Dissertations / Theses on the topic 'Mechanochemistry'
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Ralphs, Kathryn Louise. "Catalyst synthesis by mechanochemistry." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709699.
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Howard, Joseph. "Exploring mechanochemistry for organic synthesis." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/116636/.
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This thesis describes an investigation into performing organic synthesis under mechanochemical conditions. Procedures were developed for the selective mono- and difluorination of 1,3-dicarbonyls and the one-pot, two-step synthesis of fluorinated pyrazolones under ball milling. Attempts to perform a two-step mechanochemical synthesis of difluoromethylthioethers led to exciting results demonstrating that ball milling can lead to alternative reactions occurring. Finally, some initial results into the generation and reaction of organomanganese reagents under mechanochemical conditions are reported. Initial investigations into the use of mechanochemistry for organic synthesis focused on the mechanochemical formation of the C-F bond, with a particular focus on differences in selectivities observed under different milling conditions. It was found that electrophilic fluorination of 1,3-dicarbonyls could be achieved under ball milling conditions using Selectfluor. The selectivity of this process could be significantly enhanced using Liquid Assisted Grinding with acetonitrile as an additive. The possible causes of this observed change in selectivity were investigated. Further work developing a one-pot, two-step mechanochemical process was performed. A procedure for the synthesis of fluorinated pyrazolones was developed and some of the key considerations when attempting one-pot mechanochemical procedures were established by a careful optimisation. Conditions compatible with both the heterocycle formation step and the fluorination step were found and a range of fluorinated pyrazolones successfully synthesised by this method. It was observed that mechanochemistry could be used to alter the chemoselectivity of a reaction while attempting the synthesis of difluoromethylthioethers. After detailed study, a hypothesis to the origin of this alteration in selectivity was proposed. Finally, some initial results into the use of mechanochemical methods to activate manganese metal for applications in synthesis are presented.
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Ortiz-Trankina, Lianna N. "Investigating Benign Syntheses via Mechanochemistry." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613746553330943.
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Wang, Cong. "Synthesis of Polyaromatic Hydrocarbons via Mechanochemistry." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563525733261563.
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Müller, Julian [Verfasser]. "Theoretical Investigations of Covalent Mechanochemistry / Julian Müller." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1136903259/34.
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Restrepo, David. "Mechanochemistry for Solid-State Syntheses and Catalysis." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5692.
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Traditional methods of synthesizing inorganic materials, such as hydrothermal, sol-gel, calcination and grinding steps, can typically require use of high temperatures, expensive precursors or use of solvents. Because of the energy-intensive nature or environmental impact these techniques, there is a push, especially from an industrial perspective, to move towards greener approaches. Mechanochemistry is a solvent-free alternative technique that can be used to synthesize a variety of materials under ambient conditions. Due to this, there is an increase in attention towards the use of this approach in both solid-state inorganic and organic chemistry. This dissertation reports the mechanochemical synthesis of a few inorganic materials without the need of using high temperatures or solvents. Additionally, examples are presented in which mechanochemistry is used in conjunction with a secondary technique. This mechanical activation of the precursors lead to a decrease in calcination temperature and reactions times, as well as alteration of properties or unique reaction products. The synthesis of kaolinite, vanadia nanostructures, and spinels were carried out in this fashion. Mechanical activation of the precursors allowed for reduced hydrothermal treatment times in case of both kaolinite and vanadia nanostructures and the spinels are calcined at lower temperature for shorter periods of time. In addition, we report alternative template agents than previously reported for the formation of vanadia nanotubes, and report the formation of nanorods. Choosing the appropriate amine template can alter the structure and size of the material. Isomorphously substituted mixed oxides, kaolinite and spinels (MgAl2O4 and ZnAl2O4) were synthesized through a mechanically assisted process. Kaolinites are treated hydrothermally for 1 week at 250 [degrees]C to produce an X-ray pure crystalline material. The spinels undergo calcination as low as 500 [degrees]C to produce a nanocrystalline material. Rare-earth metals and transition metals were used as the substitutional atom. The substituted kaolinites exhibit strong order along the c axis, but less ordering along the a and b axes. Trivalent chromium and trivalent rare-earth metals, such as La, Ce, Pr, Nd, Eu, Gd, Ho, and Er, are used to replace aluminum in the structure. Likewise, divalent and trivalent transition, such as Mn, Ni, Cu and Cr, are used as the substitutional atoms in MgAl2O4 and ZnAl2O4. Cathodoluminescence studies on the substituted Spinel structure show that Mn2+ ions can occupy both the tetrahedral or octahedral holes to give a green and red emission, respectively. On the other hand, Cr3+ ions only occupy the octahedral holes to yield a red emission, similar to that in ruby. These isomorphously substituted materials may have potential applications in catalysis or glaze materials in ceramics. Oxidized graphite, an alternative to graphite oxide and graphene, can be synthesized rapidly by mechanochemical means. Grinding urea hydrogen peroxide adduct with graphite without the need of a solvent produces a product with an oxygen content of 5-15 wt%. The byproducts of this reaction are urea and water. This material is oxidized along the edges of the sheets, allowing it to be hydrophilic while retaining the conductivity. The material can suspend in water and processing allows for films of resistivities between 50 Ω cm-2 and 10 kΩ cm-2. It was determined that the edges are fully oxidized to yield –COOH groups. This process offers a scalable, environmentally benign route to large quantities of oxidized graphite. An alternative method for the synthesis of nanostructured vanadia is reported. This process involves mechanical grinding of vanadium pentoxide, V2O5, with an amine template, such as diphenylamine, theophylline, rhodamine 6G and rhodamine, prior to hydrothermal treatment. This allows for the synthesis of VOx nanotubes and nanorods dependent on which template is used. Diphenylamine, theophylline, and rhodamine B produce nanorods. Use of rhodamine 6G produces asymmetric VOx nanorods. In addition to the mixed metals oxides mentioned above, sodium and calcium tantalates are synthesized mechanically. This route does not require the need of elevated temperatures or expensive and hazardous materials. X-ray diffraction analysis of NaTaO3, Ca2Ta2O7, Ca4Ta2O9 and CaTa2O6 shows that these are the only phases detected after 4 h, 10 h, 27 h and 10 h of milling, respectively. During the synthesis of Ca2Ta2O7, an intermediate phase, Ca4Ta2O9, forms within 1 h, which reacts after 5 h to form the desired product. Reference Intensity Ratio analysis shows that the material synthesized mechanically is nanocrystalline Ca2Ta2O7. Nanocrystalline ZrSi2 can also be obtained through mechanochemical synthesis. This method allows for size control and results in crystallites ranging from 9 to 30 nm. Dilution with CaCl2 enables the size control process. A linear relationship exists between the concentration of CaCl2 and the crystallite size. Contrary to a typical self-propagating metathesis reaction, this process does not allow for self-propagation and requires continuous input of mechanical energy to continue. However, this method allows for non-passivated nanoparticles of ZrSi2, which can be incorporated into composites as a reinforcement material for several applications. Hard and ultra-compressible borides, such as ReB2 and OsB2, can be synthesized mechanically. The traditional synthesis of ReB2 requires excess boron due to treatment at high temperatures. This can lead to amorphous boron aggregating at the grain boundaries, which in turn, this would degrade the properties of the material. The mechanochemical approach requires mechanical treatment of Re and B powders in stoichiometric quantities for 80 h. Mechanical synthesis of OsB2 powders requires a 1:3 ratio of Os and B powders. After 12 h of milling time, h-OsB2 begins to form, and is the major phase present after 18 h. The lattice parameters corresponding to the hexagonal OsB2 were determined to be a = b = 2.9047 Å, c = 7.4500 Å, α = β = 90º, γ = 120º. Treatment of the OsB2 powder at 1050 ºC under vacuum for 6 days did not induce a phase change, suggesting the hexagonal phase is very stable. Mechanocatalysis of the depolymerization of cellulose and hydrogenation of olefins over BN are reported as well. Heterogeneous catalysis is difficult to apply to solids, such as cellulose. However, mechanical grinding of kaolin and cellulose allows for the catalysis to occur in the solid state. This process allows for a variety of different biomasses to be used as feedstock without inhibition. Kaolinite was found to be the best acid catalyst due to high surface acidity and its layered structure, allowing for up to 84% conversion of the cellulose to water-soluble compounds. This process allows for reduction of waste, insensitivity of feedstock, multiple product pathways and scalability. Hydrogenation reactions are carried out using transition-metals catalysts. These metals have desirable catalytic properties not seen in main group elements, but there is growing concern over their use. A metal-free heterogeneous hydrogenation catalyst based on frustrated Lewis pairs would significantly reduce the health, environmental, and economic concerns associated with these metal-based catalysts. We report the first metal-free heterogeneous hydrogenation catalyst. Hydrogenation of trans-cinnamic acid is carried out over defect-laden h-BN. The reactor we use is designed to maximize the defects produced in BN sheets. The introduction of defects in BN creates frustrated Lewis pairs. DFT calculations show that the carbon double bond is weakened over boron substitution for nitrogen sites, vacancies of both boron and nitrogen, and Stone-Wales defects. A new method for crystalline germanium deposition occurring at lower temperatures (210-260 [degrees]C) is reported. This method involves mechanical treatment of the precursors to reduce the particle size. A ground mixture of Ge and CuI are heated under vacuum to synthesize GeI2. In situ disproportionation of this compound at 210 [degrees]C allows for the deposition of polycrystalline Ge films onto a both glass and polymer substrates. The rate of deposition is found to be 25 ng min-1. The byproducts of this process are GeI2, GeI4 and Cu3Ge, which are valuable precursors for the synthesis of germanium nanostructures and organogermanium compounds. Mechanochemistry is also utilized for the synthesis of trisubstituted pnictides. Mechanochemical treatment of bromobenzene with either Na3Sb or Na3Bi allows for the formation of triphenylstibine or triphenylbismuthine, respectively. The synthesis of the alkali metals pnictide precursors is reported as well. The synthesis of triphenylstibine produces SbPh3 as the major product from the reaction. The synthesis of triphenylbismuthine produces more Wurtz-type coupling products, which are due to the BiPh3 acting as a catalyst. Tributyl and triphenyl analogues are reported as well. The trialkylated analogues for both Sb and Bi produce more Wurtz type coupling products. This would allow for a more cost effective and scalable, alternative methods than what is currently in use today.Ph.D.
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Chemistry
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Antunes, Isabel Alexandra Gonçalves. "Mechanochemistry of high temperature fuel cell materials." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/18657.
