Mahmoud A. Hussein

Review on: liquid crystalline polyazomethines polymers. Basics, syntheses and characterization

Liquid crystalline behavior of polymeric materials is of considerable current interest in the last decades, but due to many different and distinct characteristics. Polyazomethines liquid crystalline polymers have received considerable attention due to their potential applications and considered as one of the most important liquid crystalline material produced. This review gives a simple introduction to liquid crystalline materials including definition and classification. Moreover, we will focus on the syntheses and properties of liquid crystalline polyazomethines with flexible spacers or hybrid liquid crystalline polyazomethines. Furthermore, give a general overview of thermotropic, mesophoric properties and texture observation for desired liquid crystalline polyazomethines were shown in details.

Structure-property relationship of naphthalene based donor-π-acceptor organic dyes for dye-sensitized solar cells: Remarkable improvement of open-circuit photovoltage

Four new donor–π–acceptor organic dyes (YF01–04), containing naphthalene-substituted amines as an electron donor and cyanoacrylic acid as an electron acceptor, were designed and synthesized, and their photophysical properties and dye-sensitized solar cells (DSCs) performances were characterized. Dyes YF02 and YF04, with 2,6-disubstituted naphthalene frameworks, were superior than their analog dyes YF03 and YF01, having 1,2-disubstituted naphthalene moiety, in incident-photo-to-current conversion efficiency (IPCE) and total solar-to-electric conversion efficiency (η). The DSCs based on YF02, comprised of diphenylamine moiety as the donor, produced the highest η of 5.29% compared to 4.03% of the analog dye YF04, which has pyrrolidine as the donor. Remarkably, a high open-circuit photovoltage (Voc) of 0.799–0.807 V was achieved in the cases of YF02–03, which have diphenylamine-donors. To better understand the structure–property relationship for DSCs application, molecular modelling was performed on YF01–04 and vertical electronic excitations were calculated using long-range corrected energy functional WB97XD and CAM-B3LYP at the basis set level DGDZVP, which were in excellent agreement with the experimental results. Moreover, the equilibrium molecular geometries of dyes YF01–04 were calculated at the density function theory (DFT) level using the hybrid energy functional B3LYP and basis set DGDZVP. The torsion angles (θ) between the naphthalene moiety and diphenylamine donor in YF02 and YF03 were more twisted than that of the pyrrolidine-donor dyes YF01 and YF04, precluding efficient intermolecular π–π charge transfer, which translated into high Voc. Compared to the reference dye TA-St-CA, which is based on diphenylamine as an electron donor linked to a phenyl ring, YF02 achieved higher Voc, which indicated that naphthalene substituted with diphenylamine is more efficient in retarding charge recombinations.

Sensitive methanol sensor based on PMMA-G-CNTs nanocomposites deposited onto glassy carbon electrodes.

A new series of polymethyl methacrylate-graphene-carbon nanotubes crossbred nanocomposites in the form of PMMA-G-CNTs has been synthesized using simple dissolution procedure in organic media. The desired nanocomposites have been prepared using different loading (2 ∼ 30%) from consequently mixed GNPs/CNTs ratio and confirmed by various characterization techniques utilized to corroborate the assembly of these new hybrid series including X-ray diffraction analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. The PMMA-G-CNTs nanocomposites were deposited on flat glassy carbon electrodes (GCE) to result in a sensor that has a fast response toward methanol in the phosphate buffer phase. Features including high sensitivity, low-sample volume, reliability, reproducibility, ease of integration, long-term stability, and enhanced electrochemical responses are investigated. The calibration plot is linear (r(2)=0.9895) over the 1.0 nmol L(-1) to 10.0 mmol L(-1) methanol concentration ranges. The sensitivity and detection limit is 13.491 µA cm(-2) mmol L(-2) and 0.39 ± 0.1 nmol L(-1) (at a signal-to-noise-ratio, SNR of 3), respectively. With such excellent features of analytical parameters, the developed sensor provides a new strategy for determination of methanol in biomedical and environmental analytes with satisfactory results.

