Equilíbrio químico da formaçao de complexos de carboximetilcelulose com os íons Fe3+, Mn2+ e Zn2+ : estudo da influencia da adiçao desses complexos nas propriedades do cimento Portland

Orientadora: Ana Lucia Ramalho Merce MaiaDissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Ciencias Exatas, Programa de Pós-Graduaçao em Química. Defesa: Curitiba, 2004Inclui bibliografia e anexosResumo: O crescente uso de polímeros adicionados ao cimento Portland, na forma de aditivos, vem crescendo muito desde o início da década de 1960. Os aditivos são compostos químicos adicionados no processo de mistura com o cimento, com objetivo de fornecer melhora de desempenho em diversas de suas propriedades, tais como aumento de retenção de água da pasta fresca, impermeabilização, resistência a ataques químicos externos, durabilidade e aumentos de resistência mecânica em geral. Dentro do contexto deste trabalho, a pesquisa de novos materiais que possam promover melhoras nas propriedades do cimento Portland, foram estudadas a obtenção e a formação de complexos metálicos de carboximetilcelulose (CMC) juntamente com os íons Fe3+, Mn2+ e Zn2+ e a sua adição à massa cimentícea. Inicialmente foi realizado o estudo por titulação potenciométrica do equilíbrio químico da carboximetilcelulose (CMC) e os íons Fe3*, Mn2+ e Zn2+ onde, com o auxílio de programas computacionais de cálculo, obtiveram-se as constantes de equilíbrio de formação dos complexos entre a CMC e os íons estudados. A constante de formação dos complexos da CMC e os íons Mn2+ mostraram-se maiores que para os íons Zn2+. O cálculo não foi realizado para o sistema contendo os íons Fe3* devido à formação de produtos de hidrólise insolúveis logo no início das titulações potenciométricas. Com o objetivo de confirmar a formação e especiação dos complexos estudados pela titulação potenciométrica, foram promovidos estudos por espectroscopia no ultravioleta-visível. Os espectros obtidos apresentaram um alargamento expressivo das bandas atribuídas aos íons metálicos na presença da CMC, indicando uma interação dos grupos carboxilato da CMC e os íons metálicos. Estudos espectroscópicos no infravermelho também confirmaram a interação dos íons metálicos com os sítios básicos da CMC, ocorrendo principalmente mudanças nas bandas atribuídas aos grupos carboxilato, as quais sofrem desvios significativos quando na presença do íon metálico. Os complexos de CMC e os íons Fe3+, Mn2+ e Zn2+ obtidos foram então adicionados, na forma de solução, ao cimento Portland como aditivos de argamassas em proporção 1:3 cimento-areia. Foram realizados testes de desempenho mecânico do material endurecido, onde moldaram-se corpos de prova prismáticos e após tempos de cura de 1, 28 e 56 dias, foram então submetidos a testes de resistência à compressão e resistência à flexão em prensa hidráulica específica. Apenas um tipo de CMC testado apresentou uma melhora no desempenho mecânico da pasta endurecida, juntamente com a adição do complexo de ferro(lll) do mesmo tipo de CMC, em tempos de cura de 28 dias. Todas as demais adições não apresentaram melhoras significativas no desempenho mecânico, com exceção da adição dos íons Zn2+ apenas, que apresentaram melhoras significativas tanto na resistência à compressão quanto na resistência à flexão. Os corpos de prova rompidos com 1 dia de idade apresentaram um padrão de comportamento semelhante ao observado para os 28 dias de cura. Notou-se no entanto uma melhora significativa pela adição dos complexos de CMC-Fe, observadas anteriormente, já nas primeiras 24h de cura do material. Os corpos rompidos com 56 dias de cura não apresentaram deferenciações significativas. A análise por microscopia eletrônica de varredura (MEV) do material endurecido indicou a formação de estruturas morfologicamente diferenciadas pela adição dos complexos de CMC-Fe, o que foi observado em menores proporções para as demais adições. A melhora do desempenho mecânico do material pôde ser atribuída á formação dessas estruturas visto que, a única adição de complexos de CMC e os íons metálicos estudadas, que promoveu a melhora da resitência mecânica do material, foi aquela que apresentou-se morfologicamente diferenciada em relação às demais.Abstract: The demand on the use of polymers added to the Portland cement as additive is on the increase since the beginning of the decade of 1960. Additives are added to cements in order to improve the performance of various of its properties, such as the increase of water retention, final waterproofing, resistance for chemical attacks, durability and increases in the mechanical resistances among others. This work has aimed at the research of a new material that could promote improvements in the mechanical properties of the Portland cement attained by additions of metallic complexes of carboxymethylcellulose (CMC) together with ions Fe3*, Mn2+ and Zn2+. It was carried out potentiometric titrations to determine the stability constants of carboxymethylcellulose (CMC) and ions Fe3*, Mn2+ and Zn2+ with the aid of computational programs of calculations as well as the speciation of the systems according to variations of pH. The complexes of the CMC and Mn2+ had revealed more stable than with Zn2+. It was not possible to determine the values for the system with Fe3* due to formation of insoluble hydrolysis products in very early pH values. Ultraviolet-visible spectra were obtained to confirm the speciation of the complexes detected by potentiometric titrations. The obtained spectra showed features indicating major interactions of the metal ions and the carboxylic groups of CMC. These chemical aspects were later confirmed by infrared studies on the solids extracted from the aqueous solutions of CMC and the metallic ions. The obtained complexes of CMC and Fe3*, Mn2+ and Zn2+ were then added as aqueous solutions, to the Portland cement (ratio 1:3 cement-sand) as additives. After cure times of 1, 28 and 56 days, mechanical performance was carried out in prismatic samples previously molded by testing the impact strength and flexural properties using a hydraulic press. Only a sample of CMC showed mechanical properties improvement and also only this CMC complexed to iron (III) showed an increase in 28 days of cure time. Whilst with zinc (II), all complexes showed an improvement in the mechanical performance of the cement. The results to the obtained samples with 1 and 28 days of age presented a similar behavior in these mechanical tests. A significant improvement when the addition of the complexes of CMC-Fe was done to the cement was observed in the first 24h of cure of the material. The results for the material with 56 days of age did not present significant differences from the 28 days of the cure materials. Scanning electron microscopy of the hard materials indicated morphologically differentiated structure formation by the addition of the complexes of CMC and Fe. These differentiations seen by SEM could be the answer to the increase in the mechanical properties since the CMC - complex added materials were those showing mechanical properties improvements

