‘Green’ synthesis of silver polymer Nanocomposites of poly (2-isopropenyl-2- oxazoline-co- N-vinylpyrrolidone) and its catalytic activity

Metal-polymer nanocomposites are of great interest and mainly focused on advanced catalytic and sensor applications. Resulting from this, new copolymers composed of poly(2-isopropenyl-2-oxazoline) (PIPOx) and poly(N-vinylpyrrolidone) (PNVP) segments were prepared from highly water soluble 2-isopropenyl-2- oxazoline (IPOx) and N-vinylpyrrolidone (NVP) monomers. Finally, silver polymer nanocomposites of poly(2-isopropenyl-2-oxazoline-co-N-vinylpyrrolidone) were synthesized and reporting for the first time. All polymerizations were done in an aqueous phase with potassium persulfate as an initiator at 60 °C. The reaction time varied from 1 to 6 h in accordance with stoichiometric ratios of PIPOx and PNVP, leading to insoluble copolymers; which are termed as PIPOx_PNVP (75:25), PIPOx_PNVP (50:50), PIPOx_PNVP (25:75) and PIPOx_PNVP (10:90). Only, PIPOx_PNVP (10:90) showed adequate swelling behavior in water and some other organic solvents. All the polymers were distinguished by various physicochemical spectroscopic techniques such as UV/Visible spectroscopy, Scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and FTIR analysis. Thermogravimetry (TGA) and Differential scanning calorimetry (DSC) were used to investigate thermal stability of the samples. The metalo-polymer nanocomposites (PIPOx_PNVP-SNCs) showed an apparently improved stability even when the composites were stored in air, at room temperature. The PIPOx_PNVP-SNCs showed a remarkable catalytic activity during the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride.     

‘Green’ synthesis and optical properties of silver–chitosan complexes and nanocomposites

Silver nanoparticles were synthesized in a chitosan biopolymer by an in situ ‘green’ chemical procedure, using d-glucose as the reducing agent. The reaction intermediates (silver–chitosan complexes) as well as the obtained nanocomposites were investigated using transmission electron microscopy, UV–vis, FTIR and photoluminescence spectroscopy. The theoretical analysis of the UV–vis absorption of the Ag–chitosan complexes suggested that the significant contribution to the complex spectrum arises from clusters of silver containing 4–9 atoms. The absorption spectrum of the nanocomposite exhibited a strong surface plasmon resonance band at 406 nm. The photoluminescence behavior of the pure chitosan, the silver–chitosan complexes and the nanocomposites were discussed in terms of morphology and silver weight content.     

Effect of silicone dioxide and poly(ethylene glycol) on the conductivity and relaxation dynamics of poly(ethylene oxide)–silver triflate solid polymer electrolyte

The conducting and relaxation dynamics of Ag⁺ ions in poly(ethylene oxide) (PEO)–silver triflate (AgCF₃SO₃) solid polymer electrolytes (SPEs) containing nanosize SiO₂ filler and poly(ethylene glycol) (PEG) as a plasticizer were studied in the frequency range 10 Hz to 10 MHz and in the temperature range 303–328 K. The comparatively lower conductivity of the plasticized (PEG) PEO–AgCF₃SO₃–SiO₂ nanocomposite electrolyte system was examined by analysis of the Fourier transform infrared (FTIR) spectroscopy and conductivity data. The electric modulus (M″) properties of the SPE systems were investigated. A shift of the M″ peak spectra with frequency was found to depend on the translation ion dynamics and the conductivity relaxation of the mobile ions. The value of the conductivity relaxation time was observed to be lower for the PEO–AgCF₃SO₃ system only with nanofiller SiO₂. The scaling behavior of the M″ spectra showed that the dynamical relaxation processes was temperature-independent in the PEO–AgCF₃SO₃ and PEO–AgCF₃SO₃–SiO₂–PEG polymer systems, whereas they were temperature-dependent for the PEO–AgCF₃SO₃–SiO₂ system. However, the relaxation processes of all of theses systems were found to be dependent on their respective compositions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Sucrose-mediated sol–gel synthesis of nanosized pure and S-doped zirconia and its catalytic activity for the synthesis of acetyl salicylic acid

Nano-sized pure and S-doped zirconia was prepared by the sol–gel method in the presence of sucrose and zirconium(IV) acetylacetonate (Zr(acac)₄) as a gelation agent and Zr⁴⁺ source, respectively. Acid catalyst activity of samples was tested for the production of acetyl salicylic acid from salicylic acid and acetic anhydride as precursors, The yield (64.0%) of acetylsalicylic acid was obtained from 50 mg of S-doped zirconia calcined at 550 °C and after a 3 h reaction, was comparably higher than the yield of the reaction (13.3%) in the absence of a catalyst and under the same reaction condition.     

