The effect of hydrophobicity on thermal diffusion of acetylated dextran in aqueous solution was studied in the temperature range of 15-50 degrees C by optical beam deflection (OBD) technique. The hydrophobicity was controlled by substitution of hydroxyl groups on dextran chain with acetylated groups. The Soret coefficient S-T and thermal diffusion coefficient D-T significantly increased with an increase of temperature. The hydrophobicity plays an important role in the thermal diffusion behavior, i.e. S-T and D-T switch the sign from negative to positive magnitude with an increase of hydrophobic contents. We observed a correlation between the parameters obtained from lacopini and Piazza equation (Europhy. Lett. 63 (2003) 247-253.) and the hydrophobic content of the binary aqueous solutions. A master curve can be used to describe the temperature dependence of ST and D-T for acetylated samples. The ST linearly decreases with an increase of particle size for dextran whereas it scales linearly with the volume of particles for acetylated samples. (C) 2018 Elsevier Ltd. All rights reserved.