Journal of Kirkuk University –Scientific Studies , vol.5, No.2,2010 39 Optical properties of polymer composite PS-PC thin films Dana A. Tahir Department of Physics, College of Science- Sulaimani University Received: 3/4/2010 , Accepted:1/6/2010 Abstract The optical properties of polymer composite polycarbonate-polystyrene (PC-PS) films prepared by casting technique were studied in the visible and ultraviolent wavelength regions. It was found that the optical absorption is due to direct allowed transitions for pure and composite polymer films, while the energy gaps and the width of the tail localized states of the composite was lied in the mid values of the pure samples. The optical constants refractive index , extinction coefficient , the real and the imaginary parts of the dielectric constant have been also calculated. The dielectric constant and refractive index become more stable for composite sample. Introduction Polystyrene is very low cost and is extensively used where price alone dictates. Its major characteristics (Chanda, 2009) include rigidity, transparency, high refractive index, good electrical insulation characteristics, low water absorption, and ease of coloring and processing. A more serious limitation of polystyrene in many applications is its brittleness. This limitation led to investigation a mixture of polystyrenes with material having rubber properties (Kim, 2008). It is well known that composites can be produced exhibiting enhanced properties that the constituent materials may not exhibits (Akram, 2005; Golden, 2001). For instance, from the combination of different polymer matrices one can produced polymer-matrix composites, a material important to the electronic industry in the use of capacitors (Aoi, 1997; Jo et al, 1997). The study of optical absorption and particularly the absorption edge is a useful method for the investigation of optically- induced transitions and for the provision of information about the band structure and energy gap in both crystalline and amorphous materials. The measurement of the optical absorption coefficient, particularly near the fundamental absorption edge, provide a standard method for investigation