Oxadiazole-based polymers

Oxadiazole-based Polymers as Hole Blocking and Luminescent Materials... 

Aromatic oxadiazoles. See Oxadiazole-based polymers Arylene-vinylene copolymers alternating and random copolymerization, 346-348... 

The materials mostly used as ETLs are oxadiazole derivatives [177], which are evaporated or dispersed in the polymer matrix, polyquinoxaline derivatives [178], oxadiazole-based polymers [179], and so on [180]. Poly(9-vinylcarbazole) and PPV... 

Ma and coworkers [154] synthesized a bipolar luminescent PPV-based polymer 111, which contained both donor triarylamine and acceptor oxadiazole moieties in the backbone. A device fabricated with this polymer (ITO/PEDOT/111/CsF/Al) showed a maximum brightness of 3600 cd/m2 and a maximum luminescent efficiency of 0.65 cd/A (< el = 0.3%), about 15 times brighter and more efficient than the device of the same configuration with a nonoxadiazole polymer 112. 

Kim TH, Kim HJ, Kwak CG, Park WH, Lee TS (2006) Aromatic oxadiazole-based conjugated polymers with excited-state intramolecular proton transfer their synthesis and sensing ability for explosive nitroaromatic compounds. J Polym Sci A Polym Chem 44 2059-2068... 

Dopants also influence the emission processes from PPVs. Improved red dopants have been based on pyran dyes" while Qo doping appears to be variable" "". Doping with electron transport materials such as oxadiazoles give polymers with balanced properties for hole transport". The avoidance of low molecular weight material in the synthesis of cyano based PPVs is important" as are head to head and tail to tail chain sequences in thiophene based polymers. Head to tail tetramer sequences were the most fluorescent. Metal ion doped PPV s are claimed to be good chemosensors and broad emission is observed from titania doped PPV . Electron rich dopants enhance the emission in the red region while electro and photoinduced infrared bands from PPV are similar . ... 

Vita et al. reported the synthesis and structural characterization of a main-chain hquid crystal polymer composed of a 1,2,4-oxadiazole-based bent-core repeating unit. This provided the first experimental evidence of cybotactic order in the N phase of an LC polymer based on a bent-core monomer (55 in Figure 15 2014AML91). 

The method prevents rotational dislocations, yielding a reproducible procedure that affords a nanoporous oxadiazole-based covalent organic polymer (Oz-COP). Moreover the prepolymer was found to have an rm-precedented solubiHty that allows it to be used to form a porous polymer film. 

Brown GH, Shaw WG (1957) The mesomorphic state— liquid crystals. Chem Rev 57 1049-1157 Cardinaels T, Ramaekers J, Guillon D, Donnio B, Binnemans KA (2005) Propeller-like uranyl metallomesogen. J Am Chem Soc 127 17602-17603 Chai CP, Zhu XQ, Wang P, Ren MQ, Chen XF, Xu YD, Fan XH, Ye C, Chen EQ, Zhou QF (2007) Synthesis and phase structures of mesogen-jacketed liquid crystalline polymers containing 1,3,4-oxadiazole based side chains. Macromolecules 40 9361-9370 Chandrasekhar S, Sadashiva BK, Suresh KA (1977) Liquid crystals of disc-Uke molecules. Pramana J Phys 9 471 80... 

Fig. 7.8 Polystyrene-bound dehydrating agent (left) and polymer-supported phosphazene base PS-BEMP (right) utilized for oxadiazole synthesis.

Each of the routes discussed thus far in this section are reliant upon amidoxime-based methods. In a change from this paradigm, Makara etal. produced the polymer-supported benzotriazoles 294 and converted them easily into the iV-acyl-177-benzotriazole 1-carboximidamides 295. Cyclization with hydroxylamine gave the supported 3-amino-l,2,4-oxadia-zoles 296 which were cleaved with TFA to give the free 3-amino-l,2,4-oxadiazoles 297 (Scheme 49) <2002TL5043>. 

Single- and heterolayer polymeric light emitting diodes based on poly(p-phenylene vinylene) and oxadiazole polymers W. RieB Organic Electroluminescent Materials and Devices, S. Miyata and H.S. Nalwa, Eds., Gordon and Breach, Amsterdam, pp. 73-146... 

Jin and coworkers [123] synthesized PPV 67, containing an oxadiazole and an alkoxy group. According to UPS study, the HOMO and LUMO levels in 67 (-6.32 and -3.98 eV) are within the band gap of the parent polymer 61 without alkoxy substituents (Scheme 2.14). The external QE of PLEDs based on polymer 67 is about one order of magnitude higher than that for 61 (0.045% for ITO/67/Li Al) and a maximum brightness of up to 7570 cd/m2 was achieved for this material (using Ca cathode). 

Similar PPV-based copolymers with carbazole and fluorene units in the backbone 101 and 102 (and also similar copolymers with oxadiazole substituents 103 and 104) have been synthesized by Ree and coworkers [148], Much lower PL efficiency in films was found in this case for carbazole-containing polymers 102 and 104 (1-4%), when compared to materials prepared by Shim (95 and 96, 59-64%) (Chart 2.21). 

Blends of yellowish-green-light emissive carbazole-containing PPV-based copolymer 105 (Apl = 490, 520 nm, AEL = 533 nm) with blue-emissive oxadiazole- poly-/ -phenylene (PPP) copolymer 106 (AEL = 426 nm) allowed to tune the emission of PLEDs (ITO/polymer blend/Al) from AEL = 533 nm to AEL = 451 nm, although the device turn-on voltage was essentially higher for the blends with increased content of 106 [149] (Chart 2.22). 

H.-H. Sung and H.-C. Lin, Novel alternating fluorene-based conjugated polymers containing oxadiazole pendants with various terminal groups, Macromolecules, 37 7945-7954, 2004. 

A wide range of polymers based on other heterocyclic 5-membered rings have been investigated, including oxadiazole, pyrazole, triazole, tetrazole, and thiophene [Bass et al., 1987 Briffaud et al., 2001 Cassidy, 1980 Critchley et al., 1983 Gebben et al., 1988 Ueda and Sugita, 1988],... 

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