Influence of levofloxacin and clarithromycin on the structure of DPPC monolayers

Research on lipid/drug interactions at the nanoscale underpins the emergence of synergistic mechanisms for topical drug administration. The structural understanding of bio-mimetic systems employing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) as a lung surfactant model mixed with antibiotics, as well as their biophysical properties, is of critical importance to modulate the effectiveness of therapeutic agents released directly to the airways. In this paper, we investigate the structural details of the interaction between Levofloxacin, ‘a respiratory quinolone’, and the macrolide Clarithromycin, with DPPC monolayers at the air-water interface, using a combination of Brewster angle microscopy, polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS), surface pressure isotherms and neutron reflectometry (NR) to describe the structural details of this interaction. The results allowed association of changes in the π-A isotherm profile with changes in the molecular organization and the co-localization of the antibiotics within the lipid monolayer by NR measurements. Overall, both antibiotics are able to increase the thickness of the acyl tails in DPPC monolayers with a corresponding reduction in tail tilt as well as to interact with the phospholipid headgroups as shown by PM-IRRAS experiments. The effects on the DPPC monolayers are correlated with the physical-chemical properties of each antibiotic and dependent on its concentration

Pluronic® F127 Thermoresponsive Viscum album Hydrogel: Physicochemical Features and Cellular In Vitro Evaluation

