D-A conjugated polymers containing substituted thiophene, 1,3,4-oxadiazole and non-conjugation linkers: Synthesis and study of optical and electrochemical properties

摘要

In this communication, we report synthesis and characterization of new D-A conjugated polymers (P1-P3) consisting of electron-donating (D) 3,4-didodecyloxythiophene, electron-accepting (A) 1,3,4-oxadiazole unit and non-conjugation linkers. The conjugated segment in P1-P3 contains only five aromatic rings resulting in short conjugation length, but has an alternate D-A arrangement which significantly enhances the intramolecular charge transfer (ICT) interaction within the segment. As a result, these polymers exhibited low optical band gap in the range 2.51-2.76 eV. Fluorescence emission studies revealed that the polymer thin films emit intense blue light with emission maxima in the wavelength rage 430-480 nm. All three polymers undergo both oxidation and reduction processes under electrochemical conditions. Further, these polymers (P1-P3) exhibit low-lying HOMO and LUMO levels as a result of D-A structure of the conjugated segment. Polymer light-emitting devices were fabricated using these polymers as emissive layer with a device configuration of ITO/MoO (3)/polymer/LiF/Al. The test device based on P2 emitted blue light with a low threshold voltage of 5 V. Z-scan studies reveal that the polymers exhibit a strong optical limiting behavior. The value of the nonlinear absorption coefficient (beta) of polymers is of the order 10 (-11)m/W which indicates that these materials may be accomplished for fabricating optical limiters.