Highly oriented 3D-hexagonal silica thin films have been produced on silicon substrates by dip-coating technique, using cetyltrimethylammonium (CTAB) bromide as structuring agent. For the first time, time-resolved in situ X-ray diffraction experiments have been used to investigate the formation of such mesostructured films. Interestingly, the data shows that an intermediate mesophase appears just after film deposition (t<500 ms), characterized by one diffraction peak centered at a d spacing of 65 Å. Then after 20 s, another mesophase appears with a shorter d spacing (44 Å), which corresponds to the 3D-hexagonal structure found for the final dried film.

During the last 50 years, there has been a considerable amount of work for the elaboration of efficient luminescent materials, most of them dealing with the search for new chemical compositions. Only a very few studies have concerned the study of the influence of the microstructure of the materials on their properties of emission, especially when the grain sizes of the materials are in the nanometer range. On another side, important advances have been performed in colloid chemistry in the last years, especially in the case of II-VI chalcogenides, as a consequence on the intense activity around the physics of quantum confinement in semiconductors.

The basic idea of this work is to show that the techniques developed in the case of II-VI nanoparticles could find interesting applications for the elaboration of nanostructured luminescent materials. This is first illustrated in the case of pure CdS nanoparticles, whose properties are deeply affected by their surface state and their chemical environment. Incorporation of manganese in solid solution in the CdS particles drastically changes the emission process, which now essentially depends on the manganese content inside each particle. Finally, the extension of the synthesis process to rare earth doped oxide particles is presented, and the luminescence efficiency is discussed as a function of the size, the structure, and the chemical environment of the particles.

Wyoming montmorillonite has been modified with block copolymers of poly (styrene) (PS) and poly(ethylene oxide) (PEO). Using melt intercalation techniques, PEO-b-PS copolymers spanning a range of volume fractions and molecular weights were mixed with montmorillonite, annealed above the Tg of PS, and characterized using X-ray diffraction. Most of the block copolymers intercalated the clay, with several samples exhibiting multiple Bragg reflections from increased gallery spacing. Samples with higher PEO volume fractions were most likely to have intercalation. For a given PS block length, longer PEO blocks were more likely to produce intercalation. In general, the increased gallery spacings were close to those produced by modifying montmorillonite with PEO homopolymer.

Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid orgainc-inorganic materials [1]. These materials have shown promise as precursors for encapsulation and microelectronics applications (Figure 1). The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared by an organic base or Bronsted acid (formic or triflic acid), without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

We are currently developing a 2-step sol-gel route to metal oxide / phosphonate hybrid materials, based on the non-hydrolytic condensation of a metal alkoxide with a phosphonic acid, followed by hydrolysis / condensation of the remaining alkoxy groups. Several molecular intermediates in this process were obtained by reaction of Ti(OiPr)4 with phosphonic acids RPO3H2(R = Me, Ph, tBu):[Ti4(OiPr)2(tBuPO3)]4(1),[Ti4(μ3-O)(OiPr)5(μ-OiPr)3(PhPO3)3]·DMSO (2), [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(MePO3)3]·DMSO (3), [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(tBuPO3)3]·DMSO (4), which were characterized by single crystal X-ray structure analysis and/or NMR spectroscopy. These compounds give information on the sol-gel chemistry in our process and are structural models for the final hybrid materials. In all cases the non-hydrolytic condensation is complete, and the phosphoryl oxygen is coordinated to a titanium atom. In addition, these clusters are soluble in common organic solvents and contain hydrolyzable alkoxy groups, which make them potential building blocks in the sol gel process. Accordingly, the use of cluster 2 as a single source precursor was investigated.