Viscum album L., popularly known as mistletoe, is well known for its anti-cancer properties, and the pharmaceutical application of hydroalcoholic dry extracts is still limited due to its low solubility in aqueous media, and physicochemical instability. The Pluronic® F127 is an amphiphilic polymer, which permits the solubilization of lipophilic and hydrophilic compounds. In this investigation, physicochemical features of hydrogel containing V. album dry extract (VADE-loaded-hydrogel) were performed by: dynamic light scattering (DLS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). VADE-loaded-hydrogel presented nanometer-size micelles with volume distribution ranging from 10.58 nm to 246.7 nm, and a polydispersity index of 0.441. The sample thermal analyses (TG and DSC) showed similar decomposition curves; however, the thermal events indicated an increase in thermal stability in relation to the presence of the extract. In addition to these interesting pharmaceutical features, IC50 values of 333.40 µg/mL and >1000 µg/mL were obtained when tumor (SCC-25) and non-tumor (L929) cells were incubated with VADE-loaded-hydrogel, respectively. The optical and ultrastructural cellular analysis confirmed the tumor selectivity since the following alterations were detected only in SCC-25 cells: disorganization of plasmatic membrane; an increase of cytoplasmatic vacuole size; alteration in the cristae mitochondrial shape; and generation of amorphous cellular material. These results emphasize the promising antitumoral potential of VADE-loaded-hydrogel as an herbal drug delivery system via in vitro assays

Equilíbrio químico da formaçao de complexos de carboximetilcelulose com os íons Fe3+, Mn2+ e Zn2+ : estudo da influencia da adiçao desses complexos nas propriedades do cimento Portland

