Influência da catálise ácida e básica na preparação da sílica funcionalizada pelo método sol-gel

Nassar, Eduardo J.; Messaddeq, Younès; Ribeiro, Sidney José Lima

doi:10.1590/s0100-40422002000100006

Cited by 37 publications

(21 citation statements)

References 13 publications

(13 reference statements)

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“…The FTIR spectra of the Aerosil ® R972 and Aerosil ® A200 ( Figure 1) showed an absorption peak at about 1100 cm -1 , attributed to the asymmetric stretching vibrations of the Si-O-Si bonds of silica oxide, while the peak at 820 cm -1 can be attributed to the symmetric deformation of the Si-O-Si bonds. These are typical absorption bands for Si-O-Si network vibrations 6,20 . In Figure 1, the two narrow peaks located at 2870 and 2954 cm −1 are attributed to C-H stretching vibration of the PCL's hydrocarbon and the narrow peak centered at 1734 cm −1 is derived from the stretching vibration of the PCL's carbonyl groups (C=O) 21,22 .…”

Section: Hybrids' Structural Characterizationmentioning

confidence: 99%

Inorganic-organic hybrids based on poly (ε-Caprolactone) and silica oxide and characterization by relaxometry applying low-field NMR

et al. 2012

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Poly (ε-caprolactone) (PCL) based hybrids containing different amounts of modified (Aerosil ® R972) and unmodified (Aerosil ® A200) silica oxide were prepared employing the solution method, using chloroform. The relationships of the amount of nanofillers, organic coating, molecular structure and intermolecular interaction of the hybrid materials were investigated mainly using low-field nuclear magnetic resonance (NMR). The NMR analyses involved the hydrogen spin-lattice relaxation time (T 1 H) and hydrogen spin-lattice relaxation time in the rotating frame (T 1 ρH). The spin-lattice relaxation time measurements revealed that the PCL/silica oxide hybrids were heterogeneous, meaning their components were well dispersed. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also employed. The DSC data showed that all the materials had lower crystallization temperature (Tc) and melting temperature (Tm), so the crystallinity degree of the PCL decreased in the hybrids. The TGA analysis demonstrated that the addition of modified and unmodified silica oxide does not cause considerable changes to PCL's thermal stability, since no significant variations in the maximum temperature (Tmax) were observed in relation to the neat polymer.

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Section: Hybrids' Structural Characterizationmentioning

confidence: 99%

Inorganic-organic hybrids based on poly (ε-Caprolactone) and silica oxide and characterization by relaxometry applying low-field NMR

et al. 2012

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“…[21][22][23][24] Before functionalization with organosilanes, BEN was pre-expanded with distilled water. To this end, 5.0 g of clay was added to 100.0 mL of distilled water and vigorously stirred for 1 h. Next, 2.0 mL of one of the alkoxides was added, and the reaction was allowed to proceed under stirring at room temperature for 48 h. The material was then washed with ethanol and water, which was followed by drying at 100 °C for 24 h. The samples were kept in desiccators.…”

Section: Bentonite Functionalizationmentioning

confidence: 99%

Hybrid Materials Based on Bentonite Functionalized with Amine Groups via the Hydrolytic Sol-Gel Method

Gilberto¹,

Marçal²,

Silva³

et al. 2015

Journal of the Brazilian Chemical Society

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Bentonite is a natural clay that presents characteristics such as good capacity to exchange cations, large specific surface area, large porosity, and possibility to undergo intercalation and/or functionalization. This work reports on bentonite functionalization with organomodified alkoxides. Functionalization afforded hybrid materials displaying desirable properties for adsorption of chromium trivalent ions. Infrared absorption spectroscopy, X-ray powder diffraction, thermal analysis, specific surface area analysis, and adsorption experiments with methylene blue helped to characterize the materials and evaluate their cationic exchange capability. These techniques evidenced functionalization of the Brazilian bentonite. Kinetic and equilibrium experiments on the adsorption of chromium trivalent ions aided determination of the equilibrium time of kinetic adsorption isotherms and revealed whether the functionalized matrices adsorbed chromium trivalent ions. Chromium displayed S1 type adsorption isotherms, which confirmed that adsorption capacity originated from cooperative forces between the adsorbate and the hybrid adsorbents.

