Class I Materials

To understand the effects produced, it is necessary to distinguish between two classes of organic materials that markedly affect the CMCs of aqueous solutions surfactants class I, materials that affect the CMC by being incorporated into the micelle and class II, materials that change the CMC by modifying solvent-micelle or solvent-surfactant interactions. 

Class I Materials Materials in the first class are generally polar organic compounds, such as alcohols and amides. They affect the CMC at much lower liquid phase concentrations than those in the second class. Water-soluble compounds in this class may operate as members of the first class at low bulk phase concentrations (Miyagishi, 1976) and, at high bulk phase concentrations, as members of the second class. 

Members of class I reduce the CMC. Shorter-chain members of the class are probably adsorbed mainly in the outer portion of the micelle close to the water-micelle interface. The longer-chain members are probably adsorbed mainly in the outer portion of the core, between the surfactant molecules. Adsorption of the additives in these fashions decreases the work required for micellization, in the case of ionic surfactants probably by decreasing the mutual repulsion of the ionic heads in the micelle. 

Depression of the CMC appears to be greater for straight-chain compounds than for branched ones and increases with chain length to a maximum when the length of the hydrophobic group of the additive approximates that of the surfactant. An explanation for these observations (Schick, 1957) is that those molecules that are most effective at reducing the CMC are solubilized in the outer portion of the micelle core and are there under lateral pressure tending to force them into the inner 

Just as polar compounds that are believed to penetrate into the inner portion of the core produce only small depressions of the CMC, so, too, hydrocarbons, which are solubilized in the inner portion of the core, decrease the CMC only slightly. Very short-chain polar compounds, (e.g., dioxane and ethanol) at low bulk phase concentrations also depress the CMC, but the effect here, too, is small (Shirahama, 1965). In these compounds, adsorption probably occurs on the surface of the micelle, close to the hydrophilic head. 

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FPN No. 1) For additional information on the properties and group classification of Class I materials, see Manual for Classification of Gases, Vapors, and Dusts for Electrical Equipment in Hazardous (Classified) Locations, NFPA 497M-1991, and Guide to Eire Hazard Properties ofElammable Liquids, Gases, and Volatile Solids, NFPA 325—1994. 

Based on the strength of the electronic coupling between the metals, Robin and Day [105] have developed a system in which mixed-valence compounds are broadly distinguished in three classes. In a very weakly coupled or Class I material, only the properties of the individual mononuclear species are observed due to the lack of communication ( = 0). In the other extreme, a Class III com-... 

The CMC of the surfactant in the aqueous phase is changed very little by the presence of a second liquid phase in which the surfactant does not dissolve appreciably and which, in turn, either does not dissolve appreciably in the aqueous phase or is solubilized only in the inner core of the micelles (e.g., saturated aliphatic hydrocarbons). When the hydrocarbon is a short-chain unsaturated, or aromatic hydrocarbon, however, the value of the CMC is significantly less than that in air, with the more polar hydrocarbon causing a larger decrease (Rehfeld, 1967 Vijayendran, 1979 Murphy, 1988). This is presumably because some of this second liquid phase adsorbs in the outer portion of the surfactant micelle and acts as a class I material (Section C). On the other hand, the more polar ethyl acetate increases the CMC of sodium dodecyl sulfate slightly, presumably either because it has appreciable solubility in water and thus increases its solubility parameter, with consequent increase in the CMC of the surfactant, or because the surfactant has appreciable solubility in the ethyl acetate phase, thus decreasing its concentration in the aqueous phase with consequent increase in the CMC. 

For the class I materials, the salt (ES-I) is the primary form, obtained from the polymerization. EB-1 is prepared indirectly by de-doping the polymerization product. The class II materials are approached via the base form EB-II, which is obtained from EB-I either by dissolution in NMP or DMSO and casting, or by an... 

Dielectric materials are classified according to their temperature susceptibility. Alumina and LTCC are very stable and belong to the class I materials. High-K materials show a higher temperature dependency (class II). Figure 9.57 depicts the capacitance vs. temperature for a printed high-K capacitor embedded in LTCC. 

Dielectric materials fall into two classes Class I used for linear capacitors and Class II used for non-linear capacitors. In general. Class I materials are natural dielectrics such as glass and mica and have capacitances within the range of a couple to several hundred picofarads. When capacitors use Class I materials, the capacitance will not change with a dynamic operating voltage and frequency. Class I dielectric materials are more costly. 

Inorganic-organic hybrids are divided into two classes based on the nature of the interface. In Class-I materials the organic and inorganic phases are... 

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