• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 159
  • 85
  • 39
  • 16
  • 7
  • 7
  • 6
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 395
  • 164
  • 144
  • 124
  • 50
  • 43
  • 41
  • 40
  • 39
  • 34
  • 32
  • 30
  • 30
  • 28
  • 25
  • 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.
81

Estudo do efeito da adição de poli(glicol etilênico-b-glicol propilênico) na formação de dispersões aquosas poliuretânicas à base de poli(glicol propilênico) / Estudo do efeito da adição de poli(glicol etilênico-b-glicol propilênico) na formação de dispersões aquosas poliuretânicas à base de poli(glicol propilênico) / Study of the effects of the addition of poly(ethylene glycol-b-propylene glycol)in the formation of polyurethanics aqueous dispersions with a poly(propylene glycol) basis / Study of the effects of the addition of poly(ethylene glycol-b-propylene glycol)in the formation of polyurethanics aqueous dispersions with a poly(propylene glycol) basis

Rosiléa Braga Luciano de Almeida 06 March 2007 (has links)
Foram produzidas dispersões aquosas não-poluentes e inovadoras de poli(uretano-uréia) à base de poli(glicol propilênico) (PPG) e de copolímeros em bloco, poli(glicol etilênicob-glicol propilênico), (EG-b-PG) com teor de 7% de unidades de glicol etilênico. Os poli(uretano-uréia)s foram preparados, em duas etapas, pelo método do prepolímero. Na primeira etapa, foram obtidos anionômeros, sintetizados em massa, à base do copolímero EG-bPG, PPG, ácido dimetilol propiônico (DMPA) (gerador dos sítios aniônicos) e diisocianato de isoforona (IPDI). Ainda na primeira etapa, os grupos carboxílicos do DMPA foram submetidos à neutralização com trietilamina (TEA). Na segunda etapa, foi realizada a dispersão do prepolímero anionômero e, em seguida, foi conduzida a reação de extensão de cadeia com a hidrazina (HYD). Nas diferentes formulações, foram variadas a razão NCO/OH e as proporções de PPG e do copolímero em bloco EG-b-PG. Além disso, foram obtidas dispersões aquosas programadas para teores de sólidos de 40 e 50%. As dispersões foram avaliadas quanto ao teor de sólidos totais, tamanho médio de partícula e viscosidade. Os filmes, obtidos por vazamento das dispersões, foram avaliados quanto à absorção de água, termogravimetria (TG) e propriedades mecânicas (ensaio de tração). Os filmes vazados e os monômeros foram caracterizados por espectrometria na região de infravermelho (FTIR) As dispersões obtidas se mostraram adequadas para serem aplicadas como revestimento para madeira, metais e vidro / Non-polluting and poly(urethane-urea) aqueous dispersions based on poly(propylene glycol) (PPG) and block copolymers of poly(ethylene glycol-b-propylene glycol) (EG-b-PG) containing 7% of ethylene glycol repeating units, were produced in an innovative way. The poly(urethane-urea)s were prepared, in two steps, by the prepolymer method. In the first step, anionomers, synthesized in bulk, based on EG-b-PG, PPG, dimethylolpropionic acid (DMPA) (anionomer sites generator) and isophorone diisocyanate (IPDI) were obtained. Still in the first step, the DMPA carboxylic groups were neutralized with triethylamine (TEA), generating the anionomer groups. In the second step, the anionomer prepolymer was dispersed in water under vigorous stirring and afterwards was chain extended with hydrazine. Different formulations were obtained by varying the NCO/OH ratio, and the proportions of PPG and EG-b-PG. Besides, poly(urethane-urea) aqueous dispersions with 40% and 50% of solid contents were obtained. The dispersions were evaluated in terms of their solid-contents, particle size and viscosity. The cast films, obtained from the dispersions concernig of water absorption, thermogravimetry (TG) and mechanical properties (stress and elongation at break). The films and monomers were characterized by infrared spectrometry (FTIR). The obtained dispersions were suitable when applied as for wood, metals and glass surfaces
82

