Physicochemical properties of polysaccharide coatings based on grafted multilayer assemblies

Carboxymethyldextrans of different charge densities have been attached to flat silicon wafer surfaces using plasma polymer interlayers in conjunction with two different chemical grafting strategies. The resultant coatings have been analyzed by XPS, to verify the surface coverage of the coatings and to estimate their dry thicknesses. Electrokinetic streaming potential measurement has been used to ascertain the electrostatic properties of the coatings, and atomic force microscope colloid probe force measurements have been used to provide insights into the extension of the polysaccharide chains from the interface in aqueous environments. The results demonstrate that polysaccharide layer thickness in solution is maximized when a secondary, amine-rich polyelectrolyte interlayer is introduced onto the plasma polymer surface prior to polysaccharide attachment. An increased carboxyl density in the polysaccharide has also been shown to give rise to thicker polymer layers in solution, with the electrokinetic properties of the resultant surfaces reflecting the charge density of the coupled polysaccharide. The data demonstrate that methods exist for tailoring the steric and electrostatic properties of interfaces based on the fine control of polysaccharide grafting.