Interaction with Surfactants

In contrast to their unmodified analogues, HM-CDs interact with all major types of surfactants. The extent of binding is larger for the surfactants that bind both to the polymer backbone and the hydrophobic side chains. It is well known that, depending on the concentration, addition of surfactant can either increase or decrease viscosity of a solution of an HM polymer [35-49]. At high surfactant concentrations associations between hydrophobic parts of the polymer chains are disrupted. 

At surfactant concentrations above the viscosity maximum the number of micelles in the solution increases. This results in an increased ratio between micelles and hydrophobic groups of the polymer. In this process the decreased viscosity is a consequence of the physical network losing some of its connectivity. At high surfactant concentrations 

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A class of systems extensively investigated by means of PFG-NMR are colloids. They are usually hydrophobically modified water-soluble polymers, that is, polymers with a water-soluble skeleton bearing one or more hydrophobic units, which allow the self-assembling of the polymer in water solution and the interaction with surfactants.77... 

Photon correlation spectroscopy was used to study the effects of a series of nonionic surfactants on the Stokes radius (R) of low density lipoprotein (LDL2) particles (Jl, 32). LDL2 interacted with surfactants in a manner similar to membranes. 

In the case of the rather porous and flexible structure of sodium caseinate nanoparticles, the data show that the interaction with surfactants causes a tendency towards the shrinkage of the aggregates, most likely due to the enhanced cross-linking in their interior as a result of the protein-surfactant interaction. This appears most pronounced for the case of the anionic surfactants (CITREM and SSL) interacting with the sodium caseinate nanoparticles. Consistent with this same line of interpretation, a surfactant-induced contraction of gelatin molecules of almost 30% has been demonstrated as a result of interaction with the anionic surfactant a-olefin sulfonate (Abed and Bohidar, 2004). 

When a protein is interacting with surfactant micelles, the following intrinsic features of the micelles are suggested as being of general importance in relation to their influence on the character of the protein self-assembly (IFin et al., 2005) ... 

Early oxidation hair dyes were used in solution form these have been replaced by cream- or gel-based formulas. The oil-in-water emulsions commonly used can be supplemented with auxiliary ingredients, such as polymers to improve combing ability, as well as other conditioning additives. Extensive patent literature is available on this point [35], Gel formulations may be based on alcoholic solutions of nonionic surfactants or fatty acid alkanolamide solutions, which form a gel when mixed with the oxidant. The type (emulsion or gel) and the basic composition of the preparation strongly influence dyeing [47], Different base formulations with the same dye content yield varying color depths and shading due to the distribution of the dye between the different phases of the product, interaction with surfactants, and diffusion from the product into the hair. 

Solubilization of water. Detergency is defined as the ability of surfactant molecules to solubilize water molecules or polar substances in soft-core and hardcore RMs. Thus, micellization and solubilization are competitive processes. Any solubilized probe molecule causes a decrease in the CMC. Solubilization describes the dissolution of a solid, liquid or gas by an interaction with surfactant molecules. Addition of water has a dramatic effect on surfactant aggregation in hydrocarbons because hydrogen bonding has an appreciable stabilizing effect on reverse micelles. Solubilization for reverse micelles is phenomenologically similar to the adsorption processes (Eicke and Christen, 1978 Kitahara, 1980 Kitahara et al., 1976 Singleterry, 1955). 

The stationary phases play an important part in Liquid Chromatography using micellar mobile phases. They interact with both the surfactant and with solutes. To study the interactions with surfactants, adsorption isotherms were determined with two ionic surfactants on five stationary phases an unbonded silica and four monomeric bonded ones. It seems that the surfactant adsorption closely approaches the bonded monolayer (4.5 pmol/m2) whatever the bonded stationary phase-polarity or that of the surfactant. The interaction of the stationary phase and solutes of various polarity has been studied by using the K values of the Armstrong model. The KgW value is the partition coefficient of a solute between the... 

This shows that the cytochrome c extraction into an organic phase is carried out at a very low DOLPA concentration, in which reverse micelles cannot be formed. Also, the molar ratio required for the complete protein extraction was approximately 20, which corresponds to the number of cationic charged residues available for the electrostatic interaction with an anionic surfactant in one cytochrome c molecule. These results support the concept that proteins are extracted by electrostatic interactions with surfactant molecules, and that the existence of reverse micelles is not necessary for causing protein transfer, as mentioned above. 

