Nonionic surfactants introduction

Earlier formulations contained mainly chlorine bleach, metasiUcates, triphosphate, and nonionic surfactants. Modem manufacturers have switched to more compHcated formulations with disiUcates, phosphates or citrate, phosphonates, polycarboxylates, nonionic surfactants, oxygen bleach, bleach activator, and enzymes. The replacement of metasiUcates by disilicates lowers pH from approximately 12 to 10.5, at 1 g ADD/L water. The combined effect of decreased pH, the absence of hypochlorite, and the trend toward lower wash temperatures has paved the way for the introduction of enzymes into ADDs. Most ADD brands in Europe are part of the new generation of ADD products with enzymes. The new formulations are described in the patent hterature (55—57). 

Later we discover another parameter, the phase inversion temperature(PIT), which helps us to predict the structure of emulsions stabilized by nonionic surfactants. The PIT concept is based on the idea that the type of an emulsion is determined by the preferred curvature of the surfactant film. For a modern introduction into the HLB and PIT concepts see Ref. [546],... 

The scope of the chapter will include an introduction to the technique of neutron reflectometry, and how it is applied to the study of surfactant adsorption at the planar solid-solution interface, to obtain adsorbed amounts and details of the structure of the adsorbed layer. The advantages and limitations of the technique will be put in the context of other complementary surface techniques. Recent results on the adsorption of a range of anionic, cationic and nonionic surfactants, and surfactant mixtures onto hydrophilic, hydrophobic surfaces, and surfaces with specifically tailored functionality will be described. Where applicable, direct comparison with the results from complementary techniques will be made and discussed. 

The bismuth active substances (BiAS) method for the determination of nonionic surfactants with barium tetraiodobismuthate (BaBil4, modified Dragendorff reagent) is used in the standardized (DIN-Norm) procedure in Germany, as well as in other countries. Ba as a hard Lewis acid forms cationic coordination complexes with the polyethoxylate chain of the nonionic surfactants, which are precipitated by [Bim in the presence of acetic acid. The orange precipitate is then dissolved with ammonium tartrate solution, and the released bismuth ions are determined by potentiometric titration with pyrrolidinedithiocarbamate solution. Waters et al. optimized the BiAS procedure by introduction of a cation/anion exchange clean-up of the sublation extracts. The BiAS procedure fails to determine ethoxylates with less than five ethoxy units because these compounds are not precipitated by barium tetraiodobismuthate. Thus, this procedure is not suitable for determination of APEO metabolites, i.e., the shorter APEO and AP. ... 

It can be seen from Table 6 that anionic, cationic, and nonionic surfactants have all been exploited in formulating microemulsions for materials synthesis. Anionic and nonionic surfactants appear to be the most popular types of surfactants, with Aerosol OT (AOT) and the polyoxyethylated alkylphenyl ether surfactants (e.g., NP-5) leading. Part of the attraction of AOT and the NP surfactants is related to the fact that they permit microemulsion formulation without the need for cosurfactants. Also, a large body of information is already available on the phase behavior and structure of AOT microemulsions [121], and this makes it convenient to work with this anionic surfactant. A unique advantage of the nonionic surfactants is the fact that their use does not involve the introduction of (potentially undesirable) counterions. The ability to alter the size of the hydrophilic (oxyethylene) groups and/or the hydrophobic (alkyl) groups provides additional flexibility in surfactant selection. 

Nevertheless, it is now understood that HLB essentially depends on the surfactant, while the phase behavior and emulsion properties are also related to the water and oil phase nature, as well as to the temperature (100). The temperature was the preferred variable in the case of nonionic surfactants which are very sensitive to it, and an experimentally based concept was first introduced by Shinoda to quantify the formulation, i.e., the phase inversion temperature (PIT) (105, 106). It is known that the hydrophilicity of a nonionic surfactant decreses when temperature decreases. In water solution there exists a temperature at which the surfactant is no longer soluble and thus produces a separate phase. This so-called cloud point occurrence is related to the Shinoda PIT, which is essentially the same phenomenon, but in the presence of an oil phase whose nature could facilitate this separation and make it happen at a lower temperature. Although the PIT is limited to the liquid water temperature range of nonionic surfactants, its introduction was an important milestone because it was related not only to the surfactant, but also to the whole physicochemical environment (107), a feature that was shown to be essential by Winsor. 

An elegant innovation to aid the study of polymer/surfactant interaction was the introduction of a fluorescent label directly onto the polymer molecule by covalent bonding. [See reviews by Winnik (43,44).] This approach has been particularly useful in systems, such as combinations of nonionic polymers and nonionic surfactants, where interaction is weak. For example, pyrene-labeled hydroxypropylcellulose (HPC) gave evidence of association with weakly reactive OTG (n-octyl-P-D-thioglucopyranoside) but only at concentrations near its c.m.c. (119). Experiments with pyrene-labeled PNIPAM have been reported by Winnik et al. (120), who obtained evidence of noncooperative association of this polymer with anionic and cationic surfactants. A polymer that has been terminally labeled with pyrene groups is PEO (121) in mixtures with SDS at lower concentrations fluorescence data indicated the polymer chain cyclized. At higher concentration the pyrene groups were located in separate micelles. 

Several systematic studies addressed the enthalpy associated with the introduction of surfactants into phospholipid bilayers and phospholipid-detergent mixed micelles. These include several investigations of the enthalpy of partitioning of the nonionic surfactant octylglucoside (OG) into PC bilayers. The results of these studies (Table 9) reveal that, similar to the partitioning of alcohols, increasing the temperature results in more exothermic introduction of OG into lipid bilayers. 

Unlike mixed hydrocarbon-chain surfactants of similar molecular structure, mixtures of fluorinated surfactants and hydrocarbon-chain surfactants do not behave ideally, even when the surfactants have a similar hydrophilic group. Mixtures of anionic fluorinated surfactants with anionic hydrocarbon surfactants exhibit a positive deviation from the ideal relation (Fig. 7.4). In contrast, surfactant mixtures containing a nonionic surfactant or oppositely charged ionic surfactants exhibit a negative deviation from ideal predictions. The formation of mixed micelles is governed by hydrophobic interactions between hydrocarbon and fluorocarbon chains and electrostatic effects [66]. Introduction of nonionic surfactants into micelles of anionic fluorinated surfactants reduces electrostatic repulsion between the ionic head groups. Apparently, the resulting electrostatic effect overcomes the hydrophobic interaction between the fluorocarbon and hydrocarbon chains. 

Mass spectrometric detection allows analysis of most nonionic surfactants without deriva-tization. Thermospray, electrospray, or atmospheric pressure chemical ionization interfaces permit direct introduction of the effluent of the LC into the MS and make the MS a very selective detector for nonionics. Quasimolecular ions are produced for each discrete compound, so that the HPLC system is not required to separate both by degree of ethoxylation and by alkyl character. A relatively simple HPLC separation, coupled with MS anal-... 

For nonionics, the CMCs may be markedly affected by the size and nature of the hydrophilic group. For ionic surfactants, the CMC is increased on introduction of additional ionic groups for example, the CMC of C10CH (COOK)2 is 0.13 M while it is 0.024 M for CnCOOK.1... 

The consumer need for a milder dishwashing liquid was met in the early 1990s with the successful introduction of Palmolive Sensitive Skin and the milder positioning of Ivory LDLD. The use of nonionic and amphoteric surfactants resulted in clinically milder and less irritating products. In the last decade, however, further improving mildness was a significant objective for the major players in the LDLD market. Dawn Hand Care was the first to introduce protease, an enzyme that is claimed to soften skin by exfoliation of the top layer. 

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