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Thickening of structured acrylate latices with butyl acrylate/styrene/2-hydroxyethyl methacrylate/acrylic acid copolymer showed that association of the thickener based on hydrophobically modified ethoxylated polyurethane (HEUR) with the latex particles was considerably affected by hydrophobicity of the particle shell surface controlled by various content of styrene units in the copolymer. In contrast, the thickening mechanism of hydrophobically modified alkali-soluble emulsion (HASE) and, consequently, the viscosity of thickened materials depends predominantly on the excluded volume of swollen thickener particles and the influence of the styrene content is negligible. [Copyright &y& Elsevier]