Polyelectrolytes amphiphile complex

Lehmann, P., Symietz, C., Brezesinski, G., Krass, H., Kurth, D.G. Langmuir and langmuir-blodgett films of metallosupramolecular polyelectrolyte-amphiphile complexs. Langmuir 21, 5901-5906 (2005). doi 10.1021/la050841p... 

Fig. 12 Formation of Langmuir bottom left) and L-B bottom right) films of the polyelectrolyte-amphiphile complex PAC at an air-water interface. Adapted from [60]. Reprinted with permission from the American Chemical Society...

The complexation of polyelectrolyte with surfactants, which include numerous low and medium weight amphiphiles as well as lipids, has been investigated for many years nearly exclusively in solution as reviewed by Goddard [112]. Since 1994, starting with work by Antonietti et al. [15], polyelectrolyte-surfactant complexes (PE-surfs) in the solid state have also become of increasing interest. For some reviews see [1, 4-7, 113]. 

Liquid crystals combine properties of both liquids (fluidity) and crystals (long range order in one, two, or three dimensions). Examples of liquid crystalline templates formed by amphiphiles are lyotropic mesophases, block copolymer mesophases, and polyelectrolyte-suxfactant complexes. Their morphological complexity enables the template synthesis of particles as well as of bulk materials with isotropic or anisotropic morphologies, depending on whether the polymerization is performed in a continuous or a discontinuous phase. As the templating of thermotropic liquid crystals is already described in other reviews [47] the focus here is the template synthesis of organic materials in lyotropic mesophases. 

Figure 21 shows three possible routes to obtain oriented PAV films by the LB technique. In these route, it is anticipated that orientational orderliness of precursor polymers is introduced in the precursor LB films through the formation of two-dimensionally oriented monolayer of a polyelectrolyte precursor-anionic amphiphile polyion complex at the air/subphase interface and orientation of the precursor monolayers along the dipping direction dining the deposition process. As a result, it is expected to obtain oriented PAV LB films with well-developed jt-coryugation system. In this study, we successfully prepared oriented PAV films using two routes of them, b-1 and b-2 route [35-37]. The chemical structures of PAVs, their polyelectrolyte precursors and an anionic amphiphile used in this study are shown in Fig.22. 

Miyasaka, K . PVA-Iodine Complexes Formation, Structure and Properties. VoL 108, pp. 91-130. Morishima, Y. Photoinduced Electron Transfer in Amphiphilic Polyelectrolyte Systems. VoL 104, pp. 51-96. 

The complex formation of PECs and PE-surfs is closely linked to self-assembly processes. A major difference between PECs and PE-surfs can be found in their solid-state structures. PE-surfs show typically highly ordered mesophases in the solid state [15] which is in contrast to the ladder and scrambled-egg structures of PECs [2]. Reasons for the high ordering of PE-surfs are i) cooperative binding phenomena of the surfactant molecules onto the polyelectrolyte chains [16-18] and ii) the amphiphilicity of the surfactant molecules. A further result of the cooperative zipper mechanism between a polyelectrolyte and oppositely charged surfactant molecules is a 1 1 stoichiometry. The amphiphilicity of surfactants favors a microphase separation in PE-surfs that results in periodic nanostructures with repeat units of 1 to 10 nm. By contrast, structures of PECs normally display no such periodic nanostructures. 

The area per amphiphile can be adjusted by complexation of ionic amphiphiles with polyelectrolytes having the opposite charge. The areal requirements of the complex are determined by the distance of the ionic... 

The first example of an azobenzene amphiphile polyelectrolyte complex was reported by Shimomura and Kunitake. They used poly(vinylsulfate) 23 to stabilize an ammonium amphiphile (21, n = 5). Because the tertiary ammonium head group is rather large and the distance of the ionic sites in poly(vinylsulfate) is rather small, the packing of the amphiphiles is not sipti-ficantly loosened by the complexation. In this case, the influence of the poylelectrolyte on the spectral properties and the photoisomerization is small. 

Rod—coil copolymers are a type of amphiphile that can self-assemble into a variety of ordered nanostructures in a selective solvent.36-37-71 In solvents that selectively dissolve only coil blocks, rod—coil copolymers can form well-defined nanostructures with rod domain consisting of the insoluble block. This results in an increase of the relative volume fraction of the coil segments relative to the rod segments, which gives rise to various supramolecular structures. Particularly, poly(alkylene oxide) as the coil block of rod—coil molecule has additional advantages due to complexation capability with alkali metal cation, which can provide an application potential for solid polyelectrolytes and induce various supramolecular structures.72-75... 

For the present system, we demonstrate the amphiphilic character of the complexed polyelectrolyte to override its amphoteric characteristics. There-... 

FIG. 11 Schematic illustration of the different types of complexes (a) with long polymers (interchain aggregates are formed essentially in the case of Coulombic complexation of polyelectrolyte and protein) (b) with short amphiphilic polymers (hydrophobic association). 

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