Siloxane surface activity

Owen, M. J. Siloxane Surface Activity , in Silicon-based Polymer Science A Comprehensive Resource (Eds. J. M. Zeigler, F. W. G. Fearon), American Chemical Society (ACS Adv. Chem. Ser. 224), Washington, DC, 1990, Chap. 40, p. 705. 

M.J. Owen, Siloxane surface activity, in Silicon-Based Polymer Science, J.M. Zeigler and F.W.G. Fearon, eds.. Advances in Chemistry Series 224, American Chemical Society,... 

Another class of siloxane surface active agents is that of cationic siufactants, which usually contain amine groups (Scheme 10) and are widely used in cosmetic products, especially as hair softeners and conditioners [54]. A quaternary ammonium chloride has been used to modify montmorillonite, in order to obtain nanocomposites with polymethylsilsesquioxane [104]. 

Owen MJ (1990) Siloxane surface activity. In Zeigler JM, Fearon FWG (eds) Sihcon-based polymer science a comprehensive resource. American Chemical Society, Washington, D.C., pp 705-739... 

Surface active agents are important components of foam formulations. They decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic resin. In addition they can aid nucleation, stabilise the foam and control cell structure. A wide range of such agents, both ionic and non-ionic, has been used at various times but the success of the one-shot process has been due in no small measure to the development of the water-soluble polyether siloxanes. These are either block or graft copolymers of a polydimethylsiloxane with a polyalkylene oxide (the latter usually an ethylene oxide-propylene oxide copolymer). Since these materials are susceptible to hydrolysis they should be used within a few days of mixing with water. 

The unique surface characteristics of polysiloxanes mean that they are extensively used as surfactants. Silicone surfactants have been thoroughly studied and described in numerous articles. For an extensive, in-depth discussion of this subject, a recent chapter by Hill,476 and his introductory chapter in the monograph he later edited,477 are excellent references. In the latter monograph, many aspects of silicone surfactants are described in 12 chapters. In the introduction, Hill discusses the chemistry of silicone surfactants, surface activity, aggregation behavior of silicone surfactants in various media, and their key applications in polyurethane foam manufacture, in textile and fiber industry, in personal care, and in paint and coating industries. All this information (with 200 cited references) provides a broad background for the discussion of more specific issues covered in other chapters. Thus, surfactants based on silicone polyether co-polymers are surveyed.478 Novel siloxane surfactant structures,479 surface activity and aggregation phenomena,480 silicone surfactants application in the formation of polyurethane foam,481 foam control and... 

In a recent review by Drake et al. 1 the surface activity of linear polymers and co-polymers is discussed, based on many recent references. They refer to the research correlating surface characteristics of siloxanes to the nature of end groups575 and to their concentration576 in linear polymers. A few examples of the recent work on siloxane migration to the interfaces, with the emphasis on the behavior of block577 and graft co-polymers,578 and their blends with... 

Hoffmann, H. Ulbricht, W. Surface Activity and Aggregation Behavior of Siloxane Surfactants. In Silicone Surfactants Hill, R. M., Ed. Surfactant Science Series Dekker New York, 1999 Vol. 86, Chapter 4, pp 98-136. 

In the case where foam instability is desirable, it is essential to choose surfactants that weaken the Gibbs-Marangoni effect. A more surface-active material such as a poly(alkyl) siloxane is added to destabilize the foam. The siloxane surfactant adsorbs preferentially at the air/liquid interface, thus displacing the original surfactant that stabilizes the foam. In many cases, the siloxane surfactant is produced as an emulsion which also contains hydrophobic silica particles. This combination produces a synergetic effect for foam breaking. 

The basic skeleton o7 tEe modified sorbents consists of a surface-active silica gel. Modification is in the form of a surface reaction with specially active silanes at the silanol groups of the silica gel. Following elimination of these silanol groups, new siloxane groupings are formed, on which aliphatic hydrocarbon groups are chemically bound by silicon-carbon bonds to the silica gel skeleton. Pre-coated plates with these modified silica gels are designated ... 

Hoffmann, H. and Ulbricht, W. (1999) Surface activity and aggregation behavior of siloxane surfactants. Surfactant Sci. Ser., 86, 97-136. 

---