• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • 1
  • Tagged with
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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.
1

Síntese, caracterização e estudo termoanalítico dos ftalatos, isoftalatos e tereftalatos de cobalto e manganês / Synthesis, characterization and thermoanalytical study of phthalates, isophthalates and terephthalates of cobalt and manganese

Carmo, João Paulo Santos 29 April 2016 (has links)
Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-07-26T11:39:23Z No. of bitstreams: 2 Dissertação - João Paulo Santos Carmo - 2016.pdf: 2412305 bytes, checksum: 19777a4bdead74386cf88a869674700c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-07-26T11:41:09Z (GMT) No. of bitstreams: 2 Dissertação - João Paulo Santos Carmo - 2016.pdf: 2412305 bytes, checksum: 19777a4bdead74386cf88a869674700c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-07-26T11:41:09Z (GMT). No. of bitstreams: 2 Dissertação - João Paulo Santos Carmo - 2016.pdf: 2412305 bytes, checksum: 19777a4bdead74386cf88a869674700c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-04-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / It is possible to observe an increase related research for the synthesis of coordination compounds and crystal lattices using transition metals and organic binders due to their great potential applications. The aim of this study was to synthesize the compounds Phthalate, Isophthalate and Terephthalate of Cobalt and Manganese through the reaction of the metal carbonate in excess with their acids studied. The synthesized compounds are presented in the form of crystalline solids. These compounds were characterized using analytical techniques: Simultaneous Thermogravimetric and Differential Scanning Calorimetry (DSC-TG), Fourier Transform Infrared Spectroscopy (FTIR). Thermogravimetry Analysis coupled to Fourier Transform Infrared Spectroscopy (TG-FTIR) and Differential Scanning Calorimetry (DSC). From the TG-DSC curves was possible to evaluate the thermal stability and the dehydration mechanism as well’as the empirical formula of the compounds as CoFta ∙ 2.5H2O, CoIFta ∙ 5H2O, CoTFta ∙ 4,5H2O for cobalt compounds and MnFta ∙ 0.5H2O, MnIFta ∙ 2.5H2O and MnTfta for manganese compounds. Even through the infrared spectra (FTIR), it was also possible to suggest the metal-ligand coordination mode as bridge for all compounds synthesized. / É possível observar um aumento de trabalhos referentes a compostos de coordenação e de redes cristalinas usando metais de transição e ligantes orgânicos devido aos seus grandes potenciais de aplicação. O objetivo desse trabalho foi sintetizar os compostos de Ftalato, Isoftalato e Tereftalato de Cobalto e Manganês através da reação do carbonato metálico em excesso com os respectivos ácidos estudados. Os compostos sintetizados se apresentaram na forma de sólidos cristalinos e foram caracterizados através das técnicas: Termogravimetria e Calorimetria Exploratória Diferencial simultânea (TG-DSC), Espectroscopia de Infravermelho por Transformada de Fourier (FTIR). Termogravimetria acoplada a Espectroscopia de Infravermelho por Transformada de Fourier (TG-FTIR), Calorimetria Exploratória Diferencial (DSC). A partir das curvas TG-DSC foi possível avaliar a estabilidade térmica e o mecanismo de desidratação, bem como a fórmula mínima dos compostos como sendo CoFta∙2,5H2O, CoIFta∙5H2O, CoTFta∙4,5H2O para os compostos de cobalto e MnFta∙0,5H2O, MnIFta∙2,5H2O e MnTfta para os compostos de manganês. Ainda através dos espectros de infravermelho (FTIR) foi possível sugerir o modo de coordenação entre metal-ligante como em ponte para todos os compostos sintetizados
2

Síntese, caracterização e estudo termoanalítico dos isoftalatos de disprósio, érbio, itérbio e lutécio