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Doutoramento em Ciência e Engenharia de MateriaisNos últimos anos, a mecanoquímica tem sido uma temática muito abordada na formação de materiais, motivada pelo grande interesse na preparação de nanopós. A sobressaturação estrutural de lacunas e a heterogeneidade química dos pós preparados por via mecanoquímica permitem melhoria na sinterabilidade, enquanto a elevada densidade dos agregados e a reduzido tamanho de cristalite produzem densidade em verde elevada. Estes fatores são extremamente atrativos na preparação de materiais cerâmicos óxidos densos, como é requerido na preparação de membranas eletroquímicas. Além disso, o processamento cerâmico por via mecanoquímica possibilita a síntese de novos materiais, que não conseguem ser sintetizados por outros métodos. Esta tese apresenta um estudo detalhado do processamento por via mecanoquímica de potenciais materiais de eletrólito e elétrodo para pilhas de combustível de óxido sólido de alta temperatura, e sua caracterização estrutural e eletroquímica. Por manipulação das variáveis do processo mecanoquímico pretende-se melhorar a capacidade de processamento e desenvolver novos materiais para aplicação em tecnologias de pilhas de combustível. A investigação foca-se, especificamente, no desenvolvimento de materiais de estrutura perovesquite à base de BaZrO3 e BaPrO3, com possíveis aplicações como condutores protónicos e condutores mistos, eletrónicos e protónicos, respetivamente.
In recent years, mechanochemistry has become an increasingly hot topic for the formation of materials, motivated by an explosion of interest in the preparation of nanopowders. The structural supersaturation by vacancies and chemical non-uniformity of mechanochemical powders promote enhanced sinterability, while the high density of aggregates and reduced crystallite density produce high green-densities. Such factors are highly attractive for preparation of dense ceramic oxide materials, as required for the formation of electrochemical-membranes. Additionally, mechanochemical ceramic processing may allow the synthesis of novel materials, which cannot be synthesized by other methods. In this thesis one offers a detailed study of mechanochemical processing for important potential electrolyte and electrode materials for high temperature solid oxide fuel cells and their subsequent structural and electrochemical characterisation. By mechanochemical manipulation one aims to improve the processing ability and to develop novel materials for fuel cell technologies. The research work is focused specifically on the development of perovskite materials based on BaZrO3 and BaPrO3, with potential applications as proton and mixed proton-electron conductors, respectively.
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Watari, Moyu. "In-plane mechanochemistry at model biological interfaces." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1446156/.
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When a chemical or biological reaction occurs on one surface of a microfab- ricated cantilever, a surface stress is generated resulting in cantilever bending motion. This signal transduction mechanism has recently been employed to detect DNA hybridisation and protein recognition, and has attracted much attention as a novel label-free biosensor. However, the biosensing application of cantilevers can best be realised if we develop a fundamental understanding of what causes the cantilever to bend In this thesis, I have performed systematic pH titration experiments using various self-assembled monolayers (SAMs) of alkanethiols HS(CH2) X on gold coated cantilevers, which represent a model organic system by virtue of the relatively well-defined surface chemistry. Differential surface stress measurements were taken to probe the biochemically specific interfacial forces, which were found to critically depend upon multiple factors including pH, ion species, and ionic strength of the aqueous environment, as well as chain length and terminal functional group of SAMs. These findings provide important insights into the fundamental origins of surface stress generation, which have broad implications in the study of biochemical interfaces from molecular thin films to cellular membranes.
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Sánchez, Pladevall Bruna. "Beyond conventional DFT catalysis: Mechanochemistry and solid reductants." Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/672947.
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La química computacional s'ha establert com una eina clau per entendre la reactivitat química y està dirigint la catàlisi cap a un disseny més racional. El desenvolupament constant i l'increment de la sofisticació en el camp experimental ha implicat diversos reptes pels químics computacionals, que busquen mètodes per lidiar amb aquesta classe de reaccions complexes. En aquest context, els sistemes situats a la frontera de la química homogènia i heterogènia estan guanyant importància, ja que permeten la combinació de les millors característiques de cada camp. Des d'un punt de vista teòric, les reaccions homogènies i heterogènies es simulen de maneres diferents. Hi ha una creixent necessitat d'investigar la millor manera per calcular aquesta classe de sistemes. L'objectiu d'aquesta tesi és explorar fins a quin punt els mètodes de la química homogènia es poden aplicar en sistemes situats en el límit entre l'homogènia i l'heterogènia. Especialment, la nostra atenció s'ha dirigit cap a les reaccions mecanoquímiques i les reaccions en les quals participen reductors sòlids. Amb aquest objectiu, cada capítol s'ha dirigit a l'estudi d'una o vàries reaccions en aquestes categories. Els nostres resultats demostren que els mètodes que s'utilitzen en catàlisi homogènia computacional es poden aplicar per entendre reaccions induïdes a través del molinet de boles o reductors sòlids. A més a més, hem demostrat l'importància dels models cinètics per entendre aquestes transformacions.La química computacional se ha establecido como una herramienta crucial para entender la reactividad química y está dirigiendo la catálisis hacia un diseño más racional. El desarrollo constante y el incremento de la sofisticación en el campo experimental ha implicado diversos retos para los químicos computacionales, que buscan métodos para lidiar con estas reacciones complejas. En este contexto, los sistemas situados en la frontera de la química homogénea y heterogénea están ganando importancia, ya que permiten la combinación de las mejores características de cada campo. Des de un punto de vista teórico, las reacciones homogéneas y heterogéneas se simulan de formas distintas. Hay una creciente necesidad de investigar la mejor manera para calcular este tipo de sistemas. La meta de esta tesis es explorar hasta que punto los métodos de química homogénea se pueden aplicar en sistemas situados en el “limbo” entre la homogénea y la heterogénea. Especialmente, nuestra atención se ha dirigido hacia las reacciones mecanoquímicas y las reacciones en las que participan reductores sólidos. Con este objetivo, cada capítulo se ha dirigido al estudio de una o varias reacciones en estas categorías. Nuestros resultados demuestran que los métodos que se utilizan en catálisis homogénea computacional se pueden aplicar para entender reacciones inducidas a través de molinillo de bolas o reductores sólidos. Además, hemos demostrado la importancia de los modelos cinéticos para comprender estas transformaciones.
Computational chemistry has been established as a crucial tool for the understanding of chemical reactivity and is driving catalysis towards a more rational design approach. The constant development and the increasing sophistication of experiments has raised numerous challenges for the computational chemists, who seek methods to deal with such complex transformations. In this context, systems located on the frontier of homogeneous and heterogeneous worlds are gaining importance, as they permit the combination of the best features of each area. From a theoretical perspective, homogeneous and heterogeneous reactions are modelled through substantially different approaches. There is thus an increasing need to investigate the most suitable manner to model these types of systems. The goal of this thesis is to explore to what extend methods commonly employed for the study of homogeneous reactions can be applied to systems located in the “limbo” between homogeneous and heterogeneous fields. Specifically, our attention has been directed towards mechanochemical reactions and homogeneous reactions with participation of solid reductants. To this end, each chapter has been devoted to the study of one or several transformation(s) within these categories. Our results demonstrate that methods emerging from computational homogeneous catalysis can be indeed applied to rationalize transformations induced through ball-milling techniques and reactions involving solid reductants. Moreover, we have demonstrated the importance of microkinetic modelling to provide a full understanding of these transformations.
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Li, Xiaomeng. "THE EFFECT OF SIDE CHAINS ON POLYMER MECHANOCHEMISTRY." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron158964792452756.
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Wilton, Howard Vincent. "Studies in organic mechanochemistry / by Howard Vincent Wilton." Thesis, The University of Sydney, 1997. https://hdl.handle.net/2123/27526.
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This work describes the mechanochemical reactions at ambient temperatures of a number of simple organic compounds (biphenyl, naphthalene, deuteronaphthalene, anthracene, phenanthrene, Chlorobenzene, hexachlorobenzene, teflon and biphenylcarboxylic acid) in the presence of inorganic matrices (mainly calcium oxide, alumina and silica). The atmosphere of the reactive mixture was air, nitrogen, oxygen, and in one case, hydrogen.
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CABRAS, VALENTINA. "Green Synthesis Approach to Coordination Polymers by Mechanochemistry." Doctoral thesis, Università degli Studi di Cagliari, 2017. http://hdl.handle.net/11584/249603.
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The field of Metal-Organic Frameworks, also known with the abbreviation MOFs, has been subjected to an accelerated growth in the last 15 years. The process of mixing quickly available metal precursors with organic ligands—many of which are commercially available—to produce a wide range of frameworks, is capturing the interest of chemists and materials scientists worldwide.
There is an important link between MOF chemistry and fields of inorganic and coordination chemistry, there is also a conceptual link into the field of materials chemistry that has evolved applications ranging from catalysis to energy storage. Organic chemistry is also able to contribute to the MOFs design by the synthesis of new ligands with the aim of giving different properties to the MOF wall. X-ray crystallography and solid-state chemistry provide information about the structures of MOFs so that the process of designing and synthesizing MOFs can be refined to control a targeted property of those frameworks.
My PhD thesis aims to explore, especially from the point of view of synthetic and structural, morphological, thermal and textural characterizations, the chemistry of Coordination Polymers (CPs) and Metal-Organic Frameworks (MOFs). Mechanochemical synthesis has been adopted as a powerful method for environmentally-friendly CPs and MOFs synthesis. The experimental section, have been divided in four parts: the first part concerns the efficient mechanosynthesis of an iron(III) trimesate MOF and its usage for the adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from a simulated low-sulfur diesel fuel. In the second, the structural, thermal and morphological properties of CPs based on unsatured Ni(II) dithiophostato/ dithiophospnonato complexes and 4,4’-bipyridine as linker are outlined. The third part dials with an array study of reactivity under mechanochemical conditions of a set of CPs based on the same unsatured Ni(II) complexes with different topologies of polydentate ligands. The final part is dedicated to the attempt to obtain thio-functionalized ligands for design, synthesis and future application in CP/ MOF architecture.
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McKinnie-Hill, J. S. "Mechanochemistry : an interesting approach to the pre-treatment of biomass." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.679263.
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A technique that is becoming more widespread in usage and popularity, ball milling has been used successfully in the pretreatment of sodium lignosulphonate (NaLS), a waste biomass material. The ball milled material produced higher yields of commercially valuable aromatic products, particularly vanillin in an industry standard copper-catalysed aerobic oxidation reaction. Through the optimisation of the parameters of this pretreatment technique both for NaLS alone and NaLS with sodium hydroxide and calcium oxide as additives, the vanillin yield after oxidation of the pretreated material could be increased by over 100 %. The generation of vanillin in NaLS in the solid state during ball milling was also observed for the first time confirming that mechanochemical transformation of the NaLS was taking place. Despite the difficulties associated with the analysis of such a heterogeneous and complex biopolymer, SEM imaging, GPC analysis and 2-D NMR analysis were used to identify some of the major chemical and physical changes occurring in the material during mechanochemical pretreatment. An HPLC analytical method for accurate measurement of the main oxidation products was also developed. The effect of using milling media of a different material on the pretreatment and subsequent oxidation reactions revealed that this pretreatment is transferable between different types and scale of equipment but that the results are sensitive to both materials of construction and storage conditions for analytical samples. The extrapolation of this pretreatment technique to other reactions of NaLS, hydrogenolysis for example, and to other biomass substrates was also investigated but with varying degrees of success, indicating that the mechanochemical changes can be subtle and highly reaction specific. Initial attempts at providing more mechanistic information were made through the synthesis and transformations of some simple lignosulphonate model compounds. These provided confirmation that the mechanistic scenario is complex and that several pathways are likely to be operating in parallel in the transformations of both model and polymer substrates.
