Growth Mechanism of Polyelectrolyte Multilayers

Keywords Chain interpenetration Chain conformation Layer-by-layer Electrostatic interaction Specific ion effect Ion pair Chain rigidity Chain architecture 

The sequential layer-by-layer (LbL) deposition of oppositely charged polyelectrolytes on a solid substrate can generate a polyelectrolyte multilayer (PEM) [1-3]. Because of the potential applications of PEMs in various fields, the growth of PEMs has been investigated extensively [4—7]. In general, the formation of PEMs 

Liu and G. Zhang, QCM-D Studies on Polymer Behavior at Interfaces, SpiingerBiiefs in Molecular Science, DOI 10.1007/978-3-642-39790-5 4, The Author(s) 2013 

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Fig. 12 Alternative models to explain the non-linear growth mechanism of polyelectrolyte multilayer. The substrate is the horizontal slab. The film resulting from successive polymer adsorption steps is shown in different level of gray, a Island model, b Dendritic model. Reprinted with permission from Ref. [162]. Copyright (2011) American Chemical Society...

Schlenoff JB, Dubas ST (2001) Mechanism of polyelectrolyte multilayer growth charge overcompensation and distribution. Macromolecules 34 592-598... 

The research efforts, both theoretical and experimental, have tried to understand mainly the growth mechanism, and the dependence of the adsorbed amount of material on the number of adsorbed layers, N, as well as on the developments of the potential applications of this type of materials [13]. Despite this extensive research certain physico-chemical properties related to these systems remain not well-understood yet [16]. This lack of knowledge affects especially to the understanding of the growth mechanism, internal structure and molecular properties of polyelectrolyte multilayers, and to their cross relationships [80, 90-95]. 

The formation of polyelectrolyte multilayers by the LbL approach is the result of an intricate balance between different contributions that determines both the growth and structure of the PEMs as well as the properties of the obtained films. Among the factors that govern the assembling of these polyelectrolyte layers special attention must be paid to the competence between mainly electrostatic interactions and entropic contributions to the assembling. The interplay between these contributions determines different physico-chemical properties of the obtained films such as the ionic pairing, the roughness, and the hydration of the films that play a main role in the mechanical properties and permeability of the multilayers. 

Arys, X., Laschewsky, A. and Jonas, A.M. Ordered polyelectrolyte multilayers . 1. Mechanisms of growth and structure formation a comparison with classical fuzzy multilayers . Macromolecules, 2001. 34(10) p. 3318-3330. 

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