Dip-coating of sol-gel solutions is a complex dynamic process that is difficult to model because it is associated with time-dependent evaporation-induced concentration and viscosity gradients in the solution. It is, however, highly used in the coating technology because it is simple and provides excellent reproducibility. Existing fair models have been proposed some decades ago to describe this method, but they are based on Newtonian and nonevaporating liquids and require several important assumptions and simplifications. In this work, we present a simple experimental study of sol-gel film formation by dip-coating, through which we propose a general semiexperimental model to predict the final film thickness. Spectroscopic ellipsometry was used as the main technique to obtain the film physical thickness and optical density for various dip-coating processing conditions (withdrawal speeds from 0.01 to 20 mm · s -1 and temperatures from 25 to 60°C) and for several different chemical solutions (TiCl 4 , TEOS, and MTEOS, all in the presence, or not, of block PEO-b-PPO copolymer templates in EtOH/H 2 O, with concentrations from 10 -1 to 10 -3 mol · L -1 ). We show that phenomena that are difficult to assess during deposition, such as viscosity variation, evaporation cooling, chemical reaction, and thermal Marangoni flow, may not have to be taken into account. The influences of various experimental parameters are discussed together with the limitations and the full potentiality of the dip-coating technique. We show that two regimes of film formation independently exist at extreme withdrawal speeds, while they combine into a third regime at intermediate speeds. Although the first regime is well-known and is governed by gravity-induced viscous drag at higher speeds, the second one is barely used and is governed by interdependent evaporation and capillarity rise at lower speeds. We show that both regimes can be selected to build up films with a tunable thickness and that a minimum thickness exists for each given solution at a critical speed for which we believe that the capillarity rise effect perfectly counterbalances the viscous drag. We also show that the capillarity regime is well-suited when one needs to deposit thick films from highly diluted solutions.

Innovative strategies to produce well-defined nanoparticles and other nanostructures such as nanofibres, quantum wells and mesoporous materials have revitalized materials science for the potential benefit to society. Here, we report a controlled process, involving soft-chemistry-based deposition, template-assisted mesostructured growth, and tuned annealing conditions that allows the preparation of ordered mesoporous crystalline networks and mesostructured nano-island single layers, composed of multicationic metal oxides having perovskite, tetragonal or ilmenite structures. This strategy to obtain meso-organized multi-metal-oxide nanocrystalline films (M(3)NF) bridges the gap between conventional mesoporous materials and the remarkable properties of crystalline ternary or quaternary metallic oxides. Nanocrystalline mesoporous films with controlled wall thickness (10-20 nm) of dielectric SrTiO(3), photoactive MgTa(2)O(6) or ferromagnetic semi-conducting Co(x)Ti(1-x)O(2-x) were prepared by evaporation-induced self-assembly (EISA) using a specially designed non-ionic block-copolymer template. A tuned thermal treatment of the mesoporous films permits the transfer of the wall structure into nanocrystallites, with all tectonic units being tightly incorporated into mechanically stable ordered tri- or bidimensional nanocrystalline networks. This methodology should allow multifunctionalization, miniaturization and integration during development of devices such as smart sensors and actuators, better-performing photocatalysts, and fast electrochromic devices. On the other hand, organized arrays of dispersed ferromagnetic or ferroelectric nanoparticles are promising materials for spintronics and for cheap, non-volatile 'flash' memories.

This work describes the detailed structural investigation of mesophase-templated mesoporous silica films by 1D and 2D X-ray scattering techniques and transmission electron microscopy. The films are prepared by sol−gel dip coating with 2D hexagonal templating mesophases, yielding 2D mesoporous structures consisting of cylindrical pores whose axes are aligned parallel to the surface. It is shown that drying and thermal treatments induce an unidirectional shrinkage of the layers in the direction of the normal of the film. The true rectangular symmetry is only evidenced by 2D X-ray scattering in two different scattering geometries. 1D diffraction gives only an apparent hexagonal symmetry. It is furthermore shown that although the cylinder axes are randomly orientated within the plane parallel to the surface, there are large domains with well aligned 2D planar unit cells perpendicular to the surface. It is demonstrated that this preferential ordering is destroyed by nanoparticle seeding with amorphous silica or maghemite particles.

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Mesostructured materials can be obtained by combining ionic surfactants [1] or block copolymers [2] with the synthesis of metallic oxides through soft chemistry. Amongst the nonsilicate mesoporous materials, alumina is very attractive since the Al 2 O 3 has perfectly controlled mesoporosity associated with hardness, hydrolytic stability, amphoteric character, and thermal stability of the g-transition-oxide phases. Indeed, alumina offers a range of possibilities for applications in ultrafiltration of salts, [3] as an adsorbent in environmental cleanup, [4] as an automobile exhaust catalyst, [5] as a heterogeneous catalyst support for hydrodechlorination, [6] and in petroleum refinement. [7] In state-of-the-art syntheses, ordered mesoporosity has been reported for boehmite, [8] gibbsite, [9] and alumina [2,5,10] through the template approach, and also by porogen bead inclusion, [11] by ordered mesoporous carbon (CMK) nanocasting, [12] and by anodization.[8a] However, none of these materials combines pure crystalline g-Al 2 O 3 of high thermal stability with a well-ordered porosity that has a narrow distribution and is adjusted on the mesoscopic scale.Herein, we describe the preparation and characterization of nanocrystalline g-Al 2 O 3 layers with contracted face-centered cubic (fcc) mesoporosity that are stable up to 900 8C. These coatings were prepared by combining the block copolymer structuring approach [13] and the evaporationinduced self-assembly (EISA) method associated with layer deposition, [14] which has already led to mesoporous silica, [11] transition-metal oxide, [15] and even perovskite [16] layers. Here we show that such fcc-mesostructured alumina layers can be prepared reproducibly by a simple method by which one may * adjust the mesopore dimension with a relatively narrow size distribution, * tune the nature of the oxide framework between amorphous alumina to fully nanocrystalline g-Al 2 O 3 , * create up to 55 % volume of open porosity at 900 8C,

