First, Friedel-Crafts reactions were used for the acylation process. For this, polystyrene (PS) was reacted with propionic anhydride in the presence of Lewis acid catalyst. The amount of acyl group linked PS as a result of acylation has been identified as volumetric. Second, the bromination and lithiation reactions of acylated PS containing carbonyl groups were realized. Also, the lithiated PS containing acyl groups has been modified a second time with various isocyanates and isothiocyanate derivatives in the presence of n-BuLi catalyst. Some important reaction parameters were assigned in order to optimize the process. The structure all of the products were characterized by Fourier transform infrared, 1 H NMR (Proton Nuclear Magnetic Resonance), and thermogravimetric methods. In addition, reaction yields were determined according to the result of elemental analysis. Dual functionalization yields were realized between 62.2% and 69.9%. For kinetic analysis, the TG=DTG (Thermal Gravimetric Analysis/Differantial Thermal Analysis) data obtained at three different heating rates were processed by Kissinger-Akahira-Sunose method. The results demonstrated that the acylation reaction, bromination and lithiation reactions, and dual functionalization reactions with cyanate derivatives can be carried out to obtain a significantly functionalized polymer.