Carbohydrate-modified siloxanes

Summary The wetting behavior of liquid siloxanes and aqueous solutions of carbohydrate-modified siloxane surfactants on perfluorinated surfaces has been investigated. Siloxanyl moieties in surfactants level off to a large extent the influences of other structural elements. The donor-acceptor portions of the surface tension and the interfacial tension solid/liquid converge and amount to about 1-2 mN/m. The contact angle is not a linear function of the surface tension. It results from the superposition of surface tension and interfacial tension solid/liquid, both independent of each other. 

For that purpose carbohydrate-modified siloxane surfactants bearing four independent structural elements (i) siloxanyl moiety (si), (ii) spacer (sp), (iii) carbohydrate unit (ch) and (iv) modifying element (mo) have been synthesized [4, 5, 6]... 

A. Synthetic Methods for Carbohydrate - Modified Siloxane Surfactants... 

A broad variety of carbohydrate-modified siloxane surfactants have been synthesized and tested as surfactants [72-75] or in cosmetic formulations [76-79]. Such compounds are currently produced on an industrial scale (see for example Scheme 5) and their use has gradually increased due to their excellent biodegradabilify, good dermatological compatibility, and the absence of toxic effects. 

B. Applications of Carbohydrate Modified Siloxanes in Polymer Stabilization... 

Attempts have been made to prepare microemulsions of hexamethyldisiloxane or longer PDMS, using carbohydrate modified siloxane surfactants [78, 79], but the approach was not succesful due to the siloxane insolubility of the amphiphile [53]. The addition of ethanol was helpful, but only in certain cases. 

Other chemical reactions can be performed in the presence of carbohydrate modified siloxane surfactants. For example, a glucose substituted cyclosiloxane has been successfully used to stabilize silver nanopartieles (Figure 2) [102],... 

M. Haupt, S. Knaus, T. Rohr, H. Gruber, J. Macromol. Sci. Pure Appl. Chem. 2000, A37(4), 323-341. Carbohydrate modified polydimethylsiloxanes. Part 1. Synthesis and Characterization of carbohydrate silane and siloxane building blocks ... 

Recent developments in this research field and especially our experimental results on the synthesis, properties and applications of siloxane-containing surfactants will be reviewed. Our main interest is to propose new surfactants or alternative synthetic procedures, and new stabilization systems for polymeric nanoparticles. Carbohydrate modified (poly)siloxanes with different architectures have particularily been studied and tested, due to their biocompatibility and bioavailability. 

This class of substances has been studied only in the last few years and thus it has not been thoroughly characterized. Commercial synthesis of carbohydrate-modified siioxanes turns out to be difficult because of the need for extensive use of protecting groups, hydrolysis of connecting bonds, or decomposition of the siloxane backbone under acidic reaction conditions. Only a few applications are known, e.g., for the modification of contact lenses [20,21] and the production of glass fibers [22]. A polyglycoside-modified siloxane has been developed that can be used as a water-in-oil (w/o) emulsifier in cosmetics [23]. 

R. Wagner, Y. Wu, L. Richter, S. Siegel, J. Weissmuller, J. Reiners, Appl. Organometal. Chem., 1998, 12(12), 843-853. Silicon-modified carbohydrate surfactants IX dynamic wetting of a perfluorinated solid surface by solutions of a siloxane surfactant above and below the critical micelle concentration. ... 

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