Surfactant molecules attachment

The proposed mechanism of effect of surfactant and ultrasound is reported in Fig. 7.5. The long chain surfactant molecules attach to surface of nanoparticles due to physical adsorption. Only thin layer is adsorbed onto the CaC03 nanoparticles. Due to presence of ultrasound and use of surfactant will control the nucleation. Surfactant keeps the particles away from each other by preventing flocculation due to change in surface tension of reaction mass. The concentration of additives was changed from 0.2 to 1.0 g/L. Addition of 0.2 g/L tripolyphosphate shows the increase in the rate of precipitation which is determined from the Ca(OH)2 consumption. Polyacrylic acid shows the least rate of precipitation (0.115 mol/1), which... 

The effect of linear charge density ( ) on the interaction has been a part of many studies. These studies have shown that with the decrease in there is a less effective screening of the charges on the surfactant molecules attached to the backbone of polymer. This results in a larger repulsion and consequently a smaller aggregation number. From a thermodynamic point of view, less work is needed to move the polyelectrolyle from the micelle when the charge density is small. A decrease in the aggregation number with the decrease in % is consistent with an increase in CAC. 

The small-angle neutron-scattering experiments have proven that the surfactant molecules attach to the polymer chains in the form of micelles. The surfactant micelles on polymer chains are similar to the micelles in the polymer-free surfactant solution. The only difference is the aggregation number, which is less for a surfactant-polymer system compared to the polymer-free solution. However, the radius of gyration of the polymer molecule in a surfactant-polymer system is comparable to that of a free macromolecule (Ruckenstein et al. 1987) in the absence of any surfactant. 

The flotation of minerals is based on different attachment forces of hydrophobized and hydrophilic mineral particles to a gas bubble. Hydrophobized mineral particles adher to gas bubbles and are carried to the surface of the mineral dispersion where they form a froth layer. A mineral is hydrophobized by the adsorption of a suitable surfactant on the surface of the mineral component to be flotated. The hydrophobicity of a mineral particle depends on the degree of occupation of its surface by surfactant molecules and their polar-apolar orientation in the adsorption layer. In a number of papers the relationship was analyzed between the adsorption density of the surfactant at the mineral-water interface and the flotability. However, most interpretations of adsorption and flotation measurements concern surfactant concentrations under their CMC. 

The pore diameter of the resulting materials, their specific surface area and mesopore volume depend on the size of attached ligands (see Table 1). The presence of bonded alkylsilyl groups (appropriate ratio C H) and a successful removal of all surfactant molecules and pyridine (complete absence of nitrogen) was shown by means of the elemental analysis. Table 1 contains also the surface coverage of the bonded ligands. 

This micelle is comprised of surfactant molecules consisting of long hydrocarbon tails attached to an anionic lyophilic group. Typically, there are 50-100 molecules in the micelle. Some counterions in the medium are adsorbed on the aggregate, whereas others form the diffuse ionic environment. Some workers believe that there is considerable penetration of the medium into the micelle. Micelles are important for detergent action, with oily dirt particles dissolved in the hydrocarbon interior of the micelle. 

FIGURE 9 Attachment of surfactant molecules to crystal surfaces. 

Fig. 3.11. Folding of T4 DNA by the addition of the gemini surfactant. Distributions of the long-axis length of T4 DNA at different concentrations [cs] of the surfactant. Coil, partially folded, and completely folded states are distinguished by the different colorings. Also shown are FM and AFM images with the corresponding schematic representation of the partially folded state ([cs] =0.2 pM) and completely folded state ([cs] = 1.0pM). The FM and AFM observations are of the same DNA molecules attached to a mica surface. A rings-on-a-string structure is clearly seen for the partially folded DNA, while the completely folded DNA assumes a network structure composed of many fused rings (see [19] for more details)...

There is a way to suspend even smaller monomer particles in water such that the monomer droplets are stable and do not aggregrate to form a separate layer. Essentially, a surfactant (soap) is used to form an emulsion. Surfactant molecules consist of a polar head (hydrophilic) group attached to a non-polar (hydrophobic) tail, such that it looks something like a tadpole, as depicted in Figure 3-46. 

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