Self-assembled natural and synthetic clay−polymer films have been prepared by sequential adsorption of poly(diallyldimethylammonium chloride) (PDDA) and clay particles onto mica. The influence of pH, polymer concentration, and clay particle size on the building and roughness of mono- and multicycle depositions was investigated. The monocyclic deposition gives a submonolayer of clay particles. The thickness of the films increases linearly with the number of cycles in the deposition process, thus giving an average increase of thickness per cycles which depends on clay particle size and PDDA concentration. The film roughness is affected by the same parameters and increases with particle size of the clay and PDDA concentration. Optimal conditions for the deposition of smooth multilayer films consist of the combined use of a 0.05−0.5% (w/w) aqueous solution of PDDA and a 0.05% (w/w) clay suspension at pH = 9−10. The film formation was modeled assuming a deposition of homogeneous layers partially covering the surface. The model indicates that Laponite films are characterized by significantly higher surface coverages than natural clay films.

Ammonium-functionalised monodisperse silica spheres have been prepared and spread together with sodium dodecylsulfate at the air-water surface. The resulting particulate films have been deposited on various substrates. The Langmuir isotherm has been used to estimate the density and refractive index of the particles. The films exhibit vivid optical diffraction due to a high degree of ordering of the particles. The lattice constant of this two-dimensional opal structure has been determined by atomic force microscopy at 536 nm. Optical diffraction of the films has been established and explained in terms of a Bragg-like diffraction. The lattice constant, as determined by optical diffraction, is found to be in good agreement with the AFM measurement, within experimental error. We consider this Langmuir-Blodgett deposition of 2D opal as a promising route for the preparation of active layers in photonic band gap devices and materials.

Fuzzy assembled multicompound films consisting of natural and synthetic colloidal clay particles, poly(diallyldimethylammonium chloride) (PDDA) and the dyes methylene blue (MB+) and 4-{4-[N-allyl-N-methylamino]phenylazo}benzenesulfonic acid, sodium salt (NAMO-) have been prepared. The organization of the clay particles was imaged by means of atomic force microscopy. Fuzzy assembled glass/clay/methylene blue films have been investigated by visible spectroscopy, and the spectra were explained in terms of the substrate−clay interaction and clay particle overlap. Glass/clay/PDDA/NAMO films were investigated by means of absorption spectroscopy, polarized absorption spectroscopy, and second harmonic generation. The nonlinear optical properties of the films were found to be determined by the adsorbed amount of NAMO and its noncentrosymmetric organization. These factors are in turn governed by the substrate type, the PDDA concentration, and the clay type. Optimized second harmonic generation for the glass/laponite/PDDA/NAMO films was found in which the clay particles are deposited onto a (3-aminopropyl)trimethoxysilane modified glass surface and PDDA chains are adsorbed from a 0.1 M solution.

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