Gamal Saad

Conducting filler based on chitosan and grafted polyaniline (Ch-g-PANI) was prepared with different grafting ratios and used as fillers for polyester powder coating system. Differential scanning calorimetry is applied to study the effect of Ch-g-PANI on the curing of the polyester powder coating. The activation energy calculated by isoconversional Kissinger method was increased by either increasing the Ch-g-PANI content or the content of polyaniline in the filler, suggesting the contribution of the filler in the curing reactions. The cured samples were characterized using FTIR and TG analyses. Thermogravimetric analysis showed that the total thermal stability was enhanced upon the filler addition as detected from the values of integral procedural decomposition temperature. Furthermore, a dielectric study showed that the dielectric constant and loss were increased upon increasing of the filler. Vogel–Fulcher–Tammann equation was well-fitted when used to examine the dependence of α-relaxation on the temperature and the dielectrically calculated Tg values were comparable to that measured by DSC. The shielding effectiveness toward microwaves was enhanced by increasing the filler content. POLYM. ENG. SCI., 59:372–381, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics Engineers

The aim of the present work was to investigate the preparation of polyelectrolyte hydrogel as potential drug carrier for antibacterial Ciprofloxacin drug (CFX), intended for controlled release formulation. Hydrogel of N-trimehtyl chitosan (TMC)/sodium carboxymethyl xanthan gum (CMXG) was prepared and ciprofloxacin was employed as a model drug to investigate the loading and release performance of the prepared hydrogel. FTIR, DSC, TGA and SEM analysis were used to characterize the TMC/CMXG hydrogel and its CFX loaded hydrogel. The results showed that the ciprofloxacin was successfully incorporated and released from the prepared hydrogel without the loss of structural integrity or the change in its functionality. The encapsulation efficiency of CFX within the prepared hydrogel was found to be increased with increasing the concentration of drug reaching about 93.8 ± 2.1% with concentration of CFX 250 µg/ml. It was shown also that the drug is entrapped within the gel without significant interaction as confirmed from FTIR spectra and DSC analysis. In vitro release study in phosphate buffer saline (PBS), indicated the steady rise in cumulative drug release with the highest release amount, reaching about 96.1 ± 1.8% up to 150 min, whereby the gel with high drug loading efficiency (3.52 ± 0.07%) displayed faster and higher release rate than that of gel containing a smaller amount of drug (0.44 ± 0.01%). The release kinetics of loaded drug followed zero-order kinetics. CFX drug loaded hydrogel showed high activity against the gram positive and gram negative bacterial strains due to the successful released of CFX from the CFX loaded hydrogel into the tested bacterial strains with the highest diameter of inhibition zone against Escherichia coli (67.0 ± 1.0) as compared to reference antibiotic, Gentamicin (28 ± 0.5). Cytotoxicity of the prepared hydrogel was examined in vitro using lung human normal cell lines and showed the highest cell viability (97 ± 0.5%) at concentration up to 50 µg/ml. Consequently, TMC/CMXG hydrogel can be proposed as new controlled release drug delivery system. © 2018

The effect of introducing a lateral methyl substitution into the previously investigated laterally neat four-ring analogues, 4-substituted phenylazo phenyl 4ʹ-(4ʺ-alkoxyphenylazo) benzoates (Ina–e), on their mesophase behaviour was investigated for the newly prepared five homologous series of 4-substituted phenylazo phenyl 4ʹ-(3ʺ-methyl-4ʺ-alkoxyphenylazo) benzoates (IIna–e). Within each homologous series, the alkoxy group varies between 6, 8, 10, 12, 14, and 16 carbons, while the substituent, X, is a polar group that alternatively changes between the electron-donating (CH3O and CH3) groups, and the electron-withdrawing (Br and NO2) groups, including the unsubstituted homologues (IInc). Their mesophase stabilities were determined by DSC and phases identified by PLM. The results showed that independent of the alkoxy-chain length or the polarity of the substituent X, the nematic phase is predominant with relatively high stability and wide temperature ranges. All compounds show a good thermal stability in the mesophases domain, except the nitro and Br substituted derivatives bearing short alkoxy chain length. Comparison of the mesophase behaviour was also made between the present series and corresponding three-ring laterally CH3-substituted azo/ester analogues. UV-vis absorption spectra revealed that derivatives with electron donating or an electron withdrawing groups exhibited redshifts of the π→π* transition compared with unsubstituded derivative. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.

