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Thin films of polyethylenimine and alkyltrimethylammonium bromides at the air/water interface

We have prepared and analyzed thin film structures formed by polyethylenimine and alkyltrimethylammonium bromide (CnTAB) surfactants at the air/water interface, using both surface and bulk sensitive techniques. In initial experiments it was observed that hexagonal arrays of rodlike micelles surrounded by the polymer were formed at the solution surface, with the principal axis of the micelles runni

Boronic acid dendrimer receptor modified nanofibrillar cellulose membranes

Cellulose nanofibrils from sisal of typically 4-5 nm diameter and ca. 250 ± 100 nm length are reconstituted into thin films of ca. 6 m thickness (or thicker freestanding films). Pure cellulose and cellulose composite films are obtained in a solvent evaporation process. A boronic acid appended dendrimer is embedded as a receptor in the nanofibrillar cellulose membrane. The number of boronic acid bi

Mesoporous silver films from dilute mixed-surfactant solutions by using dip-coating

A dilute mixed-surfactant solution to synthesize mesoporous silver films by using a dip-coating method was used for the creation of films over a large area of substrate. The method allows facile creation of films over a large area of substrate, unlike electrochemical deposition, and uses smaller amounts of surfactant than typical LLC syntheses. The silver ions in the solution, deposited in the int

Formation of CTAB-templated mesophase silicate films from acidic solutions

We have examined the effect of the different components in the spontaneous formation of surfactant-templated mesostructured silicate films grown at the air/solution interface. The rate of film formation shows differing dependencies on the concentrations of the silica precursor, tetramethoxysilane, the surfactant template, cetyltrimethylammonium bromide (CTAB), water and the solution pH. Further, w

Characterization of the structure of mesoporous thin films grown at the air/water interface using X-ray surface techniques

Grazing incidence X-ray diffraction (GIKD) and X-ray reflectivity have been used in situ to study the structure of surfactant-templated silica films grown at the air/water interface at different depths in the film. The results confirm that cylindrical silica-encased surfactant micelles are predominantly organized into a two-dimensional hexagonal structure, with the long axis parallel to the surfac

Self-assembly and phase behaviour of PEI : Cationic surfactant aqueous mixtures forming mesostructured films at the air/solution interface

Self-assembly processes and corresponding phase boundaries depend on the structure of interacting molecules. We have studied the effect of surfactant head-group structure and counterion on the self-assembly processes occurring in aqueous mixtures of the cationic polymer polyethylenimine (PEI) and the cationic surfactants cetyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB) and cety

Ultrathin carbon film electrodes from vacuum-carbonised cellulose nanofibril composite

A novel way to produce ultrathin transparent carbon layers on tin-doped indium oxide (ITO) substrates is developed. The ITO surface is coated with cellulose nanofibrils (from sisal) via layer-by-layer electrostatic binding with poly(diallyldimethylammonium chloride) or PDDAC acting as the binder. The cellulose nanofibril-PDDAC composite film is then vacuum-carbonised at 5008C. The resulting carbon

Mesoporous titanium dioxide films using partially fluorinated surfactant templates in ethanol

Mesoporous titanium dioxide films have been produced via a self assembly pathway at the air-ethanol interface using partially fluorinated surfactants as structure directing agents. The high level of surface activity displayed by partially fluorinated compounds in alcohols has been used to generate an ordered film at the air-solution interface, as titanium oligomers condense into an ordered inorgan

Liquid crystal codendrimers with a statistical distribution of phenolic and mesogenic groups : Behavior as langmuir and langmuir - Blodgett films

The first series of carbosilane liquid crystal codendrimers with groups of different polarity has been synthesized. The chemical structure of the newly synthesized materials and the composition of the codendrimers were studied by NMR spectroscopy and MALDI-TOF MS. It was found that the codendrimers tend to form stable Langmuir films at the air-water surface. The influence of composition and genera

Structural evolution of surfactant - Silica film-forming solutions, investigated using small-angle neutron scattering

Time-resolved small-angle neutron scattering has been used to investigate the evolution of micelles in the subphase of surfactant-templated silica film-forming solutions. Two samples have been prepared using cetyltrimethylammonium bromide (CTABr), as the structure-directing agent, and different amounts of tetramethoxysilane (TMOS) (CTABr/TMOS molar ratio 0.093, 0.139). The solutions have been repr

Accessibility of dye molecules embedded in surfactant-silica hybrid materials in both powder and film forms

Two CTABr-silica mesophases have been prepared, one of them as a powder with hexagonal structure containing Congo Red, the other one as a film with cubic structure containing Disperse Red 1. In the former case the dye has been occluded via co-entrapping, whereas in the latter it has been covalently anchored to the silica matrix via a co-condensation route. In both systems, the dye molecules proved

Accessibility to gases of dye molecules in hybrid surfactant-silica mesophases

Two types of CTABr-silica mesophases have been prepared, one of them a powder with hexagonal structure containing Congo Red, another one a film with cubic structure containing Disperse Red 1. In the former case the dye has been occluded via co-entrapping, whereas in the latter it has been covalently anchored to the silica matrix via a co-condensation route. In both systems, the dye molecules prove

Underpotential surface reduction of mesoporous CeO 2 nanoparticle films

The formation of variable-thickness CeO 2 nanoparticle mesoporous films from a colloidal nanoparticle solution (approximately 1-3-nm-diameter CeO 2) is demonstrated using a layer-by-layer deposition process with small organic binder molecules such as cyclohexanehexacarboxylate and phytate. Film growth is characterised by scanning and transmission electron microscopies, X-ray scattering and quartz

Macroscopic, mesostructured cationic surfactant/neutral polymer films : Structure and cross-linking

Mesostructured films of alkyltrimethylammonium bromides or cetylpyridinium bromide and polyethylenimines that spontaneously self-assemble at the air/water interface have been examined using a range of surface sensitive techniques. These films are unusual in that they can be micrometers thick and are relatively robust. Here we show that the films can be cross-linked and thus removed from the liquid

Template-induced crystal growth

The process of "mineralisation" in biology leads to a diversity of inorganic structures based on silica or calcium carbonate. Some of these are composite and, at the same time, highly crystalline. In all cases a molecular or self assembled "template" species has been identified as the promoter for the crystallisation of the new structure. In biology these "templates" are the end step in the convey

Concentration-dependent formation mechanisms in mesophase silica-surfactant films

The development of surfactant-templated mesoporous films grown at the air/water interface was investigated using specular and off-specular X-ray reflectivity techniques. The samples were prepared in acidic conditions using cetyltrimethylammonium bromide (CTABr, 0.075 M) and different concentrations (0.27-0.88 M) of tetramethyloxysilane (TMOS). At CTABr/TMOS molar ratio between 0.277 and 0.093, the