Synthesis of polymer nanomaterials or composites is a key component of polymer nanotechnology. When nanometric inorganic compounds are added to polymer particles, the polymer particles become better, resulting in large packages that depend on the inorganic components present in the polymers. One of the easiest and quickest methods for making polymer nano composites is solvent casting. Various polymer composite strains, mixed metal oxide synthesis methods, and characterization procedures have all been covered in this chapter. A variety of properties, including dielectric, optical and non-optical, electrical, mechanical, thermal, florescence, and phosphorescence, are currently improved by the use of metal oxides and their polymer composites. The procedure for creating mixed metal oxide nanoparticles is covered in this chapter.