• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 22
  • 12
  • 8
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 60
  • 28
  • 21
  • 13
  • 12
  • 11
  • 10
  • 10
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

TETRATHIAFULVALENES : Ligands Multifonctionnels et Nouveaux Systèmes Donneur-Accepteur

Riobé, François 05 November 2009 (has links) (PDF)
Ce travail a exploité les remarquables propriétés électroniques du tétrathiafulvalène (TTF) au sein de deux nouveaux systèmes : les TTF-bis-oxazolines et les TTF-triazines. La fonctionnalisation du TTF par des groupements oxazolines a permis l'introduction de la chiralité sur le donneur. Les structures cristallines des molécules synthétisées ainsi que celles de leurs intermédiaires sont reportées. Nous présentons diverses approches employant ces composés comme précurseurs de matériaux mulifonctionnels. Les TTF-bis-oxazolines ont par ailleurs servi comme ligands chiraux pour des matériaux. Des complexes de cuivre ont permis de réaliser différentes réactions de catalyse homogène énantiosélective. Nous nous sommes intéressés, dans ce dernier cas, à l'influence de l'état rédox du TTF sur l'activité catalytique et l'induction chirale de ces complexes. Dans une seconde partie, nous reportons la synthèse de nouveaux systèmes Donneur-Accepteur associant le TTF (D) à une plateforme triazine (A). Les études théoriques et expérimentales réalisées sur une diade D-A et une triade D-A-D ont permis de caractériser parfaitement le transfert de charge intramoléculaire présent dans ces systèmes. La 2-TTF-4,6-bis-méthoxy-1,3,5-triazine apparaît comme un bon candidat pour l'électronique moléculaire.
32

Development of New Synthesis of Sulfur-oxazoline Ligands

Huang, Nan-Yuan 03 October 2011 (has links)
This thesis is the use of commercially available methyl 2-iodobenzoate as the starting material and was prepared into iodine - oxazoline compound 118. Then, we undergo copper-catalyzed cross-coupling reactions of compound 118with thiols, and were readily facilitated to afford the corresponding desired products 127¡B136 in good to excellent yields. This method not only modified short- comings of that adding strong base to synthesis of sulfur-oxazoline ligands in past years but also has a good yield performances, the yield is 70 -87%. And we will use this strategy to undergo one pot reaction of carbon-sulfur coupling in future. In the end, we used new sulfur-oxazoline ligands127¡B128 in the Pd-catalyzed asymmetric alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate. and reaction ee% were high, with the best result of 99% and 93% conversion.
33

Aminophosphine-oxazolines

Blanc, Catherine Agbossou-Niedercorn, Francine January 2005 (has links)
Reproduction de : Thèse de doctorat : Chimie organique et macromoléculaire : Lille 1 : 2004. / Titre provenant de la page de titre du document numérisé.
34

Étude des poly(2-alkyl-2-oxazoline)s munis d'extrémités hydrophobes en solution aqueuse et à linterface eau/air

El Hajj Obeid, Rodolphe January 2009 (has links)
Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal
35

Avaliação do copolímero de acrilonitrila e 2-vinil-2-oxazolina na eficiência de Iinibição de corrosão química / Evaluation of copolymer of acrylonitrile and 2-vinyl-2-oxazoline in the efficiency of corrosion inhibition chemical

Wemerson Vieira de Paula 30 March 2010 (has links)
Polímeros heterocíclicos são macromoléculas de elevado desempenho que incluem uma grande variedade de materiais, desde simples polímeros lineares preparados a partir de monômeros do tipo heterocíclicos vinílicos, até polímeros funcionalizados e reticulados. Neste trabalho realizou-se a modificação química da poliacrilonitrila com a incorporação de grupos 2-vinil-2-oxazolina em diferentes teores (10% e 20%). Os copolímeros de acrilonitrila e 2-vinil-2-oxazolina obtidos foram caracterizados por espectroscopia na região do infravermelho e o seu comportamento térmico analisado por calorimetria diferencial de varredura e análise termogravimétrica. Os copolímeros heterocíclicos foram avaliados como inibidores de corrosão para aço-carbono em solução aquosa de HCl 10%, alcançando, em alguns casos, uma eficiência de inibição superior a 75%, com diferença estatisticamente significativa (P < 0,05, ANOVA) para a poliacrilonitrila não modificada. / Heterocyclic polymers are high-performance macromolecules that include a variety of materials, from simple linear polymers which are prepared from heterocyclic monomers like vinyl, to functionalized polymers or lattices. In this work polyacrylonitrile was chemically modified with incorporation of 2-vinyl-2-oxazoline groups at different contents (10% and 20%). Copolymers of acrylonitrile and 2-vinyl-2-oxazoline were characterized by spectroscopy in the infrared region, differential scanning calorimetry and thermogravimetric analysis. The synthesized heterocyclic copolymers were evaluated as corrosion inhibitor on carbon steel against aqueous solution of HCl 10%, and in some cases inhibition efficiencies more than 75% were determined, with statistically significant difference (P < 0.05, ANOVA) to the unmodified polyacrylonitrile.
36