Conventional composites filled with clay as well as intercalated nanocomposites, and exfoliated nanocomposites based on a glassy epoxy matrix have been synthesised. Flexural moduli of these materials were measured in three-point bending at various clay contents. For a given clay content, stiffness improvements depended not only on the dispersion of the clay on the microscale, but also on the exfoliation of the clay layers at the nanolevel. Dynamic mechanical measurements indicated a decrease of intensity in the glass transition peak with the extent of exfoliation of the clay and the clay content, suggesting a restriction of the molecular mobility of the polymer in the vicinity of the clay layers. A shift in Tg of 20°C towards lower temperature for the epoxy resin cured at 160°C was possibly caused by thermal degradation of compatibilizing agents at high temperature.

Functional trialkynylorganotins were obtained by alkynylation of the corresponding organotin trichlorides. When functional organotin trichlorides were not stable, a selective monoalkynylation of tetraalkynyltins by Grignard reagents was used. It was the first example of selective monoalkylation reactions of symmetrically tetrasubstituted tin compounds. Then, reactions of the functional trialkynylorganotins with alcohols, water and carboxylic acids afforded respectively the corresponding functional monoorganotin alkoxides and oxides, and monoorgano-oxotins carboxylates.

Alumina particles were treated under various conditions with different diphenylphosphinate compounds: diphenylphosphinic acid, ethyl diphenylphosphinate, and trimethylsilyl diphenylphosphinate. The balance between surface complexation (namely grafting) and surface phase transformation (formation of bulk aluminum phosphinate phase) was investigated by IR and solid-state 31P MAS NMR spectroscopy, using the model crystalline phase Al(O2PPh2)3 synthesized in a parallel work as a reference. Satisfactory grafting was obtained either by using diphenylphosphinic acid in aqueous medium at pH about 6, or by using ethyl diphenylphosphinate in organic medium as coupling agents.

The combination of sols containing silica polymers, prepared by the sol-gel method under conditions of nearly linear chain growth, with solutions of the biopolymer chitosan has allowed us to obtain hybrid materials in the form of films or particles. In these hybrid nanocomposites, the organic and inorganic phases are associated through hydrogen bonds. In this work we present the preparation of hybrid xerogels of spherical morphology and their transformation into hollow spherical particles of silica with high specific area (276 m2/g) and a pore volume of 0.23 cm3/g. The xerogel particles were obtained by precipitation and subsequent drying. Thereafter, chitosan was extracted partially with acetic acid (5%) and finally the product was calcined at 550°C for two hours. The SEM micrograph shows that the silica particles were obtained as hollow spheres with size in the range between 10 and 100 μm. By using larger magnification, it was found that much smaller spheres of about 0.01 μm constitute the surface of these hollow spheres. Porosimetry shows the presence of micropores as well as mesopores. The observed morphology is discussed on the basis of a coprecipitation process conditioned by an association of both organic and inorganic phases in the precursor hybrid sol.

The synthesis of ORMOCER®*s (inorganic-organic polymers) for optical applications is studied in detail. Producing waveguide materials with the desired low optical losses at wavelengths of 1310 and 1550 nm requires a thorough control of the initial inorganic network formation, because absorption losses are particularly due to Si-OH bonds beside aliphatic C-H bonds. Therefore, the synthesis of UV- or thermally curable organopolysiloxane resins with minimized Si-OH content is crucial. The investigation of the sol-gel reaction of organoalkoxysilanes by 29Si-NMR spectroscopy provides a detailed insight into the influence of reaction conditions on the species and networks formed. Reaction parameters were optimized towards the formation of ORMOCER® resins suitable for waveguide applications. Finally, the material synthesis is completed by crosslinking organically polymerizable units present in the ORMOCER® resin to establish the inorganic-organic hybrid network. The experimental work is accompanied by computational chemistry. Calculating electronic properties is of value in predicting silane reactivities as well as spectroscopic data of intermediates. Molecular modeling is a convenient tool for the visualization of structural details on the molecular level.

This paper is a concise review of some recent works which highlights the interest of phosphonate groups RP (O)32- in the field of organic/inorganic hybrid materials, as a general alternative to silicon coupling agents in anchoring of an organic group to an inorganic support or within an inorganic network. Examples, focused on metals of groups 4 and 13, illustrate various synthetic routes, from the hydrothermal synthesis of two- or three-dimensional metal phosphonates, to the introduction of organic moieties into oxide matrices by sol-gel processing, without excluding the grafting of metal oxide surfaces.

