Ahmed S. Hammam

Liquid crystalline polymers: I. Main chain thermotropic poly(arylidene-ether)s containing cyclopentanone moiety linked with polymethylene spacers

Abstract A new series of poly(arylidene-ether)s containing cyclopentanone was synthesized by polycondensation of 4,4′-diformyl-α,ω-diphenoxyalkane 1 – 4 and 4,4′-diformyl-2,2′-dimethoxy-α,ω-diphenoxyalkane 5 – 8 with cyclopentanone. The inherent viscosity of the polymers were in the range of 0.38–1.23 dl/g. Their thermotropic liquid crystalline properties were examined by DSC, optical polarizing microscopy using a heated stage, and thermogravimetric analyses. Almost all the polymers exhibited thermotropic liquid crystalline properties. In most cases the mesophase extends up to 358°C, where the thermal decomposition prevents further observations. The polymer 14 with ( n = 4), having high molecular weight, was synthesized in high yields and showed better solubility in organic solvents, such as halogenated hydrocarbons. In addition, the crystallinity of some polymers was examined by X-ray analysis, and they showed some degree of crystallinity.

Arylidene Polymers. Ii. Synthesis and Characterization of Some New Polyesters of Diarylidenecyclopentanone

Abstract New polyesters formed by interfacial polycondensation of 2,5-bis(4-hydrox-ybenzylidene)cyclopentanone (I) and 2,5-bis(4-hydroxy-3-methoxybenzyli-dene)cyclopentanone (II) with 4,47prime;-diphenic, isophthaloyl, terephthaloyl, adi-poyl, suberoyl, and sebacoyl dichlorides were obtained. The yield and the values of the reduced viscosity of the produced polyesters were found to be affected by the type of organic phase, the quantitative ratio of organic to aqueous phase, the concentration of the hydrogen chloride acceptor, and the contribution of benzyltriethylammonium chloride as a catalyst. In order to characterize these polymers, the necessary model compounds were prepared from I, II, and benzoyl chloride. The resulting polyesters were confirmed by IR, elemental analysis, viscometry, DTA, DSC measurements, and thermogravi-metric analysis. The crystallinities of all polyesters were examined by x-ray analysis, and the electrical properties of the polyesters were tested.

Arylidene Polymers VII. Synthesis and Characterization of New Polyesters of Diarylidenecycloalkanones Containing an Azo Group in the Main Chain

A new interesting class of linear, unsaturated polyesters based on diarylidenecycloalkanones containing an azo linkage in the polymer main chain have been synthesized by interfacial polycondensation of 4,4′-azodibenzoyl chloride or 3,3′-azodibenzoyl chloride with 2,5-bis(p-hydroxybenzylidene)cyclopentanone, 2,5-divanillylidenecyclopentanone, 2,6-bis(p-hydroxybenzylidene)cyclohexanone and 2,6-divanillylidenecyclohexanone at ambient temperature. The resulting polyesters were characterized by elemental analyses, IR spectroscopy, solubility and viscometry measurements. The thermal properties of the polymers were evaluated by TGA and DSC measurements and correlated to their structural units. X-ray analysis of the polymers showed that polyesters based on the meta azo linkage were totally amorphous whereas, polyesters with the para azo linkage had some degree of crystallinity. The UV-visible spectra of certain polymers were measured in m-cresol solution and showed a characteristic absorption band at 438-465 nm due to n-π* transition. In addition, the electrical properties of all polyesters were measured.

Liquid crystalline polymers VIII: thermotropic liquid crystalline poly(hydrazone–ether)s containing bis-thiophene linked to the main chain through spacers of various lengths

A new series of poly(hydrazone–ether)s was synthesized from 3,4-dimethylthieno [2,3-b] thiophene-2, 5-dicarbohydrazide, II and 4,4′-diformyl-α, ω-diphenoxyalkanes or 4,4′-diformyl -2,2′-dimethoxy -α, ω-diphenoxyalkanes. The inherent viscosities of the polymers were in the range 0.22 – 0.56 dIg−1. Majority of the polymers were soluble in concentrated H2SO4. Their thermotropic liquid crystalline properties were examined by DSC, an optical polarizing microscopy using a hot stage and thermogravimetric analyses. The polymers exhibited almost thermotropic liquid crystalline properties. In most cases, the mesophases extended up to 430°C, where thermal decomposition prevented further observation.

Synthesis of new triphenodithiazine- and indolocarbazolediones of biological interest

Tetrabromo-p-benzoquinone reacted with excess aromatic amines to give 2,5-dirylamino-3,6-dibromo-p-benzoquinones. The latter molecules on heating with sodium sulfide in alcohol in the presence of air gave triphenodithiazinediones. Heating with copper powder in nitrobenzene transformed these compounds into the respective indolocarbazolediones. Comparative antimicrobial and antifungal activities of the studied compounds were determined and discussed.

Synthesis of new quinoxalinophenazinediones and tetrahydrobenzodipyrrolotetrones of biological interest

The reaction of two equivalents of sodium azide with diarylaminodibromo-p-benzoquinone (I) in DMF for 15–24 h produced quinoxalinophenazinediones together with a byproduct identified as diarylaminodiaminobenzoquinone. On the other hand, the reaction of bromanil with active methylenes, such as diethyl malonate and ethyl acetoacetate, resulted in disubstitution products which, on treatment with primary amines, cyclized into benzodipyrroletetrones. Comparative antifungal and antibacterial studies were made.

Reaction of 2,3-Dichloro-1,4-naphthoquinone with Some Active Methylene Compounds in Different Basic Media

Reaction of 2,3-dichloro-1,4-naphthoquinone with some active methylene compounds, such as malononitrile and cyanoacetamide, under various basic conditions has been investigated. A mechanism for these reactions is proposed.