derived building blocks are often more attractive than the virgin carbohydrates for polymer chemists. In this thesis, we aim to 1) develop a new family of difunctional bio-based building blocks, and 2) utilize these new building blocks as AA monomers to synthesize step-growth polymers, such as polyesters and polyamides. Ideally, the new polymers are expected to be semicrystalline, preferably having high melting (Tm) and high glass transition temperatures (Tg), and can be used as the potential fully or partially bio-based engineering plastics. Isohexides (1,3:4,6-dianhydrohexitols), a group of secondary, rigid diols, as well as their derivatives are interesting carbohydrate-derived building blocks for various types of step-growth polymers, such as polyesters, polyamides and polycarbonates. Due to the intrinsic rigidity of the structures, isohexides are capable of increasing the glass transition temperatures when incorporated into polymers. However, the relatively poor reactivity of the secondary hydroxyl groups of isohexides has been recognized as a main drawback, which often results in low molecular weight or discolored polymers. In order to overcome these problems, as well as utilizing the rigidity of the isohexide skeleton, a new family of 1-carbon extended isohexide-derivatives were designed and synthesized by transforming the less reactive secondary hydroxyl functionalities into more reactive ones. Based on a key dinitrile intermediate, viz. isoididedinitrile (IIDN), the novel isohexide-derived building blocks were obtained. They are: isoidide-2,5-dicarboxylic acid (IIDCA) and its dimethyl ester (IIDMC), isoidide-2,5-dimethanol (IIDML) and isoidide-2,5-dimethyleneamine (IIDMA). After optimization of the respective synthetic routes, these building blocks were obtained at sufficient scales (5–20 g/batch) and high purities (>99.5%) to be suitable for polymerizations. Three series of polyesters based on the novel 1-carbon extended isohexides were synthesized. The first series of polyesters is based on isoidide dicarboxylic acid (IIDCA) and linear alkylene diols. Unexpectedly, they have rather low Tm (60–100 °C) values whereas the recorded low Tg values (-30–18 °C) were approximately expected. The second series of polyesters is fully based on renewable, isohexide-derived monomers. The combination of both isohexide-based AA/BB monomers gave significantly higher Tg values (45–85 °C) than the partially linear aliphatic polyesters of the first series. Importantly, this part of the project revealed the promising characteristics (reactivity, rigidity and thermal stability) of isoidide-2,5-dimethanol (IIDML) for potential applications in performance polymers with high Tg and Tm. Therefore, the third series of polyesters was entirely focused on IIDML-based semi-aromatic systems. The Tg and Tm values of these polyesters were found to exceed even those of the conventional PET and PBT polyesters, confirming our expectation that IIDML is a promising rigid cyclic diol for engineering plastic applications. Two series of semicrystalline (co)polyamides were synthesized from the new isoidide 2,5-dimethyleneamine (IIDMA) or from a mixture of IIDMA and 1,6-hexamethylene diamine with the biobased dicarboxylic acids sebacic acid or brassylic acid. A combination of melt polymerization of nylon salts with solid-state polycondensation (SSPC) processes afforded the desired copolyamides with maximum number average molecular weight (Mn) of 49,000 g/mol. Analysis by temperature dependent soldi state NMR and FT-IR spectroscopies revealed that the new diamine IIDMA exist in both the crystalline and amorphous phases of the copolyamides. Given the sufficiently high Tm values (~200 °C) of the copolyamides containing less than 50% of IIDMA, these bio-based semicrystalline copolyamides can be useful for engineering plastic applications. By comparing the thermal properties of the polymers based on the new isohexide-based building blocks, i.e. IIDCA, IIDML and IIDMA, with relevant reference polymers, systematic structure-thermal properties studies of each series of polymers were conducted. This work objectively evaluated the relative rigidities, reactivities and thermal stabilities of these new building blocks with respect to those of the parent isohexides, as well as with respect to their linear, cyclic aliphatic and aromatic analogues. Both the experimental (i.e., single crystal X-ray diffraction) and computational-aided methods (i.e., Density Functional Theory (DFT)) were employed to elucidate the structural characteristics of the isohexide-based building blocks, as well as to understand the specific thermal properties of the polymers based thereon. Additional efforts were invested to expand the dinitrile platform to the other stereo-isomers. The isomeric isohexide dinitriles were synthesized by base-induced epimerization. The strong non-nucleophilic organic base 1,8-diazabicycloundec-7-ene (DBU) was found to be a suitable catalyst for such type of isomerization. A kinetic study on the epimerization of three dinitrile isomers revealed an equilibrium between the three possible isomers in THF. Single crystal X-ray diffraction studies demonstrated several structural characters of these molecules regarding their symmetry and linearity. Density Functional Theory (DFT) calculations further supported the base-induced epimerization mechanism. This work concerns a pioneering study of deoxy-1-carbon-extended isohexide-based building blocks. All the monomers and polymers synthesized, characterized and evaluated in this thesis are entirely new. Suitable synthetic laboratory-scale protocols were developed for all the monomers and polymers. The reported study of the structure-thermal properties relations, as well as the crystal structure elucidation by single crystal X-ray diffraction and DFT, are also of high importance concerning the field of isohexide-based polymers and will certainly prove to be very useful for drawing conclusions on the industrial feasibility of such bio-based materials.

