A novel polysiloxane softener bearing dodecyl side groups (dodecylpolysiloxane [DDPS]) was synthesized by copolymerization of octamethylcyclotetrasiloxane with dodecyltrimethoxysilane and hexamethyldisiloxane. Chemical structure and film morphology of the synthesized polysiloxane are characterized and investigated by infrared spectrum, H-1-NMR, field emission scanning electronic microscope, and atomic force microscope. The experiment results indicate that DDPS can form a hydrophobic film on both the cotton fiber and silicon wafer surface. At an amplification of < 80,000 (of the original fiber) and the observation rule (working distance) of > 200 nm, DDPS shows a relative smooth resin film the treated fabric/fiber surface. But as the observation rule decreases to 2 nm-almost to a molecular scale-the DDPS film mostly exhibits an inhomogeneous structure and uneven morphology in its atomic force microscope images. There are many low or high peaks that appeared in DDPS topography. Consequently in 2 mu m(2) scanning field, the root mean square roughness of DDPS film reaches to 0.199 nm, which is 2.46 times rougher as compared with that of polydimethylsiloxane film. (c) 2006 Wiley Periodicals, Inc.