A novel diureapropyltriethoxysilane bis(aminopropyl)-terminated-poly(dimethylsiloxane) (1000) (PDMSU) sol−gel hybrid was synthesized and applied on cotton to make it water repellent. Surface-energy values of PDMSU deposited on an aluminum substrate were determined, and the contact angle for water was assessed for impregnated cotton fabrics. The stability of the coatings was determined by repetitive washing, and their degradation was investigated with the help of the infrared attenuated total reflection (ATR) technique. The structure of PDMSU was studied by ATR and 29Si NMR spectroscopy. The results showed the active role of the urea groups in PDMSU/cotton interface bonding, but washing led to the relaxation of the urea−urea associations, as inferred from the appearance of a new amide II band at 1541 cm-1.