1 Results Polymeric light-emitting diodes (PLEDs) have attracted much scientific and technological research interest due to a number of advantages over inorganic or organic small molecules for use in LEDs: better processability,lower operating voltages,faster response times,lower production costs,and high flexibility.Polyfluorene has been selected for the polymer backbone,because of its large band gap,facile substitution at the C9 position of fluorene,good chemical and thermal stability,and high photoluminescence and electroluminescence quantum yields.One of the major advantages of polyfluorene derivatives is that their electronic properties can be tuned by modification of the comonomer block.Obviously,it is important to study the relationships between molecular structures of a comonomer block and EL properties of polyfluorene derivatives.In this presentation,we report the relationships based on modification of molecular structures of comonomer blocks. 1 Results Polymeric light-emitting diodes (PLEDs) have attracted much scientific and technological research interest interest to a number of advantages over inorganic or organic small molecules for use in LEDs: better processability, lower operating voltages, faster response times, lower production costs, and high flexibility. Polyfluorene has been selected for the polymer backbone, because of its large band gap, facile substitution at the C9 position of fluorene, good chemical and thermal stability, and high photoluminescence and electroluminescence quantum yield. One of the major advantages of polyfluorene derivatives is that their electronic properties can be tuned by modification of the comonomer block. Obviously, it is important to study the relationships between molecular structures of a comonomer block and EL properties of polyfluorene derivatives. In this presentation, we report the relationships based on modification of molecular structures of comonomer blocks.