To increase the compatibility between cellulose fibers and polyester matrix an original method for grafting hydrophobic oligoesters onto cellulose was proposed. Two kinds of cellulose substrates were employed as cellulose films and microcrystalline cellulose powder. Different oligoesters containing reactive end groups based on poly(DL-lactic acid) PDL-LA, poly(e-caprolactone) PCL and poly(3-hydroxyalkanoate)s PHA were first prepared and characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). The carboxylic end groups of the polyesters were activated using thionyl chloride (SOCl(2)) to increase the esterification reaction with the hydroxyl groups of the cellulose. The esterification was realized in a heterogenous medium without any catalyst by deposition of chloride oligoesters in solution (2-100 g L (1)) onto cellulose film at different temperatures (25-105 degrees C) during 1-12 h. The successful grafting on the various substrates was confirmed on the basis of FTIR spectroscopy, contact angle measurement, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). In particular, it is shown that a small quantity of grafted oligoesters led to a significant increase of the hydrophobic character of the cellulose with a contact angle near 130 degrees. The increase of hydrophobicity of cellulose is independent of the nature and length of grafting oligoesters. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1183-1192, 2011