Isotropic solutions

The coupling constants of the hyperfme and the electron Zeeman interactions are scalar as long as radicals in isotropic solution are considered, leading to the Hamiltonian... 

Technora. In 1985, Teijin Ltd. introduced Technora fiber, previously known as HM-50, into the high performance fiber market. Technora is based on the 1 1 copolyterephthalamide of 3,4 -diaminodiphenyl ether and/ -phenylenediamine (8). Technora is a whoUy aromatic copolyamide of PPT, modified with a crankshaft-shaped comonomer, which results in the formation of isotropic solutions that then become anisotropic during the shear alignment during spinning. The polymer is synthesized by the low temperature polymerization of/ -phenylenediamine, 3,4 -diaminophenyl ether, and terephthaloyl chloride in an amide solvent containing a small amount of an alkaU salt. Calcium chloride or lithium chloride is used as the alkaU salt. The solvents used are hexamethylphosphoramide (HMPA), A/-methyl-2-pyrrohdinone (NMP), and dimethyl acetamide (DMAc). The stmcture of Technora is as follows ... 

The detection of Hquid crystal is based primarily on anisotropic optical properties. This means that a sample of this phase looks radiant when viewed against a light source placed between crossed polarizers. An isotropic solution is black under such conditions (Fig. 12). Optical microscopy may also detect the Hquid crystal in an emulsion. The Hquid crystal is conspicuous from its radiance in polarized light (Fig. 13). The stmcture of the Hquid crystalline phase is also most easily identified by optical microscopy. Lamellar Hquid crystals have a pattern of oil streaks and Maltese crosses (Fig. 14a), whereas ones with hexagonal arrays of cylinders give a different optical pattern (Fig. 14b). 

FIG. 35 The phase behavior of dodecane sulfonic acid with water. O, Doubly refracting material appears as the isotropic solution is cooled. <3, Isotropic solution appears as the liquid crystal is heated. CD, Crystalline solid disappears on heating. Pairs of solid points connected with the vertical dashed lines mark the appearance and disappearance of pseudoisotropy as samples are heated. The area ABC, within which the intermediate mesophase exists alone, is not precisely determined. 

The phase behavior of a-ester sulfonates has been studied in detail with methyl laurate and methyl palmitate [58]. In both cases, at higher temperatures, as the surfactant concentration increases, there is a transition from an isotropic solution to a hexagonal liquid crystalline phase and finally, at high surfactant concentrations, to a lamellar liquid crystal (Fig. 4). The crystal/liquid-crys-tal phase transition occurs at even higher temperatures as the chain length increases. On the other hand, chain length has practically no influence on the... 

Nuclear spins can be considered as dipoles that interact with each other via dipolar couplings. While this interaction leads to strongly broadened lines in soUd-state NMR spectroscopy, it is averaged out in isotropic solution due to the fast tumbUng of the solute molecules. In Uquid-state NMR spectroscopy, the dipolar interaction can only be observed indirectly by relaxation processes, where they represent the main source of longitudinal and transverse relaxation. 

Berry, G.C. Static and Dynamic Light Scattering on Moderately Concentraded Solutions Isotropic Solutions of Flexible and Rodlike Chains and Nematic Solutions of Rodlike Chains. VoL 114, pp, 233-290. 

Void RR, Prosser RS, Deese AJ (1997) Isotropic solutions of phospholipid bicelles a new membrane mimetic for high-resolution NMR studies of polypeptides. J Biomol NMR 9 329-335... 

A few synthetic helical polymers are known to act as chiral selectors.7a,918d l8k i9d i9h ancj are widely used as chiral stationary phases (CSP) in gas or liquid chromatography.73,53 Recently, it has been reported that the preference of one helical sense in isotropic solution can be induced by some interaction between optically inactive polymers and chiral solvents/additives. Examples of this include poly(n-hexyl isocyanate)18d l8k and poly(phenylacetylene)s bearing functional group.19d 19h The polysilane derivatives also show chiral recognition ability in solution at room temperature. Poly(methyl-ft-pinanylsilane) includes two chiral centers per bulky hydrophobic pinanyl side group28 and... 

