Synthesis, Photophysics, and Electroluminescence of New Quinoxaline-Containing Poly(p-phenylenevinylene)s

Abstract

Four new soluble poly(p-phenylenevinylene) (PPV) derivatives containing one or two quinoxaline moieties per repeat unit, either in the main chain or as pendants to the main chain, were synthesized, characterized, and explored as emissive and electron transport materials in polymer lightemitting diodes (LEDs). Polymers containing one quinoxaline moiety per repeat unit (QXPV1 and QXPV3) showed low melting transitions (<100 °C), whereas those with two quinoxaline moieties per repeat unit (QXPV2 and QXPV4) had relatively high glass transition temperatures (>140 °C). The polymers emit blue to green light (404-536 nm) in dilute solution and blue-green to yellow light (470-563 nm) in the solid state. The photoluminescence emission was well-described by single-exponential decay with lifetimes ranging from 200 ps to 2.2 ns in both dilute solution and thin film, indicating lack of intermolecular emissive species in the solid state. PPV derivatives with quinoxaline moieties in the main chain (QXPV1 and QXPV2) showed facile reversible electrochemical reductions with electron affinities of 2.63-2.75 eV. As emissive materials in LEDs, greenish-yellow electroluminescence with a brightness of up to 450 cd/m 2 was obtained from single-layer diodes of QXPV1 with aluminum cathode in air.

Poly(phenylenevinylenes)

“…Similarly, the blue-emitting copolymer 52, which bears oxadiazole and carbazole pendent groups, is synthesized by coupling of 1,4-divinylbenzene with the corresponding dibromide monomer [98]. Additional examples include attachment of PPV-based oligomer on the side chain of helical peptide scaffolds [99], and preparation of bipolar PPV bearing electron-donating triphenylamine and electron-accepting quinoxaline moieties [100]. It should be noted that the Heck reaction is regioselective but not regiospecific, although trans-vinylene is usually the major product [101].…”

The synthesis and characterization of novel dipolar fluorescent materials based on a quinoxaline core

“…The highest V value of 0.78 was observed for 11f, which is higher than that of small molecules and polymers containing quinoxaline units [24][25][26]. The difference of quantum yields might be happened during the process of exciton migration [33] or might be due to the change of the molecular size [34].…”

“…Similarly, quinoxaline is a useful n-type building block with high electron affinity (electronaccepting character) and good thermal stability. Moreover, quinoxaline has been successfully incorporated in small molecules and polymers as the electron-transport component of OLEDs [23][24][25][26][27].…”

Synthesis of a novel fluorescent and ion sensitive monomer bearing quinoxaline moieties and its electropolymerization

“…The interest on these materials lies not only on the fact that they can be utilized as fluorescence probes in some chemosensors [1] but also their potential use in high technology applications including light emitting devices and solar cells [2][3][4][5]. Some quinoxaline derivatives are able to coordinate to various anionic species [6,7], and therefore they can be used as metal ion chelators [8][9][10]. In some cases, these applications might require the integration of quinoxaline moieties into a polymer matrix.…”

“…Quinoxaline containing polymers prepared via condensation reaction were first used as heat and chemical resistant materials and applied later in polymer light emitting devices [32,33]. Karastatiris et al investigated the photophysical and emissive properties of poly(p-phenylene) derivatives containing quinoxaline moieties and reported that these materials exhibits greenish-yellow electroluminescence [6]. Thermal and optical properties of 2,7-carbazole and quinoxaline based alternating copolymers were investigated by Morin and Leclerc [31] and the low band gap of quinoxaline containing copolymer was attributed to the strong intramolecular interaction between donor and acceptor groups.…”