In a previous paper, we studied the adsorption of a polyelectrolyte, polyethyleneimine ion (PEI), onto Leacril in order to increase the amount of the reactive dye Remazol Brilliant Blue R (RBBR) taken up by these fibers. We observed that this polycation changes the fibers zeta potential sign at low concentration, ca. 0.03 g/L, and thus the RBBR adsorption onto Leacril is improved when implementing the PEI treatment. The aim of this work is to study the PEI effect related to the amount of dye adsorbed by Leacril. For this purpose, we present data on streaming potential, adsorption isotherms, and surface free energy component determination as a function of the PEI concentration used in the pretreatment, as well as a function of the RBBR concentration used in the dyeing solutions. Adsorption experimental results show that the amount of RBBR taken by the fibers increases with the PEI concentration used in the pretreatment, and this effect becomes significant at higher concentrations of RBBR solution. The zeta potential increases to positive values in the range of low concentrations of dye solution when Leacril fibers have been pretreated with the polyelectrolyte. From surface free energy component determinations it is worth noting that the electron-donor component, gamma(-), decreases with the RBBR concentration in the treatment. The results we have obtained suggest that the interaction between the amine group of the PEI previously adsorbed and the reactive beta-sulfato-ethysulfonyl group of the dye can be responsible for the improvement in dye uptake. (c) 2007 Elsevier Inc. All rights reserved.