Orientadora: Ana Lucia Ramalho Merce MaiaDissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Ciencias Exatas, Programa de Pós-Graduaçao em Química. Defesa: Curitiba, 2004Inclui bibliografia e anexosResumo: O crescente uso de polímeros adicionados ao cimento Portland, na forma de aditivos, vem crescendo muito desde o início da década de 1960. Os aditivos são compostos químicos adicionados no processo de mistura com o cimento, com objetivo de fornecer melhora de desempenho em diversas de suas propriedades, tais como aumento de retenção de água da pasta fresca, impermeabilização, resistência a ataques químicos externos, durabilidade e aumentos de resistência mecânica em geral. Dentro do contexto deste trabalho, a pesquisa de novos materiais que possam promover melhoras nas propriedades do cimento Portland, foram estudadas a obtenção e a formação de complexos metálicos de carboximetilcelulose (CMC) juntamente com os íons Fe3+, Mn2+ e Zn2+ e a sua adição à massa cimentícea. Inicialmente foi realizado o estudo por titulação potenciométrica do equilíbrio químico da carboximetilcelulose (CMC) e os íons Fe3*, Mn2+ e Zn2+ onde, com o auxílio de programas computacionais de cálculo, obtiveram-se as constantes de equilíbrio de formação dos complexos entre a CMC e os íons estudados. A constante de formação dos complexos da CMC e os íons Mn2+ mostraram-se maiores que para os íons Zn2+. O cálculo não foi realizado para o sistema contendo os íons Fe3* devido à formação de produtos de hidrólise insolúveis logo no início das titulações potenciométricas. Com o objetivo de confirmar a formação e especiação dos complexos estudados pela titulação potenciométrica, foram promovidos estudos por espectroscopia no ultravioleta-visível. Os espectros obtidos apresentaram um alargamento expressivo das bandas atribuídas aos íons metálicos na presença da CMC, indicando uma interação dos grupos carboxilato da CMC e os íons metálicos. Estudos espectroscópicos no infravermelho também confirmaram a interação dos íons metálicos com os sítios básicos da CMC, ocorrendo principalmente mudanças nas bandas atribuídas aos grupos carboxilato, as quais sofrem desvios significativos quando na presença do íon metálico. Os complexos de CMC e os íons Fe3+, Mn2+ e Zn2+ obtidos foram então adicionados, na forma de solução, ao cimento Portland como aditivos de argamassas em proporção 1:3 cimento-areia. Foram realizados testes de desempenho mecânico do material endurecido, onde moldaram-se corpos de prova prismáticos e após tempos de cura de 1, 28 e 56 dias, foram então submetidos a testes de resistência à compressão e resistência à flexão em prensa hidráulica específica. Apenas um tipo de CMC testado apresentou uma melhora no desempenho mecânico da pasta endurecida, juntamente com a adição do complexo de ferro(lll) do mesmo tipo de CMC, em tempos de cura de 28 dias. Todas as demais adições não apresentaram melhoras significativas no desempenho mecânico, com exceção da adição dos íons Zn2+ apenas, que apresentaram melhoras significativas tanto na resistência à compressão quanto na resistência à flexão. Os corpos de prova rompidos com 1 dia de idade apresentaram um padrão de comportamento semelhante ao observado para os 28 dias de cura. Notou-se no entanto uma melhora significativa pela adição dos complexos de CMC-Fe, observadas anteriormente, já nas primeiras 24h de cura do material. Os corpos rompidos com 56 dias de cura não apresentaram deferenciações significativas. A análise por microscopia eletrônica de varredura (MEV) do material endurecido indicou a formação de estruturas morfologicamente diferenciadas pela adição dos complexos de CMC-Fe, o que foi observado em menores proporções para as demais adições. A melhora do desempenho mecânico do material pôde ser atribuída á formação dessas estruturas visto que, a única adição de complexos de CMC e os íons metálicos estudadas, que promoveu a melhora da resitência mecânica do material, foi aquela que apresentou-se morfologicamente diferenciada em relação às demais.Abstract: The demand on the use of polymers added to the Portland cement as additive is on the increase since the beginning of the decade of 1960. Additives are added to cements in order to improve the performance of various of its properties, such as the increase of water retention, final waterproofing, resistance for chemical attacks, durability and increases in the mechanical resistances among others. This work has aimed at the research of a new material that could promote improvements in the mechanical properties of the Portland cement attained by additions of metallic complexes of carboxymethylcellulose (CMC) together with ions Fe3*, Mn2+ and Zn2+. It was carried out potentiometric titrations to determine the stability constants of carboxymethylcellulose (CMC) and ions Fe3*, Mn2+ and Zn2+ with the aid of computational programs of calculations as well as the speciation of the systems according to variations of pH. The complexes of the CMC and Mn2+ had revealed more stable than with Zn2+. It was not possible to determine the values for the system with Fe3* due to formation of insoluble hydrolysis products in very early pH values. Ultraviolet-visible spectra were obtained to confirm the speciation of the complexes detected by potentiometric titrations. The obtained spectra showed features indicating major interactions of the metal ions and the carboxylic groups of CMC. These chemical aspects were later confirmed by infrared studies on the solids extracted from the aqueous solutions of CMC and the metallic ions. The obtained complexes of CMC and Fe3*, Mn2+ and Zn2+ were then added as aqueous solutions, to the Portland cement (ratio 1:3 cement-sand) as additives. After cure times of 1, 28 and 56 days, mechanical performance was carried out in prismatic samples previously molded by testing the impact strength and flexural properties using a hydraulic press. Only a sample of CMC showed mechanical properties improvement and also only this CMC complexed to iron (III) showed an increase in 28 days of cure time. Whilst with zinc (II), all complexes showed an improvement in the mechanical performance of the cement. The results to the obtained samples with 1 and 28 days of age presented a similar behavior in these mechanical tests. A significant improvement when the addition of the complexes of CMC-Fe was done to the cement was observed in the first 24h of cure of the material. The results for the material with 56 days of age did not present significant differences from the 28 days of the cure materials. Scanning electron microscopy of the hard materials indicated morphologically differentiated structure formation by the addition of the complexes of CMC and Fe. These differentiations seen by SEM could be the answer to the increase in the mechanical properties since the CMC - complex added materials were those showing mechanical properties improvements

