Factors affecting phase behaviour

Of the many factors which affect the nature of the phase diagram of ionic surfactants, the most influential is probably the nature of the solubilizate. Ekwall 

Homogeneous mesomorphous phase displaying lamellar structure (mucous woven type). 

Homogeneous mesomorphous phase displaying normal two-dimensional tetragonal structure. 

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It was a century ago that researchers started to study the factors affecting the behaviour of water-oil-surfactant systems but it is only with the introduction of Winsor s R theory (1954) that the formulation effects could be interpreted. Winsor s R theory was the first qualitative description of the formulation, paving the way to an understanding of how intermolecular interactions among the different chemical species present in a system are related to its behaviour. Throughout the following decades, several empirical experimental correlations such as the phase inversion temperature (PIT), semiempirical ones such as the cohesive energy ratio (CER), and models based on thermodynamics such as the surfactant affinity difference (SAD) or the hydrophilic-lipophilic deviation (HLD) [15, 143, 144] led... 

While it is believed that solute-solute interactions are not as large as solute-solvent interactions, there is clear evidence that some type of solute-solute interaction is present in SCF/high molecular mass systems. Lockemann [49] studied the phase behaviour of the ternary system C02/methyl myristate/methyl palmitate and found that these two components can be separated using SC CO2. However, the separation factor, which dictates the degree or difficulty of separation, is dependent on the composition of the feed to be separated and the operating pressure and temperature. They found that while the composition does not significantly affect the separation factor, better separation can be achieved at lower composition of the component to be extracted. 

The morphology of IPNs can be determined by electron microscopy. The morphology has a great influence on the physical and mechanical behaviour. The phases differ, however, in amount, size and shape, sharpening of their interface and degree of continuity. The factors affecting morphology are chemical compatibility of the polymers, interfacial tension, crosslink density of the networks, polymerization methods and IPN composition. 

In the case of electrochemically promoted (NEMCA) catalysts we concentrate on the adsorption on the gas-exposed electrode surface and not at the three-phase-boundaries (tpb). The surface area, Ntpb, of the three-phase-boundaries is usually at least a factor of 100 smaller than the gas-exposed catalyst-electrode surface area Nq. Adsorption at the tpb plays an important role in the electrocatalysis at the tpb, which can affect indirectly the NEMCA behaviour of the electrode. But it contributes little directly to the measured catalytic rate and thus can be neglected. Its effect is built in UWr and [Pg.306]

We performed a systematic molecular and behavioural screen to identify locomotor factors secreted by the SCN. To find secreted factors not previously documented in the SCN, we screened a hamster SCN cDNA library in a yeast secretiomtrap system (Klein et al 1996). We then carried out a behavioural screen in which newly identified and previously documented (Earnest et al 1999, Miller et al 1996, Ma et al 1992) SCN factors were tested for an effect on circadian locomotor activity by constant infusion into the 3rd ventricle of hamsters for 2 to 3 weeks (Kramer et al 2001). In general, constant infusion of a SCN locomotor factor should alter locomotor activity reversibly without affecting the underlying SCN circadian clock. A locomotor inhibitory factor, for example, should block locomotor activity for the duration of the infusion. Because the SCN clock should not be affected, the circadian rhythm of locomotor activity should reappear with its expected phase and period upon cessation of the infusion, fn contrast, constant infusion of SCN factors involved only in outputs other than locomotor activity should have no effect on locomotor behaviour. 

Apart from a few general rules, the alloying behaviour of metals is rather empirical. The classical rules of Hume-Rothery [220] explain this behaviour reasonably well. Such factors as size, electronegativity, valency, electron concentration, free energy, formation of intermediate phases and isomorphism are found to influence the alloying tendency of metals. However, size and electronegativity are the two most important factors, and they profoundly influence the solubility of the solute atoms and greatly affect the crystal structures of the alloys. 

It must be emphasised that the various stages of phase separation and the final structures obtained depend on many factors, some of which are considered in later sections. The previous paragraphs represent idealisations of what may happen during real polymer blend processing. One of the most important factors that determine the behaviour of a polymer blend is the way that temperature affects the AG i curve, which is now considered. 

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