Interaction between Water-soluble Polymer and Dyes -Solubilization of Dyes by a Water-soluble Polymer-

Abstract

The interaction of nonionic dyes with sodium poly (styrene sulfonate) (PSSNa) was investi gated by means of solubility measurement and equilibrium dialysis. The solubilities of p- aminoazobenzene (PAAB) and naphthalene (NA) increase in the presence of PSSNa. The increase in solubility depends on the degree of sulfonation (D. S.) of the polymer but is independent of the molecular weight when its value is above 9 x10⁴ (D. S. =100%). The smaller the D. S., the larger becomes the solubilization. The solubilizing effect of PSSNa is remarkably larger than those of sodium p-ethylbenzenesulfonate (EBSNa) and sodium p-toluenesulfonate (PTSNa), and the effect is enhanced by the presence of NaCl. In the case s of EBSNa and PTSNa, the addition of NaCl brings about salting out. The solubilities of PAAB and NA in aqueous PSSNa solution increase linearly with concentration of PSSNa and the tendency accords with the results of equilibrium dialysis.
The thermodynamic quantities of trans fer of PAAB from water to the aqueous solutions of PSSNa and aromatic sulfonates are ΔH_tr < 0, ΔS_u.tr < 0, and ΔH_tr > 0, ΔS_u.tr > 0, respectively.
It was suggested that the interaction between PAAB and PSSNa could be inte rpreted in terms of partition of PAAB between polymer and aqueous phase similar to the dyeing system of nonionic dye and polymer. The mechanism of solubilization of PAAB in the presence of PSSNa and PTSNa was explained in terms of an exothermic interaction of PAAB with the PSSNa moiety and of an entropy contribution due to the water structure change.