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This is relatively new method of multilayer structure deposition proposed by Decher and Hong in 1991 [25]. It is based on consecutive physical adsorption of alternatively charged molecules from the solutions onto solid substrate. Thus, the driving force of adsorption is the ionic attraction between opposite charges and no covalent bonds need to be formed.

 

 

Molecules which form a monolayer of a given type must be of bipolar structure with identical charges at the ends. In this case the process of adsorption stops itself after full covering of the surface because electrostatic repulsion between identically charged molecules prevents further adsorption. The process can be continued only if the substrate with previously deposited monolayer is immersed in the solution of oppositely charged bipolar molecules.

 

 

Method of layer-by-layer adsorption was first developed for cationic and anionic bipolar amphiphiles. Then it was extended to alternate deposition of amphiphiles with polyelectrolytes, polyelectrolites of different types, polyelectrolytes with proteins, and polyelectrolytes with nucleic acids.

 

 

"Superlattices" of complex compositions including the films built up by the combination of LB and layer-by-layer adsorption methods were also prepared and investigated.

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Basic principles of the method

                                                       are described in Refs. [25-27].

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