Lyotropic properties

Critical micellar concentrations (CMCs) of sucrose fatty acid esters have been determined by various methods, for mixtures and for pure derivatives (Table III).95,126,390 395 Studies on the lyotropic properties of sucrose... 

In spite of the frequent use of ammonium sulfate, other hydrophobic association promoting salts can be useful at neutral pH. In that way, it is possible to select the degree of lyotropic property adapted to the antibody to purify (see Table 6). 

Ferrocene was functionalized at the 1,1 -positions by a sugar moiety (1-amino-l-deoxy-D-sorbitol) and a long alkyl chain 44 in order to obtain lyotropic properties. The substituents, in particular the sugar framework, were selected in view of successful investigations performed with organic-type amphiphilic carbohydrate surfactants. Compound 44 showed both thermotropic and lyotropic mesophases. In the bulk, a SmA phase formed from 98 to 137 °C. When 44 was mixed with an excess of water, a fluid phase was obtained. For the thermotropic SmA phase, a r/-layer spacing... 

Due to their importance for life sciences, for example the formation of biological membranes, and their technical importance as surfactants and soaps, potential lyotropic properties of amphiphilic compounds are much better investigated than other ones of different molecular types the broad field of surfactant liquid crystals is discussed in Chapter VII of this volume. 

For amphotropic liquid crystals it is obvious that the so-called surfactants (including for example soaps) are the best investigated, as documented in two reviews [61, 62]. Therefore, an own chapter of this book is dedicated to that field of supramolecular chemistry (see Chapter VII of this volume). Since the lyotropic properties of this type of amphotropic liquid crystals are discussed there in detail, we focus now mainly on the thermotropic behavior of such compounds. 

The o ,a -alkylenedisulfate salts of lithium, sodium, and potassium, M(03S0(CH2) 0S03)M with n=l2, 14, 16, and 18, were reported to possess lyotropic properties in water, with the supposed existence of two critical micelle concentrations.The second cmc was explained by the existence of a rearrangement of the existing aggregates into another type of aggregate. 

Most of the rigid rod systems form a liquid crystalline phase when cast from a suitable solvent and hence exhibit lyotropic properties. 

Lyotropic Properties (Hofmeister Series Ion-Specific Effects)... 

In addition to their lyotropic properties, Hpids can also behave as thermotropic liquid crystals in a similar fashion to the rod-like liquid crystal molecules described in Chapter 2. In aqueous solution, the primary organization of the lipid phase is lyotropic however, the internal structural organization of the bilayer will vary as a function of temperature. In thinking about these thermotropic Hpid phases, it is helpful to consider the lipid to be in the lamellar phase, then to vary the temperature of this phase and look at the effects of temperature on molecular ordering within the bilayer. Lyotropic organization itself is also dependent on temperature, but more weakly so. For the following discussion, assume that the Hpids are organized in a lamellar phase composed of stacked Hpid bilayers. 

Figure 2 displays a comparison of the dependence of the hydrodynamic radii os derived from QELS measurements (Eq. 2) on CD vesicles and porphyrin/ CD systems as a function of CD concentration. In the absence of TPPS, mean values for the vesicles increase from 120 to lOOOnm, as a function of the CD concentration (in the range 1 x 10 -6 x 10 " M) thus confirming the lyotropic properties of CD. On adding TPPS (high values of the porphyrin/CD ratio), sensitive increase of the mean vesicle occurs. 

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