Adsorption of anionic amphiphilic polyelectrolytes onto amino-terminated solid surfacesReport as inadecuate




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The adsorption behavior of several amphiphilic polyelectrolytes of polymaleic anhydride-alt-styrenefunctionalized with naphthyl and phenyl groups, onto amino-terminated silicon wafer has been studiedby means of null- ellipsometry, atomic force microscopy AFM and contact angle measurements. Themaximum of adsorption, Gplateau, varies with the ionic strength, the polyelectrolyte structure and thechain length. Values of Gplateau obtained at low and high ionic strengths indicate that the adsorptionfollows the -screening-reduced adsorption- regime. Large aggregates were detected in solution by meansof dynamic light scattering and fluorescence measurements. However, AFM indicated the formation ofsmooth layers and the absence of aggregates. A model based on a two-step adsorption behavior wasproposed. In the first one, isolated chains in equilibrium with the aggregates in solution adsorbed ontoamino-terminated surface. The adsorption is driven by electrostatic interaction between protonatedsurface and carboxylate groups. This first layer exposes naphtyl or phenyl groups to the solution. Thesecond layer adsorption is now driven by hydrophobic interaction between surface and chains andexposes carboxylate groups to the medium, which repel the forthcoming chain by electrostatic repulsion.Upon drying some hydrophobic naphtyl or phenyl groups might be oriented to the air, as revealed bycontact angle measurements. Such amphiphilic polyelectrolyte layers worked well for the building-up ofmultilayers with chitosan.Nota general

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Author: Urzúa Acevedo, Marcela; - Briones, X. G.; - Carrasco, L. P.; - Encinas, M. V.; - Petri, D. F. S.; -

Source: http://repositorio.uchile.cl/



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