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Yeboue, Kouadio Yves. "Peptide Synthesis by Mechanochemistry : From Fundamental studies to Scale-Up." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS077.
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Compte tenu du durcissement des politiques environnementales vis-à-vis des polluants produits par l’industrie chimique et de la demande croissante de la part des consommateurs et des citoyens, il est impératif de trouver des méthodes alternatives aux procédés utilisant des quantités importantes de solvants et réactifs nocifs pour la santé et l’environnement. Les méthodes classiques de synthèse de peptides en font partie et nécessitent impérativement des améliorations. Ce manuscrit décrit les récents développements des procédés mécanochimiques en synthèse peptidique, procédés qui permettent un changement de paradigme par rapport aux procédés classiques utilisant des solvants. Ces procédés mécanochimiques sont utilisés au cours de cette thèse pour solutionner des problèmes d’épimérisation de peptides fréquemment rencontrés lors de l’emploi de la stratégie de couplage par fragment en solution. La preuve de faisabilité du couplage peptidique par ligation chimique native par broyage à billes a également été apportée au cours de cette thèse. L’approche de synthèse peptidique par mécanochimie a enfin été utilisée pour mettre au point des conditions efficaces permettant de monter en échelle la synthèse de peptides en utilisant le procédé d’extrusion réactive, ouvrant les portes à un transfert de la synthèse à l’échelle industrielle. L’ensemble de ces conditions mécanochimiques se sont avérées particulièrement efficaces quant à la synthèse de peptides avec des temps de réaction très faibles, d’excellents rendements, des taux d’épimérisation très faibles, un faible impact environnemental et une grande productivitéDue to the restriction of the environmental policies regarding the pollutants, it is urgent to find alternative methods to the processes that used large amount of highly toxic solvents and chemicals. Because of their negative environmental impact, conventional peptide synthesis methods require improvements. The use of mechanochemical processes allow to efficiently reduce the environmental impact by eliminating or replacing toxic solvents and chemicals. During this work, mechanochemical methods have been used to solve the peptide epimerization issues, frequently encountered during peptide fragment coupling strategy in solution. Additionally, by using these methods, peptide synthesis through native chemical ligation was also demonstrated. Furthermore, the use of the reactive extrusion process has enabled to efficiently work on large scale, thereby opening the boulevard to implement the peptide mechanosynthesis in industries. Finally, these methods have led to the desired peptides with noteworthy isolated yields, very short reaction times, low epimerization rate, low environmental impact and high productivity
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Kotani, Ryota. "Chemistry on Flapping Fluorophores That Bridges Photochemistry and Polymer Mechanochemistry." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263486.
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Caiti, Massimiliano. "Mechanochemistry: a new approach to depolymerize cellulose via solid-solid reaction." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14434/.
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Cellulose is both insoluble in water and resistant against hydrolysis. These features pose major problems for its conversion into platform chemicals, first of all glucose. Herein, is demonstrated that the combination of mechanical forces and the presence of solid acid catalysts leads to the full conversion of cellulose into oligosaccharides. In this way mechanochemistry results an available route to depolymerize cellulose via solid-solid reaction. In this work is described the whole developed methodology which permits to obtain a quantifiable final products from the milling of a cellulosic substrate. Furthermore is reported the analytic method constructed thanks to which it is possible to determine the cellulose conversion and thus compare the performances of various solid acids tested. This study has moreover allowed to understand important catalyst features that enhance the depolymerization rate, such as the distribution of the acid sites on a inert support. Amberlyst 15, producing 100% of oligosaccharides in 15 hours of milling at 500rpm, is resulted the more active catalysts among those studied. Thanks to its high activity were performed performances comparison of the different ball mills employed.
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Herskowitz, Lawrence J. "Kinetic and statistical mechanical modeling of DNA unzipping and kinesin mechanochemistry." THE UNIVERSITY OF NEW MEXICO, 2011. http://pqdtopen.proquest.com/#viewpdf?dispub=3440145.
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Kumar, Sandeep Ph D. Massachusetts Institute of Technology. "Multi-scale mechanics of monolayer graphene membranes : elasticity, fracture, and mechanochemistry." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97838.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 305-319).
Graphene, owing to its remarkable material properties, is considered as an ideal material for a broad range of nano-scale applications. The performance of any graphene-based device would depend upon the material's response to deformation and its intrinsic resistance to failure. Nano-indentation is a useful technique to obtain such information, but analysis of the nano-indentation of graphene poses unique challenges, due to the multi-scale nature of the underlying processes. A sub-nm scale arises due to the atomic-level activities antecedent to material failure via deformation-induced lattice instability. While elastic instabilities are captured by continuum-level analysis, the soft-mode instabilities are not. Further, the potentially unstable region remains in contact with the nanoindenter and is subjected to high contact stresses which may trigger a strong mechanochemical interaction between graphene and the indenter surface. Such interactions may non-trivially affect the point of elastic to inelastic transition, as well the atomistic mechanism controlling it. A second length-scale, at least two orders of magnitude larger, is set by the scale of the indenter. For these reasons, an accurate analysis of graphene nano-indentation must adequately treat the relevant physical phenomena across these scales, and work carried out in this thesis undertakes this task. First, we propose and calibrate a hyperelastic constitutive modeling scheme for graphene based on symmetry-invariants of the logarithmic strain measure. The model adequately describes both the nonlinear softening and the anisotropy in the material response. For a set of homogeneous finite deformations, the stress values predicted by the model compare well with the directly-calculated ab initio values, validating the fidelity of the model. For a number of biaxial deformation modes the elastic stability limits predicted on the basis of acoustic tensor analysis compare well with results from phonon calculations carried out independently using linear response density functional perturbation theory. Particularly, we show that the limit of elastic stability in equi-biaxial deformation of graphene has been widely misinterpreted as coinciding with achieving peak bi-axial stress. The present continuum formulation, supported by independent phonon calculations, clearly illustrates that an elastic shearing instability precedes the maximum stress configuration under this loading mode. Secondly, we investigate the limits of reversible deformation in graphene under various loadings using atomistic-level lattice-dynamical stability analysis. Based on this information, we construct continuum failure surface for graphene, both in terms of stress, and strain, as a smoothed representation of the envelope of all possible lattice instabilities: long wavelength as well as short wavelength, and structural as well as material failures. The third focus area examines the graphene-diamond interaction as a function of interfacial separation, based on combined density functional theory and molecular dynamic calculations. The calculated interfacial energy as a function of separation exhibits two local minima, indicating that a graphene monolayer on a diamond {111} or {100} surface has two possible equilibrium states: a physisorbed state at low compressive stress, governed by weak vdW forces, and a chemisorbed state at large compressive stress, governed by strong covalent forces. Taking the DFT/ MD energy-separation data as input, we derive a continuum traction-separation relation for graphene- diamond interface, which describes both the weak vdW adhesion and the strong chemical interaction. Finally, we show that existing interpretations of recent nano-indentation experiments on suspended graphene sheets, based on finite element simulations adopting frictionless hard contact models intended to simulate van der Waals interaction, indicate that at experimentally-measured failure loadings, the inferred strain in the graphene sheet directly beneath the diamond indenter is anomalously large compared to the fracture strains predicted by both soft-mode and acoustic lattice stability analyses. We demonstrate that this discrepancy cannot be attributed to deficiencies in the graphene constitutive model, geometric features of the indenter, or the nature of assumed kinematic boundary conditions adopted in the simulations. We examine the implications of inducing strong covalent interactions at the graphene- indenter interface in connection with measured fracture loading levels in nano-indentation experiments. Both finite element and MD simulations suggest that the shear stiction associated with such induced interactions leads to a strain-shielding effect in the graphene. The shear stiction restricts relative slip of the graphene sheet at its contact with the indenter, thus initiating a local strain-shielding effect. As a result, the spatial variation of continuing incremental strain is substantially redistributed, locally limiting the buildup of strain in the region directly beneath the indenter while adding to deformation of nearby, lower-strained regions. The shear strength of the graphene-indenter covalent interaction depends strongly on the level of hydrogen passivation on the indenter tip. Simulations show that at intermediate levels of hydrogen saturation, the strain-shielding effect redistributes strain in the graphene so that experimentally-determined fracture loading can be supported without prematurely reaching locally-limiting states of lattice deformation and stress.
by Sandeep Kumar.
Ph. D.
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Baldus, Ilona Beatrice [Verfasser], and Peter [Akademischer Betreuer] Comba. "Mechanochemistry of Disulfide Bonds in Proteins / Ilona Beatrice Baldus ; Betreuer: Peter Comba." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177040786/34.
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Ljungkvist, Oskar. "Mechanochemistry : C-H arylation and annulative π-extension reactions attempted inball mill." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-382088.
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Yu, Zhongbo. "Mechanochemistry of Human DNA G-quadruplexes Revealed by Single-molecule Optical Tweezers." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1369366966.
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Atkinson, Manza Battle Joshua. "Fundamentals and applications of co-crystal methodologies: reactivity, structure determination, and mechanochemistry." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1197.
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This thesis describes applications in co-crystal reactivity, structure determination, and mechanochemical preparation. We also investigate the solution-phase reactivities of products derived from a template-directed synthesis. Specifically, we described the acid treatment of an achiral molecular ladder of C2h symmetry composed of five edge-sharing cyclobutane rings, or a [5]-ladderane, with acid results in cis- to trans- isomerization and/or oxidation of end pyridyl groups. Solution NMR spectroscopy and quantum chemical calculations support the isomerization to generate two diastereomers; namely, an achiral and a unique chiral ladderane. The NMR data, however, could not lead to unambiguous configurational assignments of the two isomers. Single-crystal X-ray diffraction was employed to determine each configuration. One isomer readily crystallized as a pure form and X-ray diffraction revealed the molecule as being achiral based on Ci symmetry. The second isomer resisted crystallization under a variety of conditions. Consequently, a strategy based on a co-crystallization was developed to generate single crystals of the second isomer. Co-crystallization of the isomer with a carboxylic acid readily afforded single crystals that confirmed a chiral ladderane based on C2 symmetry. We also demonstrate how the stereochemistry can be retained upon treatment with acid. It will be shown how a monocyclobutane can be used as a model system when investigating the reactivity of the [5]-ladderane.
