Multilayered Clay Films:  Atomic Force Microscopy Study and Modeling

Abstract

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.

Ultrathin polymer coatings by complexation of polyelectrolytes at interfaces: suitable materials, structure and properties

“…The use of charge platelets deriving from exfoliated layered crystals seems particularly interesting to us, due to their small, molecular dimensions, and their intermediate character between polyelectrolytes and nanoobjects. This includes delaminated clay platelets such as the positively charged hydrotalcite 136,311) and the negatively charged hectorite 11,147,150,[312][313][314][315][316] , montmorillonite 11,136,138,270,285,311,[317][318][319][320][321] , or saponite 147,316) . Multilayer growth proceeds linearly after the regime of the first layers (see above) as determined by using colored polymers of opposite charge (Fig.…”

“…26 and 27). AFM and X-ray diffraction measurements show that the platelets tend to lie flat on the substrate with little overlap 312,316,319,322) . In some cases, more than one layer of platelets may be deposited 270,311,312) which may be explained on the basis of charge balances 62) .…”

“…Also, their smooth surface renders them well suited for X-ray reflectivity studies 131,312,381,382,385) and for near-field microscopy. For these purposes, mica 75,103,104,201,252,253,281,316,323,348,386,387) and float glass 19,80,131,180,182,184,185,388,389) present alternatives. Gold coated surfaces enable electrochemical studies 86,196,205,209,211,340,354,390,391) , investigations by quartz crystal microbalance (QCM) 65,86,102,119,130,202,238,266,279,305,338,339,350,…”

Fast assembly of bio-inspired nanocomposite films

“…Similar influence of PDDA solution concentration on the film roughness has already been observed for the dipping self-assembly film-formation process. 32 The higher roughness was explained using increasing concentrations of PDDA with higher amount of PDDA at the surface inducing aggregation of the clay particles and inhomogeneous incorporation of polymer.…”

Preparation of Oda-Clay Hybrid Films by Langmuir–blodgett Technique

“…[3][4][5] Thin films of clay minerals have been studied in application to modified electrodes, sensors, photochromic devices, nonlinear optical devices, and so on. [6][7][8][9][10][11][12][13][14] One of the outstanding properties of the clay is the simultaneous incorporation of polar or ionic molecules into the interlamellar spaces (intercalation) [15][16][17] resulting in hybrid materials. The property of intercalation makes it easy to prepare the composite materials.…”