Abstarct: One of the essential necessities and efficient features that can be added to biomaterials is radiopacity; since this advantage facilitates positioning and assessment of the devices using the non-destructive X-radiography technique. The radiopaque materials have been designed for a variety of medical applications such as embolization process, preparation of the implants and prosthesis, and also tracing a drug-loaded polymer or nanoparticle in the body. In a modern radiological diagnostic procedure, the radiopaque polymers are an excellent choice as contrast media since a proper insertion or implantation of prosthesis and implants has been achieved using the radiopaque biomaterials. These materials, due to the high electron density and X-ray absorption capacity, facilitate the evaluation of the tissues after a therapeutic treatment. Considering the importance of these polymers in the medical sciences, radiopaque polymers were prepared using different monomers. The poly[(methyl methacrylate)-co-(N-(4-iodophenyl)acrylamide] and poly[(methyl methacrylate)-co-(N-(3,4,5-triiodophenyl)acrylamide] were synthesized using 4-iodophenyl isocyanate and 3,4,5-triiodophenyl isocyanate moieties, as radiopacifying agents. The radiopaque PUU was synthesized using 4,4ʹ-methylenediphenyl diisocyanate (MDI) and polyethylene glycol (PEG) (Mn = 1000). 4-(4-Iodophenyl)-1,2,4-triazolidine-3,5-dione was used as a novel chain extender and radiopacifying agent. The iodinated copolymers were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance (NMR) spectroscopy, elemental analysis and Energy Dispersive X-ray (EDX) spectroscopy, Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA). The composition and iodine content of the copolymers were demonstrated via the acid-baxse and potentiometric titrations, respectively. The radiopacity of the copolymers were investigated by X-radiography. To evaluate the biocompatibility of the iodinated copolymers, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was carried out on the human embryo 3T3 fibroblast cells (NIH3T3 cell line) according to the ISO10993-5 standard. In order to modification of thermal and mechanical properties of the polymers, their nanocomposites were prepared using cloisite 20A and graphene oxide as the filler. The nanocomposites were characterized by thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD).