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Mechanisms of Heterophase Polymerization
Published in Hugo Hernandez, Klaus Tauer, Heterophase Polymerization, 2021
Micelles (or surfactant aggregates) are formed after reaching certain saturation in the continuous phase denoted as the critical micelle concentration (CMC). It should be noted that the CMC depends on temperature as well as the concentration of electrolytes and other components (also monomer) in the continuous phase. Thus, when applying CMC values to evaluate emulsion polymerization, one should use experimental data obtained under conditions as close as possible to those under polymerization. If a macromolecule is captured by a micelle, segregation of the polymer takes place and thus, a new polymer particle is formed. This mechanism of particle formation is called micellar nucleation [8]. Compare in this context the critical discussion regarding the coexistence of monomer drops and swollen micelles in Section II.
Systematic Study of Low-Cost, High-Performance Chemical Flooding as EOR for Depleted Oilfields of the Upper Assam Basin
Published in Subrata Borgohain Gogoi, Advances in Petroleum Technology, 2020
Miranda Kakoty, Subrata Borgohain Gogoi
The principal limitation of most chemical flooding is adsorption of surfactants on the reservoir rock surface. As the clay of porous media of the Upper Assam Basin is negatively charged [39], an anionic surfactant is preferred. The porous media repels the anionic surfactant and thus shows low adsorption effects. This led to the selection of anionic surfactants for the porous media of Upper Assam. BL is a highly toxic compound and can cause severe health hazards to humans and poses a threat to aquatic life if disposed of without treatment. Thus, prior to discharge, it must undergo proper treatment, which, in turn, has high financial implications. Therefore, proper strategic use of BL for surfactant EOR may not only provide economic recovery of residual oil but also save the environment from its hazards. Figure 6.1 shows the IFT behaviour of crude oil with BL, and Fig. 6.2 shows the IFT behaviour of the oil sample with different surfactant mixtures, each containing BL. The reservoir temperature of the Barail sand block is reported as 70°C–90°C. The CMC is the concentration at which the surfactant solution begins to form micelles in a large amount and all additional surfactants added to the system go to micelles.
Solution Properties
Published in Thomas J. Bruno, Paris D.N. Svoronos, CRC Handbook of Basic Tables for Chemical Analysis, 2020
Thomas J. Bruno, Paris D.N. Svoronos
Where available, the critical micelle concentration (CMC), the concentration of the surfactant above which micelles spontaneously form in water, is provided. The preferred unit is mM, but in the case of mixtures, this is provided as a percent or ppm, usually on the basis of mass (mass/mass). The CMC is dependent on temperature and the ionic strength of the solution, and is also dependent to some extent on the measurement technique. For anionic and cationic surfactants, the CMC is reduced by increasing ionic strength, but temperature has a minor effect. For nonionic surfactants, the CMC is relatively insensitive to ionic strength but increases with increase in temperature. For the values provided here, the temperature is provided where possible. If not provided, the temperature is to be regarded as ambient.
Two new cationic Gemini surfactants: synthesis, surface activity, and applicability as a corrosion inhibitor
Published in Journal of Dispersion Science and Technology, 2023
The data listed in Table 2 show that the values of CMC decrease with the increment of the experimental temperature. As we all know, the solution temperature has two opposing effects on the formation of micellar. First, the degree of hydration around the hydrophilic tail decreases with the increment of temperature, which favors the micellization process; while the latter is disruption of the water structure around the hydrophobic group by which the surfactants disfavor the micellization process.[20,23–25] By analyzing the data from Table 2, the former plays a major role. Hence the CMC values decrease with the increase of the experimental temperatures. In addition, the values of 2C12GeQS decrease by 1–3 order of magnitude than those of conventional monomeric surfactant (DTAB) and other Gemini surfactants having the same alkyl chain (12-PG-12). This may be due to that the strong hydrophobic effect among two hydrophobic alkyl tails indicates that the prepared surfactant has a greater ability to form micelles than the single-chain surfactant (DTAB).
Comparative solubilization of reactive dyes in single and mixed surfactants
Published in Journal of Dispersion Science and Technology, 2022
Sadia Noor, Muhammad Babar Taj, Senthilkumar M., Iram Naz
Surfactants are amphiphilic substances that facilitate the solubilization of additives and excipient molecules through a partitioning mechanism. These are useful products not only in nature but also in industries.[1,8,9] These molecules get adsorbed at the water–air interface even at very low concentrations and form self-aggregates (micelles). The micelle formation occurs on reaching a threshold level of concentration which is designated as critical micelle concentration (CMC). Quantification of this CMC can be estimated using various techniques: UV–Visible spectroscopy, conductometry, surface tension, and fluorometry.[10–16] The micelles are isotropic motifs of the surfactants having a hydrophilic head and a hydrophobic tail. Micellar solutions play a vital role in enhancing the solubility of less soluble or sparingly substances in aqueous media by the solubilization process.[17] Dye–surfactant aggregation provides useful insight into many industrial and chemical processes and also gives information about dye separation processes. Dye–surfactant interaction depends primarily on the nature and chemical structures of the participating dyes and surfactants.[16,18,19] The intermolecular forces which are dominant during such associations include hydrogen bonding, hydrophobic and electrostatic interactions, Van der Waals forces, and π-stacking.[20–23]
Removal of linear alkylbenzene sulfonate (LAS) by a cetyltrimethylammonium bromide (CTAB)-aided coagulation-filtration process
Published in Environmental Technology, 2022
Naoyuki Kishimoto, Shinya Hamamoto
The formation of CTAB-LAS aggregates was determined during Run A. Figure 2 depicts the absorbance at 660 nm and the zeta potential of CTAB-LAS aggregates against the CTAB/LAS molar ratio. Figure 2 clearly shows that the absorbance had a sharp peak at a CTAB/LAS molar ratio of 0.83, which meant that the aggregate formation was enhanced at this molar ratio. The critical micelle concentrations (CMC) of LAS and CTAB were reported as 1.6 mM [15] and 0.97 mM [17], respectively. Since the LAS concentration and CTAB dose in Run A were lower than the CMCs, CTAB had a positive effect on the aggregate formation of LAS. Previous research has shown that four factors mainly affect the CMC, namely the surfactant structure, the temperature of the solution, the presence of organic additives, and the presence of electrolytes [15]. Since CTAB is a cationic organic chemical, the latter two factors were thought to have contributed toward lowering the CMC. In more detail, both the hydrophobic association between the hydrophobic groups of LAS and CTAB and the electrostatic attraction between the hydrophilic groups of the anionic sulfonate in LAS and the cationic amine in CTAB would be profitable for the aggregate formation. A similar enhancement of aggregate formation was observed between perfluorooctane sulfonate and CTAB [18] and between anioic azo dyes and dodecyltrimethylammonium bromide [19].