Cyclohexanone-formaldehyde resins were modified in situ with alpha,omega-diamine polydimethylsiloxanes and alpha,omega-dihydroxy polydimethylsiloxanes. Melting points, solubilities in organic solvents, gel permeation chromatographs, Fourier transform infrared spectra, and NMR spectra of the modified resin were determined, and the surface properties of the resins were investigated by contact angle measurements. A small amount of silicon compounds seemed to effect the physical properties of the cyclohexanone-formaldehyde resins significantly. (c) 2005 Wiley Periodicals, Inc.