NEW SERIES OF BLUE-LIGHT-EMITTING POLYMERS CONSTITUTED OF 3-ALKYLTHIOPHENES AND 1,4-DI(1,3,4-OXADIAZOLYL)PHENYLENE

A new series of conjugated polymers constituted of 3-alkylthiophenes a nd 1,4-di(1,3,4-oxadiazolyl)phenylene are synthesized through precurso r polymers of polyhydrazides. The solubility of the precursor polymers and the corresponding target polymers is improved by increasing the l ength of side chains on thiophene rings, which results in a higher deg ree of the conversion from the precursors to the final polymers and th us results in longer effective conjugated length in the polymers beari ng longer side chains. The thermal stability and electrochemical prope rties of the polymers are studied. The polymers emit blue light under the irradiation of UV light in their film states. The relative fluores cence yield in solutions increases with the increase in length of side chains on thiophene rings in the polymers and reaches up to 79% for t he polymer bearing octyl side chains. The possibility of polymers bein g used as electroluminescent material in polymer light-emitting diodes (PLEDs) is demonstrated by the successful fabrication of a single-lay er device of indium tin oxide (ITO)/polymer/Ca, which emits visible bl ue light above 8 V of forward bias.