Silicon methoxylated

Dendrimers with a carbon-silicon core were prepared by a divergent hy-drosilylation - vinylation method followed by methoxylation [72], Hydrolysis and condensation resulted in gels only in the case of generation two dendrimers, while the sol-gel reaction products of generation one were still soluble, apparently due to strong cyclization characteristics of the sol-gel reactions. 

An equilibrium constant which is larger than the random value is observed for the exchange of methoxyl with methylthio groups. Similar values also have been found for the exchange of these substituents on the dimethyl-silicon moiety. 

The first step in the reaction course is the methanolysis of the Si-Cl bond that generates HCl which is capable to cleave the methoxylated bicyclic skeleton by a preliminary proton attack at the allylic position relative to the silicon. 

Figure 1. Equilibrium diagrams for the exchange on silicon (v = 4) of the following groups A methoxyl vs. ethoxyl at 150°C, B methoxyl vs. chloro at 120°C, and C dimethylaraino vs. chloro at 25°C. The dotted lines correspond to the random situation, and each curve exhibits a peak value at the value of the parameter R corresponding to the composition of the compound it represents.

Experimental examples of systems of this type include the scrambling of methoxyl, dimethylamino and chloro groups on silicon (v = 4) and of chloro, bromo, iodo and phenoxyl groups on methylgermanium (v = 3), using NMR for the molecular assays. 

Acrylic rubber can be emulsion- and suspension-polymerized from acrylic esters such as ethyl, butyl, and/or methoxyethyl acetate to produce polymers of ethyl acetate and copolymers of ethyl, butyl, and methoxyl acetate. Polyacrylate rubber, such as Acron from Cancarb Ltd., Alberta, Canada, possesses heat resistance and oil resistance between nitrile and silicone rubbers. Acrylic rubbers retain properties in the presence of hot oils and other automotive fluids, and resist softening or cracking when exposed to air up to 392°F (200°C). The copolymers retain flexibility down to -40°F (-40°C). Automotive seals and gaskets comprise a major market. These properties and inherent ozone resistance are largely due to the polymer s saturated backbone (see Table 3.13). 

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