While investigating the reactivity of a diene diacid we determined that a bicyclobutyl that bears six carboxylic acid groups results from a trimerization of the solid in pure form in the solid state. Powder X-ray diffraction and a co-crystallization are used to solve the structure of the diene and elucidate the stereochemistry of the bicyclobutyl, respectively. Having established the reactivity of the diene diacid we used hydrogen-bond-acceptor (HBA) templates to assemble the diacid in the solid state in a photoactive solid for an intermolecular [2 + 2] photocycloaddition as well as a photostable solid. To enhance strategies to generate stereocontrolled products derived from reactive co-crystals mechanochemical methods were applied to eliminate or reduce the solvent used to prepare the co-crystal solids. In particular, we show how supermolecules with olefins organized by hydrogen-bond donor and acceptor templates that react in the solid state rapidly form co-crystals via solvent-free and liquid-assisted grinding.
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Al-Terkawi, Abdal-Azim. "Fluorinated and Fluorine-Free Coordination Polymers Based on Alkaline Earth Metals via Mechanochemistry." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19246.
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Fluorhaltige-Koordinationspolymere (FCPs) wurden durch mechanochemische Reaktionen synthetisiert. Die Erdalkalimetallhydroxide, die in ihrem Wassergehalt variieren, wurden als anorganische Quellen verwendet. Die perfluorierten Benzol Dicarboxylsäuren und ihre fluorfreien Analoga wurden als organische Linker verwendet. Die erhaltenen FCPs werden mit den fluorfreien Verbindungen (CPs) verglichen, die unter den gleichen Mahlbedingungen synthetisiert wurden.
Der Austausch von Wasserstoff- durch Fluoratome beeinflusst sowohl die thermischen als auch die strukturellen Eigenschaften der FCPs. Letztere werden auch von den Unterschieden der Geometrien und von der Natur der organischen Linker beeinflusst. Während des Mahlprozesses dient Wasser dabei hauptsächlich als Vermittlermedium und zur Stabilisierung der neuen Strukturen. Die Unterschiede in den Kationengrößen zwischen Ca2+- und Sr2+-Ionen wirken sich geringfügig auf ihre Koordination durch die Dicarboxylatanionen aus. Hier kristallisieren Ca- und Sr-Verbindungen zumeist isomorph. Im Gegensatz dazu beeinflusst der große Ionenradius der Ba2+-Kationen die lokalen Koordinationsumgebungen. Die durch Mahlen erhaltenen Verbindungen sind hydratisiert und weisen eine kleine spezifische Oberfläche auf, die nach der thermischen Behandlung zunehmen kann. Die FCPs sind bis zu 300 °C stabil, während die CPs sich erst oberhalb von 400 °C zersetzen. Die hydratisierten Proben wandeln sich beim Tempern in neue dehydratisierte Phasen um. Die Phasenumwandlung kann reversible ablaufen.
Zusätzlich wurde der Effekt des Austausches einer Carboxylgruppe durch eine Aminogruppe in einem organischen Liganden untersucht. In den CPs auf der Basis von Anthranilsäure beeinflussen die unterschiedlichen Kationengrößen der Ca2+-, Sr2+-, und Ba2+-Ionen sowohl die Koordinationsumgebung als auch die Dimensionalität der CPs.Die physikalisch-chemischen Eigenschaften der neuen Materialien wurden systematisch durch verschiedene analytische Techniken.A series of fluorinated coordination polymers (FCPs) were mechanochemically synthesized using alkaline earth metal hydroxides (M = Ca, Sr, Ba) that vary in their water content as inorganic sources. The perfluorinated benzene-dicarboxylic acids and their fluorine-free analogs were used as organic linkers. The obtained FCPs are compared to their synthesized fluorine-free counterparts (CPs) under the same conditions. The presence of fluorine influences both thermal and structural properties of the resulting FCPs. The latter are also strongly affected by the difference in geometries and nature of organic linkers. Water introduced to grinding acts as a mediator for the milling process and as a reactant for stabilizing the resulting structures. The difference in cation size between Ca2+- and Sr2+-ions has a minor effect on their coordination with perfluorinated or fluorine free benzene-dicarboxylate anions. Here, Ca- and Sr-compounds crystallize isomorphously (an exception was recorded for ortho-phthalate systems). In contrast, the relatively larger size of Ba2+-cation strongly influences the coordination environment. The obtained compounds by milling are hydrated and exhibit small surface areas that can increase after thermal post-treatment. The FCPs are stable up to 300 ˚C. On the other hand, the nonfluorinated CPs begin to decompose above 400 ˚C. The hydrated samples transform into new dehydrated phases upon thermal annealing. The hydrated-dehydrated phase transformation can be reversible. Moreover, the effect of replacement of one carboxylic group by an amino group in an organic ligand was explored. In the CPs based on anthranilic acid, the variations in cation size between Ca2+-, Sr2+-, and Ba2+-ions affect both coordination environment and dimensionality of the resulting CPs. The physicochemical properties of the new materials were systematically investigated applying different analytical techniques.
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Edginton, Ryan Stuart. "The multiscale biomechanics and mechanochemistry of the extracellular matrix protein fibres, collagen & elastin." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34619.
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Collagen is the most abundant protein in the animal kingdom and, together with elastin, forms extensive fibrous networks that constitute the primary structure of the mammalian extracellular matrix, respectively endowing it with the tensile and elastic properties that fulfil its principal role as the passive framework of the body. The fibrous proteins are distinctly hierarchically organised from the molecular scale upwards; for example, the nanoscale tropocollagen monomer assembles in arrays that form the micrometer scale microfibrils and fibrils, and thence into collections of millimetre scale collagen fibres, that in-turn, constitute functional tissues such as skin, tendon and bone. Much is known about the structure at each of these individual scales – collagen being the most extensively researched – and the macromechanics of the fibres are well established. However, far less is known about the micromechanics of these proteins, in particular how the monomers influence the functional mechanics of the macroscopic fibres. In this thesis, I explore the multiscale mechanics of collagen and elastin fibres over a range of hydrations – with fibres in direct contact with aqueous solution, and progressively dehydrated in humidity-controlled environments. I use quasi-static tensile testing to probe the macroscopic mechanical response (Young’s modulus and stress relaxation) of the fibres, and employ Brillouin and Raman microscopy to assess the longitudinal modulus in the GHz range and corresponding molecular properties of the proteins. Brillouin microscopy is an emerging technique in the biomedical field. It enables the all-optical, contact-free and non-destructive testing of tissue micromechanics through detection of frequency shifted light scattered off thermally excited acoustic waves or “phonons” in the GHz range. As one of the first studies of Brillouin light scattering in these fibres, it sets the basis for further investigation of tissue biomechanics. In particular, I provide the full description of the protein fibre micromechanics by performing angular measurements using a so-called platelet-like configuration with sample mounted onto a reflective substrate at 45° angle to the excitation beam. I derive the high-frequency longitudinal modulus, and discuss the results in comparison to the Young’s modulus, in terms of the different frequency and spatial scale of the measurements. I obtained a full description of elasticity using Brillouin spectroscopy applied to dried fibres; however, obtaining the same description in hydrated fibres is a challenge, as the Brillouin spectrum is dominated by water. An assessment of the mechanical differences between type-I and type-II collagens is also given here. Water is known to be a primary determinant of tissue biomechanics, and I identified for the first time, the critical hydration ranges between 100 and 85% relative humidity (RH) for collagen, and around 85% RH for elastin, at which point each macroscopic fibre switched from viscoelastic to plastic-like behaviour. Dehydration below these critical points was shown to severely diminish collagen fibrillar sliding, and completely rob elastin of its ability to reversibly deform under strain. The Young’s modulus increased markedly below these hydrations, and I observed a parallel increase in the longitudinal modulus at high frequencies in each protein, indicating a concomitant increase in stiffness at the two scales. The major difference observed between the two fibrous proteins is that, in the case of elastin, I observe a two-fold increase in the longitudinal modulus as the hydration is decreased from 100 to 21% RH, whilst the Young’s modulus increases by two orders of magnitude. This discrepancy was not observed in collagen, which confirmed that the protein maintained its long-range order in the form of the triple helix at all hydrations employed in this work, whilst the elastin ultrastructure experiences a liquid-to-solid state change at a critical hydration. I demonstrate through the analysis of the low-wavenumber region (< 500 cm-1) of the Raman spectrum, that the increase in molecular stiffness of both proteins, is reflected in an increase in torsional rigidity of the peptide backbone upon dehydration. Moreover in collagen, I observe a reduction in the number of inter-protein water bridges, which I propose causes a collapse of the lateral spacing between monomers and an increase in direct backbone-backbone hydrogen bonding, that further stiffens the fibre. Small strain induced reorientations of the amide III and C–C stretching modes in dehydrated collagen fibres suggest that macroscopic stresses may be transferred to the triple helix, otherwise left unperturbed in the hydrated state. I postulate that this is a result of the degraded intra- and interfibrillar sliding mechanism below the critical hydration. Hence in its dehydrated state, the collagen whole-fibre mechanics are similar to those at the molecular scale. The role of proteoglycans and glycosaminoglycans and their potential connection to hydration, is also discussed. In agreement with previous work, I found no Raman spectral changes as a result of stretching hydrated elastin fibres, indicating that even large strains e.g. 80%, have no significant effect on the structural scale probed by Raman microscopy, nor in the air-dried state where the brittle fibres break at low strains. I suggest this may imply a limited sensitivity of Raman bands to these changes, possibly an indication of elastin’s dynamic ultrastructure, or that stress is dissipated at a higher level of the fibre structure. On the macroscopic scale, it is the poroelastic nature of elastin which controls the stress relaxation under strain, and the elastic recovery is mediated by an interplay of hydrophobic interactions and hydration forces.
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Xie, Wei. "Understanding the impact of chain alignment on mechanochemical activation." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619285242977195.
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Gonzales, Manny. "The mechanochemistry in heterogeneous reactive powder mixtures under high-strain-rate loading and shock compression." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54393.
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This work presents a systematic study of the mechanochemical processes leading to chemical reactions occurring due to effects of high-strain-rate deformation associated with uniaxial strain and uniaxial stress impact loading in highly heterogeneous metal powder-based reactive materials, specifically compacted mixtures of Ti/Al/B powders. This system was selected because of the large exothermic heat of reaction in the Ti+2B reaction, which can support the subsequent Al-combustion reaction. The unique deformation state achievable by such high-pressure loading methods can drive chemical reactions, mediated by microstructure-dependent meso-scale phenomena. Design of the next generation of multifunctional energetic structural materials (MESMs) consisting of metal-metal mixtures requires an understanding of the mechanochemical processes leading to chemical reactions under dynamic loading to properly engineer the materials. The highly heterogeneous and hierarchical microstructures inherent in compacted powder mixtures further complicate understanding of the mechanochemical origins of shock-induced reaction events due to the disparate length and time scales involved.
