JOURNAL OF SCIENCES (ISLAMIC AZAD UNIVERSITY)
Year:2009 | Volume:19 | Issue:72 (CHEMISTRY ISSUE)|Papers Count:11

Introduction: The initial spark of nanotechnology goes about half century. There is a lot of space in the low levels. Molecules and atoms are subject to change and new behaviors are expected of them. Nano polymers and nano composites are a part of nano materials. They are especially important because many applications have. Conductive polymers such as polyaniline have interesting properties, conductivity, optically and electro activity. Numerous applications of this nano polymers and its composites can be visitor including electronics, sensors, protections of electrodes, absorption and transfer of heavy metals and removal of organic dye from solutions. Polyaniline protonated state has a good conductivity, but poor mechanical properties. The production of composite by polyaniline and polyamide polymers such as insulation, and using the common solvent can be added to its mechanical properties.Aim: Synthesis of polyaniline and nano conductive polymer composite with the insulating polymer to increase mechanical properties, and study of electrical properties, thermal of Pan/Ny66.Materials and Methods: At this stage, polyaniline synthesis by oxidation with ammonium persoulfate. The electrical properties of Pan/Ny66 nano composite were analyzed by 4-point probe technique. UV-Vis Spectroscopy was used for thermal stability study. The tensile strength test was used to evaluate the mechanical and stability properties. Surface morphology changes were evaluated by scanning electron micrograph (SEM) before and after the production of composite.Results: Polyaniline procces due to poor mechanical properties and low strength of its disadvantages is considered. There is no study thermal stability and electrical conductivity under such conditions. Using formic acid as a common solvent for polyaniline and nylon66, Pan/Ny66 will provide by casting method.1 to 2 ratio of polyaniline to nylon66, is sealed. The thermal stability is high by composite production. Electrical conductivity increases in the Pan/Ny66 composite.Conclusion: Casting method is used for the preparation of nano composite films. Using this method, increased on mechanical properties, thermal stability and electrical conductivity.

Introduction: Studies of aqueous electrolyte solutions almost always require consideration of non-ideality and ion-association. For many decades ion-association in electrolyte solutions has been an area of active research interest. A strong electrolyte solution deviate, partly by non-ideality and partly by ion- association from ideality. The non- ideality contribution could be evaluated by activity coefficients which can be estimated upon some theoretical models.The ion-association contribution, in turn, can be studied both theoretically and experimentally.Aim: Solubility of KNO3 in water at 25oC was determined. Upon choosing a suitable model for estimating the activity coefficient and using the iteration calculations, we estimate the ion association contribution to the solubility of considered ionic compound in the considered solvent and desired temperature.Materials and Methods: Potassium Nitrate was purchased from Merck Company and used without further purification. The saturated solution of PotassiumNitrate in deionized water was prepared at 25.0oC, and then the solubility of this salt in water was determined using Solvent Evaporating and Atomic Emission Spectrophotometric.Results: Comparison of the value of thermodynamic solubility product constant, Ksp(th), (Ksp (th) exp (D Gdisso/ RT of KNO3 and the value of solubility product constant, K'sp obtained from this work showed a great diference (K’sp=s 2 f 2±, where s represents the solubility of KNO 3 in molL-1 and f ± is the mean activity coefficient of KNO3 in saturated aqueous solution at 25οC upon Van Rysselberghe and Eisenberg model).Conclution: The difference between thermodynamic solubility product constant, Ksp (th), of KNO3 and the solubility product constant, K'sp, can be satisfactorily explained using a combination of Van Rysselberghe - Eisenberg model for estimating f and Ion- Association theories.

Introduction: Ceria and Materials based on ceria (CeO2-x) have attracted much attention due to many applications in different fields such as fuel cells, catalysis, etc.. Doping of some elements for example Sm, into ceria has improved some properties of this compound such as electrical conductivity, catalytic behavior, etc.Aim: Syntheses and characterization of Sm doped CeO2 nanotubes at room temperature Materials and Methods: Crystalline phases were determined by X-ray diffraction (XRD) and morphology of the prepared samples was studied by SEM and TEM. Elemental analysis of the prepared samples was carried out using ICP method.Results: The XRD patterns of the Sm doped CeO2 nanotubes were compared with that of CeO2 (JCPDS, 43-1002). Comparison of these patterns indicated that all samples had cubic flurorite structure. Sm-doped CeO2 patterns showed that Sm could be doped into CeO2 up to 50%. The EDAX and ICP analysis of the samples indicated that Sm was doped into the CeO2. The SEM and TEM images of the synthesized samples confirmed formation of Sm doped ceria nanotubes. The calculation of unit cell parameter (a) indicated that by doping of Sm into CeO2, “a” increased. This increase could be due to Sm ionic radii (rSmIII=0.96A), which is more than that of Ce (rCe IV=0.87 A).Conclusion: The XRD patterns of Sm-doped CeO2 showed that Sm could be doped into CeO2 up to 50% (This doping level is obtained in this work for the first time). By doping Sm into CeO2, lattice parameter of the unit cell of the samples (“a”) increased.

