New thermally stable poly(urethane-imide)s (PUIs) were synthesized to investigate aliphatic and aromatic group effects on various properties such as thermal stability and electrochemical properties. Thermal characterizations were carried out by TG-DTA and DSC techniques. TGA results showed that the PUIs derived from aromatic diisocyanates had relatively higher thermal stabilities as compared to the aliphatic diisocyanate. They have between 223-245 • C onset temperature and above 37% char at 1000 • C. Also, thermal degradation values show that PUIs have higher stability than conventional PU. DSC results showed that the new PUIs have Tg values between 134 and 138 • C. Fluorescence measurements were performed using dimethyl sulfoxide solutions and also, the optimization of the concentrations maximal emission intensity was investigated in dimethyl sulfoxide. As a result, the remarkable properties related to the fluorescence and thermal measurements of the polymers were obtained. Therefore, these polymers could be used in various application fields because of the fluorescent and thermal properties.