A two-pronged approach is taken where impact experiments in both the uniaxial stress (rod-on-anvil Taylor impact experiments) and uniaxial strain (instrumented parallel-plate gas-gun experiments) load configurations are performed in conjunction with highly-resolved microstructure-based simulations replicating the experimental setup. The simulations capture the bulk response of the powder to the loading, and provide a look at the meso-scale deformation features observed under conditions of uniaxial stress or strain. Experiments under uniaxial stress loading reveal an optimal stoichiometry for Ti+2B mixtures containing up to 50% Al by volume, based on a reduced impact velocity threshold required for impact-induced reaction initiation as evidenced by observation of light emission. Uniaxial strain experiments on the Ti+2B binary mixture show possible expanded states in the powder at pressures greater than 6 GPa, consistent with the Ballotechnic hypothesis for shock-induced chemical reactions. Rise-time dispersive signatures are consistently observed under uniaxial strain loading, indicating complex compaction phenomena, which are reproducible by the meso-scale simulations. The simulations show the prevalence of shear banding and particle agglomeration in the uniaxial stress case, providing a possible rationale for the lower observed reaction threshold. Bulk shock response is captured by the uniaxial strain meso-scale simulations and is compared with PVDF stress gauge and VISAR traces to validate the simulation scheme. The simulations also reveal the meso-mechanical origins of the wave dispersion experimentally recorded by PVDF stress gauges.
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Kar, Prasenjit. "Tribochemical properties of metastable states of transition metals." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2785.
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Koirala, Deepak P. "Mechanochemistry, Transition Dynamics and Ligand-Induced Stabilization of Human Telomeric G-Quadruplexes at Single-Molecule Level." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1397919270.
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Liu, Shiqi. "Mechanical Generation of Depolymerizable Poly(2,5-dihydrofuran)." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1619002348147551.
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Waddell, Daniel C. "Environmentally friendly synthesis using high speed ball milling." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1330024874.
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Andersen, Joel M. "Understanding the Mechanochemical Energetics of a SPEX 8000M Mixer/mill." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563273418808903.
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Slootman, Juliette. "Détection quantitative de l'endommagement moléculaire, par mécano-fluorescence, dans les matériaux mous." Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLET019.
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L’utilisation de matériaux mous, tel que des ligaments de synthèse, est limitée par la propagation d’une fissure initiée par un défaut. Mieux comprendre les mécanismes de dissipation d’énergie en pointe de fissure, permettra de mettre au point des matériaux mous mais beaucoup plus résistants.Nous avons développé une méthode permettant la visualisation en microscopie confocale de la rupture de liaisons chimiques grâce à une activation de fluorescence par rupture de liaison. Nous avons ainsi cartographié et quantifié l’endommagement moléculaire en 3D et à fort grossissement. Notre approche multi-échelle n’est possible que grâce à l’association de la chimie, de la mécanique et de la physique. Grâce à une calibration du signal fluorescent, c’est la première fois qu’une information quantitative est obtenue sur le nombre de liaisons cassées après la propagation de fissure. Les résultats obtenus par cette méthode remettent en cause la vision actuelle de la fracture des matériaux souples. En effet, nous avons montré que les ruptures moléculaires dans un élastomère se font sur une épaisseur de dizaines de microns et que cet endommagement moléculaire est couplé à la viscoélasticité et dépend donc de la température et de la vitesse. Ces informations sont indispensables et sont attendues par les modélisateurs pour le développement de modèles réalistes prédisant la fractureEngineering applications of soft materials, such as prosthetic ligaments, are limited by crack propagation initiated by a defect. A better understanding of dissipative mechanism at the crack tip will be invaluable to guide materials chemists to design and develop better soft and tough materials.We developed a method to visualize molecular chains scission based on mechano-fluorescence: fluorescence activation upon mechanically triggered bond scission. We mapped molecular damage in 3D and at high magnification by confocal microscopy. Chemistry, mechanics and physics were associated to give our multi scale approach. With the help of a calibration curve we directly quantified and mapped chains scission inside a series of model elastomers, from brittle to tough. Results obtained from this method challenge the actual molecular picture of fracture in soft material. Indeed, we proved that chain scission in elastomers occurs over a thickness of tens of microns around the crack plane and depends on strain rate and temperature as they are coupled to viscoelasticity. Theorists in physics and mechanics can use this solid experimental foundation to construct better molecular models of fracture
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McKissic, Kelley S. "Understanding the Role of Energy in Chemical Reactions from Mechanics to Photochemistry." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439562321.
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Oburn, Shalisa M. "Applications in supramolecular chemistry and solid-state reactivity: template-mediated solid-state reactions, dynamic covalent chemistry, mechanochemistry, and pharmaceutical co-crystals." Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/7004.
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Supramolecular chemistry and crystal engineering seek to control molecular packing in the solid state to influence the physical and chemical properties of crystalline solid materials. A goal of supramolecular chemistry that seeks to control molecular packing in the solid state focuses on exploiting non-covalent interactions to assemble molecules into desirable arrangements. Strategies implemented to control molecular packing rely on strong, directional interactions such as hydrogen bonding, halogen bonding, and metal coordination to direct localized arrangement of molecules in solids. In this context, small molecules can be used as linear templates in co-crystals to assemble reactive alkenes into specific geometries allowing reactivity in the solid state. A linear template method has been used to achieve [2+2] photocycloadditions of discrete assemblies containing alkenes to afford cyclobutanes in high stereospecificity and in quantitative yield.
Herein, we describe the use of a nonlinear template, in the form of 1,4-butynediol (1,4-bd), to pre-organize alkenes in the solid state. The nonlinear template of 1,4-bd hydrogen-bonds to the alkene 1,2-bis(N-pyridyl)ethene (where N = 3 or 4) to form 1D hydrogen-bonded polymers. The hydrogen-bonded polymer chains form infinite stacks which are sustained by C-H···O interactions occurring between polymer chains. The stacked alkenes undergo a UV-induced [2+2] photocycloaddition to produce rctt-tetrakis(N-pyridyl)cyclobutane photoproducts (where N = 3 and 4) in non-quantitative yields. The yield of the photoreaction is increased to nearly quantitative by applying a supramolecular catalysis approach with the 1,4-bd template.
Functional groups on reactant molecules can compete via non-covalent interactions with templates employed for the self-assembly process. One method to inhibit competition between functional groups involves chemically modifying a functional group employing a supramolecular protecting group. Here, we describe an acetyl supramolecular protecting group approach employed to mask alkenes containing phenolic and pyridyl functional groups. The acetyl protecting group prevents the phenolic substituents of the targeted alkene from participating in non-covalent interactions employed for the template-mediated self-assembly process. Thus, a cyclobutane molecule was obtained using the novel acetyl supramolecular protecting group strategy applied to a solid-state [2+2] photodimerization that affords a head-to-head cyclobutane. After deprotection, the resulting cyclobutane possessed tetrahedrally-disposed cis-hydrogen-bond-donor and cis-hydrogen-bond-acceptor groups. Thus, a purely organic three-dimensional hydrogen-bonded network based on a rare Michael O'Keeffe (mok) topology was constructed using an organic molecule synthesized in the organic solid state. The phenolic substituents of the cyclobutane adopt different orientations (syn-, anti-, and gauche-) to conform to the structural requirements of the mok net.
A challenge surrounding template-directed solid-state reactivity requires alkenes to be lined with functional groups that coordinate (or bind through other non-covalent interactions) to the template. Herein, we describe a dual approach of supramolecular assistance to covalent bond formation that utilizes a combination of imine and metal-organic chemistry to generate cyclobutanes lined with aldehyde groups. Specifically, dynamic imine chemistry was implemented to install a temporary recognition site on an aldehyde-containing alkene of cinnamaldehyde for a template-directed [2+2] photocycloaddition in the solid state. The resulting modified alkene aligns using Ag(I) ions into desirable arrangements for the covalent-bond-forming [2+2] photocycloaddition. The result is a 1D coordination polymer undergoes a UV-induced, regio-controlled [2+2] photocycloaddition in the solid state. The photoreaction proceeds stereospecifically with quantitative yield of the corresponding aldehyde-functionalized photodimer, α-truxilaldehyde. Additionally, we investigate the influence of the Ag(I) counterions on the assembly of imine containing alkenes to generate reactive assemblies for the purpose of producing aldehyde-containing cyclobutanes.
This dissertation also encompasses research pertaining to pharmaceutical solids and mechanical properties of organic molecular crystals. Specifically, we describe the discovery of two polymorphic co-crystals containing acetylsalicylic acid (aspirin) combined with 4,4’-bipyridine. The initial discovery of the form I polymorph was aided by mechanical dry-grinding, while an additional form II polymorph was revealed by rapid cooling in ethanol. The polymorphs differ by relative twists of carboxylic acid groups of the aspirin molecules and of the pyridyl rings of 4,4’-bipyridine. Additionally, the form I polymorph contains aspirin molecules that are linked via discrete catemeric methyl C-H···O interactions, while the form II polymorph is linked via both infinite methyl C-H···O catemers and centrosymmetric dimers. These results demonstrate the importance of dry mechanical grinding for the discovery of pharmaceutical co-crystals and polymorphs.
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Denlinger, Kendra L. "Polymers in the High-speed Ball Mill." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin149156005684791.
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Beillard, Audrey. "Préparation par mécanochimie de complexes NHC-métal et application en catalyse." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT172.
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Compte tenu du développement continu de nouveaux complexes organométalliques, il est impératif de trouver des alternatives aux méthodes de synthèses classiques qui utilisent des solvants toxiques, des températures de réaction élevées et qui ne conduisent pas toujours aux complexes souhaités avec de bons rendements. L’utilisation de broyeurs billes pour la synthèse de complexes NHC-métal (argent et cuivre tout particulièrement) et de leurs précurseurs a permis le développement de méthodes efficaces, générales, rapides et présentant un impact environnemental plus faible que les méthodes classiques en solution. Ces méthodes permettent aussi de donner accès à des molécules d’intérêts, difficilement synthétisables par voie classique. De nombreux complexes jusqu’alors jamais reportés dans la littérature ont ainsi pu être formés. Ces complexes ont démontré leur efficacité en tant que catalyseur dans la réaction de A3 pour la formation d’amines propargyliquesDue to the constant increase of publications reporting new organometallic complexes, it becomes urgent to develop alternative synthetic methods to the classical ones that use toxic solvents, high reaction temperatures and that do not always lead to the desired complexes in good yields. The use of ball-mills for the synthesis of NHC-metal complexes (silver and copper in particular) and their precursors has enabled the development of efficient, general, quick and more sustainable methods. These methods give an access to interesting compounds, difficult to synthesize using another pathway. Numerous complexes never reported in the literature were also formed. These complexes have demonstrated their efficiency as catalysts in the A3 reaction to form the propargylamines
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Shearouse, William C. "Development and mechanistic understanding of ball milling as a sustainable alternative to traditional synthesis." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353089340.