Introduction: The quantitative structure-property relationship (QSPR) is a successful strategy for prediction of surfactant properties based on modeling between calculated descriptors from molecular structures of the surfactants and chemical or physical properties of the solution. There are a great number of molecular descriptors that have been used in such QSPR studies, which can be divided into six types, namely constitutional descriptors, topological descriptors, electrostatic descriptors, geometrical descriptors, quantum chemical descriptors and thermodynamic descriptors. There are some reports about the applications of QSPR approaches to predict the CMC of anionic, nonionic and Gemini surfactants.Aim: In the present work, the logCMC of some tetra-alkylammonium and alkylpyridinium salts was mathematically related to the molecular structure properties.Material and Methods: All critical micelle concentrations data of this investigation were obtained from a set of cationic surfactants. They are measured in water at 25 oC. The data set consists of 44 surfactants were divided into two groups with 29 tetra-alkyl ammonium and 15 alkylpyridinium salts. The 3D molecular structures generated by ChemDraw 2005 and optimized by AM1 rotuine of MOPAC. The molecular descriptors generated ChemSAR and Dragon ver 3.0Results: OLS regression analysis provided useful equations that can be used to predict the logCMC of cationic surfactants in this study. Model (I) which was used to estimate the logarithm of CMC tetra-alkyl ammonium surfactants using four structural descriptors could be represented as:logCMC=-1.0097 - 0.1258Lc – 0.0123VH + 0.0960AHG +0.0053RHCIn=20.R2 =0.9860,s2 =0.0210F =135, model (I)The logCMC of alkylpyridinium surfactants with three descriptors can be effectively predicted using following Eq. for model (II).LogCMC=6.0291 – 0.2461Lc – 0.0011VH + 0.0249RHCIModel(II), n = 10,R2 =0.09940,s2 =0.0098,F =159, model (II)simultaneous model, which was used to estimate logCMC all cationic surfactants using four molecular structure descriptors, could be represented as log CMC = -1.4055 - 0.1529Lc - 0.0101VH + 0.1214 AHG + 0.0063RHCI n =30, R2 =0.9820,s2 =F =173,final model where n is the number of compounds used for regression, R2 is the squared correlation coefficient, s2 is the standard error of the regression, and F is the Fisher ratio for the regression.Conclusion: The results indicate that the CMC decreases as the hydrophobic character (L and V) increases and CMC increases as the hydrophilic character (A) of the surfactant increases.

