Structure and surface polarity properties of poly(vinylformamide-co-vinylamine) (PVFA-co-PVAm)/ silica hybrid materials are investigated by means of electrokinetic measurements, atomic force microscopy (AFM), and solvatochromic probes. AFM measurements show the complete covering of the silica surface 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 copolymer. The ET(30) surface polarity parameters of PVFA-co-PVAm/silica hybrid particles were investigated by two differently substituted Reichardt's dyes, 2,6-diphenyl-4-(2,4,6-triphenyl-N-pyridino)phenolate (1) and its lipophilic derivative 2,6-di(4-tert-butylphenyl)-4-[tris-2,4,6-(4-tert-butylphenyl-N-pyridino)]phenolate (2). Adsorption of the basic polymer PVFAco-PVAm on silica significantly decreases the hydrogen bond donating capacity of the former silica surface, and therefore the ET(30) surface polarity decreases linearly with increasing the content of the PVAm component of the copolymer. Furthermore, it is shown that ET(30) surface polarity values of the PVAmco-PVFA/silica particles measured with 2 in toluene correlate with the isoelectric points determined by means of electrokinetic measurements in diluted aqueous electrolyte solutions.
The postfunctionalization of polyelectrolyte (PE) poly(vinyl formamide-co-vinylamine) (PVFA-co-PVAm)
layers adsorbed on silica or titanium dioxide particles with fullerene (C60) has been investigated. The
functionalization process requires two steps, the adsorption of the (PVFA-co-PVAm) from an aqueous
solution onto the inorganic particles (silica or titanium dioxide) and the reaction of the PE-modified particles
with C60 in toluene. By means of this procedure the PVFA-co-PVAm layer on the particle surface is irreversibly
fixed by the reaction between the accessible primary amino groups of the PE and fullerene (C60). The degree
of conversion of PVFA-co-PVAm/silica with C60 has been investigated by UV−vis spectroscopy and
quantitative electron paramagnetic resonance spectroscopy. The fixing of only a small amount of fullerene
on the PVFA-co-PVAm layer strongly influences the Brønsted acid−base behavior and the surface charge
density of the whole particles as shown by electrokinetic measurements. Atomic force microscopic
investigations on smooth PVFA-co-PVAm/silicon substrates before and after C60 functionalization show
that C60 molecules form aggregates within the PE layer. Furthermore, the E
T(30) polarity parameters of
the C60-functionalized PVFA-co-PVAm layers on silica are investigated by various substituted Reichardts
dyes.
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