Cationic surfactant definition

Thus, it cannot be excluded that OH ions can serve as ionic collectors if all conditions are satisfied (sufficiently high pH, not too high electrolyte concentration and definite electrical surface properties of the particles). A quantitative evaluation of this phenomenon appears to be impossible because of lack of a DAL theory for large Reynolds numbers. At adsorption of cationic surfactants the absolute value of the potential F, of a water-air interface can be smaller than that of the particle Pjj i - Within the r.s.c. a significant decrease in T, is... 

Uses Surfactant in cosmetics hair conditioner intermediate for cationic surfactants, chemical specialties corrosion inhibitor salts as emulsifier for acid systems Trade Name Synonyms Mackine 701 [McIntyre http.V/www.mcintyregroup. com] Wheatgermamidopropyl dimethylamine hydrolyzed wheat protein Definition Wheatgermamidopropyl dimethylamine sait of hydroiyzed wheat protein Uses Antistat in cosmetics hair and skin conditioner... 

Cationic surfactants represent one of the smaller classes of surfactants, with a consumption estimated to be 700000 tons per year. Typically, reviews and market studies include in this class of materials all amine-based surfactants, whether they be charged or uncharged. In this present chapter we will use the same definition, but exclude amphoteric materials, which will be covered in the next chapter in this volume. 

Reference has already been made to the interesting finding by Laurent and Scott (65) that precipitation of various polyanion/cationic surfactant systems can be totally inhibited by the addition of a sufficient amount of simple salt. This work allowed the definition of a critical electrolyte concentration (c.e.c.), which was found to vary from system to system. Clearly, electrostatic screening effects are again involved. This phenomenon has been confirmed and examined in some detail by Lindman and co-workers (see next section). Less work has been carried out in this respect on polycation/anionic surfactant systems and, at least in some systems involving cationic cellulosic polymer/SDS combinations, resolubilization by salt addition was found not to be facile (59,103). 

In order to get definite limiting conditions we chose to analyse the motion of a nitroethane drop placed at the surface of an aqueous solution of a cationic surfactant. 

A different way was chosen to predict the behavior of the mixtures anionic polyelectrolyte/cationic surfactant [32, 33]. The formal Flory presentation is maintained but the interaction parameter, is assumed to give a complete representation of all types of interactions (including electrical). In these conditions, X, is a more or less adjustable parameter with values which can be out of the scope of the original Flory s definition. An important point, well developed... 

The two distinctive affinities in the surfactant molecule mentioned above serve as the basis for the commonly accepted definition of surfactant groups. According to the charge of their hydrophilic moiety, surfactants can be classified into four categories anionic, non-ionic, cationic and amphoteric. 

The rate constants for the reaction of a pyridinium Ion with cyanide have been measured in both a cationic and nonlonic oil in water microemulsion as a function of water content. There is no effect of added salt on the reaction rate in the cationic system, but a substantial effect of ionic strength on the rate as observed in the nonionic system. Estimates of the ionic strength in the "Stern layer" of the cationic microemulsion have been employed to correct the rate constants in the nonlonic system and calculate effective surface potentials. The ion-exchange (IE) model, which assumes that reaction occurs in the Stern layer and that the nucleophile concentration is determined by an ion-exchange equilibrium with the surfactant counterion, has been applied to the data. The results, although not definitive because of the ionic strength dependence, indicate that the IE model may not provide the best description of this reaction system. 

A new class of water soluble cellulosic polymers currently receiving attention Is characterized by structures with hydrophobic moieties. Such polymers exhibit definite surface activity at alr-llquld and liquid-liquid Interfaces. By virtue of their hydrophobic groups, they also exhibit Interesting association characteristics In solution. In this paper, results are presented on the solution and Interfaclal properties of a cationic cellulosic polymer with hydrophobic groups and Its Interactions with conventional surfactants are discussed. 

Nonionic surfactants are amphiphilic compounds the lyophilic (in particular hydrophilic) part of which does not dissociate into ions and hence has no charge. However, there are nonionics, for example such as tertiary amine oxides, which are able to acquire a charge depending on the pH value. Even polyethers, such as polyethylene oxides, are protonated under acidic conditions and exist in cationic form. Long-chain carboxylic acids are nonionic under neutral and acidic conditions whereas they are anionics under basic conditions. So, the more accurate definition is as follows nonionics are surfactants that have no charge in the predominant working range of pH. The main part of nonionics can be classified into alcohols, polyethers, esters, or their combinations. 

Synonyms Amides, coco, N-[3-(dimethylamino) propyl], lactates N-[3-(Dimethylamino) propyl] cocamide lactate Definition Lactic acid salt of cocamidopropyidimethylamine Formula RCO-NH(CH2)3N(CH3)2 HOOCCOHHCH3, where RCO- represents coconut oil fatty acids Toxicology TSCA listed Uses Surfactant, softener, conditioner for cosmetics, hair conditioners base for cationic emulsions... 

At the surface of the micelle we have the associated counterions, which in number amount to 50-80% of the surfactant ions, which as noted above is a number quite invariant to the conditions. Simple inorganic counterions are very loosely associated with the micelle. The counterions are very mobile and there is no specific complex formed with a definite counterion-head-group distance. Rather, the counterions are associated by long-range electrostatic interactions to the micelle as a whole. They remain hydrated to a great extent, and especially cations tend to keep their hydration shells. 

Amphoteric surfactants by definition are chimeric, exhibiting anionic character in alkaline solution, nonionic character near their isoelectric point, and cationic character in acidic solution [73]. As a result of their complex charge characteristics, their interactions with interfaces must be examined iudividually and as a function of pH. For example, the adsorption of alkyl betaines firom solution onto wool keratin is much greater at acidic than alkalide pH values. Although amphoteric surfactants are used extensively to improve the cosmetic attributes of many consmner products [74], their interactions with skin have received little attention. 

A more efficient method of isolating anionic surfactants is extraction as part of an ion pair (33). An inorganic salt is added to decrease the solubility of the ion pair in the aqueous phase. Sometimes, the methylene blue spectrophotometric method described in Chapter 12 is used as the cleanup step. This permits the analyst to estimate the amount of surfactant isolated before proceeding with more definitive analytical techniques. Methylene blue may be removed from the surfactant extract by passage through a cation exchange column (56). If concentration is performed by liquid-liquid extraction of the ion pair with an alkyl quaternary compound, the UV spectrum of the ion pair is identical to that of LAS alone (55). 

---