Introduction: Aromatic polyesters are certainly one of the most successful classes of high-temperature polymers. However these polymers encounter processing difficulty due to their infusibility and poor solubility in organic solvents. Therefore, more researches have been focused on maintaining considerable thermally stable and improving their solubility. These studies include: 1) Introducing rather soft segments on the main chain such as methylene and vinyl segments 2) Breaking its symmetry and regularity, thereby making crystallization impossible 3) Introducing the bulky side groups to be exempt from crystallization and 4) Destroying the hydrogen bonding by N-substitution with certain groups such as methyl.Aim: In this paper a series of novel polyesters were obtained by the solution polycondensation reaction of p-phenylene diacryloyl chloride (4) with six different of aromatic diols (5a-f) in DMAc solvent and in the presence of pyridine as a base. These polymers have a soft segment such as vinyl moiety in the main chain for improving the solubility in organic solvents in compare to aromatic polyesters. These polymers have been noticed because they can be used for preparing photosensitive liquid crystalline polymers. There are some reported papers about synthesis polyamides, polyimides, polyesters and poly (amid-co-imide) s containing p-phenylenediacrylic moiety in the main chain.Materials and Methods: All chemicals were purchased from Fluka and Merck Chemical Company. The 1H-NMR spectrum (300 MHz) was recorded on a Bruker Avance 300 spectrometer (Germany). Fourier transform infrared (FT-IR) spectra were recorded on a Galaxy series FTIR 5000 spectrophotometer (England).Results: p-Phenylenediacrylic acid (3) was prepared by the reaction of terephthal aldehyde (1) and malonic acid (2) in the presence of pyridine. The diacid (3) was then converted to p-phenylenediacryloyl chloride (4) by the reaction with thionyl chloride. Solution polycondensation reactions of diacid chloride (4) with hydroquinone (5a), 2, 7- dihydroxy naphtalene (5b), 4, 4΄-dihydroxy diphenyl sulfone (5c), bisphenol A (5d), 1, 4- dihydroxy antraquinone (5e) and phenol phethalein (5f) were carried out in DMAc solution and in the presence of pyridine as a base. The polycondensation reactions produce a series of new polyesters (6a-f) in high yields having inherent viscosity between 0.32-0.50 dL/g. The resulting polyesters were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), differential scanning calorimetry (DSC), solubility test and FT-IR spectroscopy.Conclusion: Several new polyesters (6a-f) have been synthesized by the solution polycondensation reaction of the monomer (4) with six different of aromatic diols (5a-f) in DMAc in the presence of pyridine as a base. These new polyesters are soluble in various organic solvents and have good thermal stability. These properties can make these polyesters attractive for practical applications such as processable high-performance engineering plastics.

Introduction: Hollow titania nanospheres have attracted much attention due to their wide applications in many fields, such as adsorption, catalysis and photocatalysis. Doping of different transition metals has enhanced photocatalytic properties of TiO2.Aim: Syntheses and characterization of Cr doped titania hollow nanospheres using sol-gel method and without template (for the first time).Experimental: Hollow titania nanospheres synthesized by a simple sol-gel method and calcined in different temperatures. Then the prepared samples were characterized with Xray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).Results: The XRD patterns of samples show that the maximum mole fraction of Cr doping level in TiO2 is around 30% and the crystal lattice parameter decreases with Cr doping. Pure TiO2 and Cr doped TiO2 calcined at 500 oC both are in anatase phase but for pure TiO2 with increasing calcination temperature rutile phase starts to appear. The fraction of the rutile phase is greatly reduced for Cr doped TiO2 hollow spheres in comparison with pure TiO2 hollow spheres at 700 oC. The SEM and TEM images indicate that the prepared samples are spherical. The mean diameters of the spheres are estimated using the Scherrer equation.The size of the crystal grains of the TiO2 hollow spheres increases with increasing calcination temperature and decreases with increasing calcination time.Conclusion: The maximum mole fraction of Cr doping in hollow titania spheres is around 30%. For pure TiO2 with increasing calcination temperature rutile phase starts to appear. The fraction of the rutile phase is greatly reduced for Cr doped TiO2 hollow spheres at 700 oC. The crystal lattice parameters calculated from the XRD patterns of the prepared samples show that the crystal lattice parameter (c) of the samples decreases with Cr doping.

Introduction: The genus Chaerophyllum is comprised of about 110 species; eight are described in the flora of Iran, among which two are endemic. The family Umbelliferae is rich in secondary metabolites and embodies numerous genera of high economic and medicinal value yielding flavonoids, coumarins, acetylenes, terpenes and essential oils.Aim: Investigation and identification of chemical compositions of the essential oil from Chaerophyllum Macropodum Boiss. and determining of essential oil yields.Materials and Methods: Water-distilled essential oil from the aerial parts of Chaerophyllum macropodum Boiss. was analyzed by Gas Chromatography (GC) and Gas Chromatography – Mass Spectroscopy (GC/MS) methods.Results: The yield of essential oil was 0.3% (W/W) and twenty – three constituents representing 97.0% of the oil were characterized of which b-caryophyllene (21.0%), hexyl octanoate (12.6%) and octyl acetate (11.7%) were the main compounds which were identified.Conclusion: The essential oil of Chaerophyllum macropodum aerial parts is rich in b - caryophyllene, hexyl octanoate and octyl acetate. The oil was richer in sesquiterpenes and oxygenated hydrocarbons than the other compounds.