Synthesis, characterization and corrosion inhibitive properties of new thiazole based polyamides containing diarylidenecyclohexanone moiety

The present work aimed to synthesize a new interesting series of thiazole based polyamides containing diarylidenecyclohexanone moiety 5a-5f using low temperature solution polycondensation technique. The new polymers were synthesized by the reaction of thiazole based monomer namely, bis(2-aminothiazol-4-ylbenzylidene)cyclohexanone 3 with different aliphatic and aromatic diacid chlorides using NMP, and in the presence of anhydrous LiCl as catalyst. Adipoyl, sebacoyl, oxaloyl, terephthaloyl, isophthaloyl dichlorides and biphenyl dicarbonyl dichloride were used as diacid chlorides. The structure of the model compound 4 as well as the new polymers was confirmed by correct elemental and spectral analyses. The thermal properties of those polymers were evaluated by TGA and DTG measurements and correlated to their structural units, beside X-ray diffraction analysis, solubility and viscometry measurements. The inherent viscosities for the synthesized polymers were in the range 0.6–1.03 dL/g. On the other hand the corrosion inhibitive properties of monomer 3 as well as polyamides 5d and 5f as selected examples were carried out on carbon-steel in 0.5 mol/L H2SO4 at 40 °C. The calculated inhibition efficiency (IE%) for polymer 5d was in the range (82 ± 6)% in all selected concentrations. The best value of IE% was obtained at 1 mg/L to reach 98.24% for polymer 5d and at 0.5 mg/L to reach 87.75% for polymer 5f.

New Polymer Syntheses Part 53. Novel Polyamides of Diarylidenecycloalkanone Containing Azo Groups in the Polymer Backbone: Synthesis and Characterization

A new interesting class of polyamides of diarylidenecycloalkanone containing azo groups in the polymer backbone 6 a-d was synthesized by a solution polycondensation reaction of bis 2-aminoarylidene monomers 3 a,b with 4,4′-azodibenzoyl dichlorides and 3,3′-azodibenzoyl dichlorides in NMP as a solvent, using anhydrous LiCl as a catalyst at room temperature. The model compounds 4, 5 were synthesized by the interaction of one mole of bis 2-aminoarylidene monomers 3 a,b with two moles of benzoyl chloride using anhydrous LiCl as a catalyst in NMP at room temperature. 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. X–ray analysis of the polymers showed that polyamides based on para-azo linkage have a higher degree of crystallinity than those based on meta-azo linkage in the region 2θ = 5−60°. In addition, the morphological properties of selected examples were tested by SEM.

Organometallic Ferrocene- and Phosphorus-Containing Polymers: Synthesis and Characterization

The inclusion of organometallic units into polymeric structures has attracted much attention in different fields according to the nature and behaviour of the inserted metal. Moreover, the discovery of organometallic polymers and their structural characterization initiated an explosive rebirth of organometallic chemistry. Organometallic moieties are in or pendent to the polymer backbone and examine some of the uses of the emergent metallocene polymers, and new uses are still being found for these remarkable organometallic moieties. This review gives a simple introduction to variable organometallic molecules and their characteristics. This review will focus on the syntheses and characterization of organometallic polymers, including ferrocene- and phosphorus-containing polymers. A general overview on ferrocene polymers with a special attention to ferrocene-containing liquid crystalline polymers (including a ferrocene moiety in the main chain, side-chain or dendrimers) and fullerene–ferrocene liquid crystalline polymers is presented. In addition, more details for synthesis and properties of phosphorus-containing polymers are illustrated.

Polyarylidene containing saturated silicon spacers in the polymers main chain

A new series of photoactive polymers were synthesized by condensing polymerization of different diarylidine monomers 1a,b –3a,b with 1,2-bis(chloromethylsilyl)ethane in Tetrahydrofuran and in the presence of butyllithium. These polymers were characterized by elemental and spectral analyses. The optical properties of these polymers were comparable to those of parent monomer units, by using ultraviolet–visible absorption and emission in solution, and they possessed the physical characteristics of macromolecules. In addition, the thermal properties of these polymers were evaluated by thermogravimetric analysis and DSC measurements. These polymers are thermally stable up to 207 °C except for polymer P3a up to 180 °C and underwent degradation thereafter. The polymers exhibit glass transition temperatures lower than 0 °C except for polymer P3a where its T g was at 35 °C. The molar masses of all polymers were determined by gel permeation chromatography (GPC), and all polymers have high molar masses. The starting monomers 1a, 2a, and 3b were crystallized and their structures in the crystal were determined by X-ray diffraction. The polymerizable points were found not to be in proper spatial relation to allow for solid-state polymerization.

