Ion-exchange equilibria in surface-grafted poly(acrylic acid) and homopolymer poly(acrylic acid)

Abstract

There have been a number of studies on ion-exchange equilibria of polyelectrolyte, but those studies in surface-grafted polyelectrolyte system have been rarely reported. In this study, we prepared the surface-grafted poly(acrylic acid) by chemical initiation and compared its ion-exchange equilibria between hydrogen ion and alkali-metal ion to those in homopolymer poly(acrylic acid). Surface-grafted system shows more deviation from ordinary small molecules than homopolymer does. In low pH region the surface-grafted system shows larger extent of ion-exchange and in high pH region vice versa. These phenomena are explained by higher local density of carboxylic groups and restraint exerted by hydrophobic matrix in the surface-grafted system.