Aplicação da cenoura (Daucus carota) como biocatalisador : estudos visando a síntese assimétrica da Shahidina e da Marmelina

Bonfim, Thiago Ramalho do January 2015 (has links)
Orientador: Prof. Dr. Álvaro Takeo Omori / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2015. / Este trabalho consistiu no estudo para a síntese dos compostos Shahidina 1 e Marmelina 2 ambos extraídos da planta Aegle marmelos amplamente cultivada no continente asiático. Ambos os compostos possuem centros quirais onde um dos objetivos é definir estes centros por biocatálise com o uso de cenoura (Daucus carota). Também foi explorada a formação de anéis oxazolínicos entre alcoóis e azidas pela reação de Boyer. Porém esta metodologia demonstrou alguns resultados imprevistos. Houve a formação de epóxido na redução química da cetona 17 para o álcool 19 e o método de biorredução teve que ser otimizado pois o método clássico apresentou baixas taxas de conversão. A reação de Boyer também se mostrou ineficaz quando realizada entre azidas e aldeídos conjugados. Houve a necessidade de se alterar a rota. / This work aimed the synthesis of Shahidine 1 and Marmeline 2 both extracted from Aegle marmelos plant (widely grown in Asia). Both compounds have chiral centers located next to the aromatic ring. One of the key steps was to resolve these stereogenic centers by biocatalysis with Daucus carota (carrot) root. Another key step was the formation of oxazoline ring between aldehydes and azido alcohols by the Boyer reaction. However some unexpected results were observed. For example, epoxide formation was observed in the chemical reduction of ketone 17. Also, bioreduction protocol showed low conversion rate. Besides, we observed that the the Boyer reaction between azido alcohol 19 and conjugated aldehyde were ineffective. It was necessary to change the route.
37

Avaliação do copolímero de acrilonitrila e 2-vinil-2-oxazolina na eficiência de Iinibição de corrosão química / Evaluation of copolymer of acrylonitrile and 2-vinyl-2-oxazoline in the efficiency of corrosion inhibition chemical

Wemerson Vieira de Paula 30 March 2010 (has links)
Polímeros heterocíclicos são macromoléculas de elevado desempenho que incluem uma grande variedade de materiais, desde simples polímeros lineares preparados a partir de monômeros do tipo heterocíclicos vinílicos, até polímeros funcionalizados e reticulados. Neste trabalho realizou-se a modificação química da poliacrilonitrila com a incorporação de grupos 2-vinil-2-oxazolina em diferentes teores (10% e 20%). Os copolímeros de acrilonitrila e 2-vinil-2-oxazolina obtidos foram caracterizados por espectroscopia na região do infravermelho e o seu comportamento térmico analisado por calorimetria diferencial de varredura e análise termogravimétrica. Os copolímeros heterocíclicos foram avaliados como inibidores de corrosão para aço-carbono em solução aquosa de HCl 10%, alcançando, em alguns casos, uma eficiência de inibição superior a 75%, com diferença estatisticamente significativa (P < 0,05, ANOVA) para a poliacrilonitrila não modificada. / Heterocyclic polymers are high-performance macromolecules that include a variety of materials, from simple linear polymers which are prepared from heterocyclic monomers like vinyl, to functionalized polymers or lattices. In this work polyacrylonitrile was chemically modified with incorporation of 2-vinyl-2-oxazoline groups at different contents (10% and 20%). Copolymers of acrylonitrile and 2-vinyl-2-oxazoline were characterized by spectroscopy in the infrared region, differential scanning calorimetry and thermogravimetric analysis. The synthesized heterocyclic copolymers were evaluated as corrosion inhibitor on carbon steel against aqueous solution of HCl 10%, and in some cases inhibition efficiencies more than 75% were determined, with statistically significant difference (P < 0.05, ANOVA) to the unmodified polyacrylonitrile.
38