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Haley, Rebecca. "Nickel Mediated Reactions in a High-speed Ball Mill." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535635347164016.
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ZANOLLA, DEBORA. "Mechanochemical activation of Praziquantel in a vibrational mill." Doctoral thesis, Università degli Studi di Trieste, 2019. http://hdl.handle.net/11368/2962377.
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The research activity presented in this PhD thesis was totally dedicated to the application of mechanochemistry to Praziquantel using a vibrational mill, taking also advantage of the wide network of the group collaborators, both national and international. Praziquantel is an antihelmintic drug used worldwide against Schistosomiasis, which is a parasitic diseases affecting more than 200.000 people, especially in the sub-saharian area. Despite being highly effective and safe, this drug has 2 major drawbacks: the first one is the low biopharmaceutical profile (i.e. solubility and bioavailability) and therefore the high dosage needed. The second one is the very bitter and disgusting taste, which makes even more difficult its administration, in particular in pediatric patients, the main involved. The research started with the study of many co-ground systems of Praziquantel with different polymers used as pharmaceutical excipients, both at RT and under cryogenic conditions, to evaluate the process and formulation variables, obtaining amorphous dispersion with enhanced solubility and maintained antischistosomal activity (in vitro). Moreover, other binary systems were investigated: when using amorphous mesoporous silica, drug amorphisation was dramatically increased, even after only 15 minutes grinding, enhancing also drug dissolution and maintaining its in vitro antischistosomal activity. The grinding of Praziquantel with natural/synthetic sweeteners led to samples with enhanced solubility and intrinsic dissolution rate, possibly ameliorating also the drug taste. The neat grinding of the drug by itself led to the discovery of two new polymorphic forms, Form B and Form C, which structures were solved from the synchrotron X-Ray powder pattern and validated by DFT calculations. Form B was fully characterized, comprehending the in vitro and in vivo antischistosomal activity and the analysis of the pharmacokinetic profile. Form C, though exhibiting the higher solubility among the polymorphic forms, presented a poor physical stability of about 3 months. In addition, Form B and a cyo-coground sample were included in Gelucire 50/13 microparticles obtained via spray congealing, with a significative increase of drug solubility and dissolution rate. During the Erasmus period at the University of Cambridge, Praziquantel was subjected to Liquid-Assisted Grinding, discovering three new forms, one hemihydrate and two solvates respectively with Acetic Acid and 2-Pyrrolidone. The hemihydrate was fully characterized, both at the solid-state and from the biopharmaceutical point of view, including in vitro antischistosomal analysis, while the other forms are still under characterization. At the end, different sucrose esters were used both at the solid state and as aqueous solutions in combination with Praziquantel during grinding and Liquid-Assisted grinding.
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Al-Terkawi, Abdal-Azim [Verfasser], Erhard [Gutachter] Kemnitz, Wolfgang [Gutachter] Tremel, and Gudrun [Gutachter] Scholz. "Fluorinated and Fluorine-Free Coordination Polymers Based on Alkaline Earth Metals via Mechanochemistry / Abdal-Azim Al-Terkawi ; Gutachter: Erhard Kemnitz, Wolfgang Tremel, Gudrun Scholz." Berlin : Humboldt-Universität zu Berlin, 2018. http://d-nb.info/1182541011/34.
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Jonchhe, Sagun. "SINGLE-MOLECULE MECHANOCHEMICAL STUDY OF DNA STRUCTURES INSIDE NANOCONFINEMENT." Kent State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=kent1626344589505522.
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Botti, Luca. "Mechanochemical solvent-free synthesis of Sn-β Zeolite and Ag2O/TiO2 catalysts." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11941/.
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Preparations of heterogeneous catalysts are usually complex processes that involve several procedures as precipitation, crystallization and hydrothermal treatments. This processes are really dependent by the operative conditions such as temperature, pH, concentration etc. Hence the resulting product is extremely affected by any possible variations in these parameters making this synthesis really fragile. With the aim to improve these operations has been decided to exploit a new possible strong environment-respectful process by mechanochemical treatment, which permits to carry out solvent free-solvent synthesis exploiting the Mixer Mill MM400 (Retsch) in order to have reproducible results. Two different systems have been studied in this kind of synthesis: a tin β -zeolite tested in a H-trasnfer reaction of cyclohexanone and a silver on titania catalyst used in the fluorination of 2,2 dimethyl glucaric acid. Each catalyst has been characterized by different techniques in order to understand the transformations involved in the mechanochemical treatment.
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Sezgiker, Korhan. "Production Of Nano Alumoxane From Aluminum Hydroxide." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611533/index.pdf.
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Alumina (Al2O3) is one of the most widely used engineering ceramic. It can be used in a wide range of applications like electrical/thermal insulation, wear resistance, structural refractories, cutting tools, abrasives, catalyst carriers and coatings. A traditional ceramic process has several steps (i.e. powder synthesis and processing, shape forming, drying, organic burnout and densification). Accessing powders with sizes in the range of a couple of micrometers down to several tens of nanometers is considered critical in attaining higher densities in the final ceramic bodies. Besides since significant shrinkage can be observed in the thermal treatment steps due to the excessive use of additives (e.g. binders, solvents and plasticizers) in the powder processing and forming steps, it is important to take remedies that would increase the solids loading in the initial mixtures. In addition, most of the conventional additives and solvents used in these steps are toxic and it is necessary to replace them with the environmentally benign aqueous-based alternatives.
Alumoxanes could be used as a benign aqueous-based alternative to be used as a ceramic precursor or an agent. They are a group of compounds that have nano sized boehmite cores encapsulated with the organic groups used in its production steps.
In this research work, alumoxane nano particles which can be used as precursors for nano-alumina were developed starting from aluminum trihydroxide. As a preconditioning step, grinding was applied to decrease the aluminum hydroxide particle size (≤
60 &
#956
m) to submicron sizes. This process was followed by the glycothermal ageing step, and organic derivative of boehmite was obtained. The amorphous particles thus obtained were further treated mechanochemically in a high energy ball mill with organic chemicals like acetic acid, methoxy acetic acid, stearic acid and L-lysine. After this step the observed sizes of the particles were as low as 10-100 nm. The effects of organic molecules used in each step were studied by FTIR spectroscopy and their effectiveness in exfoliation of hydroxide layers were identified with dynamic light scattering from processing solutions dispersed in aqueous medium. Moreover, in each step, structural analyses were carried out by XRD.
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LIGIOS, GIORGIO. "Sistemi e dispositivi meccanici applicati a processi fisici e chimici." Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266476.
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The present Ph.D. thesis focuses on the development of innovative mechanochemical reactors and the improvement of existing ones.
Mechanochemistry is the branch of Chemistry that relates to the effects of nonhydrostatic stresses and plastic strain on the chemical reactivity of molecules, crystals,
and other aggregates of matter. Mechanochemical transformations occur on a local basis in the presence of unbalanced mechanical stresses, which result in non-Equilibrium thermodynamic conditions. Transformations are typically driven by ball milling, a powder metallurgy technique based on the occurrence of collisions between milling tools inside a reactor. At each collision, a fraction of the powder charge inside the reactor is trapped between colliding surfaces and submitted to a mechanical load. This induces cold-welding, fracturing and plastic deformation processes mediated by the generation, migration, and interaction of lattice defects. Depending on the nature of the powder and of its surroundings, the microstructural refinement can be accompanied by
unusual physical and chemical transformations with no thermal counterpart.
In the light of this peculiarity, mechanical activation processes show great promise in different fields of science and technology. However, their considerable potential did not find yet a definite industrial exploitation due to the unfortunate limitations affecting the performance of mechanical activation devices in terms of energy efficiency and production rates.
Meeting the demand for improved mechanochemical reactors enabling innovative fundamental research and large-scale applications necessarily implies a deep revision of
the reactor design. On the one hand, it is highly desirable to enhance the collision frequency and increase the amount of powder processed per unit time while saving energy and costs. On the other, fundamental experimental observables in frictional and collisional regimens must be rendered accessible to direct investigation. These contrasting requests definitely invoke atypical lines of approach in Mechanical Engineering, which makes any research in the field challenging.
In this work, attention has been focused on a few main research issues, namely the ad hoc equipment of the reactor of a commercial ball mill following a previous
investigation of the milling tools dynamics, and the development of three reactor prototypes addressing specific research needs. Complementary activities have been also
carried out within the framework of collaborative research programmes.
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Quintin, François. "Synthèse de complexes organométalliques par mécanochimie. Catalyse, photochimie et activités biologiques." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS026.
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Connus pour leurs propriétés en catalyse et en biologie, les complexes organométalliques représentent un pan important de la chimie actuelle. Cependant, leurs synthèses restent encore compliquées d'un point de vue expérimental et environnemental (faible rendement, utilisation de solvants toxiques,...), et il demeure impératif de découvrir des méthodes de synthèse alternatives plus respectueuses de l'environnement. Cette thèse fait appel à la mécanochimie comme alternative efficace pour la synthèse de complexes organométalliques. Dans un premier temps, de nouveaux complexes NHC d'argent(I) et de ruthénium(II) ont été synthétisés par mécanochimie. Ces complexes ont ensuite été évalués dans des réactions de catalyse (transfert d'hydrogène et métathèse polymérisante par ouverture de cycle) et testés pour leurs propriétés anti-tumorales. Une seconde famille de complexes de ruthénium(II) et d'iridium(III) a été synthétisée aux broyeurs à billes, et testée en photocatalyse par mécanochimie. Lors de ces diverses réactions, il a été observé une amélioration des conditions expérimentales (temps de réaction plus court, utilisation de quantités optimales de réactifs) et environnementales (absence de solvants toxiques) accompagnée d'excellents rendementsKnown for their activities in catalysis and biology, organometallics complexes are an important part of current chemistry. However, their syntheses are still complicated from an experimental and environmental point of view (low yields, use of toxic solvents, …) and it becomes urgent to develop sustainable alternative synthetic methods. This thesis builds on mechanochemistry as an efficient alternative for the synthesis of organometallics complexes. Firstly, new silver(I) and ruthenium(II) complexes featuring NHC ligands were synthesized by mechanochemistry. These complexes were then evaluated in catalysis (hydrogen transfer reaction and ring-opening metathesis polymerization) and tested for their antitumoral activity. A second family of ruthenium(II) and iridium(III) complexes were synthesized by ball-milling, and tested in photoredox catalysis by mechanochemistry. During these different reactions, an improvement of experimental (shorter reaction time, use of optimal quantities of reactants) and environmental conditions (absence of toxic solvent) was observed, in addition to high yields
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FERRUTI, FEDERICA MARIA CAMILLA. "NEW FUNCTIONALIZATION APPROACHES OF LIGNOCELLULOSIC FEEDSTOCK TO OBTAIN NEW REINFORCING FILLERS TAILORED TO RUBBER COMPOUNDS." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/403897.
