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Advancing contact angles formed by water and aqueous ethanol solutions were measured on both bare surfaces and film-covered surfaces of acrylic, glass, hydrophilic and hydrophobic silicon, polycarbonate, polyester, and stainless steel. Each bare surface was initially characterized with respect to its hydrophilic - hydrophobic balance. Both protein films and milk films were prepared on each surface; the adsorbed mass comprising each film was measured with ellipsometry. Contact angle methods proved useful in detecting the presence of a protein film on sufficiently hydrophilic or sufficiently hydrophobic surfaces. Contact angle methods were also found to be useful for detecting the presence of a milk film on sufficiently hydrophilic solid surfaces. The results also indicated that the type of diagnostic liquid chosen for the analysis becomes an important factor for films of increasing complexity. In any event, contact angle analysis is inappropriate to quantify the actual mass of soil remaining on a solid surface. / Graduation date: 1991

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Three alkyldihydrochlorosilanes were synthesized; ethyldihydrochlorosilane, octyldihydrochlorosilane and octadecyldihydrosilane. Ethyldihydrochlorosilane was produced by the reaction of ethylsilane with mercuric chloride and the other two chlorosilanes were produced by the reaction of the alkyl Grignard reagent with dichlorosilane. Each alkyldihydrochlorosilane was reacted with porous silica in an attempt to discover the extent of reaction or the highest surface concentration of bonded groups attainable. The reaction between these alkydihydrochlorosilanes and porous silica was compared to the reaction between silica and the analogous alkyldimethylchlorosilane. The rate of reaction of both type of chlorosilane was found to be essentially the same. The maximum surface concentration of bonded surface groups attainable by alkyldihydrochlorosilanes was found to be approximately 1.3 #moles/m² greater than that attainable by alkyldimethylchlorosilanes. This increased surface coverage seemed to depend very little on the chain length of the alkyl group and was attributed to the decrease in steric hindrance of the bonding silicon atom of the silane. Surface bound silyl hydrides could be oxidized selectively and sequentially to form silane silanols. Surface silanes also appeared to reduce chloroplatinic acid, but were not observed to add efficiently to olefins. The chromatographic properties of silica modified with alkyldihydrochlorosilanes were compared to those of equivalent silicas modified with alkyldimethylchlorosilanes and alkyltrichlorosilanes before and after the surface silanes were oxidized. Both normal and reversed-phase liquid chromatographic studies were conducted. In general, it was found that alkyldihydrochlorosilanes yielded the most polar modified silicas. This greater surface polarity was attributed to an increase in the activity of water in the near surface region of the bonded phase.

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