Kinetic Study of Radical Polymerization v. Determination of Reactivity Ratio in Copolymerization of Acrylonitrile and Itaconic Acid by 1H‐NMR

Many reports exist in the literature about the application of ¹H and ¹³C‐NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on‐line ¹H‐NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least‐squares methods such as Finemann‐Ross, inverted Finemann‐Ross, Mayo‐Lewis, Kelen‐Tudos, extended Kelen‐Tudos and Mao‐Huglin. In addition, a non‐linear least‐square method (Tidwell‐ Mortimer) was used at low conversions. Extended Kelen‐ Tudos and Mao‐Huglin were applied to determine reactivity ratio values at high conversions as well.     

Statistical analysis of parameter effects on bending angle in laser forming process by pulsed Nd:YAG laser

In recent years, laser application has been introduced for bending and forming as new processes in manufacturing. The capability of laser bending demands more studies to recognize parameters influencing bending angle of sheet metals. In this study the effects of parameters such as material, laser power, beam diameter, scan velocity, sheet thickness, pass number and pulse duration on bending angle were studied by FEM initially and then followed by experiments. Furthermore, the Taguchi experimental design method was employed to pin point parameters, which significantly affect the bending process of laser bending of St12 and 304 alloy steels, which have a wide range of applications in products manufacturing. A regression analysis was conducted and a closed form equation was derived. The closed form equation can be used in industry to determine which process parameters (factors) enhance the bending angle in laser bending process.     

Asymmetric polymerization via cycloaddition reactions

The reaction of N‐phthaloyl‐L ‐leucine acid chloride (1) with isoeugenol (2) was carried out in chloroform, and novel optically active isoeugenol ester derivative 3 as a chiral monomer was obtained in high yield. Compound 3 was characterized by ¹H‐NMR, IR, and mass and elemental analysis and then was used for the preparation of model compound 5 and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione, PhTD (4), was allowed to react with compound 3. The reaction is very fast and gives only one diastereomer of 5 via Diels–Alder and ene pathways in quantitative yield. In order to explain this diastereoselectivity, a nonconcerted two‐step mechanism involving benzylic cation (BC) and aziridinium (AI) have been proposed for the Diels–Alder and ene reactions, respectively. The polymerization reactions of novel monomer 3 with bis(triazolinedione)s [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (8) and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (9)] were performed in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and gave novel optically active polymers 10 and 11 via repetitive Diels–Alder–ene polyaddition reactions. These polymers have inherent viscosities in a range about 0.18–0.22 dL/g. Some physical properties and structural characterizations of these new polymers have been studied and are reported. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1211–1219, 1999     

RAFT-mediated emulsion polymerization of vinyl acetate: a challenge towards producing high molecular weight poly(vinyl acetate)

The preparation of poly(vinyl acetate) with well-controlled structure has received a great deal of interest in recent years because of a large number of developments in living radical polymerization techniques. Among these techniques, the use of reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization has been employed for the controlled polymerization of vinyl acetate due to the high susceptibility of this monomer towards chain transfer reactions. Here, a novel water-soluble N,N-dialkyl dithiocarbamate RAFT agent has been prepared and employed in the emulsion polymerization of vinyl acetate. The kinetic results reveal that the polymerization nucleation mechanism changes from homogeneous to micellar and RAFT-generated radicals can change the kinetic behavior from conventional emulsion polymerization to living radical polymerization. At higher concentrations of the modified RAFT agent, as a result of an aqueous phase reaction between RAFT and sulfate radicals, relatively more hydrophobic radicals are generated, which favors entry and propagation into micelles swollen with monomer. This observation was determined from the investigation of the polymerization rate and measurements of the average particle diameter and the number of particles per liter of the aqueous phase. Molecular weight analysis also demonstrated the participation of the RAFT agent in the polymerization in such a way as to restrict chain transfer reactions. This was determined by examining the evolution of polymer chain length and attaining higher molecular weights, even up to 50?% greater than the samples obtained from the conventional emulsion polymerization of vinyl acetate in the absence of the synthesized modified RAFT agent.     

Optimization of parameters in preparation of PCM microcapsules based on melamine formaldehyde through dispersion polymerization

Microencapsulated phase change materials have attracted special attention due to their wide applications in saving and releasing energy. Here, microencapsulation of hexadecane (HD) in melamine formaldehyde shell was carried out through in situ dispersion polymerization in the aqueous media. Some important parameters such as stabilizer type and amount, surfactant amount, homogenization conditions as the critical affective factors on final particle size, morphology, and thermal resistance of the microcapsules were investigated extensively. The obtained microcapsules were concurrently analyzed by SEM, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. SEM images showed that the best stabilization was achieved by polyvinyl alcohol. Also, particle size, as an indication of surface area for heat transfer properties, showed a decrement by increasing stabilizer amount, surfactant amount, and homogenization speed. The amount of entrapped HD and efficiencies of microencapsulation were determined by DSC, and the reason for observing such changes were discussed in detail. Thermal stability of the microcapsules as an important property for their performance was investigated, too. The results illustrated that an improved thermal stability would be obtained by an efficient stabilization in the emulsification step. Also the highest thermal stability up to 388 °C was reached at homogenization speed of 6,000 rpm. Finally, the optimized conditions for desirable encapsulation were proposed in such systems.     

