Abstract.A new homologous series of thermally stable thermotropic liquid crystalline poly(azomethine-ether)s based on thiazole moiety were synthesized by solution polycondensation of 4,4'-diformyl-α,ω-diphenoxyalkanes, I-IV or 4,4'-diformyl-2,2'-dimethoxy-α,ω,-diphenoxyalkanes V-VIII with the new bis(2-aminothiazole) monomer X. A model compound XI was synthesized from X with benzaldehyde and characterized by elemental and spectral analyses. The inherent viscosities of the resulting polymers were in the range 0.43-1.34 dl/g. All the poly(azomethine-ether)s were insoluble in common organic solvents but dissolved completely in concentrated H2SO4 and formic acid. The mesomorphic properties of these polymers were studied as a function of the diphenoxyalkane space length. Their thermotropic liquid crystalline properties were examined by DSC and optical polarizing microscopy and demonstrated that the resulting polymers form nematic mesophases over wide temperature ranges. The thermogravimetric analyses of those polymers were evaluated by TGA and DSC measurements and correlated to their structural units. X-ray analysis showed that polymers having some degree of crystallinity in the region 2θ = 5-60°. In addition, the morphological properties of selected examples were tested by scanning electron microscopy.
A new interesting class of polyketoamine polymers based on diarylidenecycloalkanone were synthesized by suspension polycondensation. These polymers were synthesized via polymerization of 2,5-bis(4-chloroacetylbenzylidene)cyclopentanone and 2,6-bis(4-chloroacetylbenzylidene)cyclohexanone with different aliphatic and aromatic diamines including, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, 4,4'diaminodiphenylsulfone, hydrazine hydrate, 1,2-diaminoethane, 1,3-diaminopropane and 1,8-diaminooctane.Model compounds were prepared by condensation of 2,5-bis(4-chloroacetylbenzylidene)cyclopentanone and/or 2,6-bis(4-chloroacetylbenzylidene)cyclohexanone with aniline in dry benzene, and their structure was con®rmed by elemental analysis and spectroscopy. The structure of the polymers obtained was also con®rmed by the same methods. Moreover, the identi®cation of the polymers was carried out by other techniques, eg crystallinity from X-ray spectroscopy, viscosimetry, thermogravimetric analysis; the morphological properties of selected examples were tested by scanning electron microscopy. The electrical conductivity of selected examples is about 10 À12 ohm cm À1 . The results are in accord with the structure.
2-Hydrazinobenzoxazole (1), -benzimidazole (2), and benzothiazole (3) were condensed with ethyl chloroformate and/or diethyl oxalate to produce, 1,2,4-triazolo- and 1,2,4-triazino-fused ketones of the title azoles respectively. Condensation of 1 and 2 with aromatic aldehydes and/or acetic anhydride produced, 3-aryl- and 3-methyl-substituted 1,2,4-triazolo-fused azoles respectively. The hydrazines 1 and 2 cyclized with acetylacetone to produce the corresponding 2-(1-pyrazolyl) derivatives. 2-Acetylthiazolobenzimidazole reacted with hydroxylamine and/or alkylamines, to produce the corresponding condensation products. Also it condensed with aromatic aldehydes to give the chalcones. When reacted with benzenediazonium salt, it gave the corresponding 2-arylazo-substituted compounds.
A new interesting class of polyurea derivatives 5 a-c was synthesized using solution polycondensation technique by the interaction of 1 mol of 4,4 0 -bis(2 00 -aminothiazol-4 00 -yl)diphenyl ether monomer 3 with 1 mol of diisocyanate compounds in pyridine. The model compound 4 was synthesized by the interaction of 1 mol of monomers 3 with 2 mol of phenylisocyanate in pyridine, and the structure was confirmed by correct elemental and spectral analyses. The resulting polymers were characterized by elemental and spectral analyses besides solubility and viscometry measurements. The thermal properties of those polymers were evaluated by TGA, DTG, and DTA measurements and correlated to their structural units. In addition, the morphological properties of a selected example were tested by SEM, and the electrical properties of these polymers were measured. On the other hand, the corrosion inhibition properties of selected example of polyurea derivatives were carried out on steel in 0.5M H 2 SO 4 at 40 C giving cathodic inhibition.
3-Methyl-1H-quinoxalin-2-one has been doubly lithiated with n-butylithium at -78 °C in THF. The dilithio reagent thus obtained reacts with various electrophiles (iodomethane, iodoethane, D 2 O, benzaldehyde, benzophenone, cyclohexanone) to give modified 3-substituted 1H-quinoxalin-2-ones in good yields. In the reaction of the dilithio reagent with phenyl isothiocyanate the product was a tautomer of the simple substitution product. Reaction of the dilithio reagent with iodine gives an oxidatively dimerised product instead of the 3-iodomethyl derivative. Lithiations of 3-ethyl-and 3-propyl-1H-quinoxalin-2-ones, followed by reactions with representative electrophiles (benzaldehyde, benzophenone, cyclohexanone), behaved in a similar manner to give the corresponding modified 3-substituted derivatives in good yields.
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