New Polyamides and Polyoxazoles Based on Diphenyl Ether Segments in the Polymers' Backbone

Two new series of polyamides, 7 a-e and polyoxazoles 8 a-e , containing diphenyl ether segments were synthesized using a low-temperature solution of polycondensation and polycyclization reactions, respectively. Polyamides were synthesized by interaction of monomer 4 with different aliphatic and aromatic diacid chlorides, including adipoyl, sebacoyl, oxaloyl, 4,4′-azodibenzoyl and 3,3′-azodibenzoyl dichlorides. The poly-merization reaction was carried out in dry DMF as a solvent and in the presence of anhydrous potassium carbonate as a catalyst at room temperature. Polyoxazoles were obtained as cyclization products form corresponding polyamides in polyphosphoric acid. The model compounds 5 and 6 were synthesized to know the optimum polymerization procedures. The structure of the model compounds as well as the resulting polymers was characterized by elemental and spectral analyses. The synthesized polymers were soluble in protonic solvents such as formic and concentrated sulfuric giving different colors. The thermal properties of those polymers were evaluated by TGA, DTG, and DTA measurements and correlated to their structural units. FDT for polyamides was nearly complete at around 730–750°C, while for polyoxazoles it was nearly complete at around 580–650°C. The glass transition temperatures for the selected polymers were in the range of 47–74°C, while T m values were in the range of 156–315°C. X-ray analysis showed that the selected polyamides have a higher degree of crystallinity than polyoxazoles in the region 2θ = 5−60°. In addition, the morphological properties of selected examples were tested by SEM measurements. A comparative SEM study was carried out between selected polyamides and polyoxazoles.

Saudi-KAU Coupled Global Climate Model: Description and Performance

BackgroundA new coupled global climate model (CGCM) has been developed at the Center of Excellence for Climate Change Research (CECCR), King Abdulaziz University (KAU), known as Saudi-KAU CGCM.PurposeThe main aim of the model development is to generate seasonal to subseasonal forecasting and long-term climate simulations.MethodsThe Saudi-KAU CGCM currently includes two atmospheric dynamical cores, two land components, three ocean components, and multiple physical parameterization options. The component modules and parameterization schemes have been adopted from different sources, and some have undergone modifications at CECCR. The model is characterized by its versatility, ease of use, and the physical fidelity of its climate simulations, in both idealized and realistic configurations. A description of the model, its component packages, and parameterizations is provided.ResultsResults from selected configurations demonstrate the model’s ability to reasonably simulate the climate on different time scales. The coupled model simulates El Niño-Southern Oscillation (ENSO) variability, which is fundamental for seasonal forecasting. It also simulates Madden-Julian Oscillation (MJO)-like disturbances with features similar to observations, although slightly weaker.ConclusionsThe Saudi-KAU CGCM ability to simulate the ENSO and the MJO suggests that it is capable of making useful predictions on subseasonal to seasonal timescales.

New Polymer Syntheses Part 57: Thermally Stable New Ferrocene-Polyazomethines, Synthetic Methodology, and Characterization

A new interesting category of higher thermally stable polyazomethines containing ferrocene in the polymers main chain 6a–e  was synthesized by solution-polycondensation reaction of 1-(m-formylphenyl)-1′-(5-formyl-2-methoxyphenyl)-ferrocene monomer 4 with different aliphatic and aromatic diamines. A model compound 5 was synthesized from dialdehyde monomer 4 with aniline and was characterized by elemental and spectral analyses. The desirable resulting polymers were characterized by elemental and spectral analyses, in addition to solubility measurement using different solvents. The thermal properties of these polymers were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements. The redox behaviours were studied for the ferrocene polymers in comparison with both the parent ferrocene monomer and the model compound by using cyclic voltammetry (CV).