We analyze the thermodynamics of polymer-clay mixtures within the framework of density functional theory (DFT). The interaction potential between clay particles is calculated using the self-consistent field (SCF) method and is strongly dependent on the length and density of grafted short-chain organic modifiers. By combining the DFT and SCF techniques, we determine the role of the grafted chains on the equilibrium phase behavior of the mixtures.

This presentation describes a simple and practical method for self-assembling meso- and nanoparticles into three-dimensionally ordered lattices (opals) over large areas, and the use of these lattices as templates in fabricating highly ordered porous structures such as inverse opals. This method has been applied to a variety of colloidal particles, including silica colloids and polymer beads with diameters in the range of˜50 nm to ˜50 μm. Templating against the 3D opaline lattices provides an effective route to inorganic-organic composite materials and inverse opals having 3D periodic structures.

Regularly spaced polymer dots are formed on a silicon surface by rubbing a thin polymer plate against the silicon substrate. Typically, the disk-shaped dots are 10 nm in height and 160 nm in diameter, and are separated by 340 nm from each other. It is found that the substrate temperature, the rubbing rate, the polymer viscoelasticity, and wettability against a substrate surface must be within a certain range to produce the aligned dots.

The preparation of lead sulfide and cadmium sulfide quantum size particles arranged in periodic layers within organic matrices is described. Superlattices of the particles have been generated in crystals or thin films of long chain amphiphilic acids by topotactic gas-solid reactions of the lead or cadmium salts, that pack in layer structures, with H2S gas. X-ray powder diffraction and transmission electron microscopy reveal that the crystalline order of the reactant has been partially retained in the organic-inorganic composite. This approach is demonstrated by examples of organic acids bearing an aromatic ring along the hydrocarbon chain, such as derivatives of phenyl propionic and benzoic acids.

Photo-stability of (C6H5C2H4NH3)2PbX4 (X; Br and I) films was studied and the degradation processes were discussed. The prepared films were not stable against the UV-light irradiation. The PhE-PbX4 films were readily oxidized by the UV-light irradiation in air. In vacuum, the PhE-PbI4 films changed to β-phenethylamine intercalated PbI2 due to the elimination of halogen species. On the contrary, no degradation was observed for the PhE-PbBr4 films. These results suggested that the photo-irradiation induced photochemical reaction was one of the possible reasons for the degradation. To suppress the oxidation and halogen elimination induced by the photochemical reaction, PMMA-coated PhE-PbX4 films were also fabricated and their photo-stability was examined.

A method for covalent immobilization of a single dextran polymer between a gold surface and the tip of an atomic force microscope (AFM) is presented. Carboxymethylated dextran immobilized on gold by epoxythiol chemistry was activated with N-hydroxysuccinimide (NHS) and N-ethyl-N'-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) in order to make the dextran polymer reactive for the amino groups present on the previously aminosilanized AFM tip. By measuring force vs extension curves we have shown that it is possible to catch such an activated dextran polymer with an AFM tip through the formation of a covalent bond. Dextran polymers were attached even without any detectable indentation of the tip in the dextran-coated gold surface. In this so-called fly-fishing mode, attachment of multiple dextran polymers, which typically occurs when the tip is indented into the surface, are efficiently avoided.

We present a general strategy for the efficient assembly of organic molecules directly onto the silicon surface via Si-N and Si-O linkages. This is achieved from the reaction between an amine or an alcohol functional group and a chlorinated Si surface. The resulting organic monolayers are thermally stable. These methods are applicable for the assembly of a variety of functional organic molecules in both vacuum environment and solution phases.

The adsorption of a series of 1,2-bis(mercaptomethyl)-4,5-dialkylbenzenes (1), spiroalkanedithiols (2), and aliphatic dithiocarboxylic acids (3) on gold yielded new types of self-assembled monolayers (SAMs). The new SAMs were characterized by optical ellipsometry, contact angle goniometry, and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). These results were compared to those obtained from SAMs derived from normal alkanethiols (4) of analogous chain length. Comparisons of ellipsometric thickness and contact angle wettability showed that the new SAMs were well packed and highly oriented. Comparisons of the PM-IRRAS data showed that the SAMs generated from 1 and 2 exhibited slightly less crystallinity than their alkanethiolate-based analogs, while the SAMs generated from 3 exhibited comparable crystallinity to their alkanethiolate-based analogs. Moreover, the SAMs derived from 1 and 2 showed no “odd-even” wettability or PM-IRRAS effects, while those derived from 3 showed remarkably large “odd-even” effects compared to those derived from normal alkanethiols.

