Two novel polyphenylene and polyphenylenevinylene copolymers containing triarylpyrazoline units in the main chains were synthesized and characterized. The resulting copolymers were amorphous and showed excellent solubility in common organic solvents, such as dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene, toluene, and THE The polymers possessed good thermal stability with glass transition temperatures of 82 and 96 degrees C and decomposition onset temperatures of 295 and 309 degrees C, respectively. They exhibited good photoluminescence properties with high photoluminescence efficiencies. Double-layered light-emitting-diode devices with an indium tin oxide/Poly(3,4-ethylenedioxythiophene)/polymer/Ba/Al configuration could emit strong green light with external quantum efficiencies of 0.53 and 0.92%. (c) 2007 Wiley Periodicals, Inc.