Polyelectrolyte complexes polyion

Ionic polymers contain counterions that neutralize the charges on the bound ions. The counterions maybe grouped into three types (1) univalent, (2) di- or trivalent and (c) polymeric. Polymers with polymeric counterions are often called polysalts, polyelectrolyte complexes, polyion complexes, simplexes, or coacervates. 

Polyelectrolyte complexes formed by polyion pairing are of special interest, including protein-polyelectrolyte interactions such as protein-DNA complexes. A special case of polyelectrolyte complexes are polyelectrolyte multilayers (PEM) on surfaces formed by ion pairing, van der Waals interactions and counterion release of oppositely charged polyelectrolytes [2, 3]. 

IZU Izutmudov, V.A. and Sybachin, A.V., Phase separation in solutions of polyelectrolyte complexes The decisive effect of a host polyion, Polym. Sci., Ser. A, 48, 1849, 2006. 

The unique stmcture of cylindrical bmshes makes them ideal candidates to (1) experimentally and theoretically study the phase separation in quasi -ID molecular objects, (2) investigate the properties of polyelectrolyte complexes of shape-persistent polyions, (3) elucidate the adsorption on planar surfaces, and eventually (4) develop novel cationic carriers for gene transfection, as described in detail in Sect. 4. 

Polyanions and polycations can co-react in aqueous solution to form polyelectrolyte complexes via a process closely linked to self-assembly processes [47]. Despite progresses in the field of (inter-) polyelectrolyte complexes [47] (IPEC from Gohy et al. [48], block ionomer complexes BIC from Kabanov et al. [49], polyion complex PIC from Kataoka and colleagues [50, 51], and complex coacervate core micelles C3M from Cohen Stuart and colleagues [52], understanding of more complex structures such as polyplexes (polyelectrolyte complexes of DNA and polycations) [53] is rather limited [54]. It has also to be considered that the behavior of cationic polymers in the presence of DNA and their complexes can be unpredictable, particularly in physiological environments due to the presence of other polyelectrolytes (i.e., proteins and enzymes) and variations in pH, etc. 

Dragan ES, Mihai M, Schwarz S (2006) Polyelectrolyte complex dispersions with a high colloidal stability controlled by the polyion structure and titrant addition rate. Colloid Surf A... 

These particles are called by several names in literature block ionomer complexes [57], polyion complex micelles [58], complex coacervate core micelles [59] and polyelectrolyte complex micelles. An extensive review of this type of micelle has been written by Voets et al. [60]. 

During the last decade, the potential for synthesis and constmction of novel complex multicomponent self-organized IPEC-based structures has considerably increased as polyelectrolytes and polyionic species with nonlinear topology have become available. Among those are polymeric nucelles with polyelectrolyte coronas, star-shaped polyelectrolytes, and cylindrical polyelectrolyte bmshes. Polyionic species of such types themselves possess often a pronounced capability for selforganization, which is expected to be enhanced when they are incorporated into complex macromolecular structures such as IPECs. The advanced IPECs based on polyionic species with nonlinear topologies are cmisidered in Sect. 3 of this review. 

Further progress in the field of IPECs has been associated with involvement of more complex polyionic architectures, such as branched ionic (co)polymers (polyelectrolyte stars and cylindrical polyelectrolyte brushes) as well as self-assemblies of linear ionic diblock copolymers (polymeric micelles) (Fig. 6a-c), into interpolyelectrolyte complexation. Synthesis of well-defined polymeric architectures with nonlinear topology has become possible only recently due to considerable developments in living and controlled polymerizations. In this section, we briefly... 

Kramarenko EY, Khokhlov AR, Reineker P (2006) Stoichiometric polyelectrolyte complexes of itmic block copolymtas and oppositely charged polyions. J Chem Phys 125(19), 194902. doi 10.1063/1.2387173... 

The polyion complex technique [15] was proposed as a convenient preparative method to immobilize water-soluble, bilayer-forming amphiphiles and polymers as composite thin films. A water-insoluble polyion complex is precipitated when the aqueous solution of the charged bilayer membrane is mixed with a water solution of the countercharged polyelectrolyte. The polyion complex mono-layer also can be formed in situ when the charged amphiphiles are directly spread on the surface of the aqueous polyelectrolyte solution. The principle of the polyion complex LB technique has been expanded into a general and simple alternative deposition method of charged polymers by Decher [16] (this volume chapter 12). 

Polyion complex technique is a unique method of supramolecular polymerization of bilayer membranes without conventional polymerization procedures [14,50], Water-insoluble polyion complexes are precipitated when the aqueous solution of the charged bilayer membrane is mixed with a water solution of the countercharged polyelectrolyte. The polyion complexes can be formed as thin films by usual casting from organic solutions. The fundamental bilayer structure and characteristics are essentially maintained in the immobilized cast films of the polyion complexes. X-ray diffraction of the solvent cast polyion complex films reveals the layered structure with repeating spacing corresponding to the bilayer thickness [50-52]. 

Polyanion-polycation-complexes are known for a long time on an empirical basis from the mutual precipitation of proteins. Already at the end of the previous century Kossel [1] recognized the electrostatic interaction between the oppositely charged polyions as the driving force for precipitation. Willstaetter [2] also introduced the term symplexes for polyelectrolyte complexes. 

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