Four new groups of Schiff base ester liquid crystal compounds, 4-(arylideneamino)phenyl-4″-alkoxy benzoates, Ina–d, were prepared and investigated for their mesophase formation and stability. An alkoxy group of variable chain length (n = 6, and 16 carbons) is attached to the terminal phenylazo benzoate moiety. Each group constitutes two homologous series that differ from each other by the polar substituent X (CH3O, H, NO2, and F). The molecular structure of the prepared compounds was confirmed via FT-IR, 1H NMR, mass spectroscopy and elemental analysis. The mesomorphic properties were investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). For n = 6, all compounds exhibit nematic phase. Amongst them methoxy and nitro derivatives have widest mesophase range. For n = 16, nitro and flouro derivatives exhibit SmA phase, while methoxy and unsubstituted derivative are nematogenic. The change of the mesophase stability is well correlated with van der Waals volume and polarizability of the substituent X and not satisfactory with the dipole moment of the whole molecule. The mesophase behavior of binary mixtures made from each individual derivatives bearing the same substituent X but varies with alkoxy chains length is presented. Results provide insights into the role of substituent X and alkoxy chain length on the mesophase behavior within the whole composition range of the mixtures. © 2018 Elsevier B.V.

Five homologous series of the four-ring 4-substituted phenylazo phenyl 4ʹ-(4ʹ-alkoxy phenylazo) benzoates (In a–e ) were prepared and their mesophase behaviour investigated by differential scanning calorimetry (DSC) and phases identified by polarised light microscopy (PLM). Compounds prepared were structurally characterised via infrared, 1 H-NMR, mass spectroscopy, thermogravimetric and elemental analysis. Transition temperatures were first correlated with the alkoxy-chain length (n, that varies between 6, 8, 10, 14, and 16 carbons) within each homologous series, and again with the polarisability anisotropy (Δα X ) of the Ar-X bond, where X changes between CH 3 O, CH 3 , H, Br, and CN groups. Comparative studies were made to investigate the effect of introducing the extra phenyl azo moiety into the previously investigated three-ring compounds, 4-substituted phenyl 4′-(4″-alkoxyphenylazo) benzoates (IIn a–e ), 4-substituted phenylazo 4′-(4″- alkoxy phenyl) benzoates (IIIn a–e ), and 4-(4′-alkoxy phenylazo) phenyl 4″-substituted benzoates (IVn a–e ), each bear the same polar group, X, and the alkoxy group, n. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Several binary systems made from two laterally substituted azo/ester isomers, namely 2ʺ- (and 3ʺ-) methyl-4-substituted phenyl 4ʹ-(4ʺ-alkoxyphenylazo) benzoates, where the length of the terminal alkoxy group = 8 and 16 carbons, while the other terminal substituent, X, varies between CH3O, CH3, H, Br and CN groups, were investigated using differential scanning calorimetry (DSC) and phases identified by polarised light microscope (PLM). For the sake of comparison, two another binary systems made from 2ʺ- (or 3ʺ-) methyl-4-substituted phenyl 4ʹ-(4ʺ-alkoxyphenylazo) benzoates (n = 8 and X = CH3) each was mixed with its laterally neat analogue and similarly investigated. Results were discussed on the basis of constructed phase diagrams whereby various mesomorphic properties were observed dependent on X, n, and position of the lateral methyl group. In most of the cases, the mixtures exhibited eutectic compositions, while linear or nearly linear nematic and smectic A-composition temperature dependence were observed. © 2017 Informa UK Limited, trading as Taylor & Francis Group.

Five groups of 4-substituted phenyl 4ʹ-(2ʺ- (or 3″-) substituted-4ʺ-alkoxyphenylazo) benzoates (Ina-c to Vna-c) were investigated in which, within each group, the length of the terminal alkoxy group varies between 8 and 16 carbons, while the other terminal substituent, X, is a polar group that alternatively changed between the electron-donating CH3O and the electron-withdrawing Br group, in addition to the un-substituted analogue (X = H). The lateral substituent (Y) in the five groups I–V varies, respectively, between H, 3-CH3, 2-CH3, 3-F and 2-F. Their mesophase stabilities were determined by differential scanning calorimetry and phases identified by polarised light microscopy. The two newly prepared groups of compounds (IVna-c and Vna-c) are structurally characterised by infrared, 1H-NMR, mass spectroscopy, thermogravimetric and elemental analyses. Binary phase diagrams were constructed for each pair of isomers from groups IV and V bearing the same wing substituents but the lateral F is attached to different positions (2ʺ or 3″). © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Four new groups of Schiff base ester liquid crystal compounds, 4-((4ʹ-substituted phenylimino) methyl)phenyl–4″-alkoxybenzoates, Ina – d, were prepared and investigated for their mesophase formation and stability. Each group constitutes four homologous series that differ from each other by the polar substituent X (CH3O, CH3, H, and Cl). Within each homologous series, the number (n) of carbons in the alkoxy chain varies between 6, 8, 10, and 12. Molecular structures of the prepared compounds were confirmed via FT-IR, 1H NMR, mass spectroscopy, and elemental analysis. The mesomorphic properties were investigated by differential scanning calorimetry and polarised light microscopy. Comparative studies between the present series and previously investigated 4-(4-substituted phenylazo)phenyl 4″-alkoxybenzoates revealed that the phenylimino mesogenic core increases the mesophase stability rather than the azo analogues. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.