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Manufatti in gomma trovano una gran varietà di impieghi tecnologicamente rilevanti. Le proprietà meccaniche della gomma di per sé non sono soddisfacenti per le applicazioni desiderate quindi i miglioramenti necessari sono comunemente ottenuti tramite vulcanizzazione e addizione di filler rinforzanti nella matrice elastomerica. Il filler rinforzante più comune è il nero fumo il cui uso è tuttavia associato a problemi per la salute e l’ambiente. Per questa ragione molti produttori di pneumatici stanno concentrando i propri sforzi per la sostituzione del nero fumo con alternative più sostenibili. Le loro ambizioni includono l’incremento di materiali rinnovabili e la simultanea riduzione di composti derivanti da carbonfossile nella formulazione di pneumatici, contemporaneamente preservando o migliorando le proprietà meccaniche. In questo contesto il presente progetto di ricerca si è concentrato sullo sviluppo di filler rinforzanti sostenibili per compositi elastomerici in alternativa alle tecnologie legate all’industria del petrolio, con una particolare attenzione alla lignina. Nonostante la sua disponibilità a livello industriale, la complessità strutturale della lignina ha impedito la sua conversione in prodotti ad alto valore aggiunto e la progettazione razionale di materiali funzionali. Questo materiale può essere considerato una valida alternativa al nerofumo nei compositi elastomerici per le sue proprietà chimico-fisiche, le proprietà meccaniche, l’attività antiossidante e la stabilità termica. La sua combinazione con una matrice elastomerica comporta la necessità di superare la scarsa compatibilità tra i due materiali associata alla polarità della lignina che dà luogo a forti interazioni con se stessa. È stato necessario modificare la lignina per migliorare il numero e la qualità delle sue interazioni con la gomma al fine di ottenere un rinforzo meccanico della stessa. Per assicurare il rinforzo desiderato si sono esplorate e due strategie. La prima si è focalizzata sulla funzionalizzazione dei gruppi ossidrili della lignina, puntando alla formazione di legami covalenti tra la lignina stessa e la matrice gommosa durante la vulcanizzazione. È stata messa a punto una procedura innovativa per l’esterificazione meccanochimica della lignina che ha consentito di eseguire la reazione allo stato solido, avvantaggiandosi dell’energia meccanica per indurre trasformazioni chimiche, evitando l’uso di solventi organici, limitando le procedure di workup e riducendo la produzione di rifiuti rispetto alle strategie di sintesi in soluzione. Il secondo approccio è consistito nella formulazione di nanoparticelle di lignina (LNP) che sono note esibire proprietà uniche a causa del loro alto rapporto tra area superficiale e volume. Studi analitici riguardo frazioni estratte con solventi organiche hanno guidato la scelta di specifiche frazione di lignina per lo sviluppo di nanoparticelle con caratteristiche peculiari. La procedura innovativa sviluppata ha permesso di valorizzare tutto la lignina kraft di partenza in maniera efficiente. È stato possibile produrre LNP con una provata stabilità dimensionale in un ampio intervallo di pH (4,5-12) , valori ai quali normalmente la lignina si aggrega o dissolve. Lo stesso approccio ha consentito di preparare LNP specificamente funzionalizzate in maniera covalente alla superficie, un risultato mai ottenuto in letteratura al meglio delle nostre conoscenze. La messa appunto e lo scale up di queste procedure hanno permesso la formulazione di compositi elastomerici, seguito dalla valutazione delle proprietà dinamomeccaniche di una varietà di compositi che includevano lignina modificata. I risultati intriganti si sono dimostrati promettenti per lo sviluppo di compositi elastomerici tecnologicamente competitivi contenenti materiali rinnovabili.Rubber products are commonly employed in a wide variety of industries including tire manufacturing, packaging, engineering and construction. The mechanical performances of rubber itself are unsatisfactory for the desired applications so the necessary improvements are commonly obtained by vulcanization and addition of reinforcing fillers in the elastomeric matrix. The most popular reinforcing filler is carbon black whose use is however associated with health and environmental concerns. For this reason, many tire manufacturers are concentrating their efforts in replacing carbon black with more sustainable alternatives. Their ambitions include the increment of renewable materials and the simultaneous reduction of fossil-based compounds in tire formulations, while preserving pr improving mechanical performances. In this frame, the present research project dealt with the development of sustainable reinforcing fillers for rubber compounds in alternative to fossil-based technologies with a particular focus on lignin. Despite its availability at industrial scale, the structural complexity of lignin has hampered its conversion into value-added products and the rational design of functional materials. However, the concerns about toxicity and environmental concerns related to the use of fossil-based materials are eliciting investigations regarding the use of renewable resources, included lignin. This material could be considered as a valuable alternative to carbon black in rubber compounds due to its good physical chemical and mechanical properties, antioxidant activity and thermal stability. However, its combination with an elastomeric matrix requires overcoming the poor compatibility between the two materials related to the polarity of lignin which results into strong self-interactions. So, it was necessary to modify lignin in order to improve the number and quality of its interaction with rubber resulting in a reinforcing effect. To ensure the desired reinforcement, two strategies were explored in the present project. The former dealt with the functionalisation of lignin hydroxyl groups ensuring the formation of covalent bonds between lignin and the rubber matrix during vulcanization. The procedure consisted in the mechanochemical esterification of lignin, allowing running reactions in the solid state, taking advantage of mechanical energy to trigger chemical transformations, avoiding organic solvents, limiting work-up procedures and reducing wastes with respect to wet chemistry syntheses. The latter consisted in the formulation of lignin into nanoparticles (LNPs)which are acknowledged to exhibit unique properties due to their high surface to volume ratio. Analytical investigations about solvent-extracted fractions guided the choice of specific lignin fractions for the development of LNPs with peculiar features. The innovative procedure allowed valorising the whole starting kraft lignin in a material efficient manner. It was possible to produce LNPs which proved dimensionally stable in a broad pH range 4.5-12.0 where lignin normally aggregates or dissolves The same approach allowed preparing LNPs with a surface-specific covalent functionalisation, an achievement never attempted in literature, to the best of our knowledge. The setup and scaleup of those procedures allowed for the formulation of innovative rubber compounds followed by the assessment of their dynamic-mechanical properties. The intriguing results proved promising for the development of technologically valuable and competitive rubber compounds including renewable materials.
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Marques, de Oliveira Paulo Filho. "Investigation of mechanochemical synthesis of condensed 1,4-diazines and pharmaceutically attractive hydrazones." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2015. http://www.theses.fr/2015EMAC0007/document.
Full textAbstract:
L'un des objectifs des industries chimique et pharmaceutique est de développer des procédés verts évitant ou réduisant l'utilisation de solvants. Mais ne pas utiliser de solvant nécessite souvent des catalyseurs métalliques ou autre, ce qui rend les purifications délicates, comme dans le cas des synthèses de chimie fine permettant l'obtention de principes actifs pharmaceutiques. C'est ainsi que la mécanochimie a émergé en tant que voie durable pour la synthèse chimique, y compris dans le cas des transformations moléculaires organiques sous contrainte mécanique. Malgré les progrès récents de cette méthodologie, certains aspects de l'action mécanique ne sont pas totalement élucidés, en particulier ce qui concerne les mécanismes. Dans cette thèse, trois axes principaux de la mécanochimie ont été explorés. Dans une première partie, le mécanisme moléculaire de la synthèse de deux types de 1,4-diazines, la dibenzo[a,c]phenazine (DBPZ) et la 2,3-diphenylquinoxaline (DPQ), a été investigué. La RMN 13C CP-MAS a permis de mettre en évidence des intermédiaires de cette synthèse, et des mesures calorimétriques ont révélé que deux réactions se poursuivaient après broyage. La possibilité d'une réaction concertée a également été prise en compte dans le cas de la dibenzo[a,c]phenazine. La seconde partie concerne la formation de la 2,3-diphenylquinoxaline. Les paramètres du procédé ont été étudiés, dans le cas d'un broyeur à bille vibrant. L'influence des matériaux de broyage, de la taille et de la masse des billes, la granulométrie des matières premières, ainsi que la température des media de broyage ont été étudiés, permettant de déterminer une énergie d'activation apparente (Ea). Le tracé des courbes selon Arrhenius et Eyring-Polanyi a montré des changement de Ea caractéristiques de modifications au niveau du mécanisme, attribuées à l'apparition d'un possible eutectique fondant au dessus de 30°C, induit mécaniquement. Après cette étude qui a permis la compréhension de certains points fondamentaux, et d'approfondir les procédés de ces réactions modèles, une troisième partie traite de l'application de la mécanochimie à la synthèse en phase solide d'hydrazones d'intérêt pharmaceutique, et à celle catalysée de dérivés de l'isoniazide obtenus par réaction d'aldéhydes et d'hydrazines. D'une manière générale, les durées de réaction sont plus faibles, et les rendements meilleurs, qu'avec les méthodes classiques. L'influence des réactivités électronique et des hydrazines à l'état solide a été discutée. Les essais biologiques ont démontré une activité avérée des dérivés de l'isoniazide dans l'inhibition de Mycobacterium tuberculosis. Les résultats présentés dans cette thèse englobent plusieurs aspects très complémentaires de la mécanochimie. L'approche fondamentale du mécanisme est d'un accès difficile, en raison de la complexité du système, mais des avancées ont été réalisées comme la mise en évidence d'intermédiaires à longue durée de vie. Les paramètres du procédé apportent une contribution à la compréhension du mécanisme mais aussi en vue du scaling-up. Enfin, la mécanosynthèse s'est révélée être une méthode de chimie verte particulièrement adaptée à la synthèse d'hydrazones d'intérêt pharmaceutique, pour le screening de nouvelles entités ou la synthèse durable de produits de grande puretéOne of the goals of pharmaceutical and chemical industries is the development of green processes that eliminates or reduces the use of solvents. However, avoiding solvents often requires the use of metal catalysts or others, that accelerates chemical reactions, but make the purifications difficult, especially in the case of fine chemical products, such as active pharmaceutical ingredients. The mechanochemistry has emerged as a sustainable way that enables chemical synthesis, including organic molecular transformations, using the mechanical energy. In spite of the recent advances of the methodology, some aspects of the mechanical action still remain to be fully elucidated, mainly concerning the mechanisms. In this thesis, three main axes of mechanochemistry were explored. First, the molecular mechanism of 1,4-diazine mechanosynthesis, mentioning dibenzo[a,c]phenazine (DBPZ) and 2,3-diphenylquinoxaline (DPQ), is investigated by using 13C CP-MAS NMR that reveals intermediate species for DBPZ, and by calorimetric measurements that show continuation of the reaction after grinding for both reactions. The possibility of a concerted mechanism is considered for dibenzo[a,c]phenazine case. The second focus is on 2,3-diphenylquinoxaline product formation. The process parameters for a vibratory ball mill were studied. Grinding material, size and mass of the balls, granulometry of the starting material were assessed, as well as the temperature of the milling media, providing apparent activation energy (Ea). Arrhenius and Eyring-Polanyi plots presented changes in Ea indicating changes in mechanism, which was attributed to a possible mechanically induced eutectic melting after 30°C. Finally, after understanding some fundamentals and processes for those model reactions, the mechanochemical route was successfully applied to solid-state synthesis of pharmaceutically attractive phenolic hydrazones and catalyzed isoniazid derivatives synthesis, by reacting solid aldehydes and hydrazines. In general, the products were obtained in shorter times and in higher yields compared to classical thermal route. The roles of electronic and solid-state reactivity of the hydrazines were discussed. Biological assays demonstrated the great activity of isoniazid derivatives in inhibiting Mycobacterium tuberculosis. The results presented here cover the mechanochemistry at different levels. The fundamental comprehension is still difficult to access due to the complexity of the system, but some advances could be made such as the detection of intermediate species with significant lifetime. The process parameters are equally important to deduce some mechanism, but also for scale up purposes. At last, the mechanosynthesis of hydrazones showed to be a greener route to produce pharmaceuticals, for high screening of new ones, as well as for the synthesis of others, with great purity and waste reduction
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Scalise, Valentina. "Mechanochemical Synthesis of low F-Doped Aluminium Hydroxide Fluorides." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19684.
