64 Sara Llamas, Laura Fernández-Peña, Ana Mateos-Maroto et al.
ab
Reprinted with permission from Reference [220]. Copyright (2011) American
Chemical Society.
Figure 13. Alternative models for explaining the non-linear growth mechanism LbL
polyelectrolyte multilayer. (a) Island model. (b) Dendritic model.
The controversy related to the correlation between the appearance of
interdiffusion in the multilayer assembly and the non-linear growth is not
completely solved. Haynie et al. [220] have proposed that the non-linear
growth does not need of the existence of interdiffusion and can be explained
by the growth and coalescence of isolated polymer domains or by the
appearance of dendritric growth as schematized Figure 13. Thus, the
interdiffussion can be compatible with both linear and non-linear growth.
Similar conclusion have been raised by Guzman et al. [30] on the basis of the
adsorption kinetics of the layers. Thus, the growth mechanism depends on the
specific chemical characteristic and conformations of the polyelectrolytes.
5.4. Adsorption Kinetics
The same complex intricate balance of interactions affecting the
adsorption and growth of polyelectrolyte multilayers plays a central role on the
adsorption kinetics for the deposition of the successive layers. The only
quantitative model developed for the study of the adsorption kinetics of
polyelectrolyte multilayers follows the Raposo-Avrami model [23, 24, 27, 29,
35, 114] described above for the adsorption of polyelectrolytes. However, the
dependences of the characteristic times on N provide important insights on the
multilayer formation. In most of the multilayers studies in the literature, τ 1 is
rather independent on N. However, a strong dependence has been found with