Novel synthesis of polymer and copolymer nanoparticles by atomized microemulsion technique and its characterization

The present paper relates to the atomized process for the synthesis of nanoparticles of polystyrene (nPS), polyacrylonitrile (nPAN), and poly(styrene/acrylonitrile) (nP[SAN]) copolymers with different monomer ratios and with controlled particle size in the range from 10 to 100 nm. In this process, ammonium persulfate (APS) was used as thermal initiator, along with sodium dodecyl sulfate (SDS) and n‐pentanol (n‐Pt) as surfactant and cosurfactant, respectively. The effect of different parameters on particle size and morphology of polymer nanoparticles has been reported in this work. Transmission electron microscopy (TEM) study showed the changes in particle morphology of pure nPS, nPAN, and their copolymers. Structural property and interaction of PS and PAN were investigated by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD). The effect of particle size and crystalline structure on glass transition temperature (T_g) and melting temperature (T_m) were also investigated by differential scanning calorimetry (DSC). Thermal stability of polymer nanoparticles was studied by thermo gravimetric analyzer (TGA) and it showed that the copolymer nanoparticles of nP[SAN] were more stable with minimum weight loss (W_L). Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region

A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78?% to 121?%. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145?ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2?ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045?±?0.023?ng/g. Mean concentrations of PFOA were not significantly different (p?>?0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032?ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.     

Enantioselective synthesis of (−)-galantinic acid

An efficient enantioselective synthesis of (−)-galantinic acid 1, a non-proteogenic amino acid is described using Sharpless asymmetric epoxidation, dihydroxylation and the regioselective nucleophilic opening of a cyclic sulfite as the key steps.     

Photocrosslinking and photografting of vinyl polymers using poly(styrene-co-p-vinylbenzophenone-p′-tert-butyl perbenzoate) as a comonomer

Styrene has been copolymerized with low percentages of p-vinylbenzophenone-p′-tert-butyl perbenzoate (VBPE). The resulting copolymer has been used to make graft copolymer with methyl methacrylate using UV irradiation (366 nm). The grafting efficiency has been observed to increase with time of irradiation and percentage of VBPE in the copolymer. The copolymer has also been observed to crosslink efficiently with photochemical irradiation.     

Biochemical relevance of Cr(III) complexes of isoniazid: synthesis,characterization, DFT,antibacterial screening,antioxidant activity and glucose-lowering effect in STZ-induced diabetic rats

Molecular mechanism suggests that the incorporation of an antioxidant organic moiety to chromium will be a sound strategy for the synthesis of safer and more effective hypoglycemic compounds. Two Schiff base ligands were derived by condensation of isonicotinyl hydrazide with salicylaldehyde/o-hydroxyacetophenone which further yield four novel chromium(III) complexes of types [Cr(L)Cl₂(H₂O)] and [Cr(L)₂]Cl. The ligands and complexes were characterized by analytical and spectroscopic techniques. DFT study at the basic set B3LYP and TD-SCF/6-311-G level was employed to confirm the geometry of the investigated compounds. Ligands were tested for their antioxidant activity and exhibited good antioxidant activity. Assessment of insulin-like activity of the complexes was initially performed in vitro by measuring the inhibition of α-amylase. The complex with highest in vitro activity was investigated for in vivo antidiabetic activity on the model of STZ-induced diabetic rats, which demonstrated that complex 4 significantly lowers the blood glucose level in rats. Toxicity level and antioxidant activity of the complex were also tested, which exhibit good tolerance level and antioxidant activity. Histological analysis of the pancreas of animals under investigation reveals the good condition of the pancreas treated with the complex. Ligands and complexes were also tested for antibacterial activity against Escherichia coli.

     

Studies on the polymerization of methyl methacrylate activated by azobisisobutyramidine

Kinetic studies on methyl methacrylate polymerization were carried out with watersoluble 2,2′-azobisisobutyramidine (ABA). The rate of polymerization was proportional to the square root of the initiator concentration in the solvents chloroform, methanol, and dimethyl sulfoxide (DMSO), which confirms the bimolecular nature of the termination reaction. The monomer exponent was unity in chloroform but in methanol and DMSO the rate of polymerization passed through a maximum when plotted against the monmer concentration. This behavior in methanol has been attributed to be due to the enhanced rate of production of radical with increasing proportion of methanol. The rate of decomposition of the ABA has been observed to be faster in methanol than in chloroform. The situation becomes more complicated with DMSO, which was found to reduce the value of δ = (2k_t)^1/2/k_p in methyl methacrylate polymerization. The rate of polymerization was observed to be highly dependent on the nature of the solvent, the rate increasing with increased electrophilicity of the solvent. The dependence of R_p on the solvent has been explained in the light of the stabilization of the transition state due to increased solvation of the basic amidine group of the initiator with the increased electrophilicity of the solvent.     