Hydrothermal synthesis and characterization of surface-modified δ-MnO2 with high Fenton-like catalytic activity

Surface-modified δ-MnO₂ with a hierarchical structure was synthesized via a hydrothermal redox reaction between toluene and KMnO₄. Toluene is oxidized to produce benzoic acid which rapidly adsorbs onto the surface of δ-MnO₂. The δ-MnO₂ sample prepared with toluene exhibited a much higher catalytic activity for the Fenton-like oxidation of methylene blue in aqueous solution than that prepared without toluene. The enhanced catalytic activity might be attributed to the surface-bound persistent free radicals produced from the electron transfer from the adsorbed C₆H₅–COO⁻ to Mn(IV).     

Zeolite-Y encapsulated VO[2-(2′-hydroxyphenyl)benzimidazole] complex: investigation of its catalytic activity towards oxidation of organic substrates

Zeolite-Y encapsulated VO(IV)2-(2′-hydroxyphenyl)benzimidazole (ohpbmzl) was synthesized by flexible ligand approach and characterized using various physico-chemical techniques such as elemental analysis, XRD, inductively coupled plasma-atomic emission, fourier transform infrared spectroscopy, UV–vis-diffuse reflectance and electron paramagnetic resonance spectroscopy, thermogravimetric analysis, BET surface area and cyclic voltammetry (CV). Based on the results a square pyramidal structure was suggested for the encapsulated complex. Shift in UV absorbance to higher wavelength and variations in the redox potential values compared to the non-encapsulated complex in CV confirmed the successful encapsulation of the complex in the zeolite matrix. The catalytic efficacy was investigated towards oxidation of phenol, styrene, cyclohexane and ethyl benzene in acetonitrile using H₂O₂ as oxidant. Influence of reaction parameters like catalyst and substrate concentration, substrate/H₂O₂ molar ratio, and temperature were investigated to optimize the reaction conditions for maximum substrate conversion and selectivity towards desired products using the encapsulated complex. The catalytic activity was compared with vanadyl exchanged zeolite-Y (VO-Y) and non-encapsulated complex. The encapsulated complex retained its stability up to 3 runs as confirmed by recycling studies. Mechanistic pathways were proposed for all the probe reactions.     

Green synthesis of bi-component Mn3O4–MnO2 nanorods and enhanced catalytic properties

Bi-component Mn₃O₄–MnO₂ nanorods with lengths of up to 30 μm are synthesized using a simple hydrothermal method in the absence of templates. Samples were characterized by FE-SEM, HR-TEM, XRD, XPS, and N₂ adsorption–desorption. The results indicate that the Mn₃O₄–MnO₂ and Mn₅O₈ samples with various morphologies can be easily obtained via modulating Cl⁻ ions and glucose contents. Compared with that of the Mn₅O₈ samples, the bi-component Mn₃O₄–MnO₂ nanorods exhibited higher catalytic properties for oxidative decomposition of MB owing to its adjustable valence state and oxygen content.     

Synthesis of poly[2-(α-d-mannopyranosyloxy)ethyl-co-2-dimethylaminoethyl methacrylates] and its lectin-binding and DNA-condensing properties

Radical copolymerizations of 2-(α-d-mannopyranosyloxy)ethyl methacrylate (ManEMA) with 2-dimethylaminoethyl methacrylate (DMAEMA) were carried out in N,N-dimethylformamide (DMF) containing 10 vol% water at 60 °C to yield cationic glycopolymers. The number-average molecular weights (M_ns, standard Pullulan calibration) and polydispersities (M_w/M_ns) of the resulting copolymers were ranged from 17,400 to 41,700 and from 1.7 to 3.2, respectively. The compositions of the resulting copolymers were very close to those in the feed. The monomer reactivity ratios r_ManEMA and r_DMAEMA were 0.98 and 1.22, respectively. The lectin-binding properties of poly(ManEMA-co-DMAEMA) to concanavalin A (ConA) was examined using a turbidimetric assay. The clustering rate increased with increasing mole fractions of the ManEMA units in the copolymer (F_ManEMA), even under a constant concentration of the ManEMA units (50 μM), indicating the typical cluster glycoside effect. The DNA-condensing ability of the resulting copolymers was examined by a gel retardation assay using pEGFP-N1 plasmid (4.7 kbp). Though the ManEMA units interfered with the complexation of the copolymer with the plasmid DNA, complete retardation was observed under the condition of lower contents of ManEMA units (F_ManEMA < 0.2) in pure water. These findings indicate that poly(ManEMA-co-DMAEMA) is a cationic glycopolymer exerting lectin-binding and DNA-condensing abilities.     

