P-Phenylene oxadiazole

Fig. 29. Cyclic voltanunograms of a p-POD (p-phenylene oxadiazole) film on a glassy carbon electrode. Voltammograms were measured in 0.1 m BU4NCIO4 in acetonitrile with a scan rate of 10 mV/sec. Curve a is the first cycle and curve b is the sixth cycle.

All-p-phenylene oxadiazole/N-methyl hydrazide copolymers have yielded high performance fibers with tenacities of 18-21 gpd and moduli above 300 gpd through an unconventional polycondensation reaction of terephthalic acid, dimethyl terephthalate and hydrazine sulfate in fuming sulfuric acid and subsequent "reaction spinning" into aqueous acid. 

Recently, we reported (1, 2) a new class of high strength/ high modulus fibers prepared from all-p-phenylene oxadiazole/ N-methyl hydrazide copolymers. Oxadiazole homopolymers and fibers had been described earlier by Iwakura (3), Imai (4), and Frazer (5). All-p-phenylene oxadiazole/N-methyl hydrazide copolymer fibers were shown by us to give tire cord with excellent end use performance including good fatigue characteristics. In concurrent... 

Fibers (6) of p-phenylene oxadiazole/N-methyl hydrazide copolymers were prepared by polymerization of terephthalic acid (TA), dimethyl terephthalate (DMT) and hydrazine sulfate in fuming sulfuric acid (Oleum) and "reaction spinning" of the resulting polymer solution into aqueous sulfuric acid. Replacement of some of the dimethyl terephthalate used with dimethyl isophthalate (DMI) allowed the preparation of p-/m-phenylene oxadiazole/ N-methyl hydrazide copolymers. In the polymerization, a p-/m-phenylene oxadiazole polymer is formed which is methylated during the reaction ... 

The polycondensation of terephthalic acid, dimethyl terephthalate, and hydrazine sulfate results in the formation of p-phenylene oxadiazole/ iV-methyl hydrazide copolymers. The process is conducted in fuming sulfuric acid. 

H. C. Bach, F. Dobinson, K. R. Lea, and J. H. Saunders. High-strength/high-modulus fibers of p-phenylene oxadiazole/ -methyl hydrazide copolymers -a new class of high-performance organic materials. J. Appl. Polym. Set, 23 (7) 2125-2131, 1979. 

Figure 10.11 Hyrdrolysis reaction and structure of a p-phenylene oxadiazole/A/-methyl hydrazide copolymer.

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... 

H. Meng, W. Yu, and W. Huang, Facile synthetic route to a novel electroluminescent polymer — poly(p-phenylene vinylene) containing a fully conjugated aromatic oxadiazole side chain, Macromolecules, 32 8841-8847, 1999. 

J.A. Mikroyannidis and J.K. Spiliopoulos, Synthesis and optical properties of novel blue-light emitting poly(p-phenylene vinylene) derivatives with pendant oxadiazole and cyano groups, J. Polym. Sci., Part A Polym. Chem., 42 1768-1778, 2004. 

Pyrolysis and Graphitization of Polyoxadiazole. Table 1 shows electrical conductiyity at room temperature for yarious condensation polymers heat-treated at 1000 and 2500 C. For a HTT near 1000 C, poly(p-phenylene-1,3,4-oxadiazole) (POD) has the highest conductivity of 340 S/cm, twice as high as that of polyimide (KAP)... 

Values of x/gj plotted according to data in Ref. 43) and molecular weights according to data in Ref.43) (a) 4 poly(amide benzimidazole) in sulfuric acid 44) ( ) 5 poly(p-phenylene-1,3,4-oxadiazole) in sulfuric acid43) (v). The curve corresponds to theory as in Ref. 1). A and B are theoretical values for kinetically rigid Gaussian coils with strong (A) and weak (B) hydro-dynamic interactions 4 3)... 

The repeating unit of the poly(p-phenylene-l,3,4-oxadiazole) chain (Fig. 47) ) contains one rotating bond A 7 A forming an angle d 36° with the bond of the neighbouring unit. In this case in order to calculate Sf and Af in Eq. (68), 6 should be taken equal to 0. A comparison of Af with the experimental value, A, (Table 9) yields a given in Table 11. 