Influence of levofloxacin and clarithromycin on the structure of DPPC monolayers

Research on lipid/drug interactions at the nanoscale underpins the emergence of synergistic mechanisms for topical drug administration. The structural understanding of bio-mimetic systems employing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) as a lung surfactant model mixed with antibiotics, as well as their biophysical properties, is of critical importance to modulate the effectiveness of therapeutic agents released directly to the airways. In this paper, we investigate the structural details of the interaction between Levofloxacin, ‘a respiratory quinolone’, and the macrolide Clarithromycin, with DPPC monolayers at the air-water interface, using a combination of Brewster angle microscopy, polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS), surface pressure isotherms and neutron reflectometry (NR) to describe the structural details of this interaction. The results allowed association of changes in the π-A isotherm profile with changes in the molecular organization and the co-localization of the antibiotics within the lipid monolayer by NR measurements. Overall, both antibiotics are able to increase the thickness of the acyl tails in DPPC monolayers with a corresponding reduction in tail tilt as well as to interact with the phospholipid headgroups as shown by PM-IRRAS experiments. The effects on the DPPC monolayers are correlated with the physical-chemical properties of each antibiotic and dependent on its concentration

Molecular organization and doping in poly(2-methoxyaniline)/Ni(dmit)(2) films obtained with the Langmuir-Blodgett technique

The control of the properties of materials at the molecular level is pursued for many applications, especially those associated with nanostructures. In this paper, we show that the coordination compound [Ni(dmit)(2)], where (dmit) is the 1,3-dithiole-2-thione-4,5-dithiolate ligand, can induce doping of poly(2-methoxyaniline) (POMA) in molecularly ordered Langmuir and Langmuir-Blodgett (LB) films. Doping was associated with interactions between the components and the compression of the Langmuir film at the air-water interface, according to polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) data. Taking these results together with in situ UV-Vis absorption measurements, we could identify the molecular groups involved in the interaction, including the way they were reoriented upon film compression. The Langmuir films were sufficiently stable to be transferred as Y-type LB films, while the hybrid POMA/[Ni(dmit)(2)] films remain doped in the solid state. As expected, the molecular charges affected the film morphology, as observed from combined atomic and electric force microscopy measurements. In summary, with adequate spectroscopy and microscopy tools we characterized molecular-level interactions, which may allow one to design molecular electronic devices with controlled electrical properties.CNPqCNPqCAPESCAPESFAPESP (Brazil)FAPESP (Brazil

Challenging ChatGPT with Chemistry-Related Subjects

Tools based on large language models such as ChatGPT may revolutionize information retrieval and knowledge discovery, particularly with the vast amount of electronic material available. In this communication we evaluate how two versions of ChatGPT can answer complex questions on chemistry-related subjects in six topics. The tools are still insufficient to deal with subtleties of complex topics, especially as they do not have access to the whole of the scientific literature. However, the progress from ChatGPT-3 to ChatGPT-4 is an indicator that we shall soon have tools to assist scientists in surveys, reviews of the literature, and for teaching

Eletrofiação de polímeros em solução: parte II: aplicações e perspectivas Electrospinning of polymers in solution: part II: applications and perspectives

Em artigo de revisão anterior[1], o processo de eletrofiação foi discutido, incluindo suas bases teóricas e experimentais, e a obtenção de diferentes nanofibras de materiais poliméricos. Neste segundo artigo de revisão, são abordados os aspectos relacionados à aplicação de materiais eletrofiados em diferentes áreas, como médica, agrícola, sensores, processamento de outros materiais, entre outras. São também discutidas as técnicas de caracterização utilizadas mais frequentemente nestes materiais, e suas potencialidades. Esta segunda revisão é complementar à anterior e segue, em seus aspectos gerais, a mesma terminologia.<br>In our previous review[1], the process of electrospinning was discussed on the basis of theoretical and experimental aspects toward preparation of different polymeric nanofibers. In this second review, we focus on the aspects related to the application of electrospun materials in various fields such as medicine, agriculture, sensors, and processing of other materials. We discuss the most often characterization techniques used for these materials and their potential. This review complements the previous one and uses the same terminology