a) b - École Polytechnique de Montréal

organic thin films, a novel and straightforward method was developed in the last decade(G.
Decher & Hong, 1991a; Nicolau, 1985). It was observed(G. Decher & Hong, 1991a) that
polyelectrolytes with opposite charges could be assembled in an alternating layer by layer
method onto a substrate to generate a sequential multilayer organic thin film(G. Decher, Hong, &
Schmitt, 1992b). The potential utility of this method is to obtain thin, uniform electrically
conductive films on a variety of substrates, as was shown by Rubner and his group(Cheung, Fou,
Ferreira, & Rubner, 1993; Cheung, Fou, & Rubner, 1994; Cheung, Stockton, & Rubner, 1997). It
was found that two consecutive layers are strongly interpenetrated, although some researchers
believe that the layers are locally interpenetrated and diffusion from one polyanion layer to the
neighboring polyanion layer can not occur,(Farhat, Yassin, Dubas, & Schlenoff, 1999) but some
other authors mention that a network of two co-continuous layers is generated(Cheung, et al.,
1997).
In such a film-forming technique, layer-by-layer deposition of different polyelectrolytes with
opposite charges is involved to fabricate molecularly controlled ultrathin multilayer films(Tse et
al., 2007). Electrostatic interactions are the cause of the adsorption of layers. Kinetic trapping of
charge species from solution on the surface can be described as film assembly( Decher, 1997).
Repetitive deposition steps provide a precise control over the total thickness of the layers in the
range from a few angstroms up to the micrometer range. The LbL technique, unlike other film
fabrication processes such as the Langmuir-Blodgett (LB)(Blodgett, 1934; Zasadzinski,
Viswanathan, Madsen, Garnaes, & Schwartz, 1994) technique, which requires particular
equipment, has no limitation on the type of substrate and charge-bearing species. Consequently,
LbL is a simple method and considerably more versatile than other techniques.
Decher et al.(G. Decher & Hong, 1991b) developed the LbL deposition method since it has been
extensively used to construct thin films of well-defined thicknesses for a wide variety of
applications that can be divided into two categories(Decher & Schlenoff, 2003): 1) tailoring
surface interactions, such as corrosion protection(Farhat & Schlenoff, 2002), sensors(Decher,
Hong, & Schmitt, 1992a), antibacterial(Rudra, Dave, & Haynie, 2006), antistatic coating for
electrophoresis(Graul & Schlenoff, 1999), and biosensing(Yipeng Sun, 1996), and 2) fabrication
of surface base devices such as electro-optic materials(Fou, Onitsuka, Ferreira, & Rubner, 1996),
devices including nanoreactors(Joly et al., 2000), electrochromic windows(DeLongchamp &
Hammond, 2001), or even in the area of surface patterning for the deposition of quantum dots
67