Аntimicrobial and anticancer activity of new poly(propyleneamine) metallodendrimers

The synthesis, EPR characterisation and biological evaluation of two new metallodendrimers, i.e. a poly(propyleneamine) dendrimer functionalized at the external surface with 4-bromo-1,8-naphthalimide and conjugated with Cu(II) and Zn(II), was performed with the aim to evaluate their antimicrobial and anticancer activity. The antimicrobial activity was investigated in meat-peptone broth against bacteria B. subtilis and P. aeruginosa, and the yeast C. lipolytica. The results showed that the compounds inhibited effectively the tested pathogens even after their deposition on a textile fabric. Anticancer activity was investigated against three human permanent cell lines from non-small cell lung cancer (A549), triple negative breast cancer (MDA-MB-231) and carcinoma of the uterine cervix (HeLa) in the c?=?0.01–30 μM concentration range. The results suggest that these compounds are promising for application in biomedicine as anticancer drugs in the design of new effective preparations. The antimicrobial and anticancer activity may be related to the peculiar structural and dynamical properties revealed for the Cu(II) complexes, by a computer aided analysis of the electron paramagnetic resonance (EPR) spectra. This analysis indicated the formation, at the lowest Cu(II) concentrations, of a flexible rhombic Cu-N4 coordination with the internal amino groups of the dendrimer, which transformed into a Cu2-N4 coordination already at 0.25 equiv. of Cu(II).     

Poly(pyridine-2,5-diyl)–CuCl2 catalyst for synthesis of dimethyl carbonate by oxidative carbonylation of methanol: catalytic activity and corrosion influence

A -conjugated polymer, poly(pyridine-2,5-diyl) (PPy) was investigated as a support for CuCl₂ in the synthesis of dimethyl carbonate by oxidative carbonylation of methanol. The PPy–CuCl₂ adduct had high catalytic activity which was comparable to that of the homogeneous CuCl₂ catalyst. The adduct caused corrosion of stainless-steel vessels only to minor extent, compared with the homogeneous CuCl₂ catalyst. This PPy–CuCl₂ catalyst was easily recycled by filtration and showed a similar catalytic activity in the third time use. The presence of the -conjugated system in PPy, through which electrons can move, may bring about the high catalytic activity for the oxidative carbonylation of methanol, which involves Cu(II)/Cu(I) redox processes.     

2-(1′-alkoxyvinyl) thiazolidines: synthesis and study of ring-chain tautomerism

2-Alkoxypropenals react with 2-aminoethanethiol to yield mixtures of tautomeric 2-(1-alkoxyvinyl)thiazolidines and imino thiols. The ring-chain tautomeric equilibria, studied by ¹H NMR spectroscopy, were strongly dependent on the solvent polarity, ratio of reagents, and pH of the medium.     

Hydrothermal synthesis of α-SnWO4: Application to lithium-ion battery and photocatalytic activity

The high capacity anode material is required to replace the most commonly used anode - graphite to keep up the global demand to achieve the goal. Multi-metal oxide has gained keen attention for its higher theoretical capacity and relatively stable than a single metal oxide. α-SnWO₄ has a theoretical capacity of 850 mAh g^?1 which is greater than graphite (372 mAh g^?1). α-SnWO₄ has been synthesized through low-temperature hydrothermal method using tin chloride and sodium tungstate as a precursor in acidic medium (succinic acid) at 200 °C for 12 h. The obtained product has been characterized using various analytical tools such as XRD, FT-IR, UV-DRS, BET, PL, SEM, and HR-TEM. XRD analysis shows the orthorhombic phase with a crystallite size of ~25 nm α-SnWO₄has been examined as an electrode material for Li-ion battery (LIB) and displays an initial discharge capacity of 985 mAh g^?1. Columbic efficiency close to 100% has been observed for 100 cycles. The stability of the electrode material was studied at different C-rates. Band-gap calculated using UV-DRS (Eg = 1.9 eV) shows that α-SnWO₄ is a good candidate for photocatalytic degradation. Results of the photocatalytic experiment using methylene blue (MB) as a model pollutant in an aqueous medium shows good results. The above applications show that α-SnWO₄ is multifunctional materials for diverse applications.     

Synthesis and characterization of 4,4’–(dimethylsilylene) bis( phenyl chloroformate) and 4,4’–(dimethylgermylene)bis(phenyl chloroformate) and their use in the synthesis of poly(urethanes)

Summary The synthesis of 4,4–(dimethylsilylene)bis(phenyl chloroformate) and 4,4–(dimethylgermylene)bis(phenyl chloroformate) is described according to the same route for the synthesis of bisphenol–A bischloroformate. These compounds were characterized using elemental analysis, FT–IR and NMR spectroscopy. Poly(urethanes) derived from these bischlororformates containing silicon or germane in the main chain, were obtained in benzene solution by reaction with 4,4–methylenedianiline in the presence of pyridine. Poly(urethanes) were characterised by spectroscopic methods and the thermal properties (Tg and thermal stability) were compared with the homologue poly(urethane) obtained from bisphenol–A chloroformate.     