A novel one-step soft solution-processing (SSP) route called solvothermal-co-polymerization technique was successfully developed for in situ fabrication polystyrene (PS)/CdS nanocomposites embedded with CdS nanowires in ethylenediamine media at lower temperature (80–140°C). In this route, the polymerization of the styrene monomers and the formation of the CdS nanocrystallites occur simultaneously in a certain temperature range. The results show that the quantum-fined CdS nanowires with diameters 4–15 nm and lengths up to several micrometers via the present one-step route were embedded in the PS matrix and had [001] preferential orientation. Both temperature and solvent were found to play a key role in the synthesis of the nanocomposites. The produced novel hybrid nanocomposites display obvious quantum size effects and interesting fluorescence features.

Mesoporous titanium phosphates were synthesised using three different approaches, involving reactions of titanium isopropoxide with long-chain alkyl phosphates, and subsequent aging at 80°C for several days. The resulting powders were characterised using XRD, TEM and N2 sorption.

The first approach involved the classical MCM methodology, where the modified titanium precursor was added to an alkylphosphate micellar solution. The resulting solids possess an organised, lamellar mesostructure. However, removal of the surfactant, either by heating or leaching in strong basic solution, leads to the collapse of the lamellar mesostructure.

In the second route, titanium alkoxide was pre-reacted with the long-chain alkyl phosphate, then hydrolysed with a large excess of water prior to ageing. Although the structure of the as-precipitated samples could be easily tailored by changing the processing parameters such as the alkyl phosphate chain length or phosphate/titanium ratio, surfactant removal by heating invariably led to the production of microporous samples.

The third approach involved the hydrolysis of the acetylacetone-modified titanium isopropoxide with excess water. The alkyl phosphate was then introduced into the resulting suspension. Subsequent ageing under acidic conditions destabilised the particles, leading to aggregation and subsequent gelation. In contrast to the previous approaches, the pyrolysed solid contained a significant proportion of mesopores, a high porosity (40%) and a surface area exceeding 300 m2.g-1.

Hexagonal mesoporous silica layers were first prepared by the sol-gel route from solutions containing silicon alkoxides as silica precursors and alkyltrimethylammonium bromides to form the templating liquid crystal mesophase. The synthesis conditions required to obtain well-ordered crack-free layers were investigated. Two main synthesis parameters were identified. The first one is the aging time of the sol before deposition which defines the size of the inorganic cluster before the thin layer deposition and the simultaneous phase formation. The second important synthesis parameter is the surfactant volume fraction in the medium after the departure of the volatile components. Well-ordered hexagonal layers were obtained for surfactant volume fractions in agreement with the water-surfactant binary diagram. These synthesis conditions were extended to cubic and lamellar phases and to other types of surfactants, gemini (cationic surfactants with two polar head groups) and non-ionic triblock copolymers. First results concerning the extension of this approach to the preparation of alumina thin layers are finally presented.

A number of investigations are described to illustrate the use of small-angle x-ray and neutron scattering to characterize the structures of organic-inorganic composites. The organic phase in these materials is typically a polymer such as poly (dimethylsiloxane), and the inorganic phase a ceramic such as silica or titania (obtained by in-situ hydrolysis and condensation of an organosilane or organotitanate in the usual sol-gel approach). Other inorganic phases of interest include porous materials such as zeolites or Vycor glass. A major goal in such investigations is to correlate the structures of the composites with the synthetic techniques used to prepare them, and with the mechanical properties they exhibit. Carrying out scattering measurements as a function of time can also be used to obtain kinetic results on the sol-gel reactions used to generate the dispersed phase.

