Synthesis and characterization of poly(methacrylates) containing spiroacetal and norbornene moieties in side chain

A four‐step synthetic strategy was applied to achieve novel methacrylic monomers. 5‐Norbornene‐2,2‐dimethanol was prepared from a Diels–Alder reaction of cyclopentadiene and acrolein, followed by the treatment of the adduct with an HCHO/KOH/MeOH solution. The resulting 1,3‐diol (1) was then acetalized with different aromatic aldehydes having OH groups on the ring to produce four spiroacetal derivatives. The reaction of methacryloyl chloride with the phenolic derivatives led to four new methacrylic monomers that were identified spectrochemically (mass, FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopy). Free radical solution polymerization was used to prepare novel spiroacetal–norbornene containing polymethacrylates, which were characterized by FTIR and ¹H‐NMR spectroscopy and differential scanning calorimetry and thermogravimetric thermal analysis. Gel permeation chromatography was performed to determine molecular weight averages and polydispersity. The polymethacrylate having naphthalenic nuclei was recognized to be the highest molecular weight polymer (M̄_n = 12144, η_inh = 0.80 dL/g) with the highest thermal stability. All the polymers showed good solubility in a variety of common organic solvents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 30–38, 2000     

Swelling properties of CMC‐g‐poly (AAm‐co‐AMPS) superabsorbent hydrogel

A series of biopolymer‐based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free‐radical graft copolymerization of acrylamide and 2‐acrylamido‐2‐methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT‐IR spectroscopy and scanning electron microscope analysis were used to confirm the hydrogel structure. Swelling measurements of the synthesized hydrogels in different salt solutions indicated considerable swelling capacity. The absorbency under load of the superabsorbent hydrogels was determined by using an absorbency under load tester at various applied pressures. A preliminary swelling and deswelling behaviors of the hydrogels were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Determination of picomolar silver concentrations by differential pulse anodic stripping voltammetry at a carbon paste electrode modified with phenylthiourea-functionalized high ordered nanoporous silica gel

This study introduces the design of an anodic stripping voltammetric (ASV) method for the silver ion determination at a carbon paste electrode (CPE), chemically modified with phenylthiourea-nanoporous silica gel (Tu-SBA-15-CPE). The electroanalytical pro includes two steps: preconcentration of metal ions at an electrode surface, followed by quantification of the accumulated species by differential pulse anodic stripping voltammetric methods. Factors affecting the performance of the anodic stripping were investigated, including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The most sensitive and reliable electrode contained 10% Tu-SBA-15 and 90% carbon paste. The accumulation potential and time were set at, −200 mV and 300 s, respectively, and the scan rate at 50 mV s⁻¹ in the scan range of −200 to 700 mV. The resulting electrode demonstrated a linear response over range of silver ion concentration of 8.0-80 pmol/L with detection limit (S/N = 3) of 5 pmol/L. The prepared electrodes were used for the silver determination in sea and tap water samples and very good recovery results were obtained. The accuracy was assessed through recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.     

Experiments Design for Hardness Optimization of the Ni-Cr Alloy Electrodeposited by Pulse Plating

The hardness of the Ni-Cr alloy which is electrodeposited in chloride solution,is optimized by design of experiment method(central composite design).Various parameters were evaluated in order to find significant factors in this process.Frequency,duty cycle,current density and temperature were selected as efective factors.Analyses of variance(ANOVA)were performed on the results of the designed experiments.The best model which can predict the hardness of the Ni-Cr alloy electrodeposits was found whereas the frequency and quadratic behaviour of the current density were the most significant model terms.Serious interaction of the current density with frequency and duty cycle also were found in this model.Finally the optimum conditions of the factors for obtaining the maximum hardness of the Ni-Cr alloy were found.Ni-Cr alloy with hardness828 HV(electrodeposited with frequency 63 Hz,current density 1800 A/m2,duty cycle 75%and temperature31℃ bath)were assessed as the optimum deposit.The deposit under the optimum condition was investigated by scanning electron microscopy(SEM),EDX analysis,polarization method and microhardness.     

Functionally-graded shape memory alloy by diffusion annealing of palladium-coated NiTi plates

Diffusion annealing of palladium-coated Ti-Ni plates was performed at temperatures ranging from 900 °C to 1,000 °C, to accomplish a compositional gradient in Ti-rich, Ti-Ni shape memory alloys. The aim of this study was to increase the transformation temperatures and transformation temperature intervals. Palladium diffusion profiles were measured by energy dispersive spectroscopy, and the corresponding approximate diffusion coefficients of the annealed specimens were calculated. The Gaussian solution of Fick’s second law for the one-dimensional lattice diffusion of a tracer was used. The transformation behavior studies were performed by differential scanning calorimetry. It was depicted that annealed specimens show longer transformation intervals compared to the bare alloy. In addition, annealed specimens showed improved shape memory properties that were attributed to the lower amount of Ti₂Ni precipitates in the diffusion layer. The shape memory behaviour of the samples was detected using micro-indentation at room temperature, followed by heating them above the austenite formation temperature to calculate the shape recovery ratio.     

