AbstractStyrene/2‐hydroxyethyl methacrylate copolymer (PS/PHEMA) latex was prepared without soap. From an electron micrograph, this latex was found to be highly monodisperse. The surface characterization of PS/PHEMA latex was compared with that of polystyrene (PS) latex. Conductometric titration curves of these latexes revealed that both strong and weak acid groups existed on the latex surface. It was found that pH dependence of surface charges for these latexes was not very pronounced whereas negative values of ζ‐ potentials for PS/PHEMA latex were smaller than that for PS latex over the whole range of measured pH. This was interpreted on the basis of the difference in the structure of the electrical double layer for these latexes. Methylene Blue adsorption onto PS and PS/PHEMA latexes was measured as a function of pH, too. The pH dependence of the dye adsorption onto these latexes was hardly discernible. However, the amount of Methylene Blue adsorbed was somewhat greater onto PS latex than onto PS/PHEMA latex. This result might be attributed to the strength of hydrophobic interaction between dye and latex. It was suggested that PS/PHEMA latex was more hydrophilic than PS latex in spite of having about the same surface charge as PS l
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