Now consider the problems which occur In the surfactant field, e.g. In detergency, cosmetics or pharmaceuticals, where polymers are usually associated with detergents to control the surface activity of the formulations (17). In these systems the polymers are known to Interact with surfactant micelles or mlcroemulslon droplets the Interaction can be beneficial, but most often It Is a real nuisance. 

Polymers Interact with surfactants and mlcroemulslons In diverse. Interesting and technologically Important wavs(1.21. The mechanisms that are responsible for the Interactions Include the usual panoply of forces Involved In the interaction of any two different molecules lon-lon, lon-dlpole, dlpole-dlpole, and van der Waals forces all modulated by the presence of solvent and/ or other species such as dissolved salts. All may play a role. The special factors Involved in surfactant/polymer and polymer-/mlcroemulslon Interactions that form the basis for their particular interest lies in their tendencies to form a variety of supermolecular clusters and conformations, which In tuim may lead to the existence of separate phases of coexisting species. Micelles may form In association with the polymer, polymer may precipitate or be solubilized, mlcroemulslon phase boundaries may change, and so on. 

Formation of Intramolecular Structures in Polyelectrolytes in the Interaction with Surfactants in Water... 

An intramolecular structure is also formed in polymers when these interact with surfactants (Table 14). These changes in polymers by the action of S may be... 

By using modified colloidal particles as templates, silicon oxide macroporous materials with uniform submicrometer-sized pores can be synthesized.[14] Modified polystyrene emulsion microspheres (200 1000 nm) can be electronegative (sulfates) or electropositive (amidines). After these microspheres are packed in an orderly fashion, they can interact with surfactants and silicon oxides to form macroporous solid composites, and further to form macroporous materials after the removal of the templates by calcination. The sizes of the macropores in the products range from 150 to 1000 nm. Macroporous Ti02 can also be prepared in a similar way. 

The change in optimum salinity is a consequence of divalent ions interacting with surfactant or of surfactant pseudocomponents partitioning in different... 

Effects of reaction products on other transport phenomena Interactions with surfactant and polymer if they are injected... 

The function of hydrotropes in detergency has been discussed as regards their interaction with surfactant colloidal association structures, especially lyotropic liquid crystals. The main activity of the hydrotrope as a part of a liquid detergent is to avoid gelation in both the concentrated package system and under the dilute conditions in the actual laundry process. 

Several recent patents describe the benefits of polymers in LDLDs (Table 7.15). Polymers are well known to interact with surfactants and provide many interesting properties. Some of the benefits claimed in the patents summarized in Table 7.15 are soil resistance due to amino acid copolymers, polyethylene glycol as a grease release agent, increased grease removal from polyoxyethylene diamine, enhanced foam volume and duration, increased solubility, and enhanced mildness by ethylene oxide-propylene oxide copolymers. As described in these various patents, the addition of polymers to LDLDs can aid performance in many important attributes of the product. 

In NaPA solutions, the curve shows no minimum. Instead, a plateau region of relatively constant A values is observed in the concentration range where the minimum in NaPSS solutions has been detected. Again, these differences in the behavior of CPC-NaPA and CPC-NaPSS solutions can be accounted for by the specific interaction with surfactant micelles in the poly(styrenesulfonate) case. We may speculate that the PA chain forms a more loose structure with the aggregated surfactants and may retain much of its counterions. 

Hydrophobically modified water-soluble polymers (HMWSPs) exhibit enhanced solution viscosity and unique rheological properties. These properties can be explained in terms of intermolecular associations via hydrophobes. This chapter describes the synthesis and solution properties of HMWSPs, Particularly discussed are the solution properties of hydrophobically modified hydroxyethytjcellulose (HMHEC) in aqueous and surfactant systems, HMHECs interact with surfactants and thus modify solution viscosities. The structure and the concentration of the surfactant dictate the solution behavior of HMHEC. The unique solution properties of HMHEC can be exploited to meet industrial demands for specific formulations or applications. 

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