Roth, I; Simon, F; Bellmann, C; Seifert, A; Spange, S
Nucleophilic aromatic substitution reactions of fluoronitro-substituted aromatic compounds with poly-(vinylamine) (PVAm)/silica adsorbates were studied to equip silica particles with primary amino as well as several chromophoric groups. 4-Fluoronitrobenzene (1, 4-FNB), 2-fluoronitrobenzene (2, 2-FNB), 4-fluoro-3-nitroaniline (3, 4-FNA), N,N-dimethyl-4-fluoro-3-nitroaniline (4, 4-DMFNA), 1-fluoro-2,4-dinitrobenzene (5, Sangers reagent, FDNB), 1,5-difluoro-2,4-dinitrobenzene (6, DFDNB), 4-fluoro-3-nitroazobenzene (7, FNAzoB), N-(2′,4′-dinitrophenyl)-4-fluoro-3-nitroaniline (8, N-DNP-FNA), and 4-fluoro-3,4′-dinitrostilbene (9, FDNstilbene) have been used as functionalization reagents. Various chromophoric functionalities could be readily synthesized on the silica surface by this elegant method. The degree of PV Am functionalization with chromophores was determined from the redissolved fraction of the functionalized polymer by means of UV/vis spectroscopy using model compounds as references. The surface structures of the chromophores fixed on polymer-modified silica particles were studied using X-ray photoelectron spectroscopy (XPS) and UV/vis spectroscopy. Brunauer - Emmett - Teller (BET) measurements and XPS studies suggest that the chromophores introduced in the PVAm layer on silica are differently distributed in the adsorbed PVAm layers. The vertical distribution of the chromophore in the PVAm layer depends on the reactivity of the fluoroaromatic. The more reactive the fluoroaromatic, the more unaffected remains the former pore-size distribution of silica. Changes of the surface charge were investigated by means of electrokinetic measurements. © 2006 American Chemical Society.