Oxyethylene-containing nonionics

Increasing temperature for ionic surfactants usually opposes micellization due to enhanced molecular motion that reduces p. For oxyethylene-containing nonionics, temperature causes the association number to increase up to the cloud point, when phase separation occurs because polyoxyethylene becomes insoluble in water. The cloud point decreases with decreasing oxyethylene (E) chain length indeed, surfactants of the type CmE (Section 4.2) with n < 4 are insoluble in water and so the system is always phase separated. As the association number increases with temperature, the solvent quality for oxyethylene becomes worse, causing the corona to shrink. A compensation between the increase in p and a decrease in corona size results in an approximately constant overall micellar radius. 

Nowadays these compounds are usually blended with other surfactants, including nonionic types (section 9.6). In 1990 a typical low- or non-phosphate domestic detergent contained 7% linear alkylbenzenesulphonate and 6% nonionic fatty alcohol ethoxylate [16]. There is increasing use of the long-chain fatty alcohol poly(oxyethylene) sulphates previously described (e.g. 9.12) as a partial or complete replacement for linear alkylbenzenesulphonates [15] since they are made from renewable feedstocks such as tallow and palm oil [16]. 

The USPNF 23 describes polyethylene oxide as a nonionic homopolymer of ethylene oxide, represented by the formula (CHiCHiOIk, where n represents the average number of oxyethylene groups. It may contain up to 3% of silicon dioxide. 

The PIT appears to reach a constant value at 3-5% surfactant concentration when a POE nonionic containing a single POE chain length is used. When there is a distribution of POE chain lengths in the surfactant, the PIT decreases very sharply with increase in the concentration of the surfactant when the degree of oxyethyl-enation is low and less sharply when the degree of oxyethylenation is high. 

In POE nonionics containing the same number of oxyethylene units, increase in the length of the hydrophobic group increases the efficiency of oily soil removal by decreasing the CMC and hence the concentration at which solubilization commences. Optimum detergency increases with increase in the chain length of the hydrophobe to a maximum that again is dependent on the temperature of the bath. 

Measurements of the Formation of Adsorption Layers of Solutions of Nonionics Containing Oxyethylene Groups... 

Heller and Pugh (1954) correctly recognized that the stability imparted to colloidal particles by naturally occurring polymers often contains both electrostatic and polymeric components. Nonionic macromolecules, such as poly(oxyethylene), can only impart stability by virtue of their polymeric... 

A linear behavior between k and n was found for n-alkylbenzenes eluted with pure micellar eluents of the anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB), and nonionic poly[oxyethylene(10 or 23)]dodecanol (Brij 22 or Brij 35), and with hybrid eluents containing SDS or CTAB and 2-propanol. The homologues of n-alkylphenones eluted with pure and hybrid mobile phases of CTAB showed the same behavior, but linear relationships were observed between log k and nc for these compounds eluted with SDS mobile phases, the same type of correlation found in aqueous-organic systems. It seems that the... 

If, indeed, a complex containing oxyethylene groups is formed, then it should exhibit cloud point phenomena like ethoxylated nonionic surfactants. This is found to be so as shown in Fig. 8. Note the shift with pH. At different pH s, the number of dissociated APEs is different thus, a different amount of TTAB is needed to neutralize it. The decrease in pH of an APE solution when TTAB is added to it is an indication that a complex is formed. The exhibition of cloud point phenomena for mixtures of APE-TTAB is an indication that the resulting complexes have a pseudononionic character. 

Matos et al. [42] synthesized nonionic fluorinated surfactants which contained both oxyethylene and thioethylene groups ... 

The application of UV spectroscopy to the analysis of nonionic hydrocarbon-type surfactants is limited to nonionics, which contain functional groups which absorb in the UV region, such as aromatic nuclei [65]. The main functional group of nonionics, the oxyethylene ether linkage, does not absorb in the UV region. In spite of this limitation, UV spectroscopy can be useful for determining impurities in nonionic fluorinated surfactants. 

Because most fluorinated surfactants are commercial products containing several components, the toxicity of impurities in fluorinated surfactants has to be considered. Commercial fluorinated surfactants are usually sold as solutions in an aqueous solvent [10]. In some cases, the solvent may cause more systemic or local toxic effects than the surfactant itself. The solvent and volatile impurities may dominate the toxic effects produced by inhalation. Nonionic surfactants with a poly(oxyethylene) hydrophilic chain may contain 1,4-dioxane, which has shown carcinogenic activity in some animal tests. 1,4-Dioxane is a by-product found in nonionic surfactants, regardless of whether the surfactants are fluorinated. However, the concentration of 1,4-dioxane in nonionic surfactants is carefully controlled and is usually very low (about 0.1% or less). Air monitoring has indicated that at a workplace where there are nonionic fluorinated surfactants containing about 0.1 % dioxane, the 1,4-dioxane concentration in air would be below 1 ppm. 

A method was described for the determination of nonionic surfactants containing poly(oxyethylene) chains with sodium tetraphenylborate, based on the precipitatiOTi of ternary compounds in the presence of bivalent metal ions (barium salts). Titrations were monitored potentiometricaUy with a simple PVC membrane-coated aluminum wire electrode plasticized with 2,4-dinitrophenyloctyl ether. " ... 

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