Organic–inorganic hybrid melting gels

Melting gels are a class of organically modified silica gels that are rigid at room temperature, flow at temperature T1 and consolidate at temperature T2 (T2 > T1), when crosslinking is complete. The process of (a) softening, (b) becoming rigid and (c) re-softening can be repeated many times. Mixtures of mono-substituted alkoxysilanes and di-substituted alkoxysilanes have been studied in a systematic way to identify suitable melting gel compositions. The mixtures and the resulting melting gels have been characterized for their softening temperatures and consolidation temperatures. With an interest in using these materials for sealing microelectronics, their physical properties have been measured.     

One-pot sonochemical synthesis of superhydrophobic organic–inorganic hybrid coatings on cotton cellulose

Inspired by the surface structure of lotus leaves, different types of superhydrophobic cellulosic materials with contact angle (CA) of higher than 150° are currently provided. However, fabrication of these surfaces in a facile one-step coating process is one of the challenging issues. This paper describes a facile method to sonochemically synthesize superhydrophobic organic–inorganic hybrid coatings on cotton fabric by an alkaline-catalyzed co-hydrolysis and co-condensation of tetraethylorthosilicate and alkyltrialkoxysilanes. The influence of alkyl chain length (methyl, octyl, hexadecyl) of silane and reaction time was investigated. Surface structure of the fabrics was investigated by SEM, EDS, FTIR spectroscopies, and reflectance spectrophotometry. Wettability properties were studied by measuring water CA, shedding angle (SHA) and resistance to wetting by a series of ethanol–water mixtures of different surface tensions. The results showed that the treated fabrics were coated with a homogeneous thin nano-scaled coating of hybrid silica nano-particles. The fabrics demonstrated CA of higher than 150°, SHA in the range of 6–24° and different stickiness to water droplets. The fabrics treated by silanes with longer alkyl chain length and at higher reaction time revealed better water repellency. The coatings were nearly transparent, could not affect the color of the fabrics and had high stability against repeated washing. In addition, mechanical properties of the fabrics were not substantially affected.     

Organic–inorganic hybrid complexes based on a Keggin-type polyoxoanion

Two organic?Cinorganic hybrid complexes based on a Keggin-type polyoxoanion, namely [Ni₂(H₂O)₂(bipy)₄(Hbipy)][AlW₁₂O₄₀]·7H₂O 1 and [Ni₂Cl₂(bipy)₃(Hbipy)₂][SiW₁₂O₄₀]·2.5H₂O 2 (bipy?=?4,4??-bipy), have been synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray diffraction. Complexes 1 and 2 possess similar 2D layer structures, constructed from 1D zigzag chains {Ni(bipy)} _n ²ⁿ⁺ and alternatively arranged Keggin anion and bipy linkers. Photocatalytic investigations indicate that both 1 and 2 exhibit photocatalytic activity for the degradation of Rhodamine B.     

Organic–inorganic tandem route to polymer nanocomposites: kinetic products versus thermodynamic products

We report a facile single-step photochemical methodology to afford alkylsiloxane-polymer hybrid films which relies on the tandem photoacid-catalyzed polymerization of n-alkyltrimethoxysilane precursors and a diglycidyl ether organic monomer. Photoacids liberated by the UV decomposition of iodonium salt triggers simultaneously the sol–gel process and epoxy cationic polymerization. Such conditions are intended to favour the formation of kinetic products trapped by cross-linking reactions instead of the thermodynamically most stable structures, whose preference would be for macrophase segregation. Organosilane precursor exhibiting different structures and chain lengths (n-butyl, n-octyl, n-dodecyl, n-hexadecyl, isobutyl and isooctyl) were systematically investigated to afford a range of transparent alkylsiloxane-polyether hybrids. The competitive organic–inorganic reaction kinetics were investigated using in situ real-time Fourier transform infrared spectroscopy. A main emphasis has been on discussing the effect of the alkyl substituent structure on the photoinduced polymerization kinetics and the silicate networks characterized by ²⁹Si solid-state NMR. To avoid phase separation, the rate of formation of the two phases was tailored to favour concomitancy upon modulating several experimental parameters: film thickness, alkyl structure, photoacid generator concentration. Finally, the viscoelastic and surface properties were also assessed by dynamic mechanical analysis and water contact angle measurements, respectively.     