Estudo do efeito da adição de poli(glicol etilênico-b-glicol propilênico) na formação de dispersões aquosas poliuretânicas à base de poli(glicol propilênico) / Estudo do efeito da adição de poli(glicol etilênico-b-glicol propilênico) na formação de dispersões aquosas poliuretânicas à base de poli(glicol propilênico) / Study of the effects of the addition of poly(ethylene glycol-b-propylene glycol)in the formation of polyurethanics aqueous dispersions with a poly(propylene glycol) basis / Study of the effects of the addition of poly(ethylene glycol-b-propylene glycol)in the formation of polyurethanics aqueous dispersions with a poly(propylene glycol) basis

Rosiléa Braga Luciano de Almeida 06 March 2007 (has links)
Foram produzidas dispersões aquosas não-poluentes e inovadoras de poli(uretano-uréia) à base de poli(glicol propilênico) (PPG) e de copolímeros em bloco, poli(glicol etilênicob-glicol propilênico), (EG-b-PG) com teor de 7% de unidades de glicol etilênico. Os poli(uretano-uréia)s foram preparados, em duas etapas, pelo método do prepolímero. Na primeira etapa, foram obtidos anionômeros, sintetizados em massa, à base do copolímero EG-bPG, PPG, ácido dimetilol propiônico (DMPA) (gerador dos sítios aniônicos) e diisocianato de isoforona (IPDI). Ainda na primeira etapa, os grupos carboxílicos do DMPA foram submetidos à neutralização com trietilamina (TEA). Na segunda etapa, foi realizada a dispersão do prepolímero anionômero e, em seguida, foi conduzida a reação de extensão de cadeia com a hidrazina (HYD). Nas diferentes formulações, foram variadas a razão NCO/OH e as proporções de PPG e do copolímero em bloco EG-b-PG. Além disso, foram obtidas dispersões aquosas programadas para teores de sólidos de 40 e 50%. As dispersões foram avaliadas quanto ao teor de sólidos totais, tamanho médio de partícula e viscosidade. Os filmes, obtidos por vazamento das dispersões, foram avaliados quanto à absorção de água, termogravimetria (TG) e propriedades mecânicas (ensaio de tração). Os filmes vazados e os monômeros foram caracterizados por espectrometria na região de infravermelho (FTIR) As dispersões obtidas se mostraram adequadas para serem aplicadas como revestimento para madeira, metais e vidro / Non-polluting and poly(urethane-urea) aqueous dispersions based on poly(propylene glycol) (PPG) and block copolymers of poly(ethylene glycol-b-propylene glycol) (EG-b-PG) containing 7% of ethylene glycol repeating units, were produced in an innovative way. The poly(urethane-urea)s were prepared, in two steps, by the prepolymer method. In the first step, anionomers, synthesized in bulk, based on EG-b-PG, PPG, dimethylolpropionic acid (DMPA) (anionomer sites generator) and isophorone diisocyanate (IPDI) were obtained. Still in the first step, the DMPA carboxylic groups were neutralized with triethylamine (TEA), generating the anionomer groups. In the second step, the anionomer prepolymer was dispersed in water under vigorous stirring and afterwards was chain extended with hydrazine. Different formulations were obtained by varying the NCO/OH ratio, and the proportions of PPG and EG-b-PG. Besides, poly(urethane-urea) aqueous dispersions with 40% and 50% of solid contents were obtained. The dispersions were evaluated in terms of their solid-contents, particle size and viscosity. The cast films, obtained from the dispersions concernig of water absorption, thermogravimetry (TG) and mechanical properties (stress and elongation at break). The films and monomers were characterized by infrared spectrometry (FTIR). The obtained dispersions were suitable when applied as for wood, metals and glass surfaces
83

Etude des micelles biorésorbables formées par auto-assemblage des copolymères à blocks polylactide/poly(éthylène glycol) pour la délivrance contrôlée de principes actifs / Bioresorbable micelles by self-assembly of polylactide/poly(ethylene glycol)block copolymers for controlled drug delivery