In situ patterning of crystalline iron oxide thin layers has been achieved via microcontact printing (μCP) and selective deposition. μCP was used to pattern two different surface moieties of selfassembled organic monolayers (SAMs) on Au/Cr/Si substrates. An elastomeric stamp (poly(dimethylsiloxane); PDMS) having a submicron-size patterned relief structure was used to transfer either hexadecanethiol (HDT) SAMs, which are to sustain deposition of iron oxide precipitates, or hydrophilic SAMs (e.g. dithiothreitol (DTT)). Selective deposition is realized through precipitation of iron oxide phases from aqueous solutions at ambient temperature (<100°C). Aqueous solutions of 0.05 M of iron nitrate (Fe(NO3)2•9H20) containing urea under nitric acid (pH < 2) were prepared for selective depositions. X-ray photoelectron spectroscopic (XPS) results showed that iron oxide precipitates were deposited onto hydrophilic SAMs, but not onto HDT surfaces. As-deposited films onto DTT-SAM surfaces at 80°C were crystalline α-Fe2O3 (hematite). Fe3O4 and γ-Fe2O3 films were synthesized via annealing of as-deposited α-Fe2O3. Scanning electron microscopy, x-ray diffractometry, vibrating sample magnetometry, and optical microscopy were used to characterize the films' microstructures and properties.

Functionalized self-assembled monolayers (SAMs) on single-crystal Si wafers have been used as substrates for the deposition of titania and vanadia thin films. The formation of a titanium chelate was used to stabilize an otherwise spontaneously precipitating aqueous titanium solution. Uniform titania films have been synthesized from Ti(O2)2+ in aqueous HCl solutions at 80°C on sulfonated SAMs. Vanadium oxide hydrate films, V2O5·0.7 H2O, have been directly formed from aqueous vanadate solutions on NH2-terminated SAMs at 45°C. In the as-deposited films, water molecules were intercalated between the vanadium oxide layers. Subsequent annealing at 350°C in air led to nanocrystalline V2O5.

Nanocrystalline thin films of tin (IV) oxide (cassiterite) have been deposited from aqueous solutions of tin (IV) chloride and hydrochloric acid at 80°C. Substrates were {100} single-crystal silicon wafers, with and without silanol-anchored, sulfonate-terminated organic self-assembled monolayers (SAMs). Using flowing solutions, films with thicknesses of up to 1 μtm have been grown, whereas the thickness of the films from static solutions is limited to about 80 nm. The films were characterized using transmission electron microscopy and Rutherford backscattering spectroscopy. The role of the flow rate and configuration of the deposition chamber is discussed.

Highly ordered self-assembly organized silica meso-structured architecture have attracted increasing attention because these materials provide a rich source for scientific research and technological applications. This approach to meso-structured materials has been extended to non-silica oxides, especially transition-metal-oxides which might promise applications involving electron transfer and photocatalysts. We report the syntheses of TiO2 transition-metal-oxides meso-structured thin films (MSTF) using a surfactant templating processing with spin coating method. X-ray diffraction patterns of the films showed that the films generally oriented in a lamellar structure. The phase transferring in TiO2 MSTF was also investigated.

Nanocomposites of transparent, multilayer structures of different thin-films have been fabricated on single crystal silicon and quartz substrates by the new deposition technique called electrostatic self-assembly (ESA) method. The method is based on the alternating adsorption of anionic and cationic polyelectrolytes in the aqueous forms. The films were then characterized by UV/Vis spectroscopy, ellipsometry, and nano-indenter. A linear behavior of both optical absorption and film thickness as the number of bilayers increases was observed, which indicated the formation of homogeneous and uniform thin-films on both substrates. The study also observed that the films prepared by this novel method have some improved mechanical properties.

Glycidoxypropyltrimethoxysilane (GPTS) and metal alkoxides are frequently used in preparation of heterometal hybrid polymers and find application e. g. as contact lens materials and hard coatings on polymers. Such materials require a high homogeneity of the structural unit at the molecular level, which is supported by the formation of oxygen bridged heterometal bonds and their hydrolytic stability. By means of 29Si and 17O NMR the formation of heterometal bonds like Si-O-Ti, Si-O-Zr, Si-O-Ta was evidenced in GPTS-hydrolysates with Ti(OEt)4, Ti(OEt)3AcAc, Zr(OBun)4, Zr(OBun)3AcAc, Ta(OEt)5 or Ta(OEt)4AcAc (AcAc = acetylacetone ligand) as additives. Signals of heterometal bonds can be detected in 17O NMR spectra in the range of 170 to 350 ppm and are characterized in 29Si NMIR spectra by defined chemical shifts to low (Si-O-Ta) and high magnetic fields (Si-O-Ti, Si-O-Zr) in comparison with signals of Si-O-Si bonds. The use of AcAc modified metal alkoxides leads to well resolved 29Si NMR spectra, which make the distinction between homo- and heterocondensed species easier. The addition of water to the sols (2 H2O / alkoxy group) leads to a degradation of heterometal bonds in favour of more homocondensed species, which reduces the homogeneity of such hybrid materials at the molecular level.