Studying the effects of surface modification of Cr2O3 nanoparticles by 3-aminopropyltrimethoxysilane (APTMS) on its corrosion inhibitive performance

Journal of Sol-Gel Science and Technology - Cr2O3 nanoparticles were modified with 3-aminopropyltrimethoxysilane (APTMS). The APTMS grafting on the surface of the nanoparticles was analyzed by...     

pH stimuli-responsive and fouling resistance PES membrane fabricated by using photochromic spiropyran and spironaphthoxazine nanofillers for pesticide removal

New fouling resistance and stimulus–responsive nanofiltration membranes were fabricated by adding photochromic spiropyran (SPO) and spironaphthoxazine (SNO) nanofillers to the polyethersulfone (PES) matrix via the phase inversion method. The effect of SPO and SNO, as novel photoresponsive molecule nanofillers, were evaluated in terms of membrane morphology, porosity, wettability, pure water flux (PWF), antifouling resistance, and stimulus–responsive properties. All the modified membranes indicated better performance compared to the bare PES. The membrane PWF was notably enhanced from 7.7 kg/m²h for the bare PES up to 18.68 and 20.58 kg/m²h for the 0.1 wt.% SPO and SNO blended membranes, respectively. Also, the 0.1 wt.% of SNO-based PES membrane indicated the best flux recovery ratio compared to the other membranes. The photo stimulus–responsive assessment showed a color change for both SPO and SNO photochromic in membranes. In the case of variable effect investigation, the response surface methodology at three levels (pressure: 4, 5, 6 bar and flow rate: 50, 100, and 150 L/h) was applied. A suitable flux (23.39 kg/m² h) and high removal efficiency (more than 90%) was achieved at optimum conditions. Also, the modified membranes by photochromic materials were sensitive to environmental variables such as acidic and alkaline conditions by changing their color.     

Interaction of Na, Mg, Al, Si with carbon nanotube (CNT): NMR and IR study

A Quantum Mechanics (QM) is used for investigated the nature of metals transport and interaction with single-walled carbon nanotubes (SWCNTs) inter membranes. Metal species can be transported actively by a combination of SWCNT-membranes conducting channels that have been used for bio-molecular and detection. This study is based on the interaction of Na, Mg, Al, and Si with the structural features of SWCNTs in the ground state ab initio, HF theory and DFT calculation have been performed with the program Gaussian A7 package suite of programs. We used HF and DFT (B3LYP) method for calculation energy, chemical shift nucleus magnetic resonance and proportion thermodynamic by DFT-IR and DFT-NMR for RWCNT in absence and presence metals. The basis set used 6-31G and 6-31G* that increasing electronegativity metals increased the total energy. The proportion SWCNTs were changed by them. In this study presented a comprehensive on effects of metals on SWCNTs, which are on theirs electronic structure, and transfer of charge from metal to SWCNTs. The results are presented for T = 310 K, the temperature of human’s body.     

Cu immobilized on chitosan-modified iron oxide magnetic nanoparticles: Preparation,characterization and investigation of its anti-lung cancer effects

Chitosan is a linear polysaccharide and non-toxic bioactive polymer with a wide variety of applications due to its functional properties such as ease of modification, and biodegradability. In this study, a green protocol for supporting of Cu(II) on chitosan-encapsulated magnetic Fe₃O₄ nanoparticles is described. The morphological and physicochemical features of the material were determined using several advanced techniques like fourier transformed infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), inductively coupled plasma (ICP), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The average diameter of the NPs was approximately 15–25 nm. In addition, the Fe₃O_/CS/Cu(II) nanocomposite was engaged in biological assays like study of anti-oxidant properties by DPPH mediated free radical scavenging test using BHT as a reference molecule. Thereafter, on having a significant IC₅₀ value in radical scavenging assay, we extended the bio-application of the desired nanocomposite in anticancer study of lung well-differentiated bronchogenic adenocarcinoma, lung moderately differentiated adenocarcinoma, and lung poorly differentiated adenocarcinoma of human lung in-vitro conditions. In the cytotoxicity and anti-human lung studies, the nanocomposite was treated to lung cancer lung well-differentiated bronchogenic adenocarcinoma (HLC-1), lung moderately differentiated adenocarcinoma (LC-2/ad), and lung poorly differentiated adenocarcinoma (PC-14) cell line following MTT assay. The cell viability of malignant lung cell line reduced dose-dependently in the presence of Fe₃O_/CS/Cu(II) nanocomposite. The recent results suggest that Fe₃O_/CS/Cu(II) nanocomposite have a suitable anticancer activity against lung cell lines.