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54677822 | Thermal Gravimetric Analysis (TGA), Transmission Electron Microscopy (TEM), and X-Ray Analysis. Thermal gravimetric analysis (TGA) of the polymer sample was performed using a SHIMADZU DT-30 thermal analyzer.The weight loss was measured from ambient temperature up to 600 ∘ C at rate of 20 ∘ C/min to determine the rate o... | 7 |
54677822 | Conductivity Measurements. The ac conductivity was measured using Philips RCL bridge (digital and computerized) at a frequency range 0.1-100 kHz and over temperature range 30-80 ∘ C. The temperature was controlled by the use of a double wound electric oven. The ac conductivity ac value was calculated using the relatio... | 8 |
54677822 | Effect of HCl Concentration. The effect of HCl concentration on the aqueous oxidative polymerization of OPDA was investigated using constant concentration of K 2 Cr 2 O 7 at 0.3 M and monomer concentration at 0.1 M and using different concentration of HCl at 5 ± 0.2 ∘ C. The yield-time data was represented in Figure 2,... | 10 |
54677822 | Effect of O-Phenylenediamine Concentration. The effect of monomer concentration on the polymerization efficiency was investigated in the range of monomer concentration from 0.02 to 0.5 M and the data was represented in Figure 3, from which it is clear that the optimum yield formation is obtained at 0.1 M of the monomer... | 11 |
54677822 | The Kinetic where is the weight of the obtained polymer, is the time in seconds, is the molecular weight of the monomer, and is the reaction volume in liter. The initial and overall reaction rates of the polymerization reaction increase with the increase of oxidant concentration in the range between 0.05 and 0.3 mo... | 12 |
54677822 | Effect of Hydrochloric Acid Concentration. The polymerization of OPDA (0.1 mol) in 25 mL of HCl with different molarities was carried out by addition of 25 mL potassium dichromate (0.3 mol/L) as oxidant at 5 ∘ C for different time intervals.The concentration of the monomer and oxidant were kept constant during the stud... | 13 |
54677822 | Calculation of the Thermodynamic Activation Parameters. The polymerization of OPDA (0.1 mol/L) in 25 mL of 0.2 mol/L HCl in presence of 25 mL potassium dichromate (0.3 mol/L) as oxidant solution was carried out at 5, 10, and 15 ∘ C for different time periods.The yield-time curves were graphically represented in Figure ... | 14 |
54677822 | The Initial Step.Potassium dichromate in acidified aqueous solution produces chromic acid as shown in This reaction is controlled by the change in pH; the orange red dichromate ions (Cr 2 O 7 ) 2− are in equilibrium with the (HCrO 4 ) − in the range of pH-values between 2 and 6, but at pH below 1 the main species is (H... | 16 |
54677822 | Propagation Step.This step involves the interaction between the formed radical cation and the monomer to form a dimer radical cation.In the case of Cr(VI) oxidation of the organic compounds, Cr(VI) is reduced to Cr(IV) first and then to This reaction is followed by further reaction of the formed dimmer radical cations ... | 17 |
54677822 | The Elemental Analysis. The data obtained from elemental analysis using oxygen flask combustion and a dosimat E415 titrator shows that the found carbon content of (POPDA) is lower than the calculated value.This is due to the formation of chromium carbide during step of heating and measuring process while the found valu... | 18 |
54677822 | X-Ray Photoelectron Spectroscopy (XPS) Characterization (1) XPS Survey Elemental Composition.X-ray photoelectron spectroscopy (XPS) is used to study the composition of materials, which detect elements starting from Li ( = 3) and higher elements.Hydrogen ( = 1) and helium ( = 2) cannot be detected due to the low probabi... | 19 |
54677822 | The Infrared Spectroscopic Analysis of (OPDA) Monomer and Its Analogs Polymer.The IR spectra of the OPDA and its polymer (POPDA) are represented in Figure 12, while the absorption band values and their assignments are summarized in Table 3.The medium absorption band appearing at 453 cm −1 , which could be attributed to... | 20 |
54677822 | The X-Ray Diffraction Analysis and Transmission The recorded conductivity value at room temperature of POPDA was found 0.0352 S/cm which is higher than conductivity of polyaniline-polyvinyl alcohol blends 10.5 × 10 −5 S cm −1 [37] and ac conductivity of HCl doped polyaniline synthesized by the interfacial polymerizatio... | 21 |