Introduction: The effects of different solid substrates including: carbon nanofibers (CNFs), activated carbon, alumina, silica, and poly vinyl pyrolidone (PVP) were compared for high pressure synthesis of polytetrafluoroethylene (PTFE, (CF2)n) nanoparticles via the adsorption of thermally synthesized tetrafluoroethylene (TFE, C2F4) as monomer.Aim: Syntheses and characterization PTFE nanoparticles and also in this paper, a new method is proposed for the synthesis of PTFE nanoparticles via adsorption of TFE monomer on different solid substrates.Materials and Methods: Electron microscopy, FT-IR spectroscopy, and thermogravimetric analysis (TGA) were used for characterization of PTFE nanoparticles on different solid substrates.Results: under similar conditions, the average diameter of the PTFE nanoparticles was around 90 nm for CNFs, 130 nm for PVP, 150 nm for alumina and around 200 nm for silica.Conclusion: Different solid materials have various capacities for the formation of PTFE nanoparticles, depending on their size, shape, and their morphology. In fact, the amounts and the sizes of synthesized PTFE nanoparticles are strongly dependent on the nature of the solid surface substrate.

Introduction: Aldol condensation is a powerful tool for the formation of carboncarbon bond in many classes of carbonyl compounds. This reaction is performed in the presence of acids, bases or different complexes of metal (II) ions as catalyst. According to importance of this reaction, efforts were done to achieve an efficient catalyst in order to improve aldol condensation.Aims: The catalytic effect of ammonium chloride was determined in cross aldol condensation to afford the corresponding a, a' -bis (substituted benzylidene) cycloalkanones also, ammonium chloride with previously reported catalysts was compared in this reaction.Materials and Methods: Aldol condensation of cyclopentanone and benzaldehyde in ethanol was selected as model reaction. In the absence of ammonium chloride no product was obtained either at room temperature or at reflux condition. Increasing the amount of catalyst, improve the yield of reaction (room temperature). Raising the temperature of the reaction (reflux condition) caused little amount of catalyst gave higher yields. Based on the experiments with the optimized condition, aldol condensation of cyclopentanone and cyclohexanone with aromatic aldehyde with electron donating and withdrawing groups was done.Results: Ammonium chloride efficiently catalyzes cross aldol condensation of aromatic aldehydes with ketones to afford the corresponding a, a' -bis (substituted benzylidene) cycloalkanones in high yields. NH4Cl compared with previously reported catalysts reflects the wide applicability and usefulness of the method.Conclusion: NH4Cl is an efficient and readily available reagent and inexpensive catalyst in cross aldol condensations of different ketones with various aromatic aldehydes to prepare the a, a' -bis (substituted benzylidene) cycloalkanones. The reaction is a green process avoiding the use of toxic solvents and acid liquids.

Introduction: Calixarenes are obtained from the condensation of phenols with formaldehyde and possess a hydrophobic cavity capable of including molecular guests in solution. p-sulfonato calix (n) arenes are able to complex with variety of organic compounds as well as inorganic ions in water. It is known that calixarene molecules exhibit a strong sterical flexibility by comparing with cyclodextrins, and therefore there is a possibility to use calixarenes in a wide field of applications. There are many studies dedicated to calixarenes and their derivatives, most of them directed toward the selective complexation of biological substrates.Aim: The present study investigated the formation constant for complexation of alkali metal cations by the water- soluble p-sulfonatocalix (4) arene and discussed about their interactions.Materials and Methods: All the measurements were carried out at 25o C and pH=2 using a spectrophotometer. Absorbance, A, was measured by successive addition of an alkali metal cation solution (Li+, Na+, K+, Rb+, Cs+) to p-sulfonatocalix (4) arene solution. Treatment of the spectrophotometric data obtained during the titrations was conducted with the computer program Squad.Results: The complexation of alkali metal cations by p-sulfonato calix (4) arene are consistent with the formation of a 1: 1 complex resulting from electrostatic interactions between the sulfonato groups and alkali metal cations. In this study, we determined formation constants (log K) of the complexes at pH 2 and 25oC, that were log KLi+=4.5130 ± 0.06, log KNa+=4.0898 ± 0.08, log KK+=3.9556 ± 0.04, log KRb+=3.4489 ± 0.07 and log KCs+=3.1601± 0.09, respectively.Conclusion: It is concluded that Li+ forms strongest binding with p-sulfonato calix (4) arene by cation-P interactions with benzene rings and electrostatic interactions with the SO3- groups because of suitable size-fit on cavity, whereas for Rb+ and Cs+ those are week because they have not significant cation- P interaction.