| Evanescent-wave excitation of fluorescence was used to study the adsorption of Ru(bpy){dollar}sb3sp{lcub}2+{rcub}{dollar} from aqueous solution to three types of surfaces: bare silica, a dimethylethylsiloxane (C{dollar}sb2{dollar}) monolayer on silica and a dimethyloctadecylsiloxane (C{dollar}sb{lcub}18{rcub}{dollar}) monolayer on silica. The free energy of adsorption for the bare silica surface,{dollar}-26.2( pm{dollar} 0.2) kJ/mol at pH 8, was attributed to electrostatic interactions alone. The free energy of adsorption for the C{dollar}sb2{dollar} and C{dollar}sb{lcub}18{rcub}{dollar} surfaces, {dollar}-28.5( pm 0.1{dollar}) kJ/mol and {dollar}-31.5( pm{dollar} 0.1) kJ/mol, respectively, were found to have both electrostatic and nonpolar contributions, with the latter being larger by 50% for the C{dollar}sb2{dollar} surface and 100% for the C{dollar}sb{lcub}18{rcub}{dollar} surface.; A novel surface reaction, surface-confined living radical polymerization (SCLRP), has been developed to make uniform films on substrates with controlled thickness. The key idea here is to attach a special initiation molecule on substrates from which a living radical could be formed with catalysis of a metal complex. A typical example presented in this study is {dollar}rm SiOsb2{dollar}-{dollar}rm CHsb{lcub}2{rcub}CHsb{lcub}2{rcub}Csb{lcub}6{rcub}Hsb{lcub}5{rcub}CHsb{lcub}2{rcub}Cl/CuCl/Bipy{dollar} living radical initiator system. Benzyl chloride monolayer was self-assembled on silica surface. CuCl/Bipy complex was used to abstract chlorine atom from benzyl chloride to form living radical ({dollar}rm SiOsb{lcub}2{rcub}{dollar}-{dollar}rm CHsb{lcub}2{rcub}CHsb{lcub}2{rcub}Csb{lcub}6{rcub}Hsb{lcub}5{rcub}CHsb{lcub}2{rcub}bullet) at 130spcirc{dollar}C. The surface living radicals initiated the polymerization of acrylamide to form polyacrylamide (PAAm) film on silica surface.; Surface-confined living radical polymerization was applied to porous silica to make a stationary phase. The polymerization was so well controlled that it was the first time that films grown on nano-porous silica left the pores intact, as shown by its ability to separate proteins by size-exclusion. The living polyacrylamide film covers the silica surface uniformly, as shown by the highly efficient elution of lysozyme, a strongly basic protein, at pH 4.7.; Surface-confined living radical polymerization was further applied to capillary coatings. The study showed that SCRLP is a controlled means of covalently bonding both linear and cross-linked polymer films on silica. The polymerization is intrinsically confined to the surface, avoiding the problem of capillary clogging associated with polymer formed in the solution. Capillary electrophoresis of strongly basic proteins confirms that the coated capillaries provide the high efficiency expected for polyacrylamide. The cross-linked coating exhibits higher reproducibility with respect to migration time than does the linear coating. |