Experimental attempts to synthesize any of the polymers described above have not been successful except a preliminary preparation of poly-perylene (Murakami and Yoshimura, 1984). Alternative efforts are currently being made to obtain polyacenic material through pyrolysis of various organic polymers such as phenol-formaldehyde resin (Yamabe et al., 1983 Tanaka et al., 1984b), polyacrylonitrile (Teoh et al., 1982, 1983), and poly(p-phenylene-1,3,4-oxadiazole) (Murakami et al., 1983). The group of these pyrolytic polymers behaves rather like amorphous semiconductors and is considered to be composed of fragments of polyacene to graphite, that is, a sort of coke, coal, and so on. 

During the "reaction spinning" process, the methylated oxadiazole units are hydrolyzed to mono-methylated hydrazide linkages yielding fibers of the p-/m-phenylene oxadiazole/N-methyl hydrazide copolymers ... 

During the polymerization of aromatic diacids and diesters with hydrazine in fuming sulfuric acid, aromatic oxadiazole units are formed first which are subsequently methylated by monomethyl sulfate or its homologues (derived from reaction of the diester with H2SO4) forming an aromatic N-methyl oxadiazolium polymer. This polymer is hydrolyzed during the spinning operation to the fiber polymer, i.e., p-/m-phenylene oxadiazole/N-methyl hydrazide copolymer. 

The oxadiazole moiety can be introduced in a sequence of several steps in the backbone of poly(p-phenylene vinylene) (PPV). The re-... 

Aromatic PODA show a high thermal stability, which is imparted both by the aromatic unit and by the oxadiazole unit. The thermal stability increases with increasing content of p-phenylene moieties in the polymer backbone, " ... 

High aromatic PODA t5 es, such as poly(p-phenylene-l,3,4-oxadiazole), can be graphitized to yield a high quality graphite." The graphitization takes place at 2,800-3,000°C. From a heat-treated PODA film at 3000°C, an electrical conductivity of 1.4—1.8 10" Scm has been obtained. Graphite fibers with excellent mechanical properties have been obtained. 

E. Leibnitz. ZurOptimierungderSynthesevonPoly(p-phenylen-l,3,4-oxa-diazol) in Oleum (Optimization of preparation of poly(p-phenylene-1,3,4-oxadiazole) in oleum). Angew. Makromol. Chem., 204 101-110, 1993. 

T. Tsutsui, Y. Fukuta, T. Hara, and S. Saito. Electronic conduction in poly(p-phenylene-l,3,4-oxadiazole) films. Polym. J. (Tokyo), 19 719-725, 1987. 

Poly(9,9 -dihexylfluorene-2,7-divinylene-m-phenylene vinylene-stat-p-phenyl-ene vinylene), 30, 31, 51 Poly(2,5-dimethoxy-l,4-phenylene vinylene), 95 Poly(2-(A, A -dimethylamino) phenylene vinylene), 100 Poly(2-dimethyloctylsilyl)-phenylene vinylene, 99 Poly(9,9-dioctylfluorene), 31, 110 Poly(9,9-dioctylfluorene-co-lluorenone), 30 Poly(4,4 -diphenyl ether-l,3,4-oxadiazole), 334 Poly(2,6-diphenyl-l,4-phenylene oxide), 152 Poly(2,6-diphenyl-l-4-phenylene oxide), 141 Poly(dithiathianthrene), 189 Poly(2-dodecyl-p-phenylene), 36 Poly(AT-epoxypropyl)carbazole, 13 Poly(ether ether ketone), 209 Poly(ether imide), 154, 214, 264, 376 Pol(yether ketone), 213 Poly(ether nitrile), 227 Poly(ethersulfone), 209, 264... 

Mikroyannidis, J.A., Spiliopoulos, I.K., Kasimis, T.S., Kulkarni, A.P., Jenekhe, SA, 2004. Newpoly(p-phenylene vinylene) derivatives with two oxadiazole rings per repeat unit synthesis, photophysical properties, electroluminescence, and metal ion recognition. J. Polymer Sci. Part A42, 2112-2123. 

The polymers have been used in different multi-layered devices using PPV as emissive layer. Typical devices were prepared on glass substrates precoated with patterned indium-tin oxide (ITO) electrodes (resistance < 20 Q/square). In a two layer LED, the oxadiazole polymethacrylates (10a or 10b) were spin-coated on top of poly(p-phenylene vinylene) (PPV), prepared on an ITO glass substrate by the sulfonium precursor route (22). Cdcium was used as the top metal contact. A comparable device, but without the polymethacrylate, was fabricated as a reference. Both devices emitted green yellow light under forward bias potential (15 V). 

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