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

Abstract

Abstract. 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 (β) of polymers is of the order 10 −11 m/W which indicates that these materials may be accomplished for fabricating optical limiters.

In silico screening of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate and some of its derivatives for their NLO activities using DFT

“…In the present work, the NLO susceptibilities and properties of EMAB alongside some of its derivatives with stronger electron donor groups have been investigated using the DFT method. The choice of the donor groups herein (displayed in figure 1) was guided by previous works in which they were found to improve intramolecular charge transfer (ICT), thereby increasing the NLO activities of the molecules studied therein [4,20,25]. Moreover, donor groups containing electronegative atom(s) linked to π-conjugated systems were preferred herein because they often lead to higher NLO activities [3,[27][28][29].…”

“…Schiff bases, which are compounds with the general formula R 1 R 2 C=N−R 3 , where R represents an alkyl or aryl group, exhibit significant intramolecular charge transfer [7], a possible reason for which they are often used as thin-film organic solar fluorescence materials as well as in organic light-emitting diodes and optical sensors [19]. As such, they are potential candidates for NLO applications, especially when composed of strong electron donor and/or acceptor groups [23,25]. According to literature survey, the Schiff base molecule shown in figure 1, ethyl 4-[( E )-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate (EMAB) is planar, exhibits antimicrobial properties and some degree of hydrogen bonding [26].…”