Nonionic fluorinated surfactants

Water-in-fluorocarbon emulsions, stabilised with fluorinated nonionic surfactants, were investigated by small angle neutron scattering (SANS) spectroscopy [8,99]. The results indicated that the continuous oil phase comprised an inverse micellar solution, or water-in-oil microemulsion, with a water content of 5 to 10%. However, there was no evidence of a liquid crystalline layer at the w/o interface. A subsequent study using small angle x-ray scattering (SAXS) spectroscopy gave similar results [100]. 

The above results demonstrate that partially fluorinated nonionic surfactants, having a fluorinated hydrophobic chain and a nonfluorinated poly(ethylene oxide) polar chain, can be successfully used to obtain mesoporous materials with controlled morphology and pore size. The specific surface areas can be high, similar to MCM-41 materials obtained using hydrocarbon surfactants. 

Antonietti et al. described the preparation of mesoporous silica in systems containing mixtures of nonionic fluorinated surfactants and nonionic hydrocarbon block copolymer surfactants [60], The fluorinated surfactant was CF3(CF2)6-i6 C2H4(E0)4 5 and the hydrocarbon-based copolymer was poly(ethylene-co-bulylene)-block-poly(ethylene oxide). 

Note that the pore walls of the material templated using QFi7S02[C3H7] N(EO)ioH, indicated in Table 11.2, are thicker than those of MCM-41 materials [13]. The pore walls are also thicker than those obtained when using fluorinated cationic surfactants [62, 63], which resemble MCM materials, or when using nonionic surfactants with partially fluorinated alkyl tails [53]. However, the main characteristics of the materials described here are similar to those obtained by using E(CE2)s(EO)io or F(CE2)6(EO)i4 fluorinated nonionic surfactants [64, 65]. 

The fact that a determined from molecular size coincides with that obtained from surface tension fits (Table 4.5) is very nseful for applications. Thus, when fitting experimental data, we can use the value of a from molecular size, and thus to decrease the number of adjustable parameters. This fact is especially helpful when interpreting theoretically data for the surface tension of surfactant mixtures, such as SDS + dodecanol [54] SDS + CAPB [59], and fluorinated + nonionic surfactant [61]. An additional way to decrease the number of adjustable parameters is to employ the Traube rule, which states that increases with. 025kT when a CH2 group is added to the paraffin chain for details see Refs. [54,55,60]. 

Like all surfactants, fluorinated surfactants are either ionic or nonionic. Ionic surfactants can, unlike nonionic surfactants, dissociate into ions in an aqueous medium. The hydrophobic part can belong to a negative or positive ion. Some surfactants have negatively and positively charged functional groups on the same backbone. The surfactants can therefore be classified into four types ... 

RfCH=CH(CH2)90H, Rf=C6F 3 or C8F17, prepared by reacting the perfluo-roalkyl iodide with undecenol using copper(I) chloride and ethanolamine catalysis [254]. The reaction product was deacetylated in a methanol-triethylamine-wa-ter mixture to give the fluorinated nonionic surfactant (see Section 10.4). 

Selve et al. [32] synthesized fluorinated nonionic surfactants with a two-chain polyoxyethylene hydrophilic head linked to the hydrophobe via an amide bond, F(CF2)i(CH2), C(0)N[(C2H40) CH3]2. They calculated the area A per surfactant molecule adsorbed on the air-water interface from the slope of the surface tension curve using the Gibbs equation [Eq. (13)]. The area A increases with increasing number of oxyethylene units for both fluorinated and hydrocarbon sur-... 

Selve et al. [32] prepared fluorinated nonionic surfactants with a two-chain polyoxyethylene hydrophilic head linked to the hydrophobe via an amide bond. 

Krafft points for fluorinated nonionic surfactants have not been reported. However, the widespread view that nonionic surfactants do not have a BCrafft point is incorrect. Although only a few nonionic surfactants exhibit a Krafft point, an implication that the Krafft point is related to the ionic charge of a surfactant is mis-... 

Funasaki and Hada [116] examined the mutual solubility of a fluorinated nonionic surfactant [(CF3)2CF]2C=C(CF3)0(CH2CH20) CH3 (NFE, average n — IS.4) and a nonionic hydrocarbon chain surfactant CH3(CH2)u-0(CH2CH20), H (DEm, w = 5, 7, 9, or 25). Curves of the surface tension plotted against the logarithm of total surfactant concentration for mixtures of NFE and DE7 are shown in Fig. 7.34. The constancy of surface tension beyond cmc (curve a) indicates that DE7 was highly pure, unlike NFE (curve f), which is difficult to purify and therefore contained impurities. The cmc values of NFE-DE7 mixtures exhibited a maximum at a mole fraction of 0.327 for DE7. The relation between the surface tension and the mole fraction of monomeric DE7 in the mixture of NFE and DE7 monomers is shown in Fig. 7.35 with open circles. The filled circles show the surface tension at about 10-fold concentrations above cmc as a function of DE7 mole fraction in the whole system. A plateau region in the micellar composition curve indicates the coexistence of two kinds of mutually saturated mixed micelles. 

The nonionic fluorinated surfactants tested by Sakakibara et al. [192] exhibited hardly any herbicidal activity. Hence, selected fluorinated surfactants can be used safely as dispersants and adjuvants for agricultural chemicals. When compared to hydrocarbon surfactants, fluorinated surfactants are more powerful wetting agents for leaves (e.g., wheat leaves) [193],... 

Surfactants used as lubricants are added to polymer resins to improve the flow characteristics of the plastic during processing they also stabilise the cells of polyurethane foams during the foaming process. Surfactants are either nonionic (e.g. fatty amides and alcohols), cationic, anionic (dominating class e.g. alkylbenzene sulfonates), zwitterionic, hetero-element or polymeric (e.g. EO-PO block copolymers). Fluorinated anionic surfactants or super surfactants enable a variety of surfaces normally regarded as difficult to wet. These include PE and PP any product required to wet the surface of these polymers will benefit from inclusion of fluorosurfactants. Surfactants are frequently multicomponent formulations, based on petro- or oleochemicals. 

America s Du Pont and 3M and Japan s Sanyo pay particular attention to the development of fluorine-based surfactants. Air Products with its acetylene derivatives Surfynol and W. R. Grace with its sarcosinates (Hampshire Chemicals) have also focused on well-defined segments of the business. With world demand exceeding two million tons, the market of surfactants for industry is of a nature to attract a large number of operators, raw material suppliers, processors of these raw materials into anionic, nonionic, and cationic derivatives, or downstream industries that use surfactants in various formulations. 

The aggregation of fluorinated surfactants in nonaqueous solvents has also been studied. These surfactants form aggregates at lower concentrations than ordinary hydrogenated surfactants in water. Chrisment et al. have studied nonionic fluoro-alkyllipopeptides in DMSO and found progressive and very limited aggregation in this solvent as expected from the low polarity of the solvent [65], In addition, the lithium salt of nonadecafluorodecanoic acid has been studied with 19F NMR in formamide, A-methylformamide, and ethylene glycol [66],... 

Microemulsions containing fluorocarbons have been investigated as blood substitutes. For example, Cecutti et al. [55] studied these aspects of microemulsions and found that although the inherent incompatibility between hydrocarbons and fluorocarbons puts some demands on the surfactant to be used, the resulting microemulsion (prepared from fluorinated oil, water, and an nonionic surfactant) displayed oxygen absorption similar to that of blood, and at the same time the toxicity was limited and the microemulsions appeared to be well tolerated. 

---