Polysiloxanes surface activity

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... 

Y. Sela, S. Magdassi, and N. Garti Newly Designed Polysiloxane-Graft-Poly (Oxyethylene) Copolymeric Surfactants Preparation, Surface Activity and Emulsification Properties. Colloid Polym. Sci. 272, 684 (1994). 

Molecular structure and physicochemical properties of the carrier used are important for SLM stability, especially the lipophilicity, surface activity, and its solubihty in the membrane solvent. The membrane is less stable when a more surface-active compound is used as a carrier [89]. When the carrier loss is the main reason for the SLM instabihty, the membrane stabihty can be increased by attaching the carriers to a polymer or covalently hnked onto long ahphatic chains or polysiloxanes [95]. 

Sela Y, Magdassi S, Garti N. Newly design polysiloxane-graft-poly-(oxyethylene) copolymeric surfactants preparation, surface activity and emulsification properties. Colloid Polym Sci 1994 272 684-691. 

Knowledge of the polymerization and copolymerization of cyclosiloxanes and the structure of the polymers so formed is fundamental to understanding the structure-property relationships of polysiloxanes. Such knowledge in the areas of polymer stability, reactivity and surface activity is of prime importance in the industrial application of polysiloxanes. 

SURFACE ACTIVE PROPERTY OF POLYSILOXANE GRAFT COPOLYMERS... 

One of the most characteristic properties of polysiloxane graft copolymers is their surface activity. Since PDMS has a very low surface energy, it accumulates at the... 

Polysiloxane nanofilaments can be superhydrophobic. Such filaments can be subsequently patterned to present a superfunctional surface. Activation is achieved by an oxygen plasma followed by reaction with... 

To obtain homeotropic alignment by surface active agent treatment of the substrate surface, silicon compoimds are usually used as the surface active agent. Silicon compounds, such as alkoxysilanes or chlorosilanes, react with the substrate surface following Scheme 3.7.1 and pol5mierize to form polysiloxane structures near the surface. 

Also of interest are fluorosiloxane elastomers. Placing fluorine atoms into silox-ane repeat units can be useful for increasing the solvent resistance, thermal stability, and surface-active properties of a polysiloxane [12-14]. 

Owen MJ, Kendrick TC (1970) Surface activity of polystyrene-polysiloxane-polystyrene ABA block copolymers. Macromolecules 3 458-461... 

To reduce the inductive effect on the Si—C bond, the perfluorinated group has to be isolated from the silicon atom. Fluorination of an alkylsilane even in the P position yields hydrolytically unstable compounds which undergo thermal rearrangements and liberate Cp2=CR2- Fluorination of an alkyl group in the 7 position, CF3CH2CH2—, does not affect the Si— F bond significantly and the hydrolytic stability is adequate for practical use [132]. The dichlorosilane CF3CH2CH2Si(CH3)Cl2 hydrolyzes to form a polysiloxane. However, the ethylene link increases the bulkiness of the side chains, increases the hydrocarbon/flu-orocarbon ratio, and causes fluorocarbon-hydrocarbon and fluorine-silicone interactions and orientation effects which may reduce the surface activity of the fluorinated compound. 

The discussion so far has been confined to hydrocarbon—based initiators and block groups. There is no fundamental reason for not including materials of other types in the construction of such surfactants. Huorine-substituted carbon chains, polysiloxanes, and fluorinated polysiloxanes have become of increasing interest technologically because of their exceptional surface activity and utility in a wide variety of solvents and chemical environments. General interest in such materials is limited by the lack of reactive starting materials, difficulties in working with such materials (toxicity, etc.), and costs. 

The same authors developed a process of encapsulation of polymers swelled by halogenated solvents in which ozone is greatly soluble but not monomers to be grafted. After ozonization of polymers swelled in solvents, mixtures of mono unsaturated or di unsaturated monomers are added to the activated polymers. Then, grafting is operated by UV irradiation. Grafting is mainly located at the surface of the starting polymer what prevents the modification of its intrinsic properties. This process permits to produce hydrophilic polysiloxanes used in medical applications (contact lenses, tubes, catheters, etc.). 

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