Yang, Liu 20 December 2010 (has links)
Des copolymères à blocs polylactide-poly(éthylène glycol) (PLA-PEG) ont été synthétisés par polymérisation par ouverture de cycle du L- ou D-lactide en présence de PEG mono- ou dihydroxylé. La masse molaire, la composition, la cristallisation et les propriétés thermiques des copolymères ont été caractérisées à l'aide de la DSC, NMR, GPC, etc. Des micelles biorésorbables ont été obtenues par la méthode dissolution directe sans utiliser de solvants organiques. Des mesures de tension de surface ont permis de déterminer la concentration micellaire critique des copolymères. Les résultats montrent que les micelles mélange L/D sont plus stables que les micelles seules en raison de l'effet stéréocomplexation entre les blocs L-PLA et D-PLA. Les comportements d'agrégation des micelles en milieu aqueux ont été étudiés en détail. Il apparaît que les micelles mélange présentent un nombre d'agrégation inférieur à celui des micelles seules. La dégradation hydrolytique des micelles a été étudiée dans les conditions in vitro. Le paclitaxel a été utilisé comme modèle de principes actifs pour évaluer les comportements in vitro et in vivo des micelles. Les méthodes dissolutio n directe et dialyse conduisent à des résultats comparables en ce qui concerne l'efficacité d'encapsulation et la teneur en principe actif. Les micelles mélange L/D présentent une meilleure capacité d'encapsulation que les micelles seules. Les expériences in vivo montrent que le paclitaxel est distribué dans tous les organes avec concentrations élevées après injection des micelles chargées. En comparaison avec la formulation clinique et les micelles par dialyse, les micelles chargées en paclitaxel par dissolution directe présentent un effet antitumeur plus important. / A series of polylactide-poly(ethylene glycol) (PLA-PEG) block copolymers were synthesized by ring-opening polymerization of L- or D-lactide in the presence of mono- or dihydroxyl PEG. The molar mass, composition, crystallization and thermal properties were characterized by using DSC, NMR, GPC, etc. Bioresorbable micelles were obtained by direct dissolution method without using any organic solvents. Surface tension measurements were used to determine the critical micellar concentration of the copolymers. The results show that L/D mixed micelles are more stable than single ones due to strong stereocomplexation effect between L-PLA and D-PLA blocks. The aggregation behavior of micelles in aqueous medium was investigated in detail. It appears that mixed micelles present lower aggregation number than single ones. The hydrolytic degradation of the micelles was investigated under in vitro conditions. Paclitaxel was used as a model drug to investigate the in vitro and in vivo behavior of micelles as drug delivery system. The direct dissolution method yields comparable drug encapsulation efficiency and loading content as the traditional dialysis method. The drug encapsulation ability is higher for L/D mixed copolymer micelles than single micelles due to stereocomplexation. In vivo experiments show that paclitaxel is widely distributed and kept at high concentration levels in various tissues after administration of drug-loaded micelles. Compared with the current clinical formulation and micelles by dialysis, paclitaxel-loaded micelles by direct dissolution exhibit the highest antitumor ability.
84

Auto-assemblage et modélisation des copolymères à blocs amphiphiles polylactide/poly(éthylène glycol) de différentes structures de chaînes en solution aqueuse / Self-assembly and modeling of amphiphilic polylactide/poly (ethylene glycol) block copolymers with diverse chain structures in aqueous solution

Wu, Xiaohan 09 November 2012 (has links)
Une série de copolymères à blocs amphiphiles polylactide/poly(éthylène glycol) (PLA/PEG) a été synthétisée par polymérisation par ouverture de cycles, chimie clic, ou couplage des homopolymères PLA et PEG avec des extrémités de chaînes fonctionnels (OH, COOH ou NH2). Différentes configurations de PLA (PLLA et PDLA) ont été considérées pour élucider l'effet de stéréocomplexation sur les propriétés physico-chimiques des copolymères. Les copolymères présentent différentes structures de chaînes, y compris dibloc PEG-PLA, tribloc PLA-PEG-PLA du type ABA ou PEG-PLA-PEG asymétrique du type BAB-type. La masse molaire des copolymères varies de 2 000 à 20 000, et le rapport EO/LA de 1.0 to 7.0 environ. Différents agrégats formés par auto-assemblage tels que des nanotubes, polymersomes, filomicelles, micelles anisotropiques et micelles sphériques ont été obtenus par dissolution directe de copolymères, mélange de différents copolymères, ou mélange de copolymères avec surfactant dans une solution aqueuse. Des modèles théoriques ont été proposés pour simuler la formation des agrégats et expliquer l'évolution de leur taille et morphologie en fonction du rapport EO/LA, longueur de bloc, etc. / A series of amphiphilic polylactide/poly(ethylene glycol) (PLA/PEG) block copolymers was synthesized by ring-opening polymerization, click chemistry, or coupling PLA and PEG homopolymers with functional end groups (OH, COOH or NH2). Different configurations of PLA (PLLA and PDLA) were considered to elucidate the effect of stereocomplexation on the physico-chemical properties of copolymers. The obtained copolymers exhibit diverse chain structures, including PEG-PLA diblock, PLA-PEG-PLA ABA-type or asymmetric PEG-PLA-PEG BAB-type triblock structures. The molar mass of copolymers ranges from c.a. 2,000 to 20,000, and the EO/LA ratio from c.a. 1.0 to 7.0. Diverse self-assembled aggregates, including nanotubes, polymersomes, filomicelles, anisotropic micelles and spherical micelles, were obtained by dissolving the resulting copolymers, mixing different copolymers, or mixing copolymers with surfactant in aqueous solution. Theoretical models are proposed to simulate the formation of aggregates and to explain the evolution of their size and morphology as a function of EO/LA ratio, block length, etc.
85