A study on the cure characteristics of epoxy/diaminodiphenylmethane system prepared at room temperature

The curing behavior and kinetics of epoxy resin with diaminodiphenylmethane (DDM) as the curing agent was studied by many researchers, however all of them prepared the system at a high‐temperature condition (i.e., T ≥ 80°C). In this study, a mixture of epoxy/DDM was prepared at ambient temperature and its curing characteristics were studied by using differential scanning calorimetry (DSC). The autocatalytic model was used to calculate the kinetic factors in the dynamic experiments. The kinetics of the curing reaction was also evaluated by two different isoconversional models; namely Friedman method and the Advanced Isoconversional method proposed by Vyazovkin to investigate the activation energy behavior during the curing reaction. The activation energy of the curing reaction was found to be in the range of 48 ± 2 kJ/mol and might be considered to be constant during the curing. In fact, our findings were different from the result reported by other researchers for the system which was prepared at elevated temperature. Therefore, it seems that the preparation temperature of the samples influenced considerably on the curing behavior of epoxy with DDM. Finally, a time–temperature–transformation (TTT) diagram was established to determine the cure process and glass transition properties of the system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Application of thermal ultrasound-assisted liquid–liquid micro-extraction coupled with HPLC-UV for rapid determination of synthetic phenolic antioxidants in edible oils

A simple, fast, and reliable liquid–liquid micro-extraction (LLME) method assisted by thermal ultrasound approach was developed for simultaneous determination of synthetic phenolic antioxidants (SPAs) in edible oils by high-performance liquid chromatography equipped with ultraviolet detector (HPLC-UV). The synthetic antioxidants were propyl gallate (PG), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), and butylated hydroxyltoluene (BHT). The best extraction conditions were observed were methanol/acetonitrile (1:1, v/v) as the solvent, ultrasound at 4 min, and a temperature of 40°C. The linearity of the calibration curves for the optimum conditions were R² > 0.989 for all of the SPAs in a range from 1–200 μg ml⁻¹. Relative standard deviation (RSD %) for five analysis was in range of 2.83% to 4.21%. Limit of detection (LOD) and limit of quantification (LOQ) were obtained in range of 0.012–0.06 and 0.04–0.2 μg g⁻¹, respectively. With regard to recovery, a range of 91%–116% was calculated for the spiked edible oils.     

Probiotic-Induced Tolerogenic Dendritic Cells: A Novel Therapy for Inflammatory Bowel Disease?

Inflammatory bowel diseases (IBDs) are immune-mediated, chronic relapsing diseases with a rising prevalence worldwide in both adult and pediatric populations. Treatment options for immune-mediated diseases, including IBDs, are traditional steroids, immunomodulators, and biologics, none of which are capable of inducing long-lasting remission in all patients. Dendritic cells (DCs) play a fundamental role in inducing tolerance and regulating T cells and their tolerogenic functions. Hence, modulation of intestinal mucosal immunity by DCs could provide a novel, additional tool for the treatment of IBD. Recent evidence indicates that probiotic bacteria might impact immunomodulation both in vitro and in vivo by regulating DCs’ maturation and producing tolerogenic DCs (tolDCs) which, in turn, might dampen inflammation. In this review, we will discuss this evidence and the mechanisms of action of probiotics and their metabolites in inducing tolDCs in IBDs and some conditions associated with them.     

Targeted design of polyaniline-graphene oxide,barium-strontium titanate,hard-soft ferrite,and polyester multi-phase nanocomposite for highly efficient microwave absorption

The current paper focuses on synthesizing a high-efficiency microwave absorber via incorporating the nanofillers of graphene oxide-polyaniline (GO-PANI), barium-strontium titanate (BST), and soft-hard ferrite within the polyester matrix. The nanocomposite magnets of (Ba_0.5Sr_0.5Fe₁₂O₁₉)_1-x hard/(CoFe₂O₄)_x soft (x = 0.2, 0.5, and 0.8) were prepared using sol-gel auto-combustion method. The GO-PANI and BST were successfully synthesized by in situ polymerization and improved polymerization, respectively. The phase structure, chemical structure, morphology, and microwave absorption properties of the synthesized nanocomposites were characterized by X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM), vector network analyzer (VNA) techniques, respectively. The results showed that the synergistic effects of the combination of dielectric (BST), conductive (GO-PANI), and magnetic materials (hard-soft ferrites) provided the reflection loss values of less than ?20 dB (>99% absorption) in the X-band region. The minimum reflection loss of ?35 dB (>99.99% absorption) was obtained by the optimal formulation including (Ba_0.5Sr_0.5Fe₁₂O₁₉)_0.2 (CoFe₂O₄)_0.8, and the weight ratio of 1: 2 for both BST/soft-hard ferrite and hard-soft ferrite + BST/GO-PANI with the thickness of 1 mm. According to the results, the thickness factor plays a key role in improving the impedance matching. Consequently, the proposed nanocomposite can be employed as a novel kind of microwave absorbers with good impendence matching and high absorption.     

Determination of stability constants of mercury(II) by garlic organosulfur ligands with differential pulse voltammetry

Journal of Applied Electrochemistry - In this work, interactions of mercury with di allyl disulfide (DADS), dimethyl disulfide (DMDS), and diallyl sulfide (DAS) were studied by differential pulse...