54677822 | Table 1 : Solubility of poly-o-phenylenediamine (POPDA) in different solvents at 20 ∘ C. Transfer of two electrons from two monomer ions radical by H 2 CrO 4 produces para semidine salt along with chromous acid H 2 Cr 2 O 3 (Cr(IV)).The intermediately produced Cr(IV) oxidises para semidine to pernigraniline salt (PS) a... | 25 |
3326323 | Article history: Received on: 07/09/2013 Revised on: 08/10/2013 Accepted on: 12/02/2014 Available online: 27/02/2014 Microscopy of the gum revealed various shapes and sizes which disintegrated within a short time (3-5 minutes). They have thick walls, somewhat cracked and striated and also seen as translucent masses. So... | 1 |
3326323 | INTRODUCTION Gums are natural plants hydrocolloids that may be classified as anionic or non-ionic polysaccharides or salts of polysaccharides.They are translucent, amorphous substances that are frequently produced in higher plants as protective agents after injury.Thus, they are the abnormal products of plants metabol... | 2 |
3326323 | MATERIALS AND METHODS Following the identification of the A. occidentale, the gum was collected upon wounding or injuring the bark using a sterile beaker container.The gum was allowed to air dry under the shade and some brownish to red particles suspected to be cork or fragments of bark were mechanically removed.The ha... | 3 |
3326323 | RESULTS AND DISCUSSIONS From the physical examination of the gum, it can be deduced that it has varying shapes and sizes, odourless, tasteless.The crude gum was seen to be yellowish brown in colour while the purified or precipitated gum is whitish to milk in colour.Under the microscope, the crude gum appeared as large ... | 4 |
29282189 | O caráter lipofílico de doze cumarinas foi investigado por cromatografia de camada fina de fase reversa (RP TLC) em sílica RP-18. Três diferentes sistemas de solvente binário compostos por água e o modificador orgânico (metanol, tetrahidrofurano ou acetonitrilo) foram utilizados para determinar o parâmetro de retenção ... | 1 |
29282189 | Introduction The methods of relating molecular structure of solutes (expressed via descriptors) to their chromatographic (retention) behavior are commonly denoted as quantitative structure-retention relationships (QSRRs).Similarly, the aim of quantitative structure property relationship (QSPR) research is to find a fu... | 2 |
29282189 | Isolation procedure The chemical structures of the investigated coumarins 1-12 are presented in Figure 1. The plant material was collected at Gorica Hill (area of Podgorica City, Montenegro, Serbia) in Autumn 2009.A voucher specimen (P167/09) was deposited at Herbarium of the Faculty of Natural Sciences and Mathematics... | 3 |
29282189 | Reversed-phase thin-layer chromatography The TLC experiments were performed on a commercially available RP-18 TLC plates, (Art.5559, E. Merck, Germany).The plates were spotted with 1 μL aliquots of 2 mg mL -1 solutes of each compound (dissolved in CH 2 Cl 2 ), and developed by the ascending technique, without precondit... | 4 |
29282189 | Calculations For the geometry optimization, the structures were subjected to the Hyperchem Program (version 7.0, Hypercube).The optimization of three-dimensional structure was calculated by semi-empirical quantum chemical calculations with AM1 Hamiltonian.A set of molecular descriptors was selected to reflect geometric... | 5 |
29282189 | Multivariate statistical analysis and modeling PCA and PLS were performed using demo version of PLS Toolbox statistical package (Eigenvectors, Inc., version 5.7) for the MATLAB version 7.4.0.287 (R2007a) (MathWorks, Inc., Natick, MA, USA).The data were mean-centered and scaled to unit variance before any statistical op... | 6 |
29282189 | Lipophilicity of the analytes The retention parameters (R F and R M ) of coumarins were determined at several compositions of the three different binary solvent systems composed of organic modifier and water: methanol-water, acetonitrile-water and tetrahydrofuran-water.For each compound, the R M value was extrapolated ... | 7 |
29282189 | Principal component analysis (PCA) PCA carried out on the set of calculated molecular descriptors and retention data can reveal some similarities among studied compounds governed by both their intrinsic structural properties and specific interactions that occur in different chromatographic systems.Loading plots highlig... | 8 |
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