Etude, caractérisations et développement de mélanges de polymères biosourcés chargés de poudre d'Inconel 718 pour l'élaboration de composants et micro-composants via moulage par injection de poudres métalliques / Development and characterisation of biosourced polymers binders load with Inconel 718 powder to produce components and micro components by metal injection moulding process

Royer, Alexandre 24 November 2016 (has links)
Ces travaux de thèse concernent l’étude du comportement thermo-physique de mélanges de polymères biosourcés chargés de poudre d’Inconel 718 mis en forme par Moulage par Injection de poudre Métallique. Des matériaux et procédés innovants pouvant permettre une amélioration du procédé ont été étudiés. L’utilisation de polyéthylène glycol (PEG), choisi pour ses propriétés de solubilité dans l’eau, et de polymères biosourcés, pour diminuer l’impact environnemental, ont été choisi. Les nuances de polymères biosourcés ont été choisies adaptées aux conditions du procédé de moulage par injection, il s’agit d’acide polylactique et de polyhydroalcanoates. De même, l’utilisation du CO2 à l’état supercritique comme solvant, a pour objectif de diminuer le temps de déliantage ainsi que d’augmenter la qualité des composants réalisés. Les résultats obtenus ont montré une dégradation du PEG et de l’acide stéarique lors des cycles de mélangeage de de moulage par injection dans les conditions d’utilisation des polymères biosourcés. L’utilisation des mélanges chargés composés de polymères biosourcés ont permis d’améliorer l’homogénéité des composants injectés, mais ont engendré des défauts lors de l’étape de déliantage. Ces défauts ont pu être éliminés par l’utilisation de CO2 à l’état supercritique comme solvant du PEG. Ce dernier procédé a permis une diminution importante du temps de déliantage ainsi qu’une amélioration de la qualité des composants finaux. Les composants densifiés possèdent les propriétés mécaniques correspondantes à l’Inconel 718. / The works done during this PhD focuses on the study of the thermo-physical behavior of bio sourced polymer blends loaded with Inconel 718 powder (feedstock) to be shaped by the Metal Injection Molding process (MIM). First, a review of the researches related to the MIM process was conducted to identify innovative materials and processes that can improve the MIM process. Thus, the use of polyethylene glycol (PEG), selected for its properties of solubility in water, and bio sourced polymers, in order to reduce the environmental impact, were selected. The bio sourced polymers have been selected in accordance with the conditions of the injection molding process, and the choice was made to use polylactic acid (PLA) and polyhydroalkanoates (PHA and PHBV). Similarly, the supercritical CO2 as solvent was chosen to reduce the time of binder removal as well as increasing the quality of components produced. Thermo-physical, mechanical and rheological characterizations were made to determine the behavior of the different feedstock formulations. The results showed a degradation of the PEG and of the stearic acid under the conditions of use of the biopolymers, during the mixing and the injection stages. The use of feedstock made of bio sourced polymers have improved the homogeneity of the injected components, but they have generated defects during the debinding step. These defects have been eliminated by the use of CO2 in the supercritical state as solvent of the PEG. This method has significantly decrease the time of binder removal and improved the quality of the final components. Finally, densified components have the mechanical properties corresponding to Inconel 718.
86

Exposition professionnelle maternelle aux solvants organiques et malformations congenitales / Maternal Occupational Exposure to Organic Solvents and Congenital Malformations

