| Abstract
| - Positively charged polydiallyldimethylammoniumchloride, P, was found to bind strongly to the surfaceof anionic montmorrillonite, M, platelets in aqueous dispersions up toa saturation (estimated to correspond to thebinding of five P to one 1.0 nm × 200 nm M platelet) beyond whichreversible physisorption occurred. Immersionof a substrate (glass, quartz, silica-wafer, gold, silver, and evenTeflon) into an aqueous 1% solution of P and rinsingwith ultrapure water for 10 min resulted in the strong adsorption of a1.6 nm thick P on the substrate. Immersionof the P coated substrate into an aqueous dispersion of M and rinsingwith ultrapure water for 10 min led to theadsorption of 2.5 nm thick M. Repeating the self-assembly steps ofP and M for n number of times produced(P/M)nself-assembled films. Thickness of the M layer was found to dependon the external voltage applied during itsself-assembly: applying a positive potential during the self-assemblyof M increased the thickness of the M layer;application of a small negative potential decreased it slightly;however, larger negative voltages augmented it. Thestructure of self-assembled (P/M)n films havebeen characterized by a variety of techniques: X-ray diffraction,X-rayreflectivity, atomic force microscopy, transmission electronmicroscopic, and surface plasmon spectroscopicmeasurements. It was shown that clay platelets form stacks uponadsorption to the polymer layer consisting on theaverage two aluminosilicate sheets. The evolution of the surfaceroughness upon sequential deposition of P/M layerswas observed by in situ AFM. Large etchedpits, up to 700 nm diameter and 30 nm depth, were smoothedduringP/M deposition. Small pits (188 nm diameter and 14 nm deep) werecapped after one P/M deposition cycle. Surfaceroughness of (P/M)n films was estimated by anumber of methods including surface plasmon spectroscopy.Theoverall roughness did not appear to correlate with the type ofsubstrate used. On the other hand, application of anexternal electric field during the self-assembly of P stronglyinfluenced the surface morphology. Application of anegative potential during the self-assembly of P improved theuniformity and regularity of the deposited layers.
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