The design of a novel polymer-modified overlayer composed of PPAPE and GPMS on a silicon wafer for immobilization of DNA molecules is described. After hydroxylation of Si(100) surfaces, GPMS molecules were self-assembled onto these surfaces. PPAPE molecules were then covalently attached to the epoxy-terminated surfaces. The incubation time and concentration of PPAPE was found to effect both layer thickness and water CA. The type of organic solvent and the pH were found to change the nature of the PPAPE-modified surface for DNA immobilization. It is concluded that PPAPE-modified surfaces show advantages for DNA immobilization by electrostatic interactions between DNA molecules and positively charged free amino groups of the PPAPE-modified surfaces at the appropriate pH values.