Polyoxyethylenated nonionics

Effects of Structure on the Properties of Polyoxyethylenated Nonionic Surfactants... 

Polyoxyethylene nonionic detergents (Triton X-100, Nonidet P-40, Tween-20, Brij 35, etc.) are used most often in immunochemical techniques because they generally do not denature proteins. Detergents act by intercalating into phos-... 

The first version of Equation (17) suggests that a plot of In cCMC versus 1/Tis a straight line of slope A// ,c/[/ (l + m/n)] if AH°mtc and m/n are independent of T. Backtracking to Equation (9) or (15) shows that n must also be constant with respect to temperature for this to be valid. In fact, n increases with temperature for polyoxyethylene nonionics any temperature dependence of n is generally assumed to be absent in ionic systems. Even if the In cCMC versus /T plot is nonlinear, the second form of Equation (17) allows a value of AH°mc to be evaluated from the slope of a tangent to a plot of In cCMC versus T at a particular temperature. Once AG°ic and AH°mjc are known, the entropy of micellization is readily obtained from AG = AH — TAS. Example 8.4 illustrates the use of these relationships. 

Caution should be exercised when considering temperature effects on solubilization by micelles, since the aqueous solubility of the solute and thus its micelle/water partition coefLcient can also change in response to temperature changes. For example, it has been reported that although tt solubility of benzoic acid in a series of polyoxyethylene nonionic surfactants increases with temperature, the micelle/water partition coefLci rt, shows a minimum at 2C, presumably due to the increase in the aqueous solubility of benzoic acid (Humphreys and Rhodes, 1968). The increasr in Km with increasing temperature was attributed to an increase in micellar size, as the cloud point temperature of the surfactant is approached (Humphreys and Rhodes, 1968). 

Stancher, B., and L. Favretto. 1978. Gas-liquid chromatograpJiic fractionation of polyoxyethylene nonionic surfactants—Polyoxyethylene mono-n-alkyl ethers. ]. Chromatogr. 150, 447-453. 

Refractive index data are very useful for the quantitation of isotropic (liquid and cubic liquid crystal) phases, and for the calibration of cell thickness and nonflatness. Hovever, the analysis of birefringent phases using refractive index data has been found to be unreliable (9). A problem arises from the fact that the orientation of such phases relative to the direction of the light path, as veil as the system variables, influence refractive indices. In order to use refractive index data for quantitation, a phase must spontaneously orient in a reproducible fashion. Such orientation does occur in the case of fluid lamellar phases (as in short chain polyoxyethylene nonionic systems (7)), but viscous lamellar phases, hexagonal phases, and crystal phases do not orient to a sufficient degree. 

A relationship between the lipophilicity of the solubilisate, expressed by the partition coefficient between octanol and water, Poctanoi (see Chapter 5), and its extent of solubilisation has been noted for the soluhilisation of substituted barbituric acids by polyoxyethylene stearates, of substituted benzoic acids by polysorbate 20, and of several steroids by polyoxyethylene nonionic surfactants. An exhaustive survey of data for the solubilisation of some 64 dmgs by bile salt micelles revealed linear relationships between log (partition coefficient between micelles and water) and log Poctanoi ach of seven bile salts... 

Nevskaia, D.M., Guerrero-Ruiz, A., and Lopez-Gonzalez, LD., Adsorption of polyoxyethylenic nonionic and anionic surfactants from aqueous solution Effects induced by the addition of NaCI and CaCL, J. Colloid Interf. Sci., 205, 97, 1998. 

Surfactants such as mono- and diglycerides and certain types of polyoxyethylene nonionics are routinely used in yeast-raised baked goods... 

The data indicate that penetration of the monolayer occurs when the polyoxyethylene nonionic surfactants are injected into the substrate. Polar portions of surfactant molecules interact with their counterparts on the protein film through permanent dipole attraction and dipole-induced-dipole (van der Waals) interaction, and electrostatic attraction. The nature of this adsorption disrupts hydrogen bonding which partially stabilizes the tertiary protein structure. This makes the macromolecules more amenable to unfolding, and this has been observed with proteins in the presence of ionic surfactants (22) as well. 

The observation that the minimum molecular area of gliadin increases in the presence of small amounts of polyoxyethylene nonionic... 

It is generally found that the same circumstances that affect the solution characteristics of nonionic surfactants (their cmc, micelle size, cloud point, etc.) will also affect the PIT of emulsions prepared with the same materials. For typical polyoxyethylene nonionic surfactants, increasing the length of the POE chain will result in a higher PIT for a given oil-aqueous phase combination (Fig. 11.12), as will a broadening of the POE chain length distribution. The use of phase inversion temperatures, therefore, represents a very useful... 

The temperature dependence of the cmc of polyoxyethylene nonionic surfactants is especially important since the head group interaction is essentially totally hydrogen bonding in nature. Materials relying solely on hydrogen bonding for solubilization in aqueous solution are commonly found to exhibit an inverse temperature-solubility relationship. As already mentioned, major manifestation of such a relationship is the presence of the cloud point for many nonionic surfactants. 

The types of surfactants used in an emulsion polymerization span the entire range of anionic, cationic, and nonionic species. The most commonly used soaps are alkyl sulfates such as sodium lauryl sulfate [151-21-3], alkylaryl sulfates such as sodium dodecyl benzene sulfonate [25155-30-0], and alkyl or aryl polyoxyethylene nonionic surfactants (87,101-104). Product stability and particle size control are the driving forces which determine the types of surfactants employed mixtures of nonionic and anionic surfactants are commonly used to achieve these goals (105-108). 

EAN IL was used in various reactions such as Biginelli reaction, condensation reaction, nitration of phenol, synthesis of P-amino ketone, ete. Nitration of phenol using ferric nitrate and clayfen in the IL, EAN, has been reported imder irltrasound irradiation [102]. Jaeger and Tucker in 1989 reported the Diels-Alder reaction involving EAN IL [ 103], IL EAN was prepared as per the literature method. EAN was found to be a more suitable solvent and catalyst for these reactions. In the presence of EAN, the reactions proceed in a shorter time, under milder conditions, and with excellent yield of products. EAN is liqttid at room temperature and is miscible with water thus, the separation and isolation of the product becomes easier. Its autoprotolysis constant is high, and the large electroactivity area and conductivity allow it to be used as a potential solvent. Araos et al. [104] reported the stability of a variety of lyotropic liquid crystals formed by a nttmber of polyoxyethylene nonionic surfactants in the room-temperature IL EAN. 

In addition, surfactants with multiple ether linkages in the molecule showed much weaker interactions than expected with polyoxyethylenated nonionics. Data are shown in Table 9. We have suggested [13] that the double... 

Whereas a decrease of the micelle size of ionic surfactants with increase in temperature has been reported [143], micelles of many polyoxyethylene nonionic surfactants increase rapidly in size with rising temperature [59,144-149]. In some systems the rapid increase in micelle size is noted only above a characteristic transition temperature and is accompanied by an increase in micelle asymmetry. From viscosity data at elevated temperatures, it has been suggested that an increase in the extension of the polyoxyethylene chains occurs as the temperature is increased, resulting in an increase in the amount of water physically trapped by the micelles [59]. 

---