A novel waterborne polyurethane containing short fluoroalkyl groups (-CF3) was designed and synthesized. It was applied as a surface modification agent on cotton fabrics. The treated fabrics showed very good hydrophobicity and the contact angles for water reached 147 degrees. In addition, it also showed good washing durability, the contact angle still reached 130 degrees even after 30 washing cycles, and the water uptake was 1 order of magnitude less than that of the untreated cotton fabrics. (c) 2006 Published by Elsevier B.V.