Bembo Filho, Luís Henrique 25 September 2015 (has links)
Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-04-24T21:32:38Z No. of bitstreams: 2 Dissertação - Luís Henrique Bembo Filho - 2015.pdf: 4119130 bytes, checksum: d55a9605f67d7a46862ee4f963d019c5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-04-25T15:50:11Z (GMT) No. of bitstreams: 2 Dissertação - Luís Henrique Bembo Filho - 2015.pdf: 4119130 bytes, checksum: d55a9605f67d7a46862ee4f963d019c5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-04-25T15:50:11Z (GMT). No. of bitstreams: 2 Dissertação - Luís Henrique Bembo Filho - 2015.pdf: 4119130 bytes, checksum: d55a9605f67d7a46862ee4f963d019c5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-09-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Coordination compounds using dicarboxylic acids and lanthanides have attracted a great interest because their application as Metal-Organic Frameworks (MOF) and its luminescent characteristics. The heavy lanthanides isophthalates have synthesized in solid state and characterized using the techniques: Infrared absorption spectroscopy; Thermoanalytical techniques (TG-DSC simultaneously in air atmosphere and N2 atmosphere, DTG, DSC, TG-FTIR). The compounds stoichiometry were confirmed and the number of hydration waters were identified from the TG curves, defining the compounds of formula Ln2(Isoftal)3.nH2O, where Ln = Lanthanides; Isoftal = isophthalate; n = 4,5 (Dy), 7,5 (Er), 8,5 (m), 8 (Yb), and 9 (Lu). The compounds have the same thermal decomposition mechanism with formation of the respective lanthanide oxides when analyzed under air atmosphere, and formation of carbonaceous intermediates when analyzed under inert atmosphere (N2). The identity of gases during the dehydration and the decomposition of compounds identified as H2O, CO2, CO, and some traces of organic compounds, using coupled technique TG-FTIR. The infrared absorption spectra suggest that metal-ligand coordination is bridge bidentate. / Compostos de coordenação utilizando ácidos dicarboxílicos com lantanídeos têm atraído grande interesse, devido às suas aplicabilidades como compostos moleculares de estrutura porosa (MOF: Metal-Organic Frameworks) e suas características luminescentes. Os isoftalatos de alguns lantanídeos pesados foram sintetizados no estado sólido e caracterizados utilizando as técnicas: Espectroscopia de absorção na região do infravermelho; Técnicas termoanalíticas (TG-DSC simultânea em atmosfera de ar e em atmosfera de N2, DTG, DSC, TG-FTIR). A estequiometria dos compostos foi confirmada e o número águas de hidratação identificada a partir das curvas TG, definindo a fórmula dos compostos como: Ln2(Isoftal)3.nH2O, onde Ln= Lantanídeos; Isoftal= isoftalato; n= 4,5 (Dy), 7,5 (Er), 8,5 (Tm), 8 (Yb), e 9 (Lu). Os compostos apresentam o mesmo mecanismo de decomposição térmica com formação dos respectivos óxidos de lantanídeos quando analisados em atmosfera de ar, e formação de intermediários carbonáceos quando analisados em atmosfera inerte (N2). A identidade dos gases gerados durante a desidratação e decomposição dos compostos identificados, como: H2O, CO2, CO e alguns traços de compostos orgânicos, utilizando a técnica acoplada TG-FTIR. Os espectros de absorção na região do infravermelho sugerem que a coordenação metal-ligante seja na forma bidentada em ponte.
3

Synthesis and Characterization of Novel Telechelic High Performance Polyester Ionomers

