Swelling of Crosslinked Polyelectrolytes Composed of Vinyl alcohol and Acrylic acid Units

Abstract

Crosslinked copolymers of different polymer composition and density of crosslinking points were prepared by copolymerization of methylacrylate and vinylacetate in the presence of divinylbenzene as a crosslinking agent, the copolymers then being converted by saponification into polyelectrolytes containing carboxyl groups , along the chains. The degree of swelling of the sodium salts of these polyelectrolytes was measured in pure water. The osmotic coefficients in water were estimated from the degree of swelling in water, taking into consideration the effect of large deformation of the unit chains on the contractile pressure of the gel. The calculated values of the osmotic coefficient were very small and comparable to those previously found for the linear polyelectrolyte composed of the same components. The characteristic features of the results were discussed by considering the factors which may influence the activity of the counter-ions, such as the hydrolysis of the polyelectrolytes, the counter-ion fixation and the excluded volume effect of the macro-ions.