Aggregate increased water content

With increasing water content, the ionic domains swell from 40 to 50 A in diameter and the structure of fhe membrane is fhoughf to consist of spherical ionic domains joined by cylinders of wafer dispersed in fhe polymer matrix. Within this region of wafer confenf, proton conductivify steadily increases. At > 0.5, a morphological inversion occurs in which a connected network of aggregated polymer "rods" is now surrounded by water. This network continues to swell for X, = 0.5 —> 0.9 and fhe conductivify of fhe membrane approaches the values observed for Nafion solutions. 

Luttrull et al. assessed the extent of dye interaction in a series of rationally synthesized dimeric Rose Bengals (Figure 14). Based on extensive studies of the spectra of these compounds in ethanol and ethanol-water, these workers concluded that the compounds exist in an open conformation in EtOH, but that the extent of dye/dye interaction increases as the solution becomes more aqueous. Thus the extinction coefficient at the maximum decreases as the amount of ethanol in the solution decreases. The more hydrophobic the groups at C-6 (changing, for example, from Na to tributylammonium), the more changing the solvent toward an increasing water content decreases the extinction coefficient, that is, enforces aggregation. 

Figure 14 also shows the particle size as a function of water content in the microemulsion for different Ni(II) concentrations. An increase in the average diameter is observed with increasing proportion of water. The decrease in the number of micellar aggregates Nm) with water (Table 13a) is accompanied by an increase in their size. For the same Ni( II) concentration with respect to water (i.e., for the same probability of collision between the ions in the same water core), the total number of nuclei formed in the early stage of the reduction decreases with increasing water concentration, and more ions can participate in the growth process. This results in an increase in the particle size. One should also keep in mind that the total number of Ni(II) ions also increases with increasing water content. This is also shown if the size of the particles is plotted as a function of micellar droplet concentration (Fig. 15). For most of the systems studied a monotonous decrease in the size with increasing N f is observed. These results reinforce the hypothesis leading to the computation of the number of nuclei and underline the importance of the water cores as reaction cages.

There were attempts to relate the permeability of concrete to the properties of interfacial transition zone. However, the unambiguous results were not obtained. According to Roy [142], the constraction of interfacial transition zone surface does not play important role in concrete permeability, while Valenta [143] has quite opposite opinion. This problem will be discussed in Chap. 6 where the construction and properties of interfacial transition zone will be presented [144], In the light of the studies by Richet and Oliver [145] it is evident that the porosity of inteifacial transition zone in traditional concretes (w/c = 0.5 or more) has a significant influence on the permeability of concrete this permeability is a hundred times higher than in the case of cement paste and rises with the size of aggregate (Fig. 5.68). However, the effect of the transition zone on the diffusion of ions is not so evident, because the locally increased water content in this zone, decrease the w/c ratio in cement matrix outside it, which consequently limits the diffusion, thus a total effect can be negligible [145],... 

Small amounts of water can be solubilized inside the micelle via Interaction between the polar groups and the water molecules which stabilize these aggregates. If the water contents Increase above a certain limit further stabilization via Increased Interaction between the hydrophobic part and the a-polar solvent is necessary to stabilize the system, which is then called a microemulsion (15-18). In any case, the increased water contents may lead to significant changes of the micellar solution not necessarily limited to the size of the aggregates if more water molecules are incorporated but also to structural rearrangements of these aggregates. 

The conformational changes of the C-C and O-C bonds in the L2 phase with increasing water content or with increasing temperature depend on the position of the bond in the chain. These characteristic conformational changes should be correlated with the formation of varying aggregate structures in this phase. 

The order of magnitude of the factor F is constant, but its value decreases with increasing water content in the microemulsion (see Tables la and lb). This phenomenon can be easily understood because the rearrangement rate of the microemulsion decreases with the water amount and hence the number of aggregates reached by the reducing agent before rearrangement decreases. 

In many cases, under changing experimental conditions, water-containing reversed micelles evolve, exhibiting a wide range of shapes such as disks, rods, lamellas, and reverse-vesicular aggregates [15,107,108], Nickel and copper bis(2-ethylhexyl) sulfosucci-nate and sodium bis(2-ethylhexyl) phosphate, for example, form rod-shaped droplets at low water contents that convert to more spherical aggregates as the water content is increased [23,92,109,110],... 

Pt/MWNT) [20,21], fine and homogeneous Pt nanoparticles deposited on MWNTs were obtained when pure EG was used as the solvent or less water (<5vol.%) was introduced. With the increase in water content, aggregation of the metal nanoparticles occurred, the average particle size increased and the particle size distribution became wider. 

Increasing the initial concentration of zeaxanthin to 10 4 M, Figure 8.6b, produces a different dependence on the ethanol/water ratio. Under these initial conditions, adding water to a final ethanol/water ratio of 3 2 leads to a distinctly different absorption spectrum than that observed at lower initial concentration. The vibrational structure of the S2 state is preserved and a new absorption band characteristic of J-aggregates appears at 530 nm. When the water content was increased... 

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