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.
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.
Condensation of 4,4'-diacetyldiphenyl sulphide (2) with variable amounts of thiosemicarbazide (3) in refluxing ethanol and in the presence of catalytic amounts of dry piperidine afforded only 4-acetylthiosemicarbazone-4'-acetyldiphenyl sulphide (5). Condensation of 2 with excess semicarbazide hydrochloride (4) in the presence of fused sodium acetate and/or piperidine yielded 4,4'-diacetylsemicarbazone diphenyl sulphide (6), whereas use of equimolar amounts of 2 and 4 afforded 4-acetyl-semicarbazone-4'-acetyldiphenyl sulphide (7). 4-Acetylsemicarbazone-4'-acetylthiosemicarbazone diphenyl sulphide (8) was also obtained via two different routes. The effect of tautomeric structure 5d is discussed. 4-(4"-phenyl-Δ3-thiazoline-2"-acetylazino)-4'-acetyldiphenyl sulphide (9), 4-(5"-carboxyethyl-4"-thiazolidinone-2"-acetylazino)-4'-acetyldiphenyl sulphide (10), 4-(4"-thiazolidinone-2'-acetylazino)-4'-acetyldiphenyl sulphide (11) and 4-(4"-methyl-Δ3-thiazoline-2"-acetylazino)-4'-acetyldiphenyl sulphide (12) were prepared by interaction of 5 with phenacylbromide, bromodiethylmalonate, chloro ethylacetate and chloroacetone, respectively. Sulphides 9-12 were easily condensed with 3 to afford the corresponding 4-(heterocyclic moiety-2"-acetylazino)-4'-acetylthiosemicarbazone diphenyl sulphides 23-26. Oxidation of the prepared sulphides 5-7, 9-12, 23 and 25-26 using H2O2/glacial AcOH mixtures yielded only 4,4'-diacetyldiphenyl sulphone (13) as the main product in every case, besides 3 and 4 in certain cases. Unsymmetrical and symmetrical sulphones 14-22 were obtained starting from 13. The structures of the synthesized compounds are based on IR, 1H-NMR, 13C-NMR and mass spectral data. A theoretical study on some of the prepared compounds using molecular modeling was carried out.
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