Abstract
Interaction between cationic surfactants and natural gums were investigated with attention to conductivity, sodium ion activity, alkyltrimethyl ammonium ion activity and precipitation reaction in gum-surfactant mixed solutions. Among many kinds of gums, chondroitin sulfate (CHs) as a linear-polysaccharide with high charge density and gum arabic (Ar) as a branchedpolysaccharide with low charge density were mainly used in the present work.
Binding of CHs with surfactant occurred to be completed in a narrow range of markedly lower concentration than the CMC of the surfactants used and the binding curve was extremely steep. On the other hand, binding of Ar with surfactant occurred in a wide concentration range and the binding curve was rather gentle. With respect to the concentration at which surfactants will start to bind with gums, the concentration of decyltrimethyl ammonium bromide was ten times as large as that of dodecyltrimethyl ammonium bromide.
These results indicate that there will be some strong interactions between gums and cationic surfactants and that the degree of the interaction will depends on both the charge density of gums and the alkyl chain length of surfactants. This strong interaction between gums and cationic surfactants followed by the precipitation, is thought to be very useful for the discriminative tests of various kinds of gums.
