Sorption and Desorption of a Cationic Polymer by Human Hair: Effects of Salt Solutions

Abstract

Sorption of Polymer JR, a cationic cellulose ether, by human hair is greatly decreased in the presence of added electrolytes. This reflects the competition between cations of the added salt and the quaternary ammonium groups of the polymer for sorption sites in the substrate. In this respect the hair can be regarded as a “strong-acid” ion-exchanger, and it displays a selectivity to ions similar to that observed for conventional resin exchangers. Cations can be ranked in order according to their ability to decrease the sorption of Polymer JR as follows: La+++ > Al+++ < Fe+++ < Ca++ < Fe++ < Cs+ < Na+ < Li+. Salts also promote desorption of Polymer JR that is already sorbed by hair. However, selectivity is less evident in desorption than in sorption and is only observed at relatively low concentrations of salt. About half of the sorbed polymer is readily removed by salt solutions; the rest appears to be tightly attached to the substrate.