29.06.2013 Views

a) b - École Polytechnique de Montréal

a) b - École Polytechnique de Montréal

a) b - École Polytechnique de Montréal

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

on the previously formed layer, establishing a larger structure. At this step, while most of the<br />

PLL chains have diffused out onto the surface, free mobile PGA chains present in the solution<br />

start to diffuse into the multilayer. This time, charge overcompensation is the result of an excess<br />

amount of PGA chains in solution. Again, free PGA chains diffuse out, and these processes<br />

repeat themselves alternately, resulting in a continuous film reconstruction and leading to an<br />

increase in the thickness of the multilayers. Part of the free chains of either polyelectrolyte come<br />

out during the rinsing step with a free aqueous solution. The increase of thickness at each step is<br />

proportional to the mass of PGA/PLL complexes that form on the surface of the multilayer,<br />

which are proportional to the free mobile PLL or PGA chains with weak bonds, that can easily<br />

diffuse out of the film.<br />

a)<br />

Figure 2-43. Penetration of polyelectrolyte chain inward and outward of a multilayer film<br />

Some other polyanion/polycation systems showing linear evolution in thickness increment<br />

generate <strong>de</strong>nser multilayer structures and avoid polyelectrolyte diffusion insi<strong>de</strong> the film. Two<br />

b)<br />

f) e) d)<br />

c)<br />

84

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!