Polyelectrolyte interpenetration

The inner structure of polyelectrolyte multilayer films has been studied by neutron and X-ray reflectivity experiments by intercalating deuterated PSS into a nondeut-erated PSS/PAH assembly [94, 99]. An important lesson from these experiments is that polyelectrolytes in PEMs do not present well-defined layers but are rather interpenetrated or fussy systems. As a consequence, polyelectrolyte chains deposited in an adsorption step are intertwined with those deposited in the three or four previous adsorption cycles. When polyelectrolyte mobility is increased by immersion in NaCl 0.8 M, the interpenetration increases with time as the system evolves towards a fully mixed state in order to maximize its entropy ]100]. From the point of view of redox PEMs, polyelectrolyte interpenetration is advantageous in the sense that two layers of a redox polyelectrolyte can be in electrochemical contact even if they are separated by one or more layers of an electroinactive poly ion. For example, electrical connectivity between a layer of a redox polymer and the electrode is maintained even when separated by up to 2.5 insulating bUayers [67, 101-103]. 

So, the PVA/poly(sodium styrene sulphonate) [PSSNa] blend was obtained by casting aqueous solution of polymers mixture (PVA with Mw= 124,000-186,000 and HD=99% and PSSNa with Mw= 70,000). The resulted films were crosslinked with 1,2-dibromethane in gaseous phase. A semi-interpenetrating network (SIPN) in which polyelectrolyte (PSSNa) chains are trapped inside a based PVA network was obtained [44], A totally miscible blend with a very good film clarity and high mechanical resistance [44] resulted. 

In scenario (c) corresponding to semidilute solutions, polyelectrolyte chains interpenetrate. Under these circumstances, there are three kinds of screening. The electrostatic interaction, excluded volume interaction, and the hydro-dynamic interaction between any two segments of a labeled polyelectrolyte chain are all screened by interpenetrating chains. Each of these three interactions is associated with a screening length, namely, and These screening... 

Repulsive forces between Fe oxide particles can be established by adsorption of suitable polymers such as proteins (Johnson and Matijevic, 1992), starches, non-ionic detergents and polyelectrolytes. Adsorption of such polymers stabilizes the particles at electrolyte concentrations otherwise high enough for coagulation to occur. Such stabilization is termed protective action or steric stabilization. It arises when particles approach each other closely enough for repulsive forces to develop. This repulsion has two sources. 1) The volume restriction effect where the ends of the polymer chains interpenetrate as the particles approach and lose some of their available conformations. This leads to a decrease in the free energy of the system which may be sufficient to produce a large repulsive force between particles. 2) The osmotic effect where the polymer chains from two particles overlap and produce a repulsion which prevents closer approach of the particles. 

Kudaibergenov SE, Dolya NA, Tatykhanova GS et al (2007) Semi-interpenetrating polymer networks of polyelectrolytes. Eurasian Chemical Technological Journal 9 177-192... 

Liu GM, Zhao JP, Sun QY et al (2008) Role of chain interpenetration in layer-by-layer deposition of polyelectrolytes. J Phys Chem B 112 3333-3338... 

On the other hand, the increase of concentration of the polymer components leads to the suppression of the dissociation of the polyelectrolyte components due to the rise in the electrostatic repulsion within inter- and intramacromolecules and to the interpenetration of polymer chains. 

Witten TA, Pincus P. Structure and viscosity of interpenetrating polyelectrolyte chain. Europhys Lett 1987 3 315-320. 

Other nonionic hydrogels Polyelectrolyte networks Interpenetrating networks... 

Figure 3. Schematic of the electrostatically driven layer-by-layer adsorption process. It describes the case of the adsorption of a polyanion to a positively charged substrate (A), followed by washing (B), the adsorption of a polycation (C) and another washing step (D). Multilayer films are prepared by repeating steps (A) through (D) in a cyclic fashion. More complicated film architectures are obtained by using additional adsofption/washing steps and applying more than two polyelectrolytes. Note that the drawing is oversimplified with respect to polyion conformation and interpenetration of adjacent layers. Furthermore, any counterions that might be present in the films were omitted for reasons of clarity.

The hydrophobic polyelectrolyte chain appears rigid due to the electrostatic repulsion along the chain. In the concentrated solutions, the electrostatic repulsion will be gradually screened due to interpenetration of polyelectrolyte chains (Dobrynin and Rubinstein 2001). According to (4.68), the critical overlap concentration for the transition from the dilute solution to the concentrated solution is... 

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