Fluorinated alkylsilane

The flow control elements or valves developed in Sandia were plugs of nonporous monolithic polymer prepared from fluorinated acrylates via UV-initiated polymerization directly in one of the channels. The reason for using the fluorinated monomers is to manage the surface energy, decrease their friction in channel, enable actuation at a low pressure, as well as to avoid both swelling and shrinking in solvents typically used in reversed-phase separations such as water and acetonitrile. The friction could be further decreased by modification of the valve channel with fluorinated alkylsilane. However, the latter may be counterproductive in systems used for the separation of proteins and peptides because they tend to adsorb on highly hydrophobic surfaces. 

Zhou et al. [43] used the same experimental apparatus to evaluate the mechanical performance of cotton fabric that was rendered superhydrophobic by incorporation of polyaniline and fluorinated alkylsilane via a facile vapor phase deposition process. The applied pressure was 3.68 kPa. The authors demonstrated that their surface could maintain water APCAs greater than 150° for 600 abrasion cycles but they did not mention anything about hysteresis values. 

The water contact angle on flat stainless steel surface, after coating with fluorinated alkylsilane, FTS, is about 105° 3° [11,29]. The morphologies of various structures were analyzed using SEM before and after silaniza-tion, and the thin layer of fluorinated alkylsilane did not affect the surface morphology. The contact angle (CA) and contact angle hysteresis (CAFI) of various structures were measured as discussed above. 

A kinetic study of the hydrodefluorination of C F H in the presence of EtjSiH indicated a first-order dependence on both [fluoroarene] and [ruthenium precursor] and a zero-order dependence on the concentration of alkylsilane, implying that the rate-limiting step in the catalytic cycle involves activation of the fluoroarene. The regioselectivity for hydrodefluorination of partially fluorinated substrates such as CgFjH has been accounted for by an initial C-H bond activation as shown in the... 

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. 

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