Preparation and characterization of phosphonium montmorillonite with enhanced thermal stability

Patel, Hasmukh A.; Somani, Rajesh S.; Bajaj, Hari C.; Jasra, Raksh V.

doi:10.1016/j.clay.2006.09.012

Cited by 196 publications

(110 citation statements)

References 18 publications

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“…For example, to change the polarity of the nanoparticles and promote dispersion in organic solvents or polymers chemical treatment by cation exchange or grafting using organosilanes has been extensively practiced. [15][16][17] In addition, surface functionalization has been used to improve the stability of the nanoparticles and avoid aggregation in various media. 18,19 Surface functionalization is typically carried out in the presence of organic solvents.…”

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confidence: 99%

An improved process for the surface modification of SiO2 nanoparticles

Livi

Giannelis

2012

Green Chem.

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A phosphonium ionic liquid is used as an activator of silanol groups to improve the surface functionalization of silica nanoparticles with fluorosilanes in supercritical CO 2 .Due to their excellent optical, electrical and mechanical properties as well as their unique advantages such as high surface area, nanoparticles can play a key role in many nanotechnology applications. 1,2 For example, significant R&D resources have been devoted to nanoparticle technology in diverse fields including electronic and biomedical devices, automotive parts, coatings, drug delivery, gene delivery, catalysis and polymers. [3][4][5][6][7][8][9][10][11][12][13][14] For several of these applications surface functionalization is an important requirement. For example, to change the polarity of the nanoparticles and promote dispersion in organic solvents or polymers chemical treatment by cation exchange or grafting using organosilanes has been extensively practiced. [15][16][17] In addition, surface functionalization has been used to improve the stability of the nanoparticles and avoid aggregation in various media. 18,19 Surface functionalization is typically carried out in the presence of organic solvents. In some instances and to make the process greener, supercritical CO 2 (scCO 2 ) has been used in place of conventional solvents. However, the grafting density tends to be relatively low. It has been reported that small amounts of a highly basic ionic liquid (<0.5 wt%) can generate silanoates on the surface of silica. We combine here the use of an ionic liquid in scCO 2 to increase the grafting density of fluorosilane on silica. The process results in doubling of the grafting densities with the resulting nanoparticles exhibiting CO 2 -philic behavior. In addition to the increased reactivity and higher grafting density the new process offers the following additional advantages: (i) this is a one-step process, (ii) the use of organic solvents is completely eliminated, (iii) the lengthy steps of purification and drying of the silica are replaced by dilution and filtration, (iv) the ionic liquid can be recovered and reused.We note that our process differs from previous reports using scCO 2 in that low pressures (80 instead of 400 bar) and less amounts of silane (only 10 wt% compared to a 3-10 times molar excess of the corresponding coupling agents used in the literature) are required. 20,21 In addition, previous reports utilizing scCO 2 were limited to dry, fumed silica instead of aqueous dispersions used in our approach. While the primary particles of fumed silica are small and comparable to that of colloidal silica, drying tends to lead to particle agglomeration.While the method can be applicable to different oxides we demonstrate it here using colloidal silica and three different fluorosilanes: (i) perfluorooctyl-methyldimethoxysilane (DMS), (ii) perfluorooctyl-trichlorosilane (TCS), and (iii) perfluorooctyltriethoxysilane (TES). Triphenyloctadecyltriphenylphosphonium iodide (C 18 P I − ) was used as the surface activator. The synthesi...

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confidence: 99%

An improved process for the surface modification of SiO2 nanoparticles

Livi

Giannelis

2012

Green Chem.

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“…The FTIR spectrum of Na + -MMT shows four main absorption peaks at 3646, 3480, 1655, and 1059 cm -1 (Figure 2). The bands between 3500 and 3700 and near 3400 cm -1 are indicative of MMT (Patel et al, 2007). Absorption peaks at 3646 and 3480 cm -1 are assigned to the -OH in the Si-OH and Al-OH groups of the tetrahedral and octahedral sheets of MMT and water molecules (Avalos et al, 2008).…”

Section: Resultsmentioning

confidence: 99%

Effect of Trihexyltetradecylphosphonium on Thermal Degradation Properties of Low Linear Density Polyethylene/Montmorillonite Nanocomposites

Abdullah¹,

Mamat²,

Awang³

et al. 2013

IJTech

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Low linear density polyethylene/organo-montmorillonite (LLDPE/OMMT) nanocomposites at 1-5 wt% OMMT loading were prepared by the melt intercalation technique. The OMMT was synthesized via an ion exchange reaction by replacing the interlayer of sodium ions (Na + ) in the repeating unit of silicate layers of montmorillonite (MMT) with the cationic surfactant in the form of trihexyltetradecylphosphonium (THTDP) ions. The obtained OMMT and its nanocomposites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and elemental and thermogravimetric analyses. The interlayer spacing of MMT expanded from 1.41 to 2.29 nm due to the accommodation of THTDP ions in the intergallery of OMMT. The introduction of THTDP in the interlayer of OMMT rendered better dispersion of OMMT layers in the LLDPE/OMMT nanocomposites and significantly improved the thermal degradation properties of nanocomposites as compared to the pristine LLDPE.

