Surface-active agents, grafting

Alkenylsuccinic anhydrides made from several linear alpha olefins are used in paper sizing, detergents, and other uses. Sulfosuccinic acid esters serve as surface active agents. Alkyd resins (qv) are used as surface coatings. Chlorendric anhydride [115-27-5] is used as a flame resistant component (see Flame retardants). Tetrahydrophthalic acid [88-98-2] and hexahydrophthalic anhydride [85-42-7] have specialty resin appHcations. Gas barrier films made by grafting maleic anhydride to polypropylene [25085-53-4] film are used in food packaging (qv). Poly(maleic anhydride) [24937-72-2] is used as a scale preventer and corrosion inhibitor (see Corrosion and corrosion control). Maleic anhydride forms copolymers with ethylene glycol methyl vinyl ethers which are partially esterified for biomedical and pharmaceutical uses (189) (see Pharmaceuticals). 

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. 

Grafting of Monomer to Surface-Active Agents. A recent patent claims the preparation of a F/T stable poly(vinylacetate-vinylbenzoate) copolymer emulsion in the presence of a graft polymer of vinylacetate on a polyalkylene glycol (21). 

The degree of dispersion depends on the degree of grafting, where the graft acts almost as a surface-active agent to keep the rubber in a colloidal dispersion in the matrix. The effectiveness of the graft appears... 

The membranes were prepared by volume grafting of acrylic acid onto polypropylene activated by soft oxidation of the polymer in the presence of tert-butylhydroperoxide as the initiator and sodium dodecylsulphate as the surface active agent. During the preparation, samples of preactivated polypropylene film were immersed in aqueous solution of acrylic acid of 1,84 mol/dm concentration for periods of time ranging from 4 up to 14 hrs. The monomer penetrating the film by sorption was polymerized within the film at 358 K. 

Instead of fixing H" " or OH ions on the surface, it is of course possible to adsorb other simple ions or to carry out other chemical reactions (e.g., grafting, complexing), but the most spectacular results have been obtained using surface active agents and polymers. 

Graft copolymers in which chemically-different polymer-segments are combined within the same molecule have found many important applications in the polymerusing industries. For example, graft copolymers are used in adhesive and coating compositions, as dispersants and also for biomedical use. To the Colloid Scientist graft copolymers are very attractive since, in principle, they offer the means by which macromolecular surface-active agents of precisely-tailored architecture can be... 

The use of dimethyldichlorosilane as a coupling agent for the grafting of VOx structures on the MCM-48 surface, produces a material that is simultaneously hydrophobic (inmiscible with water) and very active (all V-centers are accessible, even for water molecules and the catalytic activity for methanol oxidation has increased). The VOx surface species are grafted by the Molecular Designed Dispersion of VO(acac)2 on the silylated surface, followed by a calcination in air at 450°C. These hydrophobic MCM-48 supported VOx catalysts are stable up to 500°C and show a dramatic reduction in the leaching of the V-centers in aqueous media. Also the structural stability has improved enormously. The crystallinity of the materials does not decrease significantly, even not when the samples are subjected to a hydrothermal treatment at 160°C and 6.1 atm. pressure. 

An amino-functional spacer arm is introduced at the 5 position of the ODN in the last step of its automated synthesis. ODN can be grafted via various functions available on flat carriers (such as flat silicon surfaces or wafers covered in silane) or on latex particles. Table 2 shows a list of various activation agents used and the reactive group resulting from the activation depending on the compound involved when available, the maximum grafting amount is also reported. 

Figure 5.3 Various designs of textile structures loaded with active agents (a) active agent incorporated in fibers/filaments (core/shell or matrix structure), (b) active agent incorporated into coating/impregnation film, and (c) active agent incorporated in microparticles attached to the textile surface (by grafting or via binder).

The well-established surface activity of block and graft copolymers, make them of great practical interest as dispersants, emulsifiers, wetting agents, foam stabilizers, flocculants, demulsifiers, viscosity modifiers, etc in many industrial and pharmaceutical prepara-... 

Free-radical method usually requires a surface activation by a direct attachment of initiator molecules or by the introduction of surface active sites (i.e., vinyl groups in surface graft polymerization of vinyl monomers). In particular, organosilane coupling agents (i.e., chloro- and alkoxysilanes) are commonly employed to introduce active sites onto inorganic oxide surfaces. 

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