Head group polyelectrolyte

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. 

The polar, ionic and even non-ionic head-group interactions of lipid membranes and other surfactants, (as indeed for many polymers and polyelectrolyte intra-molecular interactions) and the associated curvature at interfaces formed by such assemblies will be dependent on dissolved gas in quite complicated ways. Fluctuating nanometric sized cavities at such surfaces will be at extremely high pressure, (P = 2y/r, y= surface tension, and r the radius) resulting in formation of H and OH radicals. The immediate formation of Cl radicals and consequent damage to phospholipids offers em explanation of exercise-induced immunosuppression (through excess lactic acid CO2 production), perhaps a clue to the aging process. 

Fig-1 The model system. An amphiphile, in most cases with an ionic hydrophilic head group and two aliphatic tails at the air/water interface with easy manipulation of surface pressure, it, and molecular area, A. Polyelectrolyte dissolved in the subphase may bind to the monolayer... 

This family of noncovalently bonded PLCs may also include polyelectrolyte + surfactant complexes which, as will be seen, can also give rise to liquid crystalline mesophases. In these complexes there is only a flexible alkyl chain attached to the ionic head group in the small molecule constituent, with no rigid aromatic core present. Since surfactants themselves are frequently thermotropic liquid crystals, it is not surprising that their complexes with polyelectrolytes may produce PLCs, in both cases driven by the incompatibility between the ionic and aliphatic parts leading to amphitropic systems [27]. 

Counterions condense on a polyelectrolyte when the charge density, created by the head groups along the polyelectrolyte exceeds a critical value (i). As increases, more counterions condense so that the net charge density of the polyelectrolyte remains at the critical value. Constant net charge density has been demonstrated by using pH (2,3), refractive index (4), ultrasound absorption (5), and C NMR relaxation rates (Q. 

Due to the high water solubility of a divalent cationic head-group, a violo-gen amphiphile 3 (n = 12, m = 5) [56] could not form a stable monolayer on a pure water subphase. A monolayer is stabilized when an anionic polyelectrolyte is added to the water subphase. Pressure-area (ji-A) isotherms of the complex monolayers are shown in Fig. 4. The shape of the pressure-area isotherms is strongly dependent upon the chemical structure of the anionic polyelectrolyte. A condensed monolayer was formed over a highly diluted solution (ca. 0.06 mM)... 

Su et al. (Xiao et al., 2008) fabricated a new type of thermotropic liquid-crystalline photosensitive supramolecular ionic self-assembly of polyelectrolyte and functional unit azobenzene IL crystal (azo-ILC), where the thermal and phase behaviors can be modulated by changing the spacer length (methylene units in azo). Ma et al. (Ma et al., 2008) found that the addition of very small amounts of an alcohol or water into tri-n-decylmethylphosphonium chloride and bromide salts (IPlOX) induced the formation of liquid crystalline, where strong association between the hydroxyl groups of alcohol or water and the head groups of IPlOX is indicated. 

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