Garlantezec, Ronan 27 January 2011 (has links)
L’objectif général de ce travail était d’étudier la relation entre exposition professionnelle maternelle aux solvants organiques et malformations congénitales.Ce projet s’est appuyé sur les données de la cohorte PELAGIE. Il s’agit d’une cohorte mère enfant avec inclusion de 3 421 femmes en début de grossesse en population générale en Bretagne. L’exposition aux solvants était définie par différentes méthodes (expositions déclarées, matrices emplois-expositions, dosages urinaires de métabolites de solvants chlorés et d’éthers de glycol).Nous avons mis en évidence une relation entre l’exposition aux solvants mesurée par des méthodes indirectes et les malformations congénitales. Puis, pour un échantillon aléatoire de451 femmes, nous avons étudié les déterminants de la détection urinaire des métabolites de solvants. Enfin, dans le cadre d’une étude cas-témoins dans la cohorte, la relation entre métabolites urinaires de solvants et malformations congénitales a été étudiée. / The aim of this project was to study the relation between maternal occupational exposure to solvents and congenital malformations.This project used data from the PELAGIE study. This is a mother child cohort which had included 3 421 women from the general population at the beginning of their pregnancy in Britany. Occupational exposure to solvents was assessed by different methods (self-report, job exposure matrix, and urinary determination of glycol ethers and chlorinated solvents metabolites).We have shown an association between solvent exposure using indirect method of assessment and congenital malformations. Using a randomized sample of 451 women, we have studied the occupational and non occupational determinants of urinary detection of glycol ethers and chlorinated solvents metabolites. Finally, we have studied in a nested case-control study, the relation between urinary solvent metabolites and congenital malformations.
87

Conception et synthèse de nouvelles molécules cages pour des applications en IRM du Xénon / Conception and synthesis of new molecular cages for Xenon MRI applications

Delacour, Léa 19 September 2011 (has links)
L'Imagerie par Résonance Magnétique (IRM) est une technique d'imagerie médicale largement répandue dans les milieux hospitaliers pour le diagnostic de pathologies. Elle repose classiquement sur la détection du proton (IRM 1H) et permet de visualiser des tissus en profondeur avec une très bonne résolution temporelle et spatiale. Cependant, cette méthode souffre encore de sa faible sensibilité. Une des solutions consiste en l'introduction et la détection de xénon hyperpolarisé. En effet, le xénon est un gaz non toxique, très sensible à son environnement chimique et adapté pour l’IRM. Cependant, il n'est spécifique d'aucun récepteur biologique et nécessite des molécules particulièrement adaptées pour son encapsulation. La détection de cibles spécifiques se fait par des biosondes constituées de molécules cages fonctionnalisées par une antenne de reconnaissance d'un récepteur spécifique. Le xénon vient s'encapsuler dans cette molécule hôte et permet la localisation de la cible biologique. Parmi les molécules cages répertoriées dans la littérature, les cryptophanes présentent la plus forte affinité connue pour le xénon et sont donc les plus prometteuses. Les cryptophanes sont des molécules cages constituées de deux unités de type cyclotribenzylène reliées entre elles par trois chaînes pontantes. Ils ont été synthétisés pour la première fois par l'équipe d'A. Collet au Collège de France au début des années 1980. L'objectif de cette thèse a été de synthétiser et de fonctionnaliser de nouveaux cryptophanes. / Non-invasive proton magnetic resonance imaging (1H MRI) is a powerful clinical tool for the detection of numerous diseases. Although MRI contrast agents are often used to improve diagnostic specificity, this technique has limited applications in molecular imaging because of its inherently low sensitivity when compared to nuclear medicine or fluorescence imaging. Laser-polarized 129Xe NMR spectroscopy is a promising tool to circumvent sensitivity limitations. Indeed, optical pumping increases the nuclear spin polarization of xenon by several orders of magnitude (104 to 105), thus small amounts of gas dissolved in biological tissues (blood, lungs…) can be rapidly detected with an excellent signal-to-noise ratio. In addition, the high polarizability of the xenon electron cloud, which induces a very high sensitivity to its environment, makes this nucleus very attractive for molecular imaging. Detection of biomolecules can be achieved by biosensors, which encapsulate xenon atoms in molecular cages that have been functionalized to bind the desired biological target. Cage molecules such as cryptophanes have high affinity for xenon and thus appear as ideal candidates for its encapsulation. During this PhD thesis we worked on the synthesis and the functionalization of new cryptophanes.
88