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“…[12][13][14][15][16][17] Porém, os cátions quaternários de amônio não conseguem suportar temperaturas de processamento muito elevadas, 18-21 sendo assim, argilas organofílizadas por meio de um sal de amônio são menos adequadas para utilização em materiais que utilizam altas temperaturas de processamento, como em polímeros contendo argilas como reforço, que são submetidos a processos de extrusão. 20 Na literatura, a estabilidade térmica dos sais de fósforo é descrita sendo superior à apresentada por sais de amônio. 10,[20][21][22][23] Compostos de fósforo são utilizados em diversas aplicações, tais como retardantes de chama para papeis e têxteis, e também como absorvedores de radiação ultra violeta em materiais poliméricos.…”

Section: Introductionunclassified

“…20 Na literatura, a estabilidade térmica dos sais de fósforo é descrita sendo superior à apresentada por sais de amônio. 10,[20][21][22][23] Compostos de fósforo são utilizados em diversas aplicações, tais como retardantes de chama para papeis e têxteis, e também como absorvedores de radiação ultra violeta em materiais poliméricos. A adição de argilas organofilizadas com sais de fósforo vem sendo investigada em matrizes poliméricas visando aumentar sua resistência térmica e retardância à chama.…”

Section: Introductionunclassified

Organofilização E Silanização De Argila Bentonita

Baruel¹,

Dutra²,

Baldan³

et al. 2017

Quim. Nova

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One of the most usual applications is their incorporation into organic materials. Nonetheless, natural clays are hydrophobic being incompatible with organic medium. Clay organophilization can be reached by several methods such as by exchange of the interlayer sodium cations by organic cations, and by silanization of the clay layers. In this study the bentonite clay was organophilized by the addition of the methoxymethyltriphenylphosphonium chloride (CTFF). Further, the organoclay was silanized with (3-glycidyloxypropyl) trimethoxysilane (GPTMS). X-ray fluorescence results, infrared and XPS spectroscopy showed the presence of phosphorus in the organophilic clay. The interlayer space, obtained by X-ray diffraction, increased in 55% after the CTFF addition showing the cationic exchange in the clay lamellar region. After the silanization of the organoclay the interlayer space was slightly reduced from 1,78 nm to 1,72 nm, indicating that the silane molecules were preferential bound in the clay edges.Keywords: organoclay; bentonite; silane; quaternary phosponium salt. INTRODUÇÃOA argila é definida como um material terroso, de granulação fina, apresenta alta plasticidade em água 1-3 e é formada pelo empacotamento de lamelas cristalinas.1,3-5 A bentonita uma das argilas de maior interesse tecnológico, 3,6,7 apresenta em sua configuração cátions interlamelares, que podem ser trocados por cátions orgânicos ou inorgânicos quando presentes em solução aquosa, influenciando suas propriedades físico-químicas e alterando seu espaçamento basal, essa propriedade é chamada de capacidade de troca catiônica (CTC). [2][3][4]8,9 O termo bentonita é comumente usado para designar argilas constituídas principalmente por argilomineral ou argilominerais esmectíticos, sendo o argilomineral mais frequentemente encontrado a montmorilonita. Essa classe de argilas é constituída principalmente por silicatos de alumínio e magnésio do tipo 2:1, no qual uma folha octaédrica está entre duas folhas tetraédricas. Esse silicato possui deficiência de cargas positivas em sua estrutura cristalina, resultando em excesso de cargas negativas, que é contrabalanceado por cátions interlamelares alcalinos, Na+ ou K+. A montmorilonita é caracterizada pela sua capacidade de troca catiô-nica, que permite que os cátions inorgânicos sejam substituídos por cátions orgânicos, aumentando seu caráter apolar, e possibilitando sua incorporação em meios orgânicos.3 Após a troca catiônica as argilas são denominadas argilas organofílicas ou organofilizadas, e a partir dessas é possível se obter complexos argila-compostos orgânicos.2,10 As argilas organofilizadas são mais facilmente incorporadas em sistemas orgânicos, como em cosméticos, tintas à base de solventes orgânicos, polímeros apolares e lubrificantes. A substituição de cátions de sódio por cátions orgânicos, em geral, causa um aumento da distância basal da argila, o que pode ser observado pela técnica de difração de raios-X (XRD) e, usualmente, quanto maior a cadeia orgânica do sal maior será a distância interlamelar ...

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Preparation and characterization of phosphonium montmorillonite with enhanced thermal stability

Cited by 196 publications

References 18 publications

An improved process for the surface modification of SiO2 nanoparticles

An improved process for the surface modification of SiO2 nanoparticles

Effect of Trihexyltetradecylphosphonium on Thermal Degradation Properties of Low Linear Density Polyethylene/Montmorillonite Nanocomposites

Organofilização E Silanização De Argila Bentonita

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