Lyotropic influence

That the Stern -correction is necessary for the understanding of the differences between electrolytes of one valency type (lyotropic influence) was already explained in Part II. 

Fig. 29 shows the same for KI, KBr, KCl and KF. In both figures so-called lyotropic influences of the anions are clearly seen, these causing the curves to bundle... 

In the flocculations or coacervations which are discussed in this paragraph indications of this kind are indeed very clearly present. The required concentrations of the neutral salt are here not necessarily very high, on the contrary they are frequently relatively low. In so far as lyotropic influences are also found in the coacervations or flocculations now in question, they are not due to a binding of the water as mentioned above, but to the fact that the interaction between the ionised groups of the colloid and the ions of the salt is influenced by the same factors (radius, polarisability) which determined the order of the ions in the lyotropic series. 

On the other hand we find complex flocculation or coacervation rather at relatively low electrolyte concentrations. They are the more pronounced the greater the charge density of the colloid. The effectiveness of the ions is in the main determined by their valency over which lyotropic influences are superposed. We sometimes find here that the sequence of the ions is just the opposite of that in the normal lyotropic series (for example of the monovalent anions, with the positive proteins, compare also p. 299, Fig. 22) and we have in this a clear indication of the complex character of the flocculation. 

For the interpretation of individual differences between ions of the same valency (lyotropic influences) in the salting in of globulins the considerations on ion sequences as treated in 2s, p. 376 (c.f. also p. 429, 6f.) may also be helpful. 

The mixing of nematogenic compounds with chiral solutes has been shown to lead to cholesteric phases without any chemical interactions.147 Milhaud and Michels describe the interactions of multilamellar vesicles formed from dilauryl-phosphotidylcholine (DLPC) with chiral polyene antibiotics amphotericin B (amB) and nystatin (Ny).148 Even at low concentrations of antibiotic (molar ratio of DLPC to antibiotic >130) twisted ribbons are seen to form just as the CD signals start to strengthen. The results support the concept that chiral solutes can induce chiral order in these lyotropic liquid crystalline systems and are consistent with the observations for thermotropic liquid crystal systems. Clearly the lipid membrane can be chirally influenced by the addition of appropriate solutes. 

Most of the work on transport in lyotropic liquid crystals has dealt not with thin oriented layers but with samples made up of many small regions with varying orientations. Transport coefficients obtained from these experiments are thus averaged over orientation. The macroscopic structure of the liquid crystal can significantly influence transport. 

Lyotropic liquid crystals Due to the influence of a penetrating solvent which intercalates into the lattice, a long-range orientational order depending on the individual lyotropic phase is given, but no positional ordering can be observed. Common examples are soaps or the double layers of lipid structures. 

The affinity is influenced by salt concentration in accordance with the Hofmeister series. It is increased in the presence of lyotropic anions such as sulphate and decreased in the presence of chaotropic anions at the other end of the series such as thiocyanate. Anions from the middle of the scale such as chloride have little effect on binding. 

Since most liquid crystalline phases used today are lyotropic mesophases with a relatively small magnetic susceptibility anisotropy, it should be noted that the orientation of the director is also influenced by the inertial torque when... 

The results showing augmentation of the surfactant alcohol ratio for maximum aqueous solubility with added electrolytes are not amenable to a similarly simple explanation, and the influence of the presence of electrolytes must be discussed against the relative stability of the inverse micelles and of the lyotropic liquid crystalline phase with which the inverse micellar solution is in equilibrium (7). 

Lyotropic liquid crystal phases are formed by amphiphihc molecules (surfactants, block copolymers) in solution, driven by repulsive forces between hydrophobic and hydrophihc parts. In a polar solvent, the hydrophihc parts associate with the solvent, whereas the hydrophobic parts interact to form the interiors of micelles (as in low-molecular smfactants). Micelles can be spherical, rod-like or discotic in shape. The contour of the micelle is determined by the relative sizes of the hydrophihc and hydrophobic groups. MiceUe shapes are influenced by solvent, concentration and temperatme. 

In practice, double layers are rarely entirely diffuse, and to analyse such features as the lyotropic sequence in. and the influence of adsorbates on, colloid stability, it is necessary to also compute the Gibbs energy AG for Gouy-Stem layers. 

Later, Perzon et al. ) reported the same sequence for the influence of electrol 4es on the stability of CjgCOOH monolayers. In sec. 11.3. lOh, (see table 11.3.8), we discussed and interpreted lyotropic sequences for double layers on a variety of solids. It depends on the nature of this solid how the sequence looks. It now appears that the present sequence is the same as it is on oxides like a-Fc203 and Y-AI2O3. For Li as the counterion the interaction with the head groups is mainly of an electrostatic origin, and strong. For the large, hydrophobic cations TMA and TEA this type of... 

Friberg SE, Wohn CS, Lockwood FE. The influence of solvent on nonaqueous lyotropic liquid crystalline phase formed by triethanolamine oleate. / Pharm Sci 1985 74(7) 771-773. 

Triphenylenes provided with nonionic di(ethylene oxide) side-chains (25f)132 134 or with ionic alkyl chains (25g)135 form supramolecular polymers in water.136 The arene—arene interactions of the aromatic cores allow for the formation of columnar micelles . At low concentrations the columns are relatively short, and the solutions are isotropic. At higher concentrations the longer columns interact and lyotropic mesophases are formed.133 Computer simulations showed that in the isotropic solution the polymerization of the discotics is driven by solute-solute attraction and follows the theory of isodesmic linear aggregation the association constants for dimerization, trimerization, and etc., are equal and the DP of the column thus can easily be tuned by concentration and temperature.137 138 At higher concentrations the sizes of the columns are influenced by their neighbors, the columns align, and the DP rises rapidly. 

The influence of lyotropic compounds on the specific rotation of levoglucosan (6) is completely negligible.385-387 The o.r.d spectrum of 6 is a simple, negative curve257 (compare Ref. 388). 

The extensive research on microemulsions was prompted by two oil crises in 1973 and 1979, respectively. To optimise oil recovery, the oil reservoirs were flooded with a water-surfactant mixture. Oil entrapped in the rock pores can thus be removed easily as a microemulsion with an ultra-low interfacial tension is formed in the pores (see Section 10.2 in Chapter 10). Obviously, this method of tertiary oil recovery requires some understanding of the phase behaviour and interfacial tensions of mixtures of water/salt, crude oil and surfactant [4]. These in-depth studies were carried out in the 1970s and 1980s, yielding very precise insights into the phase behaviour of microemulsions stabilised by non-ionic [5, 6] and ionic surfactants [7-9] and mixtures thereof [10]. The influence of additives, like hydro- and lyotropic salts [11], short- and medium-chain alcohols (co-surfactant) [12] on both non-ionic [13] and ionic microemulsions [14] was also studied in detail. The most striking and relevant property of micro emulsions in technical applications is the low or even ultra-low interfacial tension between the water excess phase and the oil excess phase in the presence of a microemulsion phase. The dependence of the interfacial tension on salt [15], the alcohol concentration [16] and temperature [17] as well as its interrelation with the phase behaviour [18, 19] can be regarded as well understood. 

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