Anionic fluorinated surfactants mixtures

The segregation and phase sequence of semifluorinated cat-anionic surfactant membranes at different excess surface charges was investigated by freeze-fracture transmission electron microscope (FF-TEM), X-ray diffraction (XRD), and NMR. The thermal behavior of the membranes was evaluated by conductivity, rheology, and deuterium NMR ( H NMR). The cat-anionic fluorinated surfactant mixtures can form faceted vesicles and punctured lamellar phase when there is excess surface charge. The cationic and anionic fluorinated surfactants are stiff in the membranes, like phospholipids in the frozen ciystalline or gel phase. ... 

Research on the micelle structure and interactions of fluorinated surfactants is ongoing with the main focus on mixed-surfactant systems. Mixtures of fluorinated and nonfluorinated surfactants may consist of anionic, nonionic, or cationic components. Most of the systems investigated so far have contained a fluorinated anionic surfactant and an anionic hydrocarbon surfactant. Anionic fluorinated surfactant mixtures with nonionic or cationic hydrocarbon-type surfactants have been investigated as well. The nonionic fluorinated hydrocarbon surfactant mixtures and cationic fluorinated hydrocarbon surfactant mixtures have been the subject of only a few studies. 

A keen interest in microemulsions of fluorocarbons in water was kindled by the need for synthetic oxygen earners in blood (see Section 10.4). Gerbacia and Rosano [121] prepared a stable fluorocarbon emulsion using a mixture of fluorinated and hydrocarbon-type nonionic surfactants. The droplet size was not determined, however, and the emulsions were not characterized. Oliveros et al. [122] prepared perfluorinated microemulsions consisting of four components (1) sodium perfluorooctanoate, an anionic fluorinated surfactant (2) 2,2,3,3,4,4,4-heptafluoro-1-butanol (3) perfluorohexane (4) water. The pseudoternary-phase diagram (Fig. 4.40) shows two regions. Mi and Mi, of respective W/0 and OAV microemulsions [122]. These optically transparent microemulsions were characterized by nuclear magnetic resonance spectroscopy. 

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. 

The existence of cdc was demonstrated by Funasaki and Hada [110] with mixtures of an anionic fluorinated surfactant, Neos Ftergent (NF), [(CF3)2CF]2C=C(CF3)0C6H4S03Na [sodium / -(perfluoro-3-isopropyl-4-methy]pent-2-en-2-oxy)benzenesulfonate], and hydrocarbon surfactants. Funasaki and Hada [110-116] found mixtures of fluorinated and hydrocarbon surfactants to contain, under appropriate conditions, one type of mixed micelle or two kinds of mixed micelles one rich in one of the surfactants and the other rich in the other surfactant. The coexistence of two kinds of mixed micelles in a solution de-... 

The mutual miscibility of anionic fluorinated surfactants and hydrocarbon surfactants increases with increasing temperature, similar to the miscibility increase of fluorocarbon and hydrocarbon liquid mixtures [76,120]. In the LiFOS-LiTS system, the solubility of LiFOS increased substantially in the LiTS-rich micelle but only slightly in the LiFOS-rich micelle [99]. In comicellar systems, such as NF-STS [112] and LiFOS-LiDS [76], the temperature dependence of mutual miscibility exhibits a critical solution temperature (cst) that corresponds to the transition from two types of micelle to one type of mixed micelle. Above the cst, only one kind of mixed micelle exists below the critical solution temperature (cst), two types of micelles can coexist. 

The miscibility of an anionic fluorinated surfactant with an anionic hydrocarbon surfactant is affected by the electrolyte concentration in the micellar solution [121]. Excess counterions increase the binding of the counterions to ionic head groups and reduce electrostatic interactions between the head groups. Furthermore, the cst and the composition of the surfactant mixture at cst depend on... 

An AFFF agent for extinguishing or preventing fires has been formulated with a mixture of an amphoteric fluorinated surfactant, A -[(dimethy-lamino)propyl]-2(or 3)-(l,l,2,2-tetrahydroperfluoroaIkylthio)succinamic acid, an anionic fluorinated surfactant, perfluoroalkanoic acid, and an ionic and a nonionic nonfluorinated surfactant [151]. 

Schroder [20] studied the biodegradation of an anionic, a cationic, and a nonionic surfactant. The anionic fluorinated surfactant, Fluowet PL 80, was found to be a mixture of a phosphonic acid, C F2 +iPO(OH)2, and a phosphinic acid, (C F2 +i)2PO(OH). The phosphinic component was adsorbed on activated sludge, whereas the phosphonic component of the fluorinated surfactant remained in the aqueous phase. Biodegradation of the perfluoroalkane chain did not occur, and no metabolites were detected [20a],... 

The mixture of anionic fluorinated alkylphosphinic and -phosphonic acid surfactants with perfluorinated alkyl moieties was examined using ESI-FIA-MS-MS(—). For CID in the negative mode, precursor ions at m/z 399, 499 and 599 were selected [22]. From all precursor ions only one product ion at m/z 79 ([PO3]—) besides the [M — H] ion was... 

The free-radical addition of TFE to pentafluoroethyl iodide yields a mixture of perfluoroalkyl iodides with even-numbered fluorinated carbon chains. This is the process used to commercially manufacture the initial raw material for the fluorotelomer -based family of fluorinated substances (Fig. 3) [2, 17]. Telomeri-zation may also be used to make terminal iso- or methyl branched and/or odd number fluorinated carbon perfluoroalkyl iodides as well [2]. The process of TFE telomerization can be manipulated by controlling the process variables, reactant ratios, catalysts, etc. to obtain the desired mixture of perfluoroalkyl iodides, which can be further purified by distillation. While perfluoroalkyl iodides can be directly hydrolyzed to perfluoroalkyl carboxylate salts [29, 30], the addition of ethylene gives a more versatile synthesis intermediate, fluorotelomer iodides. These primary alkyl iodides can be transformed to alcohols, sulfonyl chlorides, olefins, thiols, (meth)acrylates, and from these into many types of fluorinated surfactants [3] (Fig. 3). The fluorotelomer-based fluorinated surfactants range includes noiuonics, anionics, cationics, amphoterics, and polymeric amphophiles. 

A mixture of an anionic (Fluorad F-95) and a cationic fluorinated surfactant (Fluorad FC-134) has been recommended for foam suppression in organic liquids [140]. 

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