The characterization of multilayers from tri-O-isopentyl cellulose assembled by the Langmuir-Blodgett technique is described. The analysis of ultrathin films by X-ray reflection confirmed a homogeneous overall film quality but did not show any Bragg reflection. However, investigation of a superstructure in terms of an alternating multilayer sample from deuterated and nondeuterated isopentylcellulose ethers by neutron reflection revealed a perfectly periodic layer structure. The inhence of the degree of substitution of the isopentylcellulose ethers on the formation and structure of multilayers was investigated as well. Multilayers of partially substituted isopentylcellulose exhibit a periodical film structure composed of double layers. The perfection of the films is not influenced by the residual OH functions. The in-plane structure of tri-O-isopentylcellulose multilayers was investigated by electron diffraction in transmission geometry. The cellulose ether forms a helix of 3-fold symmetry, and the helix axes are preferentially oriented parallel to the dipping direction. Upon annealing a three-dimensional crystalline film of layered structure is obtained in which the chains are packed in a monoclinic unit cell. The very small diameter of the cellulose derivatives of less than 10 &molecule in the layered superstructures and the observation that very perfect and homogeneously oriented multilayers are obtained by the Langmuir-Blodgett technique augment the toolbox of molecular architects interested in the rational construction of supramolecular architectures.

The spreading behavior of poly (silane) s at the air-water interface of a Langmuir trough was investigated. Force-area diagrams of poly(silane)s with various side groups and different molecular weights were recorded. Stable monomolecular layers were not obtained for alkyl substituents. In the case of p-alkoxyphenyl and, even better, m-alkoxyphenyl residues attached to the silicon backbone, stable monolayers were obtained that could be transferred to solid hydrophobic substrates by applying the Langmuir-Blodgett technique. These transferable poly(silane)s have a rodlike shape and form dense rafts at the water surface. Multilayers consisting of up to 600 monolayers of this raftlike structure with the rods preferentially oriented into the dipping direction have been obtained. The order parameter describing the degree of orientation of the rods with regard to the dipping direction was determined from the dichroic ratio of the band of the silicon-silicon chromophores at 397 nm for the m-alkoxyphenyl-substituted poly (silane). The order parameter could be improved substantially by annealing the samples subsequent to deposition of the layers at temperatures up to 150 °C. Samples thus obtained have the character of a monodomain nematic liquid crystal of molecularly defined thickness. Details of the structure were further elucidated by X-ray reflection and polarized IR spectroscopy.

Mesostructured materials can be obtained by combining ionic surfactants [1] or block copolymers [2] with the synthesis of metallic oxides through soft chemistry. Amongst the nonsilicate mesoporous materials, alumina is very attractive since the Al 2 O 3 has perfectly controlled mesoporosity associated with hardness, hydrolytic stability, amphoteric character, and thermal stability of the g-transition-oxide phases. Indeed, alumina offers a range of possibilities for applications in ultrafiltration of salts, [3] as an adsorbent in environmental cleanup, [4] as an automobile exhaust catalyst, [5] as a heterogeneous catalyst support for hydrodechlorination, [6] and in petroleum refinement. [7] In state-of-the-art syntheses, ordered mesoporosity has been reported for boehmite, [8] gibbsite, [9] and alumina [2,5,10] through the template approach, and also by porogen bead inclusion, [11] by ordered mesoporous carbon (CMK) nanocasting, [12] and by anodization.[8a] However, none of these materials combines pure crystalline g-Al 2 O 3 of high thermal stability with a well-ordered porosity that has a narrow distribution and is adjusted on the mesoscopic scale.Herein, we describe the preparation and characterization of nanocrystalline g-Al 2 O 3 layers with contracted face-centered cubic (fcc) mesoporosity that are stable up to 900 8C. These coatings were prepared by combining the block copolymer structuring approach [13] and the evaporationinduced self-assembly (EISA) method associated with layer deposition, [14] which has already led to mesoporous silica, [11] transition-metal oxide, [15] and even perovskite [16] layers. Here we show that such fcc-mesostructured alumina layers can be prepared reproducibly by a simple method by which one may * adjust the mesopore dimension with a relatively narrow size distribution, * tune the nature of the oxide framework between amorphous alumina to fully nanocrystalline g-Al 2 O 3 , * create up to 55 % volume of open porosity at 900 8C,