Cationic polystyrene latex was prepared from the comonomer N, N′-dimethylaminoethylmeth-acrylate without an emulsifier using 2, 2′-azobis (2-amidinopropane) dihydrochloride as initiator. Subsequently, the ζ potential of that latex in various acid dye solutions of pH 3 was measured at different temperatures as a function of dye concentration Cd. The ζ potential of the latex turned from positive to negative values with increasing dye concentration. Plotting ζ versus ln Cd at different temperatures resulted in straight lines with a constant, temperature independent slope. The surface adsorption of various acid dyes on latex calculated from ζ potential increased with increasing dye concentration.
The order of magnitude of the free energy of dyeing Δ_??_, obtained from the slopes of the ζ-ln Cd lines decreased in the following order: Roccelline > Orange IV>Orange I>Orange II. In addition, heats Δ_??_ and entropy Δ_??_ of dyeing were found to be negative and positive respectively.
The values obtained for Δ_??_, Δ_??_ and Δ_??_ suggest that in addition to electrostatic interactions, hydrogen bond, van der Waals force and hydrophobic interactions govern the adsorption of acid dyes by cationic polystyrene latex.