The main goal of this work was to synthesize and evaluate the effect of dehydration temperature on the potential application of hydroxy sodalite zeolite membrane. Hydroxy sodalite zeolite membranes were synthesized via direct hydrothermal method onto a tubular alumina support without seeding in a hot air oven. The synthesized membranes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Permeation tests of H2 and CO2 were carried out in order to investige the applied dehydration temperature effect on the performance of the synthesized membranes. The performance of the synthesized membrane dehydrated at 100 ºC tended to high selectivity compared to that of the rest samples and the maximum separation factor (~21) was achieved with acceptable permeances about 3.810-8 and 1.8*10-9 mol.m-2.Pa-1.s-1 for H2 and CO2, respectively. The low selectivities observed for two other synthesized membranes (dehydrated at 150 and 200 ºC), indicating the formation of defects during the dehydration of these membranes at high temperatures.

Recently, the synthesis of silver nanoparticles has become an important subject in the bionanotechnology field. Many different chemical and physical methods could be used for silver nanoparticles synthesis, but they are limited due to the usage of toxic chemicals and the production of dangerous by-products. However, the usage of plant extract for silver nanoparticles synthesis is a green single-step method without using toxic chemicals. Herein, silver nanoparticles were synthesized using Lithospermum officinale root aqueous extract and their antioxidant activity was evaluated in vitro. The results showed that 1 ml of the extract could reduce 9 ml of silver ions (1 mM) to silver nanoparticles by heating the reaction mixture (60 ºC) for 6 hours at pH 7.0. The synthesized silver nanoparticles were detected by UV–Vis spectroscopy, TEM, FT-IR, DLS, and XRD. The synthesized silver nanoparticles spectrum had a maximum peak at 390nm, and TEM analysis indicated spherical particles, higher stability (zeta potential: -15.3 mV) and an average size of 7 nm. The antioxidant activity of the synthesized silver nanoparticles was 0.07 mg/ml compared to L. officinale root aqueous extract (0.142 mg/ml) which indicated higher antioxidant activity. So, it is concluded that the synthesized silver nanoparticles could be considered a clinical therapeutic potential due to its antioxidant property.

In this work, acrylic acid-based HBP and various monomers and polymers from itaconic acid have been synthesized and evaluated to gain a deeper understanding about the structure-properties relationship of UV-curing hyperbranched polymers. The focus was placed on the use of itaconic acid as it has the potential to be a bio-based alternative to acrylic acid for a range of UV-curing applications such as additive manufacturing, coatings or printing inks. Six acrylated HBP were synthesized and evaluated to determine the impact of each building block on the final properties. A novel simple synthesis pathway was developed that did not require the use of activated reagents leading to highly substituted materials while avoiding all gelation risk. The material showed higher reactivity towards UV-curing and higher mechanical and thermal properties than materials previously described. Novel building blocks from itaconic acid were developed using a simple and scalable process. Eight monoesters of itaconic acid were synthesized using simple and more complex cyclic alcohols. These monomers were reacted with a vegetable oil and the characterization of the resulting material showed that cyclohexyl itaconate was the most promising candidate. Hyperbranched polymers from itaconic acid were synthesized through different strategies. As simple esterification reactions lead to undesired side-reaction when the difunctional itaconic acid is used, several alternative pathways were investigated and are described. The most successful strategy involved the reaction of itaconic anhydride with a (branched) core followed by an end-capping reaction with an epoxide. Applying this strategy, 13 hydroxyalkyl terminated HBP_It were developed using a variety of core, generations and end groups. These promising materials exhibited good reactivity and properties and are good candidates to be used as UV-curable material or additive tougheners. Finally, novel reactive diluents from itaconic acid were synthesized, the first of their kind due to the challenging reactivity of itaconic and the lower intrinsic reactivity towards UV-curing. These monomers were found to greatly improve the viscosity, the reactivity, and the thermal and mechanical properties when mixed with UV-curing resins derived from itaconic acid.

