Cylindrical Polyelectrolyte Brushes

In the following text recent progress in the field of polyelectrolyte brushes is reviewed. In the first section the theory of polyelectrolyte brushes is briefly summarized and some more recent simulation results are shown. In the next section several aspects of the synthesis and the elucidation of the physicochemical properties of polyelectrolyte brushes are discussed. In the following section adaptive and responsive polymer surfaces based on mixed polyelectrolyte brushes are introduced, followed by a section on cylindrical polyelectrolyte brushes, in which charged polymer chains are attached to the backbone of other polymers. Finally some perspectives for further developments in the field of polyelectrolyte brushes are given. 

In the following text we focus on cylindrical brushes prepared by polymerization of macromonomers, in particular on two systems. First, cylindrical brushes consisting of poly-2-vinylpyridine side chains and a poly-methacrylic main chain are discussed these were converted into cationic polyelectrolyte brushes by quaternization of the pyridine units by alkyl halides. The second system comprises sulfonated anionic cylindrical brushes, i.e. polymacromonomers with polystyrene side and main chains and polymacromonomers with polymethacrylic main and polymethacrylic acid side chains. 

Table 6 Light-scattering and IR characterization of cylindrical polyelectrolyte brushes prepared by quaternization of PVP brushes...

In summary, the light-scattering investigations support the results obtained by conductivity measurements that the effective charge density of cylindrical polyelectrolyte brushes is much smaller than for linear flexible polyions. 

Table 10 Light-scattering characterization of cylindrical polyelectrolyte brushes in aqueous 10-2 mol L-1 NaCl solution ...

Polyelectrolyte brushes constitute a new class of material with very interesting physicochemical properties. The strong stretching of the polymer chains due to segment-segment interactions and electrostatic forces introduce completely new physical properties into monolayers consisting of polyelectrolyte brushes and also into cylindrical brush systems. With the develop-... 

For any practical application of polyelectrolyte brushes the influence of multivalent ions, hydrophobic ions, and other polyelectrolyte molecules present in a contacting solution on to the structure of the surface-attached layers or the cylindrical polyelectrolyte brushes are of utmost importance. In particular, study of the interaction of brushes with other polyelectrolyte molecules in solution might open an avenue for the understanding of interaction of proteins or other charged biomolecules such as DNA, as a special form of charged macromolecules, with charged surfaces. It has become clear that not only the influence of the surface on to the conformation of the protein, but also the influence of the protein on the structure of the polymer layer is important. 

Inter-Poly electrolyte and Surfactant Complexes of Cylindrical Polyelectrolyte Brushes... 

Cylindrical polyelectrolyte brushes can form complexes with oppositely charged surfactants and polyelectrolytes. Although the polyelectrolyte cylindrical brushes behave similarly to their linear analogs when forming complexes with surfactants, their distinctive cylindrical nanostructures make it possible to visualize directly the morphology changes by microscopy such as AFM. 

Abstract This review reports advances in experimental and theoretical research on interpolyelectrolyte complexes based on polyionic species of star-shaped polyelectrolytes, cylindrical polyelectrolyte brushes, and micelles of ionic amphiphilic block CO- and terpolymers. 

Keywords Co-assembly Cylindrical polyelectrolyte brushes Interpolyelectrolyte complexes Ionic amphiphilic block copolymers Micelles Polyelectrolytes Star-shaped polyelectrolytes... 

IPECs Based on Cylindrical Polyelectrolyte Brushes 3.1 Experimental Results... 

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... 

Fig. 6 A polyelectrolyte star (a), a micelle with a polyelectrolyte corona (b), and a cylindrical polyelectrolyte brush (c)...

Fig. 11 Charge mismatch for IPECs of cylindrical polyelectrolyte brushes with DNA (a) excess of DNA and (b) excess of the cylindrical polyelectrolyte brush. Reprinted with permission from [71] Copyright 2007 American Chemical Society...

Fig. 12 Snapshots of the typical conformation of (a) the bare (uncomplexed) cylindrical polyelectrolyte brush, and (b,c) its IPECs with the linear GPE at the degrees of charge compensation of 0.25 (b) and 0.5 (c). Reprinted from [74] with permission from the Royal Society of Chemistry Copyright 2009...

Neither the main nor the side-chain dimensions of ionic cylindrical brushes differ significantly from their uncharged counterparts. Obviously, the osmotic swelling is not significant for the present small side-chain lengths, i.e. Psc<50. The intermolecular structure factor of ionic cylindrical brushes are difficult to interpret. The intermolecular distances derived from the peak of the structure factor is different for H+ and Cs+ counter-ions and is always significantly smaller than the mean distance calculated from the concentration of the particles and the known molar mass. Thus, a two state model may also be postulated for the present cylindrical polyelectrolyte structures. 

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