Polyamide desalination membrane characterization and surface modification to enhance fouling resistance

Van Wagner, Elizabeth Marie 31 January 2011 (has links)
The market for polyamide desalination membranes is expected to continue to grow during the coming decades. Purification of alternative water sources will also be necessary to meet growing water demands. Purification of produced water, a byproduct of oil and gas production, is of interest due to its dual potential to provide water for beneficial use as well as to reduce wastewater disposal costs. However, current polyamide membranes are prone to fouling, which decreases water flux and shortens membrane lifetime. This research explored surface modification using poly(ethylene glycol) diglycidyl ether (PEGDE) to improve the fouling resistance of commercial polyamide membranes. Characterization of commercial polyamide membrane performance was a necessary first step before undertaking surface modification studies. Membrane performance was found to be sensitive to crossflow testing conditions. Concentration polarization and feed pH strongly influenced NaCl rejection, and the use of continuous feed filtration led to higher water flux and lower NaCl rejection than was observed for similar tests performed using unfiltered feed. Two commercial polyamide membranes, including one reverse osmosis and one nanofiltration membrane, were modified by grafting PEGDE to their surfaces. Two different PEG molecular weights (200 and 1000) and treatment concentrations (1% (w/w) and 15% (w/w)) were studied. Water flux decreased and NaCl rejection increased with PEGDE graft density ([microgram]/cm2), although the largest changes were observed for low PEGDE graft densities. Surface properties including hydrophilicity, roughness and charge were minimally affected by surface modification. The fouling resistance of modified and unmodified membranes was compared in crossflow filtration studies using model foulant solutions consisting of either a charged surfactant or an oil in water emulsion containing n-decane and a charged surfactant. Several PEGDE-modified membranes demonstrated improved fouling resistance compared to unmodified membranes of similar initial water flux, possibly due to steric hindrance imparted by the PEG chains. Fouling resistance was higher for membranes modified with higher molecular weight PEG. Fouling was more extensive for feeds containing the cationic surfactant, potentially due to electrostatic attraction with the negatively charged membranes. However, fouling was also observed in the presence of the anionic surfactant, indicating hydrodynamic forces are also responsible for fouling. / text
89

Estrutura e comportamento em solução de copolímeros anfifílicos do tipo poliéter glicol

