Highly positively polarized silver nanoparticles were prepared using the strong interactions between the metal surface and phthalate oxygen atoms of poly(ethylene phthalate) (PEP) in a PEP/$AgBF_4$ composite without a reducing agent or surfactant. The prepared silver nanoparticles were monodispersed (mean diameter, 5 nm), as confirmed by transmission electron microscopy (TEM) image, X-ray diffraction (XRD) and UV-visible spectroscopy. Furthermore, X-ray photoelectron spectroscopy (XPS) revealed that PEP served as a highly positively polarizer for silver nanoparticles.