Trisiloxane surfactants silane, compared

Summary Organomodified trisiloxanes show remarkable surface activity. Thus they can be used as additives in detergents, foaming agents or agrochemicals. However, this class of compounds has a limited range of applications, since it is susceptible to hydrolytic decomposition in aqueous solution. The hydrolysis occurs at the silicon-oxygen-bonds present within the molecules. Recently, a new class of silane surfactants free of Si-0-bonds has been developed. These silane surfactants proved to be hydrolytically stable even under extreme pH. Furthermore they exhibit surfactant properties comparable to those typical of trisiloxane surfactants. 

By using a recently developed magnesium hydride technology, the trisiloxane lyophobic part in superspreading surfactants can be substituted by a trimethylsilane moiety. This synthetic route leads to both nonionic and ionic silane surfactants, which are hydrolytically stable even under extreme pH. Aqueous solutions of these new surfactants exhibit surface tension and wetting properties comparable to the traditional organomodified trisiloxane surfactants. The combination of hydrolytic stability and biodegradability offers chance for the widespread application of these silane based surfactants. 

To sum it up we can stress that the substitution of the trisiloxane lyophobic part by a trimethyl silane moiety yields both nonionic and ionic silane surfactants. Aqueous solutions of these new surfactants are extremely stable in both alkaline and acidic conditions due to the fact that the siloxane substructure is left out. The surfactant properties of these substances are to a great extent comparable to the abilities of trisiloxane wetting agents. 

Several methods have been employed to study the effect of replacing the trisiloxane by a trimethylsilyl group on the surfactant properties. The results (Table 2) show that the silane surfoctant B is comparable to the trisiloxane derivative A (Fig. 23) in terms of surface activity the interfacial tensions are somewhat higher. 

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