Structure and surface polarity of poly(vinylformamide-co-vinylamine) (PVFA-co-PVAm)/silica hybrid materials

Structure and surface polarity properties of poly(finylformamide-co-vinylam ine) (PVFA-co-PVAm)/ silica hybrid materials are investigated by means of e lectrokinetic measurements, atomic force microscopy (AFM), and solvatochrom ic probes. AFM measurements show the complete covering of the silica surfac e with the PVFA-co-PVAm layer, which. has a thickness between 0.5 and 2 nm depending on the content of the poly(vinylamine) (PVAm) component of the co polymer. The E-T(30) surface polarity parameters of PVFA-co-PVAm/silica hyb rid particles mere investigated by two differently substituted Reichardt's dyes, 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridino)phenolate (1) and its lipo philic derivative 2,6-di(4-tert-butylphenyl)-4-[tris-2,4,6-(4-tert-butylphe ny (2) Adsorption of the basic polymer PVFA-co-PVAm on silica significantly decreases the hydrogen bond donating capacity of the former silica surface , and therefore the E-T(30) surface polarity decreases linearly with increa sing the content of the PVAm component of the copolymer. Furthermore, it is shown that E-T(30) surface polarity values of the PVAm-co-PVFA/silica part icles measured with 2 in toluene correlate with the isoelectric points dete rmined by means of electrokinetic measurements in diluted aqueous electroly te solutions.