Oligomeric Phases

The di-substituted silanes such as methyloctyldichlor-silanes produce oligomeric bonded phases but this involves a more complicated procedure. The silica is first reacted with methyloctyldichlorsilane to link methyloctylchlorosilyl groups to the surface. The product is then treated with water, which hydrolyses the methyloctylchlorosilyl groups to methyloctylhyd-roxysilyl groups with the elimination of hydrochloric acid. The hydroxy product so produced is then reacted with more methyloctyldichlorsilane, attaching another methyloctylchlorosilyl group to the previous groups. This process of alternately treating the product with the silane reagent and then water can be repeated until eight, 10 or more oligomers are linked to each other and attached to each sterically available hydroxyl group on the surface. It should be noted, however, that hydroxylation of the bonded moiety is not the only possible reaction that can take place with the water. There will be situations where it will be sterically possible for a water molecule to react with two adjacent chains and thus produce some cross-linking. However, a small amount of cross-linking would indeed strengthen the bonded system and could be advantageous.

The product is finally treated with trimethyl-chlorosilane, or some other capping reagent, to eliminate the last hydroxyl groups formed at the end of the oligomer. The oligomers are layered over the surface and this helps to exclude solutes from interaction with any residual surface hydroxyl groups, making the product extremely stable with almost no polar characteristics. However, due to the complexity of the synthesis (which, ideally, needs to be carried out in a fluidized bed for efficient reaction), oligomeric phases are expensive to manufacture and, consequently, are not generally available.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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