Block nonionic surfactants

As seen in Table 15.1, the most important EO/PO block nonionic surfactants are those derived from propylene glycol and ethylenediamine as initiators, commercially known as Pluronics and Tetronics. Their general formulae can be written as follows ... 

As mentioned earlier, the most commonly employed alkylene oxides for producing block nonionic surfactants are the very reactive three-membered cyclic ethers such as EO and PO. Particularly, EO is highly flammable, explosive in some condition, and also toxic and an irritant for skin and eyes. For these reasons, the reactor employed in the synthesis, described earlier, must be equipped with sophisticated safety devices, process monitoring systems, and distributed control systems (DCS) to keep the reaction in safety condition and avoid gas-phase decomposition and the so-called runaway... 

In most cases, these active defoaming components are insoluble in the defoamer formulation as weU as in the foaming media, but there are cases which function by the inverted cloud-point mechanism (3). These products are soluble at low temperature and precipitate when the temperature is raised. When precipitated, these defoamer—surfactants function as defoamers when dissolved, they may act as foam stabilizers. Examples of this type are the block polymers of poly(ethylene oxide) and poly(propylene oxide) and other low HLB (hydrophilic—lipophilic balance) nonionic surfactants. 

Nonionic Surfactants Polyoxyalkylene Block Copolymers, edited by Vaughn M. Nace... 

The poloxamers manufactured by BASF (Cheadle, UK) are known as Pluronic PE block copolymers those manufactured by ICl (Cleveland, UK) as Synperonic PE nonionic surfactants. 

Nonionic surfactants, including EO-PO block copolymers, may be readily separated from anionic surfactants by a simple batch ion exchange method [21] analytical separation of EO-PO copolymers from other nonionic surfactants is possible by thin-layer chromatography (TLC) [22,23] and paper chromatography [24], and EO-PO copolymers may themselves be separated into narrow molecular weight fractions on a preparative scale by gel permeation chromatography (GPC) [25]. 

Ethylene oxide is an important intermediate chemical not only for the production of nonionic surfactants like fatty alcohol ethoxylates, alkylphenol ethoxy lates, or propylene oxide/ethylene oxide block copolymers, but also for manufacturing of anionic surfactants like alcohol ether sulfates. 

V M Nace, Nonionic surfactants polyoxyalkylene block copolymers (New York Marcel Dekker, 1996). 

Hunter R., S.F., F. Kezdy, The Adjuvant Activity of Nonionic Block Polymer Surfactants I. The Role of Hydrophile-Lipophile Balance, Journal of Immunology. 127, 1244, 1981. 

Chu B, Zhou Z (1996) Physical chemistry of polyoxyalkylene block copolymer surfactants. In Nace VN (ed) Nonionic surfactants polyoxyalkylene block copolymers, vol 60. Marcel Dekker, New York... 

V.M. Nace, Nonionic Surfactants Polyoxyalkylene Block Copolymers, Surfactant Science Series, Vol. 63, Marcel Dekker, New York, USA, 1996. 

Hunter R, Strickland F, Kezdy F (1981) The adjuvant activity of nonionic block polymer surfactants. J Immunol 127 1244-1250... 

Edens, M. W. (1996). Applications of polyoxyethylene block copolymer surfactants. In Nonionic surfactants. Polyoxyalkylene block copolymers, Vol. 60, (ed. V. N. Nace), p. 185. Marcel Dekker, New York. 

The clouding behavior of nonionic block copolymeric surfactants in water is an interesting feature inLuencing their practical usefulness. The clouding phenomenon results from the attractive interactions between PEO chains at elevated temperature in water. In other words, water becomes a less good solvent for PEO with increasing temperature. The molecular mechanism behind this has been disputed. A reasonable explanation is found in the conformational equilibrium of the PEO chains as suggested by Karlstrom (1985). 

Wetting agents Adhesion promoters Optical property modifiers Pigments Ionic and nonionic surfactants Silanes, titanates, block and graft copolymers Inorganic Ti, Fe, and Cr oxides, Cd, Ba, and Pb sulfides, sulfates, and chromates... 

The second repulsive energy (referred to as steric repulsion) is produced by the presence of adsorbed surfactant layers of nonionic surfactants, such as alcohol ethoxylates or A-B, A-B-A block, or BA graft copolymers, where B is the anchor chain and A is the stabilizing chain [mostly based on polyethylene oxide (PEO) for aqueous systems]. When two droplets or particles with adsorbed PEO chains of thickness 5 approach a separation distance h such that h < 28, repulsion occurs as a result of two main effects. The first arises as a result of the unfavorable mixing of the PEO chains, when these are in good solvent conditions. This is referred to as Gm x and is given by the following expression ... 

Whitmarsh, R. (1996) Nonionic surfactants. In. V. Nace (ed.), Polyoxyalkylene Block Copolymers. Dekker, New York. 

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