Synthesis and Characterization of Novel Amphiphilic Diblock Copolymers Poly (2-Ethyl-2-Oxazoline)-b-Poly (Vinylidene Fluoride)

Aljeban, Norah 06 1900 (has links)
Poly (2-ethyl-2-oxazoline)-based amphiphilic diblock copolymer has the potential to form promising membrane materials for water purification due to the thermal stability and good solubility in aqueous solution and also for gas separation because of the presence of polar amide group along the polymer backbone. Moreover, their self-assembly into micelles renders them candidate materials as nanocarriers for drug delivery applications. In this study, a novel well-defined linear PEtOx-based amphiphilic diblock copolymer with a hydrophobic fluoropolymer, i.e., PVDF, have been successfully synthesized by implementing a synthesis methodology that involves the following four steps. In the first step, poly (2-ethyl-2-oxazoline) (PEtOx) was synthesized via living cationic ring-opening polymerization (LCROP) of 2-ethyl-2-oxazoline (EtOx) monomer. The “living” nature of LCROP allows the desirable termination to occur by using the proper termination agent, namely, water, to achieve the polymer with a terminal hydroxyl group, i.e., PEtOx-OH. The hydroxyl end group in PEtOx-OH was converted to PEtOx-Br using 2-bromopropionyl bromide via an esterification reaction. In the third step, the PEtOx-Br macro-CTA was subsequently reacted with potassium ethyl xanthate to insert the necessary RAFT agent via nucleophilic substitution reaction to obtain PEtOx-Xanthate. It s worth mentioning that this step is vital for the sequential addition of the second block via the RAFT polymerization reaction of fluorinated monomer, i.e., VDF, to finally obtain the well-defined amphiphilic diblock copolymer with variable controlled chain lengths. Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR) and Fourier Transform Infrared Spectroscopy (FT-IR) confirmed the structure of the macroinitiator and final copolymer, respectively. Size Exclusion Chromatography (SEC) determined the number-average molecular weight (Mn) and the polydispersity index (PDI) of the obtained copolymer. Furthermore, the polymorphism of the diblock copolymer characterized by X-Ray Diffraction (XRD) indicated that the copolymer displays the electroactive α-phase. The resultant amphiphilic diblock copolymer exhibits spherical micelles morphology, as confirmed by Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM). Moreover, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) investigated the thermal decomposition behavior of the copolymer and determined the glass transition temperature (Tg ≈ 70 °C), melting temperature (Tm ≈ 160-170 °C), and crystallization temperature (Tc ≈ 135-143 °C) of the diblock copolymer, respectively.
39

Synthesis of Amphiphilic Block Copolymers for Use in Biomedical Applications

Carmichael-Baranauskas, Anita Yvonne 16 June 2010 (has links)
The research presented in this thesis focuses on the synthesis of three amphiphilic block copolymer systems containing poly(ethylene oxide) (PEO) blocks. The polymer systems were developed for use in biomedical applications. The first of these is a series of poly(ethylene oxide-b-oxazoline) (PEO-b-POX) diblock copolymers for use in the progress towards novel non-viral gene transfer vectors. Poly(ethylene oxide-b-2-ethyl-2-oxazoline) (PEO-b-PEOX) and poly(ethylene oxide-b-2-methyl-2-oxazoline) (PEO-b-PMOX) were investigated. The PEOX block was hydrolyzed with acid to form linear polyethylenimine (L-PEI). The polycation L-PEI is well known for its DNA binding efficiency but the water solubility of the resulting DNA/polymer complex is limited. Addition of a PEO block is directed towards the formation of a water dispersible DNA/copolymer complex. Dynamic light scattering of the PEO-b-PEOX and PEO-b-PEI block copolymers indicated that both systems existed as single chains in aqueous solution at pH 7. PEO copolymers also play a significant role in the formation of magnetic magnetite nanoparticles, which are dispersible in water at biological pH (pH =7). There is significant interest in the design of magnetic nanoparticle fluids for biomedical applications including magnetic field-directed drug delivery, magnetic cell separations, and blood purification. For use in vivo, the magnetite nanoparticles must be coated with biocompatible materials. Such polymers render the nanoparticles dispersible in water. Harris1 et al. synthesized PEO based, polyurethane triblocks with pendant carboxylic acid groups for use in formation of stable aqueous magnetic fluids. Building from this work, two polyurethane and polyurethaneurea systems were synthesized with 1300 g/mol PEOX and 2500 g/mol and PEOX2070 g/mol poly(ethylene oxide-co-propylene oxide) tailblocks, respectively. The PEO/PPO random copolymer contained about 25 weight percent PPO, and this disrupted the capacity of the PEO to crystallize. The PEOX based urethane triblocks were synthesized through reacting the tailblocks with the monomers for the center block whereas the PEO/PPO based polyurethaneurea was synthesized through forming the central urethane block with pendant acid groups first and then terminating the copolymer with the monofunctional copolymer. Terminal amine groups on the PEO/PPO tailblock afforded a triblock linked with two urea groups. The new polyurethanes with the PEOX tailblocks and the new polyurethaneurea with the PEO/PPO tailblocks could be utilized to efficiently stabilize magnetite nanoparticles in water. / Master of Science
40