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“…38,39 Na gelificação em meio ácido de Bronsted, como reações principais, ocorre o ataque do ácido ao oxigênio ligado ao silício, Si -OH ou Si -OR, propiciando sua saída e, consequentemente, facilitando o ataque nucleofílico ao silício, de grupos H 2 O no caso de hidrólise ou Si -OH para condensação.…”

Section: Método Sol-gel De Sínteseunclassified

Materiais híbridos à base de sílica obtidos pelo método sol-gel

Benvenutti¹,

Moro²,

Costa³

et al. 2009

Quím. Nova

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Recebido em 16/12/08; aceito em 16/3/09; publicado na web em 17/9/09 SILICA BASED HYBRID MATERIALS OBTAINED BY THE SOL-GEL METHOD. This review deals with silica based hybrid materials obtained by the sol-gel method. It involves concepts, classifications and important definitions regarding the sol-gel method that allows obtaining materials with organic and inorganic components dispersed in a molecular or nanometric level. We discuss the properties and characteristics of hybrid materials related to experimental synthesis conditions. We devote a special attention to the nanostructured materials, where the self-organization is imposed by the organic component. Finally, we present some important applications of these materials based on their specific properties.Keywords: organic-inorganic materials; silsesquioxanes; silica based hybrid xerogels. INTRODUÇÃOO desenvolvimento da ciência dos materiais trouxe importantes contribuições no avanço da tecnologia. A busca constante por novos materiais com desempenho e propriedades otimizadas para aplicações inovadoras e o aperfeiçoamento de materiais já existentes é um desafio e um dos motivos da evolução técnica e científica atual.1-8 Nesse contexto, encontra-se a possibilidade de combinar no nível molecular ou nanométrico os componentes orgânico e inorgânico, resultando em novos materiais conhecidos como híbridos organo-inorgânicos.9 Esses materiais híbridos, além de oferecerem a oportunidade de combinar de forma sinérgica as propriedades físico-químicas inerentes de seus constituintes, permitem obter novas propriedades, resultantes da combinação de seus componentes, devido ao tamanho reduzido dos domínios que os compõem.10-13 Para alcançar esse nível tão reduzido de dispersão, pode-se utilizar o método sol-gel de síntese, que envolve a formação de uma rede polimérica inorgânica por reações de gelificação a baixas temperaturas. As reações resultam na transição de um líquido para um sólido, sendo que os reagentes precursores dos componentes, orgânico e inorgânico, que são geralmente alcóxidos de silício ou de metais como alumínio, titânio, zircônio, se encontram inicialmente dissolvidos nesse líquido. No decorrer do processo, as reações de gelificação levam à formação de um estado sol, que se caracteriza por apresentar oligômeros que formarão cadeias de dimensões coloidais e partículas primárias dispersas. A evolução desse processo forma o estado gel que apresenta conectividade entre as unidades de dimensões coloidais, formando uma rede tridimensional, entrelaçada macroscopicamente observável.14 Além da possibilidade de obter os componentes orgânico e inorgâ-nico altamente dispersos, o método sol-gel de síntese apresenta outras características interessantes, tais como: i) as reações de gelificação são processadas a baixas temperaturas, o que permite inserir à matriz sólida biomoléculas como enzimas, proteínas e anticorpos, de difícil incorporação por outros métodos que utilizem temperaturas mais elevadas;15-17 ii) possibilidade de obter materiais sob diferentes configurações ...

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Influência da catálise ácida e básica na preparação da sílica funcionalizada pelo método sol-gel

Cited by 37 publications

References 13 publications

Inorganic-organic hybrids based on poly (ε-Caprolactone) and silica oxide and characterization by relaxometry applying low-field NMR

Inorganic-organic hybrids based on poly (ε-Caprolactone) and silica oxide and characterization by relaxometry applying low-field NMR

Hybrid Materials Based on Bentonite Functionalized with Amine Groups via the Hydrolytic Sol-Gel Method

Materiais híbridos à base de sílica obtidos pelo método sol-gel

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