Siloxanes and polysiloxanes silicones

Although siloxanes are often classed as organometallic compounds, they are conveniently described in this chapter because of their structural relationship to silicates. 

In contrast, Pb02 shows acidic (but no basic) properties, forming [Pb(OH)g] when treated with alkali. Crystalline salts such as K2[Sn(OH)g] and K2[Pb(OH)g] can be isolated. 

---

Industrially produced organo-silicon compounds include monomeric low molecular compounds, almost exclusively belonging to the class of silanes, and oligomers and polymeric compounds including oligomeric silanes, polysilanes, oligomeric silazanes, polysilazanes and particularly oligomeric siloxanes and polysiloxanes (silicones). 

Figure 2.6 Reagents used for the deactivation of silanol groups on glass surfaces. A - disilazanes, B > cyclic siloxanes, and C -silicon hydride polysiloxanes in which R is usually methyl, phenyl, 3,3,3-trifluoropropyl, 3-cyanopropyl, or some combination of these groups. The lover portion of the figure provides a view of the surface of fused silica with adsorbed water (D), fused silica surface after deactivation with a trimethylsilylating reagent (E), and fused silica surface after treatment with a silicon hydride polysiloxane (F).

The entire area of organosilicon chemistry blossomed with Kipping s preparation of such compounds by the more convenient Grignard process. These silanes turned out to be of paramount importance since they hydrolyzed readily to form compounds containing Si-0 bonds, both linear and cyclic.12,22,24 28 These new materials were first called silicoketones or silicones by analogy with ketones in the organic area. Structural studies, however, showed that they did not contain the Si=0 double bond. Thus, the silicone name is a misnomer, but it has persisted, at least in casual usage. However, the terms siloxanes and polysiloxanes are preferred. 

Siloxane. See Polysiloxane Silicone Siloxane, dimethyl-. See Dimethylsiloxane Siloxane emulsion. See Silicone emulsion Siloxanes. See Silicone Siloxanes and silicones, 3-[(2-aminoethyl amino]propyl, methyl, dimethyl, docosanoates. See Dimethicone propylethylenediamine behenate... 

Two major classes of hydrophobic chemical substances can be applied to glass in ultrathin layers to inhibit surface wetting. Siloxanes or polysiloxanes or silicones are polymers with a backbone of alternating silicon and oxygen atoms. These macromolecules are quite chemically inert, show resistance to water, and exhibit stability at high and low temperatures. The most common siloxane polymer, polydimethylsiloxane, is composed of the monomeric (i.e., repeating) unit illustrated in Fig. 7.5.1. 

Burger, C. Kreuzer, F. H. Polysiloxanes and Polymers Containing Siloxane Groups. In Silicon in Polymer Synthesis Kricheldorf, H. R., Ed. Springer Berlin, 1996 pp 113-222. 

The commercial importance of polysiloxanes (silicone polymers) was discussed in Sec. 2-12f. The higher-MW polysiloxanes are synthesized by anionic or cationic polymerizations of cyclic siloxanes [Bostick, 1969 Kendrick et al., 1989 Noll, 1968 Saam, 1989 Wright, 1984]. The most commonly encountered polymerizations are those of the cyclic trimers and tetra-... 

It is well known that organosilicon compounds do not become equally well attached to all mineral substrates. While silicates always readily lend themselves to coating with silane and polysiloxane [19-21], the same cannot always be said of calcium carbonate [19, 20]. Calcium carbonate (calcite), a widely used filler, is generally considered difficult to cover with silanes. Given the proven, good attachment of silicone resin to calcium carbonate fillers in silicone resin emulsion paints [2, 22], the question arises as to whether only higher polymeric siloxanes are able to form hydrophobic protective coatings on calcium carbonate. 

C. Burger, F.-H. Kreuzer, "Polysiloxanes and Polymers Containing Siloxane Groups", in Silicon in Polymer Synthesis, (Ed. H. R. Kricheldorf), Springer, Berlin, 1996, p.ll3. 

Hydrolysis in the silicones is usually just a special case of the reaction with organic halides. The most important reaction is the preparation of siloxanes by the hydrolysis of chlorosilanes and the subsequent condensation to form the commercially important polysiloxanes (see Chap. 15). Diethyl silane diol, (CjHs)2Si(OH)s, and the corresponding di-n-propyl and di-n-butyl diols have been made by hydrolyzing the dichlorosilanes. The trimethyl and triethyl silicon hydroxides have been prepared by the hydrolysis of complex organic silicon compounds containing the aceto and the amino group, respectively. ... 

CAS 64365-23-7 68937-54-2 68938-54-5 Synonyms Dimethylmethyl (polyethylene oxide) siloxane Dimethylsilox-ane/glycol copolymer Polyoxyethylene-grafted polydimethylsiloxane Polysiloxane polyether copolymer Siloxanes and silicones, dimethyl, hydroxy-terminated, ethoxylated propoxylated Classification Silicone glycol surfactant... 

Dimethyidiphenyl siloxanes and silicones. See Phenylmethyl polysiloxane Dimethyidithiocarbamate zinc salt. See Zinc dimethyidithiocarbamate N,N-Dimethyl-1-dodecanamine-N-oxide Dimethyldodecylamine-N-oxide N,N-Dimethyldodecylamine oxide N,N-Dimethyldodecylamine-N-ox-ide. See Lauramine oxide... 

Aminopropylmethylsiloxane/dimethylsiloxane copolymer Siloxanes and silicones, dimethyl-. See Dimethylsiloxane Siloxanes and silicones, dimethyl, diphenyl. See Phenylmethyl polysiloxane... 

The Study of the thermal degradation of these same hybrid silicones [35] was achieved in comparison to the classical polydimethyl and polytrifluo-ropropylmethyl siloxanes, and the authors showed that the introduction of perfluoroalkylene segments - C6H4 - (CF2)x - C6H4 - into the main chain of the polysiloxane increased the thermal stabiUty both under inert and oxidative atmosphere. 

Dimethyidiphenyl siloxanes and silicones. See Phenylmethyl polysiloxane Dimethyl diphenyl thiuram disulfide CAS 10591-84-1... 

See Phenylmethyl polysiloxane Siloxanes and silicones, dimethyl, [(12-hydroxy-1-oxooctadecyl) oxy]-terminated. See Dimethiconol hydroxystearate Siloxanes and silicones, dimethyl, 3-hydroxypropyl methyl-, ethers with PEG dihydrogen phosphate, compds. with N,N -bis [3-(di methyl ami no) propyl]-C18-unsaturated amide dimers. See Dilinoleamidopropyl dimethylamine dimethicone copolyol phosphate,... 

The hydrosilylation of 1-heptene, allyl glycidyl ether, and allylpolyether by heptamethyl(hydrosiloxane) and their respective polysiloxanes catalyzed by rhodium siloxide complex in imidazolinum ionic liquids, especially [TriMIM]MeS04, gives heptylglycidoxjdunctional (poly)siloxanes and silicone polyethers with high yield and selectivity. The catalytic system can be easily separated and successfully reused up to five times (123). 

The liquid stationary phases used with capillary columns are similar to those used in packed columns. The most common stationary phases are polysiloxanes (silicones) that contain various substituents that modify the polarity of the phase. Polydimethyl siloxane (methyl silicone) is nonpolar. Replacing methyl groups with increasing numbers of phenyl substituents increases the polarity of the silicone. For example, J W DB-1, or a similar stationary phase sold by other companies, has the same properties as methyl silicone (SE-30 or DC-200) and is used with nonpolar... 

---