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Die Mechanochemie ist eine effekive und überzeugende Methode zur Herstellung von Alumniumhydroxidfluoriden (Al(OH)3-xFx) mit einem sehr geringen Fluorgehalt. Durch den Prozess des Mahlens werden strukturelle Defekte in den Kristalliten erzeugt, die zu einer zunehmenden Amorphisierung des Kristallsystems führen. Die partielle Fluorierung von Alumniumhydroxid während des Mahlprozesses führt dabei zu einer noch stärkeren Amorphisierung und zur Bildung von Alumniumhydroxyfluoriden. Eine wichtige Rolle bei der resultierenden Produktzusammensetzung spielt die Variation der Synthesebedingungen, wie der Grad der Fluorierung, der Dauer des Mahlprozesses und des Wassergehalt der Edukte.
Folglich wurde zuerst der Einfluss von Wasser und dessen Bedeutung durch die verschiedenen Kombinationen von Oxid- und Hydroxid- (Al(OH)3, Al2O3), sowie Fluorid-Quellen mit oder ohne Kristallwasser (β-AlF3.3H2O, α-AlF3) bei der mechanochemischen Synthese von hochgestörten Alumniumhydroxidfluoriden untersucht.
Um den optimalen Fluorierungsgrad zu ermitteln, wurden verschiedene Aluminiumhydroxidfluoride mit Al/F-Molverhältnissen von 1:1.5 bis 1:0.05 über die mechanochemische Syntheseroute hergestellt. Eine tiefergehende Charakterisierung der Struktur- und Oberflächeneigenschaften der entsprechenden Produkte erfolgte mittels XRD, 27Al- und 19F-Festkörper-NMR, thermischer Analyse, Stickstoffabsorptions- und Zeta Potentialmessungen. Mit γ-Al(OH)3 und β-AlF3•3H2O als Hydroxid- und Fluorid-Quellen wurden dabei ab einem Verhältnis Al:F von 1:0.25 und hin zu höheren Fluoridanteilen besonders ungeordnete Strukturen erzeugt. Der Fluorierungsgrad betrifft dabei besonders die Ausbildung von 4- und 5-fach koordinierten Al-Zentren, die sonst nicht in den Edukten vorkommen. Diese Spezies beeinflussen die Bildung von Alumniumoxid und ermöglichen den Phasenübergang zu α-Al2O3 schon bei tieferen Temperaturen.
Der Einfluss der Mahldauer auf die Struktur und Oberfläche wurde am Beispiel von γ-Al2O3 im Detail untersucht. Die mechanochemische Synthese beeinflusst dabei die Absorption von Fluor an der Grenzschicht von γ-Al2O3 zu Wasser stark. Die Dauer des Mahlprozesses gewinnt daher einen großen Einfluss auf die entstehenden Produkte. Da Fluor nicht im Bulk von γ-Al2O3 vorkommt, kann mit der 19F-Festkörper-NMR eine Zuordnung der unterschiedlichen an der Oberfläche adsorbierten F-Spezies getroffen werden.The mechanochemical approach opens a reliable and effective strategy for the formation of aluminium hydroxide fluorides with a very low F-content. Milling has the effect of introducing structural defects, causing amorphisation. The fluorination by milling creates a further and drastic increase of this degree of amorphisation. Synthesis conditions (milling time, fluorination degree, water content) play a crucial role in the product composition. Firstly, the significant role played by water in the mechanochemical synthesis of highly distorted aluminium hydroxide fluorides was evaluated. The importance of water in the synthesis was considered by a separated combination of O/OH sources (Al(OH)3, Al2O3) and fluorine sources with or without structural water (β-AlF3.3H2O, α-AlF3). Concerning the degree of fluorination, different aluminium hydroxide fluorides with varying Al/F molar ratios from 1:1.5 up to 1:0.05 were successfully synthesized by mechanochemical reactions. The characterization of the products by XRD, 27Al and 19F MAS NMR, thermal analysis, nitrogen adsorption and zeta potential techniques allows a detailed understanding of the structure and surface properties of the products. Using γ-Al(OH)3 and β-AlF3•3H2O as OH- and F-sources, respectively, strongly disordered products were obtained with an Al: F molar ratio higher than 1:0.25. The degree of fluorination affects the amount of 4- and 5-fold coordinated Al sites, not present in the reactants. Obviously, these species affect the phase transition to alumina, by decreasing the transition temperature of the formation of α-Al2O3. The influence of the milling time was considered by studying the power of a high energy ball milling process on the structure and at the surface of γ-Al2O3. The mechanochemical treatment strongly influences the adsorption of fluorine at the γ-Al2O3/ water interface. The time of the treatment has relevant importance on these processes. Since fluorine is not originally present in the bulk of γ-Al2O3, 19F MAS NMR studies allow the discrimination of different F-species adsorbed at the surface or present as metal fluoride particles in γ-Al2O3 powders after adsorption experiments.
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Konnert, Laure. "Préparation par mécanochimie de dérivés d'acides aminés et d'hydantoïnes." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS279.
Full textAbstract:
Le développement d'une chimie soucieuse de l'environnement doit passer par la recherche de solutions concernant l'utilisation de solvants organiques. Ces solvants sont souvent toxiques et volatiles et créent, surtout dans le cas des solvants halogénés, des dégâts environnementaux. L'objectif premier de ce projet est de développer des alternatives à l'utilisation en chimie de solvants organiques toxiques et volatiles. Plus précisément, le but est de mettre au point des méthodes de transformations chimiques qui permettent de diminuer fortement l'utilisation de solvant ou de les remplacer par des solvants alternatifs. Le développement de ces méthodes par mécanochimie a permis d'atteindre cet objectif. Plusieurs méthodologies ont été développées et appliquées à la protection des acides aminés ainsi qu'à la synthèse de molécules bioactives que sont les hydantoïnes, avec notamment la préparation de composés pharmaceutiques tels que la phénytoïne et l'éthotoïne, deux médicaments prescrits contre l'épilepsieThe development of environmentally-friendly chemistry has to go through the search for solutions concerning the use of organic solvents. Such solvents are often toxic and volatile, and create, especially in the case of halogenated solvents, environmental damage. The primary objective of this project is to develop alternatives to the use in synthetic chemistry of toxic and volatile organic solvents. Specifically, the goal is to develop methods of chemical transformations that can greatly reduce the use of solvent or replace them with alternative solvents. The development of these methods by mechanochemistry enabled to achieve this goal. Several methodologies have been developed and applied to the protection of amino acids and the synthesis of bioactive molecules such as hydantoins, including the preparation of pharmaceutical compounds such as phenytoin and ethotoin, two drugs prescribed against epilepsy
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Kulla, Hannes. "In situ Untersuchungen der mechanochemischen Synthese von Cokristallen: Einfluss von Reaktionsparametern am Modellsystem Pyrazinamid." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20047.
Full textAbstract:
Die Mechanochemie findet zunehmend Verwendung für die Synthese neuer Verbindungen. Dennoch sind die beim Mahlen stattfindenden Prozesse weitestgehend unverstanden. Dahingehend wurde in dieser Arbeit eine Dreifachkopplung aus in situ Synchrotron-Röntgenbeugung, Raman-Spektroskopie und Thermographie entwickelt, um mechanochemische Reaktionen unter realistischen Bedingungen in Echtzeit zu verfolgen. Dadurch konnten tiefgreifende Einblicke in den Reaktionsverlauf und Temperaturverlauf beim Mahlen erhalten und neue metastabile Verbindungen isoliert werden. Für die Bildung pharmazeutischer Cokristalle diente Pyrazinamid als Modellsystem. Es konnten neue binäre und ternäre Verbindungen synthetisiert, detailliert charakterisiert und deren Kristallstruktur aufgeklärt werden. Die Abhängigkeit der Stabilität polymorpher Cokristalle von der Temperatur und den Synthesebedingungen konnte gezeigt werden. In Konkurrenzreaktionen konnten Trends hinsichtlich der bevorzugten Bildung eine bestimmten Cokristalls beobachtet werden. Mittels in situ Untersuchungen wurde der Einfluss zentraler Reaktionsparameter, wie die Mahlfrequenz, der Kugeldurchmesser, der eingesetzte Ausgangsstoff und die Zugabe von Lösungsmittel, auf die Induktions- und Reaktionszeit der Reaktion ermittelt. Basierend auf den gewonnenen Erkenntnissen konnte ein Diffusionsmechanismus für die mechanochemische Cokristallbildung abgeleitet werden.Mechanochemistry is increasingly applied for the synthesis of new compounds. Still, the processes taking place during milling are far from being understood. In this thesis, a triple coupling of in situ synchrotron X-ray diffraction, Raman spectroscopy and thermography has been developed to follow mechanochemical reactions under realistic conditions in real time. This allowed deep insights into the reaction and temperature progression during milling and the isolation of new metastable compounds. For the formation of pharmaceutical cocrystals pyrazinamide served as a model system. New binary and ternary compounds were synthesized, characterized in detail and their crystal structure solved. The dependence of the stability of polymorphic cocrystals on temperature and synthesis conditions could be shown. In competitive reactions, trends regarding the preferred formation of a certain cocrystal have been observed. The influence of important reaction parameters, such as the milling frequency, the ball diameter, the starting material used and the addition of solvent, on the induction and reaction time of the reaction was determined by means of in situ investigations. Based on the gained knowledge, a diffusion mechanism for the mechanochemical cocrystal formation could be derived.