The article reports plasma enhanced chemical vapor deposition (PECVD) of SiOxCyHz polymers on polyester fabric using tetraethylorthosilicate (TEOS) and hexamethyldisiloxane (HMDSO) precursors. Modulated discharge was used to study the effect of duty cycle on the hydrophobic properties of plasma treated-polyester fabrics. Ton and Toff periods in modulated discharge were adjusted in such a way to get duty cycle values of 0.25, 0.50, 0.83, and 1.00, respectively. The hydrophobicity of the treated samples was evaluated by static contact angle measurement. Incorporation of Si?O, Si?CH3 groups on the surface of polyester fabric was evidenced in Fourier transform infrared (FTIR) spectroscopic analysis. In addition, organicinorganic character of HMDSO plasma polymer derived under modulated discharge and continuous wave discharge was investigated by FTIR spectroscopy. For equal treatment durations (Ttotal), the plasma polymer deposited under pulsed discharge at lower duty cycle showed relatively higher organic content indicating comparatively greater structural retention of the original monomer in modulated discharge. However, structural analysis showed that treatment duration is more critical factor than duty cycle in determining organic character of SiOxCyHz plasma polymers. Ash content results indicated that plasma polymerization proceeds even during Toff period. Evaluation of mechanical properties of polyester fabrics showed decrease in tear strength in both TEOS and HMDSO plasma-treated samples. The durability of plasma polymers to washing showed promising prospects of use of PECVD for functional finishing of polyester fabrics. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012