In this research, bimetallic catalysts including Pd and Pt was synthesized on the composite of carbon nanotube (CNT) with Nafion and compared with Pd-Pt synthesized on CNT considering the key role of catalysts in PEMFC electrodes. The difference between the electrodes fabricated from these two synthesized catalysts was in the adding time of Nafion. The synthesized catalyst can enhance the performance of gas diffusion electrode (GDE) in cathode reaction (Oxygen Reduction Reaction or ORR) of polymer electrolyte membrane fuel cell (PEMFC) compared to commercial Pt/C catalyst. The bimetallic catalyst was synthesized in two steps. Pd and Pt were reduced at the first and second step, respectively. To reduce metals on support, the impregnation method were used along with hydrothermal. The electrochemical performance of the electrodes in ORR was studied through the Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). Inductively coupled plasma (ICP), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM) techniques were applied to characterize the catalyst. The results have confirmed that the timing of Nafion addition can influence the electrode performance for ORR.

The research described in this thesis entails the synthesis of comb-like polymeric materials with long alkyl methacrylates side chains and their cold flow properties evaluations in crude derived as well as Gas-To-Liquid (GTL) diesel fuels produced by Sasol’s proprietary Fischer Tropsch technology. Statistical copolymers of styrene with methacrylate pendant alkyl chain lengths ranging from C18 to C22, as well as blend alkyl chains of C16 – C24 were selected for this study, and prepared via Atom Transfer Radical Polymerization (ATRP) as the chosen controlled radical polymerization technique. The design of the polymeric materials of interest was based on obtaining polymers with two major constituents viz. crystallizable fractions and the amorphous/non-crystalline fractions. The crystallizable fraction would co-crystallize with the fuel’s paraffin wax fractions thus preventing the paraffins from forming unfavorable large 3-D crystal matrix, while the non-crystalline part would aid in disrupting crystal growth and modifying the crystal structures. The first part of the study focused on using ATRP to synthesize various statistical copolymers of interest in a controlled manner. The second part of the study dealt with applications of the synthesized polymeric additives in diesel fuels’ cold flow applications. Within the applications, two application areas were looked at viz. cold flow improvers and wax dispersants or wax antisettling applications. The synthesized statistical copolymers were evaluated for their cold flow properties for selected diesel fuels, with the focal aim of gaining fundamental understanding into factors influencing crystallization responses of the selected middle distillate fuels and the respective polymeric additives. The physicochemical properties of the copolymers were followed via crystallization interactions of both the diesel fuel and the comb-type polymeric additives. These interactions were assessed through Differential Scanning Calorimmetry (DSC), low temperature optical microscopy, Cold Filter Plugging Point (CFPP) and Pour Point (PP) tests. The influence of varying styrene contents of the statistical copolymer was investigated. The crystallization response in GTL diesel fuels demonstrated the significant influence in the structure/property activity of the additive as well as the fuel. Based on crystallization modifications observed, the polymeric additives illustrated solvent matrix selectivity in different fuels studied. Copolymers with too high, too low or no crystalline components promoted the unfavorable wax crystallization, as observed in the case of homopolymers of alkyl methacrylates for example. These polymeric types did not facilitate good solubility of the polymeric additive in the diesel matrix therefore leading to minimal interactions with the diesel matrix. Obtaining polymeric additives with just the appropriate balance of the two components was therefore crucial. Such polymers in the diesel fuels evaluated demonstrated a lowering of Wax Appearance Temperature (WAT) also known as Cloud Point (CP) by 5 degrees and also managed to obtain ?CFPP of 6 degrees. These results allowed an insight into the crystallization operating mechanisms of the statistical styrene-alkyl methacrylate copolymers. The results illustrated that the statistical copolymer additives indeed displayed both cloud point depressants and crystal growth inhibitors qualities. These results were however diesel fuel specific since the polymeric additive demonstrated different crystallization activities in different GTL diesel fuels used in the study. In the second application area, wax antisettling additives (WASA) or wax dispersing (WD) additives were investigated. Compounds that contained long alkyl chains and ionic charges were evaluated as wax dispersants for crude derived as well as GTL diesel fuels in combination with the synthesized ATRP statistical copolymers. The WD included quaternary salts, ionic liquids and gemini surfactants. Gemini surfactants were synthesized and in a novel application they were investigated for wax dispersing properties in crude oil derived diesel. Together with the evaluated statistical copolymers the surfactants were found to be efficient wax dispersants. These systems demonstrated the ability to facilitate a further size reduction and modifications in wax crystals, as evidenced by low temperature microscope from 10µm needles to smaller dot-like structures. A further lowering of the CFPP (?CFPP ˜ 12 °C) was achieved with some of the evaluated gemini surfactants.