Sedimentation analysis of organic–inorganic hybrid colloids

Hybrid organic–inorganic latex particles are synthesized to combine the beneficial properties of the constituents which thus lead to synergistic improvement in the properties. The properties of hybrid particles are dependent on the successful hybridization process, thus controlling or tuning of such processes by effective characterization is immensely important. Analytical ultracentrifugation provides these characterization possibilities owing to its high statistical capability and ability to characterize multiple parameters. The use of different detection methodologies can help in generating valuable information on the overall size and density distributions of the particles. Apart from that, it is also possible to quantify the presence of any free polymer and inorganic particles in the hybrid latex which would affect the properties of hybrid latexes. By following the densities of the pure and hybrid particles, it is also possible to quantify the amounts of the constituent phases in the hybrid particles. The density gradients generated in preparative ultracentrifugation also provide additional possibilities for the characterization of the hybrid particles which have densities higher than the measurable range in the analytical ultracentrifuge. Evolution of hybrid particles can also be studied as a function of time. It also provides advantage of separation of the various fractions for further characterization.     

Dissolution mechanisms of wood cellulose fibres in NaOH–water

Four wood pulps and a microcrystalline cellulose were dissolved in a NaOH 8%–water solution. Insoluble fractions and clear solution fractions were isolated by centrifugation and were observed by optical microscopy and transmission electron microscopy. Molecular weight distribution, carbohydrate composition and cellulose II content were measured. The dissolution of wood cellulose fibres in NaOH 8%–water solutions occurs by successive dismantlement and fragmentation steps governed by the swelling and the shearing of the original structure. The cellulose from insoluble and clear solution fractions is in both case converted in cellulose II and the insoluble fractions contain embedded mannans. Besides, the molecular weight distributions of cellulose from insoluble and clear solution fractions reveal the existence of heterogeneities in dissolution capacity of the cellulose chains, independent to the degree of polymerization, which are related to the chemical environment of the chains in the fibre structure.     

Organic–inorganic hybrid materials based on organophosphorus coupling molecules: from metal phosphonates to surface modification of oxides

Organophosphorus acids (phosphoric, phosphonic, and phosphinic) and their derivatives (salts, esters) are highly promising coupling molecules that allow the anchoring of organic groups to inorganic solids. In this article we briefly review our contribution in the preparation of materials based on organophosphorus coupling molecules: new sol–gel routes to microporous zirconium phosphonates and metal oxide/phosphonate or phosphinate hybrids, and surface modification of metal oxide nanoparticles. The potentialities of the sol–gel and surface modification approaches are illustrated by the immobilization of organometallic metal complexes using phosphine-phosphonate molecules. To cite this article: P.-H. Mutin et al., C. R. Chimie 6 (2003).     

Organic–inorganic hybrid sol–gel pretreatments for corrosion protection of mild steel in neutral and acidic solutions

Research on Chemical Intermediates - This work aims to develop and study sol–gel-derived anticorrosion films for mild steel. Epoxy bis-silane precursor has been prepared by reaction of liquid...     

Novel multifunctional water- and oil-repellent,antibacterial, and flame-retardant cellulose fibres created by the sol–gel process

This research aimed to prepare cotton fibres with novel multifunctional water- and oil-repellent, antibacterial, and flame-retardant properties. A three-component equimolar sol mixture, which included 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, and P,P-diphenyl-N-(3-(trimethoxysilyl)propyl) phosphinic amide, was applied to the cotton fabric using the sol–gel process. The presence of the coating on the cotton fibres was confirmed by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. The functional properties of the coated cotton fabric were determined from liquid contact angle measurements and antibacterial activity, burning behaviour, and thermo-oxidative stability studies. The results demonstrate that a unique, compatible, and uniform organic-inorganic hybrid polymer network was formed on the fabric surface, which preserved its simultaneous hydrophobic (water contact angle of 135 ± 2°), oleophobic (n-hexadecane contact angle of 117 ± 1°), and bactericidal (bacterial reduction of 100 %) properties and incorporated the enhanced thermo-oxidative stability of the modified cellulose fibres.     

Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS) (Degussa), nanosized silver (Ag) (CHT) and a reactive organic–inorganic binder (RB) (CHT). Two different application procedures were used: firstly, one stage treatment of cotton fabric samples by FAS sol (i), as well as by a sol mixture constituted from all three precursors (Ag–RB–FAS, procedure 1S) (ii), and secondly, two stage treatment of cotton by Ag–RB sol and than by FAS sol (Ag–RB + FAS, procedure 2S) (iii). The hydrophobic and oleophobic properties of cotton fabrics treated by procedures (i)–(iii) before and after consecutive (up to 10) washings were established from contact angle measurements (water, diiodomethane and n-hexadecane) and correlated with infrared and XPS spectroscopic measurements. The results revealed that even after 10 washing cycles cotton treated with Ag–RB + FAS (2S) retained an oleophobicity similar to that of the FAS treated cotton, while the Ag–RB–FAS (1S) cotton fibres exhibited a loss of oleophobicity already after the second washing, even though fluorine and C–F vibrational bands were detected in the corresponding XPS and IR spectra. The antibacterial activity of cotton treated by procedures (i)–(iii) was tested by its reduction of the bacteria Escherichia coli and Staphylococcus aureus following the AATCC 100-1999 standard method and EN ISO 20743:2007 transfer method. The reduction in growth of both bacteria was nearly complete for the unwashed Ag–RB and Ag–RB–FAS (S1), but for the unwashed Ag–RB + FAS (S2) treated cotton no reduction of S. aureus and 43.5 ± 6.9% reduction of E. coli was noted. After the first washing, the latter two finishes exhibited nearly a complete reduction of E. coli but for the Ag–RB treated cotton the reduction dropped to 88.9 ± 3.4. None of the finishes retained antibacterial properties after 10 repetitive washings. The beneficial and long-lasting low surface energy effect of FAS finishes in the absence of Ag nanoparticles, which led to the “passive” antibacterial properties of FAS treated cotton fabrics, was established by applying the EN ISO 20743:2007 transfer method. The results revealed a reduction in bacteria of about 21.9 ± 5.7% (FAS), 13.1 ± 4.8% (Ag–RB–FAS (S1)) and 41.5 ± 3.7% (Ag–Rb + FAS (S2)), while no reduction of the growth of bacteria was observed for cotton treated with Ag nanoparticles after 10 repetitive washings. The physical properties (bending rigidity, breaking strength, air permeability) of finished cotton samples were determined, and showed increased fabric softness and flexibility as compared to the Ag–RB treated cotton, but a slight decrease of breaking strength in the warp and weft directions, while air permeability decreased for all type of finishes.     

Sorption of iron(III)–alginate complexes on cellulose fibres

Multivalent ions take a significant role in the sorption of soluble polysaccharides on solid cellulose substrates and thus demonstrate an important principle in structural polysaccharide organisation. Sorption of Fe(III)–alginate complexes on lyocell fibres as model for the insoluble cellulose matrix has been studied between pH 3–13, at 30 and 60 °C. Sorption maximum of the Fe(III)–alginate complex was observed at pH 3 where the sorbed amounts of alginate and iron were 6,600 and 85 mg iron per kg cellulose respectively. Under the experimental conditions used, a concentration of 0.05 mM Fe(III) is sufficient to achieve surface sorption of Fe(III)–alginate complex. The alginate sorption exhibited minor dependence on molar ratio of Fe(III) to alginate. In environmental scanning electron microscopy no deposition of Fe-hydroxides on the fiber surface was detected. The thickness of the adsorbed Fe(III)–alginate layer on the fiber surface was estimated with 12–22 nm. Tensile strength and abrasion resistance of Fe(III)–alginate treated fibers were not reduced through the sorption treatment. Alginate modified cellulose is of interest as material for medical application, as sorbent and textile finish.     

Structure and surface properties of fluorinated organic–inorganic hybrid films

Fluorinated organic–inorganic hybrid films were prepared by sol–gel process from tridecafluoroctyltriethoxysilane (PFAS), 3-glycidoxypropyltrimethoxysilane, and tetraethoxysilane (TEOS). It has been found that the fluorinated hybrid films possessed fluorinated side chains originating from PFAS as top layer, and silica network as bottom layer, which had very low surface energy and could be used as water repellent functional coatings. The outermost layer of the water-repellent film may be fully covered by the perfluoroalkyl side chains as the molar ratio of PFAS/TEOS increases up to about 0.005:1. The addition of BPA can enhance the cross-link density of fluorinated hybrid films, and make more perfluoroalkyl groups enriching at the coating film-air interface to lower the surface free energy. However, the improvement of the cross-link density of fluorinated hybrid films tends to exhibit brittleness and micro-cracks. Consequently, it can be concluded that a small BPA additive content is preferred for the formation of fluorinated hybrid films with a smooth surface and less detectable cracks.     

Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.     

Responsive microstructures on organic–inorganic hybrid films

Micro-periodic structures exhibiting shape memory have been fabricated on organic–inorganic hybrid films. The microscale structures are obtained by forming wrinkles via buckling of the stiff surface layer. The surface-modified layers are obtained by surface photopolymerization or by oxidation of the hybrid films. The microscale structures are spontaneously formed by the shrinkage of the underlayer via gelation. The surface microstructures on titania- or silica-based films with hydrophilic swellable polymers exhibit a humidity response, i.e., a shape memory effect. This is observed when the surface microstructure disappears and is subsequently recovered with cyclic variation of the surrounding humidity. Micro-rolls are also fabricated by the selective swelling of surface-modified layers.     

Elastic organic–inorganic hybrid aerogels and xerogels

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH₃SiO_1.5) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a “spring-back” behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.     

Hydrophobic modification of cellulose fibres by cationic-modified polyacrylate latex with core–shell structure

In cellulose fibre-based green packaging, the poor resistance or barrier against water or water vapour has remained as one of the key challenges. In this work, cationic polymer latex, butyl acrylate-co-styrene/2-ethylhexylacrylate-co-methyl methacrylate (BA-co-St/EHA-co-MMA), with core–shell structure was especially synthesized and used as a wet-end additive to render the fibre or paper hydrophobic. TEM observation confirmed that the latex particles obtained indeed possessed desired characteristic of core–shell structure. The experimental results showed that the cationic polymer was especially suitable for use in papermaking processes due to its high retention with cellulose fibres. The surface modification of the natural fibre by the adsorption of cationic latex on the fibre surfaces potentially created the thin films of polymers on fibre surfaces. The resulting paper is highly hydrophobic with improved barrier property, as demonstrated by the high contact angles and relatively low WVTR value. Moreover, the mechanical properties of paper were maintained or even improved in the presence of an appropriate level of the latex.     

Disintegration of periodate–chlorite oxidized hardwood pulp fibres to cellulose microfibrils: kinetics and charge threshold

Periodate–chlorite oxidized bleached hardwood kraft pulp fibre samples with six levels of charge densities ranging from 0.5 to 1.8 mmol/g were gradually disintegrated to microfibrils using a high-shear homogenizer. The disintegration kinetics and mechanisms were studied by a flow fractionation method, and the properties of the resulting particles were determined using low shear viscosity and transmittance measurements. The particles formed during the disintegration were visualized with a charge-coupled device camera and by field-emission scanning electron microscopy. The result showed that cellulose fibres with a low charge density disintegrated at a low rate and produced ragged fibres and bunches of microfibrils via bursting of the fibre walls, whereas those with a higher charge density broke down at a high rate and microfibrils were formed through swelling and the creation of balloon structures. A carboxyl content of 1.2 mmol/g was found to be the threshold value for the efficient formation of high aspect ratio microfibrils and also for the change in the disintegration mechanism in the high-shear homogenizer.     

Preparation and characterization of a novel organic–inorganic hybrid nanostructure: application in synthesis of spirocompounds

Research on Chemical Intermediates - Immobilization and heterogenization of acidic/basic groups or organic tags on inorganic supports have found many important applications in recent years. In this...     

Naked eye detection of cadmium using inorganic–organic hybrid mesoporous material

A novel and low-cost optical sensor for the naked eye detection of Cd²⁺in aqueous media based on mesoporous silica containing 4-(2-pyridylazo)resorcinol (PAR) as a probe molecule anchored by N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAC) was prepared. The effects of various factors such as pH, solvent volume, temperature, reaction time, amount of the material, and the presence of various ions were studied in order to optimize operating conditions. The detection was based on the color change of PAR from orange-yellow to purple as a result of complexation with Cd²⁺. The intensity of the Cd-PAR complex varies linearly with the Cd²⁺concentration, from zero to 1.78×10⁻⁷ mol dm⁻³. The detection and quantification limits for the method when determining Cd²⁺ were 1.75×10⁻⁸ and 5.77×10⁻⁸ mol dm⁻³, respectively, with a correlation coefficient of 0.99. Good chemical stability of the material was observed for a period of five months. The developed sensor was applied to the analysis of various industrial effluents and tap water samples. Electronic supplementary material Supplementary material is available for this article at