Synthèse et étude physico-chimique de copolymères amphiphiles à base de poly(2-méthyl-2-oxazoline) / Synthesis and physical chemistry study of amphiphilic copolymers based on poly(2-methyl-2-oxazoline)

Guillerm, Brieuc 16 December 2011 (has links)
Ce travail de thèse décrit l'élaboration de copolymères amphiphiles obtenus par couplage de deux homopolymères. La synthèse des copolymères s'est effectuée en deux étapes. Dans un premier temps, des homopolymères de type poly(2-méthyl-2-oxazoline) (P(MOx)) et poly(acrylate de tert-butyle) (P(At-Bu)) ont été préparés par polymérisation par ouverture de cycle cationique (CROP) et par polymérisation radicalaire contrôlée de type RAFT ou ATRP, respectivement. Puis les copolymères amphiphiles diblocs ont finalement été obtenus par une réaction de couplage polymère-polymère de type cycloaddition de Huisgen. Une étude physico-chimique de ces copolymères dans l'eau a mis en évidence la présence d'agrégats qui présentent une morphologie sphérique, des tailles inférieures à 100 nm et des concentrations d'agrégation critique de l'ordre de 10-6 mol.L-1.Les connaissances acquises sur la synthèse et l'étude des copolymères à blocs amphiphiles ont également permis le développement de copolymères greffés amphiphiles poly(-caprolactone)-g-poly(2-méthyl-2-oxazoline) (PCL-g-P(MOx)), constitués d'un bloc hydrophobe PCL sur lequel des chaînes hydrophiles P(MOx) ont été greffées. L'étude du comportement de ces copolymères dans l'eau montre la formation d'agrégats avec des caractéristiques proches de celles obtenues pour les copolymères diblocs amphiphiles. Un autre point intéressant est que la P(MOx) permet de solubiliser la PCL dans l'eau.Ces deux études illustrent l'apport de la chimie macromoléculaire pour la préparation de structures amphiphiles parfaitement définies qui s'organisent en phase aqueuse en agrégats. Ces derniers pourraient notamment être utilisés dans le domaine biomédical. / This manuscript deals with the synthesis of amphiphilic diblock copolymers obtained by the coupling of both hydrophobic and hydrophilic homopolymers. The copolymers were achieved in two steps. On the one hand, homopolymers poly(2-methyl-2-oxazoline) P(MOx)s and poly(tert-butyl acrylate)s (P(At-Bu) were synthesized by cationic ring opening polymerization (CROP) and by Reversible Addition-Fragmentation Transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP), respectively. Finally, amphiphilic diblock copolymers were achieved by Huisgen's cycloaddition. Physical chemistry studies in water proved the formation of aggregates. The latter had a spherical morphology, sizes below 100 nm and critical aggregation concentration around 10-6 mol.L-1.Knowledge acquired on the synthesis and the study of amphiphilic block copolymers led to the development of poly(-caprolactone)-g-poly(2-methyl-2-oxazoline) (PCL-g-P(MOx)) amphiphilic graft copolymers, made of a hydrophobic PCL grafted with hydrophilic P(MOx) moieties. The study of aqueous solution of such copolymers showed the formation of aggregates with characteristics close from those obtained for the diblock copolymers. Another interesting point is that P(MOx) permitted the solubilization of PCL in water.The reported work illustrated the importance of macromolecular chemistry for the obtaining of amphiphilic copolymers with controlled molecular weight and narrow molar mass distributions which self-assemble in water. Such kind of materials could be used in the biomedical field.

Page generated in 0.1067 seconds