Kang, Huaiying 04 December 2001 (has links)
Novel poly(ethylene isophthalate) (PEI) and poly(ethylene terephthalate) (PET) polymers containing terminal units derived from sodio 3-sulfobenzoic acid (SSBA) were synthesized using catalyzed melt polymerization techniques. Various concentrations of the ionic end group, SSBA, were successfully incorporated in a telechelic fashion. For comparison, polyesters containing telechelic alkyl groups with controllable molecular weights were also synthesized. Furthermore, ionic copolymers of dimethyl isophthalate and trans-cyclohexane dicarboxylate, dimethyl isophthalate and dimethyl terephthalate were synthesized to study the influences of polarity and rigidity of the polymer chain backbone on material properties. Novel branched polyester ionomers using trimellitic anhydride were also prepared. In addition to modifying the polymer compositions, PET ionomers were blended with zinc stearate to investigate the effect of plasticizer on the melt processibilty of the ionomers. FTIR spectroscopy, which was used to quantify the sulfonate end groups for all of the ionomers, indicated an absorbance peak for the S-O stretching mode between 600-700 cm⁻¹. ¹H NMR spectroscopy was used to confirm the structure of the ionic and non-ionic polyesters, as well as to verify the presence of the terminal groups. By systematically varying the chemical structure of these ionomer model systems (i.e., altering the contents of ionic functional groups), detailed characterizations were carried out, wherein the ionic interactions/aggregations in the ionomers were found to play an important role in the resulting material properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements were performed to study the effects of ionic groups and oligomer composition on the thermal properties of the polyesters. The glass transition temperatures of the ionomers revealed that the ionic interaction helped to maintain the structural integrity of the polymer chains, thus limiting their mobility. The dilute solution viscosity behavior of the ionomers exhibited upward curvature, which is a key characteristic of an ionomer. In PEI ionomers, the ionic aggregates formed at lower temperatures (<150 °C), while at higher temperatures (>150 °C), the ionic aggregations dissociated and behaved similarly to oligomers with lower molecular weights. Dodecanol was used as an effective end-capper to control the molecular weight of the non-ionic polyesters. In addition to telechelic ionic PEI and PET homopolymers, copolymers of poly(ethylene isophthalate-co-trans-1,4-cyclohexane dicarboxylate) (PEI-co-trans-CHDC) and poly(ethylene isophthalate-co-terephthalate) (PEIT) telechelic ionomers were also synthesized and characterized. Introducing trans-1,4-cyclohexane dicarboxylate into PEI ionomers decreased the polarity and packing regularity of the polymer chains. Also, the kinked-structure of dimethyl isophthalate reduced the regularity of the polymer chains in PET ionomers, thus reducing their propensity for rapid crystallization. Crystallization kinetics were studied for both ionic and alkyl telechelic polyesters, and resulting data revealed that the nature of the endgroup had a dramatic effect on crystallization from the melt state. The catalyst residue in the polymers also affected the crystallization rate for both ionic and non-ionic polyesters. With regard to the ionomers, antimony catalyst interacted with ionic aggregates, further increasing the crystallization rate. Branched PEI and PET ionomers showed an increase in melt strength. After blending with zinc stearate, the melt viscosity of the PET ionomers dropped dramatically. / Master of Science
4

A Series of Robust Copper-Based Triazolyl Isophthalate MOFs: Impact of Linker Functionalization on Gas Sorption and Catalytic Activity †

Junghans, Ulrike, Kobalz, Merten, Erhart, Oliver, Preißler, Hannes, Lincke, Jörg, Möllmer, Jens, Krautscheid, Harald, Gläser, Roger 06 April 2023 (has links)
The synthesis and characterization of an isomorphous series of copper-containing microporous metal-organic frameworks (MOFs) based on triazolyl isophthalate linkers with the general formula 3 ¥[Cu4(m3-OH)2(R1-R2-trz-ia)3(H2O)x] are presented. Through size adjustment of the alkyl substituents R1 and/or R2 at the linker, the impact of linker functionalization on structure-property relationships was studied. Due to the arrangement of the substituents towards the cavities, the porosity (pore fraction 28%–39%), as well as the pore size can be adjusted by the size of the substituents of the triazole ring. Thermal analysis and temperature-dependent PXRD studies reveal a thermal stability of the MOFs up to 230 C due to increasing framework stability through fine-tuning of the linker substitution pattern. Adsorption of CO2 (298 K) shows a decreasing maximum loading with increasing steric demand of the substituents of the triazole ring. Furthermore, the selective oxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) is studied over the MOFs at 323 K in liquid chloroform. The catalytic activity increases with the steric demand of the substituents. Additionally, these isomorphous MOFs exhibit considerable robustness under oxidizing conditions confirmed by CO2 adsorption studies, as well as by the catalytic selective oxidation experiments.

Page generated in 0.0482 seconds