Marques, Yuri Alencar 11 January 2013 (has links)
Made available in DSpace on 2016-06-02T20:37:47Z (GMT). No. of bitstreams: 1 4850.pdf: 16404751 bytes, checksum: 39c816d8c598ae34b1bd0948e9c77c6d (MD5) Previous issue date: 2013-01-11 / The solution behavior and self-assembly structural phenomena of two industrial amphiphilic polyether glycol block copolymers with different chemical structures and similar cloud points were studied. The raw industrial diol copolymer was subjected to fractionation by preparative liquid chromatography with a size exclusion column (prep-LC-SEC). Prep-LC-SEC did not achieve a molecular mass separation; nonetheless it generated a separation of fractions by means of polarity. Significant heterogeneity of chain polarity of the fractions was demonstrated by CO2 supercritical fluid chromatography (SFC). The temperature and concentration effects of the polymers in polar 2-(2-butoxyethoxy)ethanol and water (25DB) solution were investigated by means of a combination of ATR-FTIR and SAXS techniques. In ATRFTIR analysis, a hypsochromic shift was shown for the O-H absorption peak with an increase in copolymer concentration in solution. This shift was consistently observed in high as well as in low temperatures. Narrowing of the C-O peak width with increasing concentration was demonstrated. A slight bathochromic shift of the C-H peaks was observed as a result of increasing polymer concentration. SAXS evaluation of the copolymers was carried out in concentrated systems. Despite the distinct chemical structures, the scattering curves indicate that the micellar aggregation processes and structural forms of both polyether glycols in solution are significantly similar. SAXS profiles in temperatures above and close to the cloud point revealed the absence of a macromolecular organized structure of the copolymer polyethers in 25DB solution. An investigative fit of the SAXS curves with a hard sphere model (HSM K-T) support the similar solution behavior of the two block copolymers evaluated in this study. The similarities of the aggregation and structural assembly of the two industrial triblock polyether glycols in polar solutions were evidenced. The correlations of the intermolecular interactions and the self-assembly morphology of the copolymer polyethers with the microphase separation temperature, i.e. the cloud point, were demonstrated. / O comportamento e os fenômenos da estruturação e organização em solução de dois copolímeros anfifílicos poliéter glicóis industriais, com distintas estruturas químicas e pontos de névoa similares, foram estudados. O poliéter glicol diol bruto produzido em reator de escala industrial foi submetido a um fracionamento por cromatografia líquida preparativa com coluna de exclusão de tamanho (prep-LCSEC). A prep-LC-SEC não apresentou um fracionamento por massas moleculares, mas gerou uma separação de frações por polaridade de cadeias. Comprovou-se, por cromatografia em fluido supercrítico (SFC-CO2) que estas frações apresentaram heterogeneidade significativa quanto à polaridade nas cadeias. A investigação dos efeitos da temperatura e concentração dos polímeros em solução polar 2-(2- butoxietoxi)etanol e água (25DB) foi realizada por combinação das técnicas de ATRFTIR e SAXS. Na análise de ATR-FTIR, foi demonstrado um deslocamento hipsocrômico do pico da ligação O-H com aumento da concentração em solução para os copolímeros. Este efeito foi consistente em temperaturas baixas e altas. Um estreitamento na largura dos picos de absorção da ligação C-O com aumento da concentração foi demonstrado. Um leve efeito batocrômico foi observado nos picos relacionados às ligações C-H em função da concentração. O estudo de SAXS dos copolímeros poliéter glicóis foi realizado em sistemas concentrados. Apesar das distintas estruturas químicas, as curvas de SAXS indicaram que o processo de agregação micelar e as estruturas assumidas por estes polímeros em solução são significativamente similares. Os perfis de SAXS em temperaturas acima e nas proximidades do ponto de névoa revelaram a ausência de uma estrutura macromolecular organizada em solução 25DB. Um ajuste investigativo das curvas de SAXS com um modelo de esferas duras (HSM K-T) reforçou a semelhança do comportamento em solução entre os dois poliéter glicóis avaliados neste estudo. Foi evidenciada a semelhança no processo de agregação e organização estrutural destes copolímeros tribloco em soluções solventes polares. Demonstraram-se as correlações entre a interação intermolecular e a morfologia de auto-organização dos copolímeros anfifílicos poliéter glicóis com a temperatura de separação em microfase, detectada pelo efeito macroscópico de turvação em solução, i.e. o ponto de névoa .
90

Synthèse et optimisation de dendrimères et de nanoparticules d'or en vue d'applications biomédicales

Boisselier Mailfait, Élodie 04 December 2009 (has links)
Plusieurs substrats issus de la chimie organique, inorganique et organométallique ont été synthétisés et fonctionnalisés avec différents groupes chimiques, notamment des polyethylene glycol qui leur permet d’améliorer leur solubilité dans l’eau et de les rendre biocompatible pour une éventuelle application dans le milieu biomédical. Ces substrats sont des dendrimères synthétisés sur plusieurs générations, des polymères obtenus soit par polymérisation d’un dendron soit par dendronisation d’un polymère, ou encore des nanoparticules d’or qui peuvent être stabilisées par des ligands thiolates ou bien par des dendrimères de manière intra- ou inter-dendritique. Ces nano-objets ont été designés dans l’objectif d’encapsuler, de stabiliser ou d’améliorer différentes molécules biologiques telles que des vitamines (vitamine C, B3 et B6), des neurotransmetteurs (acétylcholine et dopamine) ou des agents anti-cancéreux (daunorubicine). / Several substrates resulting from the organic, inorganic and organometallic chemistry were synthesized and functionalized with various chemical groups, including polyethylene glycol which enables them to improve their water solubility and to make them biocompatible for a possible application in the biomedical field. These substrates are dendrimers synthesized for several generations, polymers obtained either by polymerization of a dendron or by dendronization of a polymer, or gold nanoparticules which can be stabilized by thiolate ligands or by dendrimers in an intra- or inter-dendritic way. These nano-objects were designed with the aim of encapsulating, stabilizing or improving various biological molecules such as vitamins (vitamin C, B3 and B6), neurotransmitters (acetylcholine and dopamine) or anti-cancerous agents (daunorubicine).

Page generated in 0.0476 seconds