Organically-modified porous silicates have been prepared according to a one-pot synthetic approach. A mixture of phenyltriethoxysilane and tetraethoxysilane was reacted with an acidic solution of cetyltrimethylammonium bromide (CTAB). Depending on the preparation conditions, not only the hexagonal (2d, p6m) but also a cubic phase has been prepared analogous to the already reported SBA-1 phase, whose X-ray pattern matches the (Pm3n) space group. To our knowledge, it is the first time that this phase is obtained with CTAB as structuring agent, which suggests specific interactions between the phenyl groups and the surfactant polar head group. The surfactant was removed by solvent extraction or calcination at 350°C, without any alteration of the ordering: a cubic porous silicate network functionnalized by phenyl groups was thus obtained. Calcination could even be performed at 600°C to prepare a pure silicate network that still exhibits the same cubic symmetry.

Thin films of mesoporous materials have been synthesized recently as lamellar, one dimensional hexagonal and cubic structures at substrate surfaces as well as at air/liquid interfaces. The present work investigates thermally induced structural changes of lamellar and one-dimensional hexagonal(1-dH) mesostructured silicate thin films, which is less known at the moment. The 1-dH films proved to be much more thermally stable than the lamellar ones; Open-pore one dimensionalhexagonalmesoporous thin films are obtained by the calcination of the films, where as the lamellarphase has collapsed after the surfactants removal.

Mesostructured siliceous cellular foams (mesocellular foams, MCFs) with homogeneous ultra-large mesopores are described. MCFs consist of uniform spherical cells 21–36 nm in diameter and possess surface areas up to 900 m2/g. Uniform windows, 7–18 nm in diameter, interconnect the cells to form a continuous 3-D pore system, which makes the MCFs attractive candidates for supports for catalysis and in separation and immobilization involving large molecules. They may be of interest in low-dielectric applications. The size of the cells can be controlled by the concentration of the added organic cosolvent. Adding small amounts of NH4F selectively enlarges the windows. We propose that the MCFs are templated by oil-inwater microemulsion droplets. The large-pore MCF materials resemble aerogels, with the benefit of a facilitated synthesis procedure in combination with well-defined pores and wall structure.

Mesophase templated silica layers seeded with magnetic or non magnetic nanoparticles are prepared. The study of the interactions between the nanoparticles and the others compounds of the synthesis solution is first described to explain the synthesis conditions allowing a homogeneous seeding. X-ray diffraction measurements are then used to study the texture of thick layers seeded with magnetic nanoparticles.

High temperature protonic conducting polymer membranes provide new technological applications in electrochemicaldevices including electrochromic displays, chemicalsensors and fuel cells. Organic/inorganimanocomposite membranes consisting of SiO2 /PEO (Polyethylene Oxides) hybrid are a remarkable family of isotropic, flexible, amorphous polymer materials, which have been synthesized through sol-gel processes. The hybrid membrane doped with acidic moieties such as monododecylphosphate or phosphotungstic acid shows good protonic conductivities at temperatures above 100°C. The protonic conducting membrane was found to be thermally stable at temperatures because of the inorganic SiO2 framework in the nanocomposites matrix.

Cooperative self-assembly processes of inorganic species and amphiphilic molecules have experienced major advances over the past six years. The ability to design these materials with spatially controlled combinations of different mesophases or compositions, and therefore different properties, would greatly enhance their utility as nanofunctional surfaces.

We present a simple lithographic procedure, which allows a deliberate control of structure and properties of a meso-ordered silica film through optical mediation. This nanostructural lithography process exploits the pH sensitivity of supra-molecular self-assembly which allows spatial control over mesophases in the thin film and a selective etching capability. Through the addition of a photoacid generator in the coating sol along with surfactant and silica source, dip coating results in continuous, ordered photosensitive films. Exposure to UV light through a mask produces local pH changes, inducing mesostructural phase transitions and an increase in the acidcatalyzed siloxane condensation rate in the exposed regions. Two surfactant systems, CTAB (CH3(CH2)15N+(CH3)3Br–) and Brij 56 (CH3(CH2)15(OCH2CH2)10OH) have been studied. X-ray diffraction, transmission and scanning electron microscopy, optical microscopy, ellipsometry, MAS-NMR and atomic force microscopy are used to characterize the patterned nanostructured surfaces.