Studies on interaction between polyanions and counterions

Abstract

Part A. The effects of surface density and counterion size upon the dissociation behavior of poly(acrylic acid) grafted on polyethylene surface were investigated. The effect of counterion size was studied in aqueous alkali metal salt solutions (LiCl, NaCl, KCl, and CsCl) by potentiometric titration methods. To study the effect of surface density, we prepared a "poly(acrylic acid) gradient surface" where the density of poly(acrylic acid) is changed gradually along the sample distance. The gradient surface was produced by the treatment of a polyethylene sheet using corona with gradually increasing power and the following graft polymerization in 10 wt\% acrylic acid solution. The prepared gradient surface was characterized by Fourier transform infrared spectroscopy in the attenuated total reflectance mode. Potentiometric titration curves for the sections of the gradient surface were obtained in the salt solutions to measure the changes of electrostatic Gibbs free energy of poly(acrylic acid) on the gradient surface. It was observed that the changes of electrostatic Gibbs free energy increase with the increasing density of poly(acrylic acid) grafted on the surface and the decreasing hydrated radius of alkali metal ion in the solution. It was difficult to remove protons from the poly(acrylic acid) on the sections with high surface density and in the solutions containing the alkali metal ion with the small hydrated radius. Part B. The information for the interaction between water molecules and a polyelectrolyte was obtained from $^{23$Na NMR studies for sodium polymethacrylate in water-methanol mixtures. The chemical shift and the line width of the $^{23}\!$Na nucleus give the information on the immediate magnetic environment and the motion of the nucleus, respectively. The change of the chemical shift for $^{23}$Na nucleus is investigated as decreasing the temperature and changing the mole fraction of water in solvent. According to this result, the hydrogen bonding ...