Polyether surfactant

Zhu, J., Shi, Z. (2003). ESI-MS studies of polyether surfactant behaviors in reversed-phase HPLC system. Int. J. Mass Spectrom. 226(3), 369-378. 

Initial degradation of silicone surfactants is thought to occur predominantly as hydrolyis of the silicone Si—O moiety, and this is known to be enhanced at acidic or alkaline pH values [3,11,12]. At neutral pH the surfactants are generally considered stable, but residual acidity or basicity of glassware is also known to catalyse their hydrolytic degradation [7]. Silicone polyether surfactants possessing the Si—O—C... 

In order to improve the activity in the absence of co-solvent, the use of a surfactant was studied in the presence of TPPTS-based catalyst [55]. Monflier et al. reported the hydrodimerization of 1 in the presence of surfactants in order to improve butadiene mass transfer in pure water solution [56-58]. Such an additive used in very low amount avoided the presence of an organic co-solvent. It was shown in the case of hydrodimerization that neutral or cationic surfactants played a significant role in the process. Similar behaviors were reported for the telomerization of 1 with 21. While 30% conversion of 1 was achieved in pure water after 24 h reaction time at 50°C using 0.4 mol% of catalyst, the conversion reached 87% when polyether surfactant (POEA) was added to the reaction medium under similar reaction conditions (Table 12). It was found that the conversion is strongly affected by the nature of the surfactant (Table 13). 

A considerable amount of experimental work has been carried out on the so-called gel emulsions of water/nonionic surfactant/oil systems [9-14, 80, 106, 107]. These form in either the water-rich or oil-rich regions of the ternary phase diagrams, depending on the surfactant and system temperature. The latter parameter is important as a result of the property of nonionic surfactants known as the HLB temperature, or phase inversion temperature (PIT). Below the PIT, nonionic surfactants are water-soluble (hydrophilic form o/w emulsions) whereas above the PIT they are oil-soluble (hydrophobic form w/o emulsions). The systems studied were all of very high phase volume fraction, and were stabilised by nonionic polyether surfactants. 

Nonionic surfactants alkylaryl polyether Surfactant/emulsifier 0.54... 

Antifoggers Fatty chain glycol and polyether surfactants... 

Gentle, T.E. and Snow, S.A. (1995) Adsorption of small silicone polyether surfactants at the air/water interface. Langmuir, 11(8), 2905-10. 

Several reports on hydrosylilation and different forms of catalysis have been produced, and theworkofMarciniecand Gulinski [2] provides further references. Schmaucks [3] describes a range of novel siloxane-polyether surfactants produced via the above described method. 

The freeze/thaw (F/T) stability of a polymer emulsion serves as a macroscopic probe for investigating the properties of the average particle in a polymer emulsion. A review of the factors which contribute to this stability is included. A study of styrene-ethyl acrylate-methacrylic acid polymers shows the existence of a minimum in the plot of minimum weight percent acid required for F/T stability vs. the minimum film formation temperature (MFT) of the polymer. This is considered to be a function of both the amount of associated surfactant and the minimum acid content. Thus, both the type of surfactant and the copolymer ratio—i.e., MFT—play major roles. Chain transfer between radicals and polyether surfactant resulting in covalently bonded surfactant-polymer combinations is important in interpreting the results. 

A number of studies have appeared on the photochemistry of chlorobiphenyls in surfactant/water solutions [75- 87]. The surfactants used in these studies are shown in Table 2. Sodium dodecylsulfonate, SDS, is an ionic surfactant, while the others are non-ionic polyethers. Surfactants form micelles which solubilize the hydrophobic chlorobiphenyls. Surfactant/water solutions are also effective at extracting chlorobiphenyls from soils. Once inside the nonpolar interiors of the micelles, the chlorobiphenyls will undergo reductive dechlorination photochemically. 

The DLVO theory does not explain either the stability of water-in-oil emulsions or the stability of oil-in-water emulsions stabilized by adsorbed non-ionic surfactants and polymers where the electrical contributions are often of secondary importance. In these, steric and hydrational forces, which arise from the loss of entropy when adsorbed polymer layers or hydrated chains of non-ionic polyether surfactant intermingle on close approach of two similar droplets, are more important (Fig. 4B). In emulsions stabilized by polyether surfactants, these interactions assume importance at very close distances of approach and are influenced markedly by temperature and degree of hydration of the polyoxyethylene chains. With block copolymers of the ethylene oxide-propylene oxide... 

It is known that silicone polyether copolymers can have limited stability in aqueous media. The stability will depend on several factors, which include pH, concentration, stmcture of the copolymer, and the molecular weight of the copolymer. In this work the stability of a wide range of copolymers was investigated in aqueous media at various pH values and concentrations. The goal was to provide formulators and users with a tool to predict the long-term stability of silicone polyether surfactants in their own applications and formulations. 

As reported in the literature, interference fringes in many vertical aqueous films are horizontal with little curvature. These films also displayed mobile surfaces, rapid and extensive surface flows and rapid rates of drainage [22, 28-30]. These features were all linked to the presence of a low surface viscosity. Based on our experimental observations, the PU films stabilised by DABCO DC 198 have low surface viscosities. This conclusion is supported by reports of measurements of low surface viscosities in polyol solutions containing silicone polyether surfactants [12, 15, 38]. 

Summary Water-in-silicone oil emulsions, stabilized by silicone-polyether surfactants, are marginally permeable to polar, but uncharged, molecules such as phenolphthalein and crystal violet. However, charged compounds, including these compounds in basic and acidic pH regimes respectively, and proteins transfer much less readily from the internal water phase to external bulk water. Transfer experiments were followed colorimetrically. These experiments shed light on the possible mechanisms by which proteins may be released from these emulsions in bioactive form simple breaking of the emulsion does not appear to be the mechanism of action. 

The most reasonable explanation for transfer is route Fig. 6B, where the material has only to diffuse through the W/O/W interface. The silicone/polyether surfactant can support relatively efficient transfer of neutral molecules, but not their charged analogues including proteins, which will have difficulty passing through hydrophobic silicones. Note that the more polar the groups, the slower is the transfer, as can be seen by the comparison of rates of transfer of crystal violet and... 

Polar neutral molecules pass relatively easily through silicone/water interfaces stabilized by silicone-polyether surfactants. By contrast, proteins and charged molecules do not. These results are consistent with a direct transfer mechanism through a water/oil/water interface aided by the surfactant. 

Water solubility up to w = 12 was observed for the nonionic polyether surfactant CgEs, although cosmfactant (up to 10 wt% pentanol) was required and no direct observation of solution microstructure was made [14]. Reports of w/c systems based on the hydrocarbon smfactant bis(2-ethyUiexyl)sodium sulfosuccinate (AOT) were published by Hutton and coworkers [15]. Again, a significant proportion of pentanol was required as a cosolvent to obtain a single-phase system and solvochromatic absorption studies suggested that no bulk water was present. 

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