Using a micro-Contact Printing (μ-CP) technique, substrates are prepared with patterns of hydrophilic, hydroxyl-terminated SAMs and hydrophobic methyl-terminated SAMs. Beginning with a homogeneous solution of silica, surfactant, ethanol, water, and functional silane, preferential ethanol evaporation during dip-coating, causes water enrichment and selective de-wetting of the hydrophobic SAMs. Correspondingly, film deposition occurs exclusively on the patterned hydrophilic SAMs. In addition, by co-condensation of tetrafunctional silanes (Si(OR)4) with tri-functional organosilanes ((RO)3Si (CH2)3NH2), we have selectively derived the silica framework with functional amine NH2 groups. A pH sensitive, micro-fluidic system was formed by further conjugation reactions with pH sensitive dye molecules.

Polymer-layered silicate nanocomposites from polyamide-11 (PA-11) were prepared and the morphology and properties have been investigated in order to link the fundamental research field of polymer crystallization with the technical important field of composite materials. Semi-crystalline polymers are known to crystallize in different phases (e. g. monoclinic, hexagonal) forming chain-folded lamellar crystals. Depending on experimental conditions (e. g. temperature, pressure) the crystal size (lamellar thickness) affects the stability of these phases. The incorporation of layered silicates acting as hard walls into semi-crystalline polymers opens new possibilities to: i) study polymer crystallization in confined dimensions, and ii) provide materials from commodity or engineering polymers with enhanced properties. The effect of an external confinement introduced by highly anisotropic silicate layers of organically modified clay minerals on crystal growth and nanocomposite properties has been studied. The composites are prepared by in situ polycondensation of polyamides and/or blending via melt extrusion. The nanocomposites exhibit a homogeneous distribution of individual silicate layers at low clay contents. The lamellar thickening growth is reduced in polyamide crystallization due to the external constrained of the silicate layers in the host polymer. Furthermore these nanocomposites show a slightly enhanced thermal stability, tensile modulus and an increased elastic behavior over a broader temperature range. No distinct glass transition has been observed at highest clay contents.

Blending the biopolymer chitosan (CHI) with poly (aminopropilsiloxane) oligomers (pAPS), and poly (ethylene oxide) (PEO) in the presence of lithium perchlorate lead to ion conducting products whose conductivity depends on the composition of the mixture. A ternary phase diagram for mixtures containing 0.2 M LiClO4 shows a zone in which the physical properties of the products - transparent, flexible, mechanically robust films - indicate a high degree of molecular compatibilization of the components. Comparison of these films with binary CHI-pAPS nanocomposites as well as the microscopic aspect, thermal behavior, and X-ray diffraction pattern of the product with the composition PEO/CHI/pAPS/LiClO4 1:0.5:0.6:0.2 molar ratio indicates that these films may be described as a layered nanocomposite. In this composite, lithium species coordinated by PEO and pAPS should be inserted into chitosan layers. Electrochemical impedance spectroscopy measurements indicate the films are pure ionic conductors with a maximal bulk conductivity of 1.7*10-5 Scm-1 at 40 °C and a sample-electrode interface capacitance of about 1.2*10-9 F.

Several new methods have been developed for the synthesis of POSS monomers from fully condensed [RSiO3/2]n and [ROSiO3/2]n (n = 6 or 8) frameworks. These methods, which all rely on highly selective base-catalyzed reactions of Si/O frameworks, provide unprecedented access to new POSS monomers and the means for manufacturing useful POSS monomers on a large scale from readily available silane monomers.

Poly (amidoamine) (PAMAM) dendrimers are used to create organic-inorganic hybrid colloids in aqueous solution. The formation of gold colloids upon reduction of a gold salt precursor serves as a model reaction to study the influence of reaction conditions and dendrimer generation on the resulting nanostructures. The hybrid particles were characterized by transmission electron microscopy (TEM), small angle neutron scattering (SANS), and small angle x-ray scattering (SAXS). A transition is found from “colloid stabilization” by low molecular mass molecules to “polymer nanotemplating” with increasing dendrimer generation, i.e, increasing molecular mass but retaining the chemical nature of the stabilizing species.