Bio-therapeutic Potential and Cytotoxicity Assessment of Pectin-Mediated Synthesized Nanostructured Cerium Oxide

In the present studies, renewable and nontoxic biopolymer, pectin, was extracted from Indian red pomelo fruit peels and used for the synthesis of cerium oxide nanoparticles (CeO₂-NPs) having bio-therapeutic potential. The structural information of extracted pectin was investigated by FTIR and NMR spectroscopic techniques. Physicochemical characteristics of this pectin suggested its application in the synthesis of metal oxide nanoparticles. Using this pectin as a template, CeO₂-NPs were synthesized by simple, one step and eco-friendly approach. The UV–Vis spectrum of synthesized CeO₂-NPs exhibited a characteristic absorption peak at wavelength 345 nm, which can be assigned to its intrinsic band gap (3.59 eV) absorption. Photoluminescence measurements of CeO₂-NPs revealed that the broad emission was composed of seven different bands. FTIR analysis ensured involvement of pectin in the formation and stabilization of CeO₂-NPs. FT-Raman spectra showed a sharp Raman active mode peak at 461.8 cm^?1 due to a symmetrical stretching mode of Ce–O vibration. DLS, FESEM, EDX, and XRD analysis showed that the CeO₂-NPs prepared were polydispersed, spherical shaped with a cubic fluorite structure and average particle size ≤40 nm. These CeO₂-NPs displayed broad spectrum antimicrobial activity, antioxidant potential, and non-cytotoxic nature.     

Normal and anti Meyer–Neldel rule in conductivity of highly crystallized undoped microcrystalline silicon films

We have studied the electrical conductivity behavior of highly crystallized undoped hydrogenated microcrystalline silicon (μc-Si:H) films having different microstructures. The dark conductivity is seen to follow Meyer–Neldel rule (MNR) in some films and anti-MNR in others, which has been explained on the basis of variation in the film microstructure and the corresponding changes in the effective density of states distributions. A band tail transport and statistical shift of Fermi level are used to explain the origin of MNR as well as anti-MNR in our samples. The observation of MNR and anti-MNR in electrical transport behavior of μc-Si:H is discussed in terms of the basic underlying physics of their origin and the significance of these relationships.     

Microwave‐Assisted Rapid and Efficient Synthesis of New Series of Chromene‐Based 1,2,4‐Oxadiazole Derivatives and Evaluation of Antibacterial Activity with Molecular Docking Investigation

A new series of novel chromene‐based oxadiazole derivatives were synthesized from a variety of chromene‐based amidoximes with readily available carboxylic acids under conventional oil bath heating as well as under microwave irradiation. The use of commercially available EDCI and HOBt as coupling reagents in DMF combined with microwave heating resulted in high yields and purities of the product 1,2,4‐oxadiazoles in an expeditious manner. This methodology is successfully applied to synthesize 18 numbers of new 2H‐chromene‐substituted 1,2,4‐oxadiazole derivatives in good to high yields. The structure of the product was ascertained by X‐ray crystallographic analysis. All the synthesized compounds were evaluated for their in vitro antibacterial activity against two different pathogenic bacterial strains, that is, Escherichia coli (MTCC614) and Klebsiella pneumoniae (MTCC4031). The obtained results from in vitro antimicrobial assays indicated that 6g and 6h exhibited good antibacterial activity nearer to the standard drug, gentamicin. The molecular docking studies showed that compounds 6g and 6h show hydrogen bonding interaction with the bacterial target DNA gyrase of E. coli.     

Investigation of photo‐oxidative effect on morphology and degradation of mechanical and physical properties of nano CaCO3 silicone rubber composites

Photo‐oxidative degradation of treated and untreated nano CaCO₃: silicone rubber composite was studied under accelerated UV irradiation (≥290 nm) at different time intervals. Prolonged exposure to UV leads to a progressive decrease in mechanical and physical properties along with the change in behavior of filler‐matrix interaction. This was due to decrease in cross‐linking density with increase in mobility of rubber chains. Meanwhile, synthesized nano CaCO₃ was modified with stearic acid for uniform dispersion in rubber matrix. The increase in carbonyl (>CO), hydroxyl (? OH), CO₂, and alkene functional groups on the UV exposed surface of treated and untreated nano CaCO₃: silicone rubber composites at different time intervals was studied using Fourier transform infrared (FTIR) spectroscopy. The change in morphological behavior of filler‐matrix interaction after UV exposure was studied using SEM. Overall, the study showed that the treated nano CaCO₃: silicone composites were affected more by UV exposure than untreated nano CaCO₃: silicone composites and pristine composite after UV exposure. This effect was due to peeling of stearic acid from the surface of CaCO₃, which makes the rubber chains slippery and thus separation of filler and rubber chains takes place with initiation of fast‐degradation. Copyright © 2011 John Wiley & Sons, Ltd.