Polyhydrazides based on furanic diacid chlorides and furanic dihydrazides were prepared. The properties of the products are discussed in terms of the backbone structure and the polycondensation technique employed. Their cyclodehydration was carried out by heating in SOCl2 to give new polyoxadiazoles consisting of alternating furanic units and 1,3,4-oxadiazole rings.
A solution polyaddition procedure was applied to prepare furanic polyacylsemicarbazides based on 2,2 -isopropylidene-bis(5-(2-furoyl) hydrazide) and aliphatic or aromatic diisocyanates. Model compounds were prepared to facilitate the synthesis and the characterization of the polymers. A systematic study of reaction parameters (the nature of the organic phase, the temperature, the reaction time, and the concentration of monomers) was carried out. High MW polymers were obtained after 12 h reaction at 20 • C with 0.2 M monomer solutions in dimethylacetamide. In fact, the polyacylsemicarbazides obtained had inherent viscosities ranging from 0.63 to 0.85 dL/g. There showed good solubility in aprotic polar solvents. The 1 H and 13 C-NMR spectra were consistent with the expected structures. These furan-based polyacylsemicarbazides are thermally stable up to 290 • C, but exhibit a complex thermal behavior. This was explained by the cyclohydration of acylsemicarbazide groups into NH-substituted oxadiazoles, resulting in rigid and high melting polymers, less stable, however, than conventional aromatic polyoxadiazoles.
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