Poly-1,3,4 oxadiazoles

Poly(1,3,4-oxadiazole-2,5-diyl-vinylene) and poly(l,3,4-oxadiazole-2,5-diyl-ethynylene) were synthesized by polycondensation of fumaramide or acetylene-dicarboxamide with hydrazine sulfate in PPA to study the effect of the two repeating units on polymer electronic and thermal properties (55). 

Oxadiazole is aromatic, having an estimated resonance energy of 167.4 kJ mol-1. The ring is stable to heat, a property which has been exploited in the production of heat-resistant poly-1,3,4-oxadiazoles (Section 4.23.5.2). 

Poly-1,3,4-oxadiazoles have a high thermal stability and have been used in film materials. Heat-resistant polymers have been prepared by incorporating 1,3,4-oxadiazole units into polymers (70MI42300) and heat-resistant polyamides have been synthesized from 3,5-bis(4-aminophenyl)-l,3,4-oxadiazole and isophthaloyl chloride (73MI42301). 

Oxadiazoles are acquiring greater significance in the stabilizing167 and preparation of macromolecular materials.38,168 Thus poly-1,3,4-oxadiazoles with aliphatic substituents are used as films, although aryl derivatives can be used neither as fibres nor films. The high thermal stability of these compounds is worthy of note. 

Di- and tetraphenylsilyl-containing heterochain and heterocyclic polymers such as poly-1,3,4-oxadiazoles, poly-4-phenyl-1,2,4-triazoles, polynaphthylenebenzimida zoles, etc. 04MI54. 

Polyhydrazides and poly(amide-hydrazide)s with redox-active carbazole and triphenylamine units have been synthesized [49]. The resulting poly( 1,3,4-oxadiazole)s andpoly(amide-l,3,4-oxadiazole)s show high glass transition temperatures of 288-330 °C and a high thermal stability. The polymers show a weak to medium photoluminescence with emission maxima of 474-506 nm. In addition, the materials show an enhanced redox stability and electrochromic performance. 

The ultraviolet resistance of poly( 1,3,4-oxadiazole) fibers can be improved, by the addition of 4,4 -azodibenzoic acid [50]. The tensile strength retention of the oxadiazole fibers containing 4,4 -azodibenzoic acid is much higher than that of the fibers without the azo groups after accelerated irradiation by an iodine-gallium lamp. Also the fibers with 4,4 -azodibenzoic acid in the molecular chain by copolymerization show a better UV stability than the fibers simply blended with the same amount of 4,4 -azodibenzoic acid. 

Gomes D, Borges C, Pinto JC. Effects of reaction variables on the reproducibility of the syntheses of poly-1,3,4-oxadiazole. Polymer 2004 45(15) 4997-5004. 

Aromatic polyhydrazides are well known from the work of Frazer, Wallenberger and Sweeny (1,2) as precursors to poly-1,3,4-oxadiazoles. Poly-amide-hydrazides have been described in detail by Black, Preston, and coworkers (3,4,5) and by Culbertson and Murphy (6). High tenacity, high modulus fibers have been made from poly(terephthalie hydrazide)(7) and from polyamide-hydrazides with ordered structures (5). 

Oxalon Grodno KHIMVOLO- KNO Poly(oxadiazole) fiber... 

Oxamidrazone, NHj—NH—C(NH)—C(NH)—NH—NH2, is produced from dicyan and hydrazine, and its isomer converted with terephthaloyl chloride to poly(terephthaloyl oxamidrazone), PTO. PTO can be converted to a poly(triazole), a poly(oxadiazole), or to a metal ion chelated polymer ... 

Poly(triazoles) and poly(oxadiazoles), each with two hetero rings per repeat unit, are obtained by the process described in the previous section. Poly(triazoles) with one triazole residue per structural element are produced from terephthalic acid and hydrazine with subsequent cyclocondensation of... 

The poly(triazole) produced has a very high glass transition temperature of 260 C. It can be wet or dry spun from formic acid. The fibers still retain 30% of their original elongation at break even at 300 C. But to obtain poly(oxadia-zole) fibers, poly(phenylene hydrazide) is spun. Water is eliminated from their drawn or undrawn fibers to produce poly(oxadiazole) fibers. 

Damaceanu, M.-D. Musteata, V.-E. Cristea, M. Bruma, M., Viscoelastic and Dielectric Behavior of Thin Films Made from SUoxane-Containing Poly(oxadiazole-imide)s. Eur. Polym. J. 2010,46,1049-1062. 

Much work has been done on this interesting group of condensation polyimides [219]. Trying to combine the good thermal stability of other heterorings and the availability of polyimide monomers, a considerable number of mixed polyheterocycles has been synthesized. Among other heterocyelic copolyimides, poly(imidazole imide)s [220,221], poly(oxadiazole imide)s [222,223], poly(benzazole imide)s [224,225], poly(quinoxaline-imide)s [226], and poly(quinazolinedione imide)s [227] have been synthesized. 

---