Structuring of bridged silsesquioxanes via cooperative weak interactions: H-bonding of urea groups and hydrophobic interactions of long alkylene chains

Moreau, Joël J. E.; Pichon, Benoît P.; Bied, Catherine; Man, Michel Wong Chi

doi:10.1039/b504635a

Cited by 46 publications

(58 citation statements)

References 36 publications

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“…[33][34][35] Small ¢ values (on the order of 40-60 cm -1 ) are related to strong H-bonds, while ¢ values in the range 70-100 cm -1 are characteristic of less strong H-bonds. 18,20,21 Using the maximum of the fitted Lorentzian peaks, the resulting values for our samples are ¢ -(U-1) ) 106 cm -1 and ¢ (U-2) ) 102 cm -1 . These values are located in the range where hydrogen bonds cannot be characterized as strong, with the more ordered sample (U-2) exhibiting a slightly higher value of the strength of these bonds.…”

Section: Resultsmentioning

confidence: 99%

Photoluminescence of Bridged Silsesquioxanes Containing Urea or Urethane Groups with Nanostructures Generated by the Competition between the Rates of Self-Assembly of Organic Domains and the Inorganic Polycondensation

et al. 2006

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The aim of this study was to investigate the changes produced in the nanostructures and the photoluminescence spectra of bridged silsesquioxanes containing urea or urethane groups, by varying the relative rates between the self-assembly of organic domains and the inorganic polycondensation. Precursors of the bridged silsesquioxanes were 4,4‘-[1,3-phenylenebis(1-methylethylidene)]bis(aniline) and 4,4‘-isopropylidenediphenol, end-capped with 3-isocyanatopropyltriethoxysilane. The inorganic polycondensation was produced using either high or low formic acid concentrations, leading to transparent films with different nanostructures as revealed by FTIR, SAXS, and 29Si NMR spectra. For the bridged silsesquioxanes containing urea groups the self-assembly of organic domains was much faster than the inorganic polycondensation for both formic acid concentrations. However, the arrangement was more regular and the short-range order higher when the rate of inorganic polycondensation was lower. The photoluminescence spectra of the most ordered structures revealed the presence of two main processes: radiative recombinations in inorganic clusters and photoinduced proton-transfer generating NH2 + and N- defects and their subsequent radiative recombination. In the less-ordered urea-bridged silsesquioxanes a third process was present assigned to a photoinduced proton transfer in H-bonds exhibiting a broad range of strengths. For urethane-bridged silsesquioxanes the driving force for the self-assembly of organic bridges was lower than for urea-bridged silsesquioxanes. When the synthesis was performed with a high formic acid concentration, self-assembled structures were not produced. Instead, large inorganic domains composed of small inorganic clusters were generated. Self-assembly of organic domains took place only when employing low polycondensation rates. For both materials the photoluminescence was mainly due to radiative processes within inorganic clusters and varied significantly with their state of aggregation.

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Section: Resultsmentioning

confidence: 99%

Photoluminescence of Bridged Silsesquioxanes Containing Urea or Urethane Groups with Nanostructures Generated by the Competition between the Rates of Self-Assembly of Organic Domains and the Inorganic Polycondensation

et al. 2006

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“…The self-organization of these hybrid materials is imposed by the rigidity of the organic groups chemically bonded in a bridged way to the inorganic moiety. [11][12][13][14][15] In recent times it was demonstrated that self-organized materials can also be obtained using bridging charged organic groups. 16,17 It is important to point out that the selforganization in silica-based hybrid material has always been associated with the presence of bridging organic groups.…”

