Synthesis and characterization of some new aromatic polyoxadiazoles through cyclodehydration of polyhydrazides |
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Authors: | Kaveh Parvanak Boroujeni Bahman Tamami Amir Abdulmaleki Shahriyar Osfouri Abdulhamid Fadavi |
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Affiliation: | (1) Department of Chemistry, Shahrekord University, 115, Shahrekord, Iran;(2) Department of Chemistry, Shiraz University, Shiraz, Iran;(3) Department of Chemistry, Isfahan University of Technology, Isfahan, Iran;(4) Department of Engineering Chemistry, Persian Gulf University, Bushehr, Iran;(5) Department of Chemistry, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran |
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Abstract: | A series of new polyhydrazides containing pyridine heterocyclic ring, bearing bulky aromatic pendent groups, were synthesized
from the reaction of diacid chlorides with dihydrazides via low-temperature solution polycondensation. All the polymers were
readily soluble in polar solvents such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), and 1-methyl-2-pyrrolidone (NMP) and showed
inherent viscosities equal to 0.38–0.68 dL/g. They indicated glass transition temperatures (T
g) ranging from 190 to 220 °C. Polyhydrazides were subjected to cyclodehydration to prepare poly(1,3,4-oxadiazole)s either
by thermally or chemically cyclodehydration approximately in the region of 150–320 °C. The poly(1,3,4-oxadiazole)s, made by
chemically cyclodehydration exhibited T
gs of 220–250 °C and inherent viscosities equal to 0.38–0.62 dL/g, while the PODs made via thermally cyclodehydration of polyhydrazides
did not show any glass transition and exhibited inherent viscosities equal to 0.39–0.66 dL/g. The former polymers were soluble
in conc. H2SO4 and partially soluble in hot DMF, NMP, DMSO, and DMAc, and the latter were only soluble in conc. H2SO4. They had useful levels of thermal stability and were stable up to 450 °C in nitrogen. The structure of polymers was fully
characterized by IR and NMR spectroscopies. |
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