As a particular example of materials with high spatial symmetry, we consider first an isotropic chiral bulk medium. Such a medium is, for example, an isotropic solution of enantiomerically pure molecules. Such material has arbitrary rotations in three dimensions as symmetry operations. Under rotations, the electric and magnetic quantities transform similarly. As a consequence, the nonvanishing components of y(2),eee, y 2)-een and y,2)jnee are the same. Due to the isotropy of the medium, each tensor has only one independent component of the xyz type ... 

From the form of the polarization it is clear that in order to observe any nonlinear optical effect, the input beams must not be copropagating. Furthermore, nonlinear optical effects through the tensor y eee requires two different input frequencies (otherwise, the tensor components would vanish because of permutation symmetry in the last two indices, i.e., ytfl eee = Xijy ) For example, sum-frequency generation in isotropic solutions of chiral molecules through the tensor y1 1 1 has been experimentally observed, and the technique has been proposed as a new tool to study chiral molecules in solution.59,61 From an NLO applications point of view, however, this effect is probably not very useful because recent results suggest that the response is actually very low.62... 

Concentrated (isotropic) solution p3. Once the concentration exceeds p2 the polymers have a tendency to align with each other. They still show a degree of disorder but over a limited concentration range both the dynamics and distribution of particles in space are substantially modified. This isotropic state is maintained up to a concentration pT which is of the same order as (bL2) l ... 

Since the rate constants of bimolecular diffusion-limited reactions in isotropic solution are proportional to T/ these data testify to the fact that the kt values are linearly dependent on the diffusion coefficient D in water, irrespective of whether the fluorophores are present on the surface of the macromolecule (human serum albumin, cobra neurotoxins, proteins A and B of the neurotoxic complex of venom) or are localized within the protein matrix (ribonuclease C2, azurin, L-asparaginase).1 36 1 The linear dependence of the functions l/Q and l/xF on x/t] indicates that the mobility of protein structures is correlated with the motions of solvent molecules, and this correlation results in similar mechanisms of quenching for both surface and interior sites of the macromolecule. 

Figure 8. Binary phase diagram of Cj GE -water system. G gel phase, N neat phase, I isotropic solution, II two liquid phase...

The hydrotropic action of a dicarboxylic acid is discussed against the general features of hydro-tropic action the liquid crystal/isotropic solution equilibrium. It is shown that the hydrotropic action of the dicarboxylic acid in question, 8-[5(6)-carboxy-4-hexyl-cyclohex-2-enyl] octanoic acid, depends on its conformation at an interface. 

The carboxylic acids were combined with hexylamlne and water in order to study the association structures formed. The hexyl-amine was chosen because it did not by Itself form a liquid crystalline phase with water. Fig. 3A. Water dissolves in the amine to a maximum of 60% to form an isotropic solution. The liquid crystal is formed first at a certain octanoic acid amine ratio, approximately 0.1. The liquid crystalline phase forms a large region reaching to a weight fraction of 0.61 of the acid, corresponding to a 1 1 molar ratio of the two species. 

The results are straight forward and the interpretation immediately evident. The liquid crystalline phase formed in these extremely water rich systems was destabilized by the dicarboxylic acid and transformed to an isotropic solution. The conclusion that the hydrotropic action of the dicarboxylic acid is intimately related to its capacity to destabilize a liquid crystalline phase also under the water-rich conditions during actual laundering conditions appears well justified. 

As is well known, hydrotropes are incorporated in liquid detergent formulations in order to produce transparent (isotropic) solutions at high solids concentrations which will be stable under varying conditions of temperature and... 

In that case the self diffusion coefficient - concentration curve shows a behaviour distinctly different from the cosurfactant microemulsions. has a quite low value throughout the extension of the isotropic solution phase up to the highest water content. This implies that a model with closed droplets surrounded by surfactant emions in a hydrocarbon medium gives an adequate description of these solutions, found to be significantly higher them D, the conclusion that a non-negligible eimount of water must exist between the emulsion droplets. 

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