Section: Introductionmentioning

confidence: 99%

An innovative series of layered nanostructured aminoalkylsilica hybrid material

Trindade

Stoll

Pereira

et al. 2009

J. Braz. Chem. Soc.

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Uma nova série de amostras de material híbrido à base de sílica, contendo o grupo catiônico amoniopropil ligado na forma pendente, foi obtida usando-se o método sol-gel de síntese, variandose a razão molar entre o precursor inorgânico e o precursor orgânico. A análise termogravimétrica mostrou que as amostras são termicamente estáveis até 260 °C. Os resultados obtidos por difratometria de raios X, microscopia eletrônica de transmissão, ressonância magnética nuclear de 29 Si e análise elementar são compatíveis com o modelo estrutural de camadas de silsesquioxano com distâncias basais de até 5,4 nm, contendo sílica amorfa no espaço entre as camadas.An innovative series of silica-based hybrid materials containing pendant cationic ammoniumpropyl groups was obtained using the sol-gel method, by varying the molar ratio of the inorganic and organic precursors. Thermogravimetric analysis showed that samples were thermally stable up to 260 °C. Results obtained by X-ray diffractometry, transmission electron microscopy, 29 Si nuclear magnetic resonance and elemental analysis were compatible with a silsesquioxane layered structural model showing basal distances up to 5.4 nm, containing amorphous silica in the interlayer space. Keywords: nanostructured materials, layered hybrid materials, silsesquioxanes IntroductionThe development of organic-inorganic silica-based hybrid materials has received growing attention in the last decades. These materials present characteristics of the individual components as well as new unexpected properties.1-6 A satisfactory method to obtain these hybrid materials is the sol-gel synthesis, which allows dispersion of the components in nano or molecular scale, combining their physicochemical properties or producing new ones. Among this ensemble, the self-organized silica-based hybrid materials are very promising, because a great quantity of novel materials with attractive properties can be obtained. [7][8][9][10][11][12] They can be prepared using proper organosilane precursors presenting two or more polycondensation points, which are gelified together with an inorganic alkylorthosilicate precursor. The self-organization of these hybrid materials is imposed by the rigidity of the organic groups chemically bonded in a bridged way to the inorganic moiety. [11][12][13][14][15] In recent times it was demonstrated that self-organized materials can also be obtained using bridging charged organic groups. 16,17 It is important to point out that the selforganization in silica-based hybrid material has always been associated with the presence of bridging organic groups. Up to the present time, as far as we know, the synthesis of self-organized silica-based hybrid materials containing pendant organic groups has not been reported.Another kind of hybrid materials can be obtained by gelation of organosilanes without addition of alkylorthosilicate inorganic precursors. These materials, called silsesquioxanes, have elevated organic content and can also present self-organization properties. Among them, the polyhe...

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“…Self-assembly can occur previous to or during the polycondensation of terminal groups, induced by strong hydrogen bonds, aromatic p-stacking, or van der Waals interactions between (CH 2 ) n groups. [15][16][17][18][19][20][21][22][23][24][25][26] When the self-assembly and polycondensation processes take place simultaneously, the organization attained in the final material depends on their relative rates. [26] A variety of structures and properties has been reported for self-assembled bridged silsesquioxanes.…”

Section: Full Papermentioning

confidence: 99%

“…[21] Long-range ordered lamellar structures with a macroscopic organization in compact sheets were obtained combining the association properties of urea groups by H-bonds and those of long hydrocarbon chains. [17,18,[22][23][24] The selfassembly could also be produced just by the hydrophobic interactions between long alkylene chains. [25] The aim of this study was to generate a new family of bridged silsesquioxanes using a precursor synthesized by the reaction of a primary amine (1 mol) with glycidoxypropyl(trimethoxysilane) (GPMS, 2 mol) ( Figure 1).…”

Section: Full Papermentioning

confidence: 99%

Bridged Silsesquioxanes with Organic Domains Self‐Assembled as Functionalized Molecular Channels

Romeo

Fanovich

Williams

et al. 2007

Macro Chemistry & Physics

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A bridged silsesquioxane was obtained from a precursor synthesized by the reaction of glycidoxypropyl(trimethoxysilane) (2 mol) with cyclohexylamine (1 mol). The polycondensation in the presence of formic acid produced a hybrid material exhibiting a short‐range order based on elongated organic channels accommodating the pendant cyclohexyl fragments, bounded by inorganic domains. The presence of functional groups in the organic channels (tertiary amine, ether, hydroxyl), can be used to retain small organic molecules capable of forming hydrogen bonds. Aspirin was used as a probe to illustrate this possibility.magnified image

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Structuring of bridged silsesquioxanes via cooperative weak interactions: H-bonding of urea groups and hydrophobic interactions of long alkylene chains

Abstract: International audienc

Cited by 46 publications

References 36 publications

Photoluminescence of Bridged Silsesquioxanes Containing Urea or Urethane Groups with Nanostructures Generated by the Competition between the Rates of Self-Assembly of Organic Domains and the Inorganic Polycondensation

Photoluminescence of Bridged Silsesquioxanes Containing Urea or Urethane Groups with Nanostructures Generated by the Competition between the Rates of Self-Assembly of Organic Domains and the Inorganic Polycondensation

An innovative series of layered nanostructured aminoalkylsilica hybrid material

Bridged Silsesquioxanes with Organic Domains Self‐Assembled as Functionalized Molecular Channels

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