Enzymatic synthesis,thermal and crystalline properties of a poly(β–amino ester) and poly(lactone-co-β–amino ester) copolymers

Ethyl 3-(4-(hydroxymethyl)piperidin-1-yl)propanoate (EHMPP) was prepared in quantitative yield under mild conditions via Michael addition reaction of 4-piperidinemethanol with ethyl acrylate. EHMPP underwent condensation polymerization in the presence of a lipase catalyst (CALB) to form poly[3-(4-(methylene)piperidin-1-yl)propanoate] (poly(MPP) or PMPP). Ring-opening and condensation copolymerization of EHMPP with ω-pentadecalactone (PDL) led to the synthesis of novel poly(PDL-co-MPP) copolymers, whose compositions were readily controlled by varying the monomer feed ratio. NMR analyses, including statistical analysis on repeating unit sequence distribution, indicate that the copolymers are totally random polymers. TGA analysis revealed that the degradation temperature of PMPP is approximately 160 °C lower than that of PPDL and that all poly(PDL-co-MPP) copolymers degrade in two well defined weight loss steps attributable to thermal degradation of MPP and PDL unit fractions in the polymers. The crystallinity of the polymers was studied by DSC analysis. Although PMPP and the copolymers rich in MPP units do not easily crystallize upon cooling from melt, the homopolymer and all copolymers obtained via precipitation from solution are semi-crystalline materials. WAXS analysis showed that the copolymers rich in PDL (≥51 mol%) crystallize in PPDL lattice and those with ≤21 mol% PDL content develop PMPP-type crystals while in the copolymer with 36 mol% PDL, PMPP-type and PPDL-type crystals co-exist. PMPP and poly(PDL-co-MPP) represent a new type of biodegradable poly(β–amino esters) that are potentially useful biomaterials for specific biomedical applications (e.g., gene delivery).     

Synthesis of poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) and its inclusion compound of β-cyclodextrin

Well-defined amphiphilic poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) (PNIPAM-b-PCL) block copolymers have been successfully prepared in two steps. PNIPAMOH is firstly prepared by using 4,4′-azobis(4-cyano-1-pentanol) as bifunctional initiator, and then PNIPAM-b-PCL copolymer is synthesized via a ring-opening polymerization of CL using PNIPAMOH as a macro-initiator in the presence of stannous octoate as a catalyst. The PNIPAM-b-PCL copolymers self-assemble to form spherical micelles of 50–130 nm in diameter, which can be modulated by the chain length of PCL block. The inclusion complexes are fabricated by treating PNIPAM-b-PCL with β-cyclodextrin and they are characterized by infrared and ¹H NMR spectroscopies, X-ray powder diffraction, thermogravimetric analysis, and differential scanning calorimetry.     

A novel 3D silver(I) coordination polymer exhibiting unprecedented μ3- and μ4-bonding modes of 2-aminopyrazines

The unprecedented μ₃- and μ₄-bonding modes of NH₂pyz (NH₂pyz = 2-aminopyrazine) are observed for the first time in a novel 3D Ag(I) coordination polymer [Ag₇(NHpyz)₆(ClO₄)]_n (1) which was obtained by reaction of Ag₂O, NH₂pyz and NaClO₄ in H₂O/CH₃OH/NH₃ media under ultrasonic treatment. Compound 1 is a 3D framework with infinite 1D Ag belts incorporating diverse Ag···Ag interactions. Moreover, 1 exhibits photoluminescence maximized at 494 nm upon 300 nm excitation at room temperature, which may be mainly assigned to ligand-to-metal charge transfer (LMCT) mixed with metal-centered (d-s/d-p) transitions. Semiconducting behavior of 1 was also measured at room temperature with σ value of 6.78 × 10^?6 S cm^?1.     

Synthesis and properties of poly[2-(4′-oxyphenylene)-5-benzimidazole] and a proton-exchange membrane produced on its basis

A monomer of the A-B type, 3,4-diamino-4′-carboxydiphenyloxide, has been synthesized via a series of consecutive transformations of 5-chloro-2-nitroaniline. The homopolycondensation of the monomer in Eaton’s reagent at 140°C yields poly[2-(4′-oxyphenylene)-5-benzimidazole] soluble in organic solvents. A membrane containing 51% H₃PO₄ (2.9 acid molecules pert monomer unit) and possessing a proton conductivity of 0.025 S/cm at 160°C is produced by doping a polymer film with 60% H₃PO₄.     

A randomly branched poly(hydroxyl-β-amino amide): synthesis and complexation

A novel type of polycation with high density of discrete charge, diversified amino group type and abundant hydrophilic short-chains was synthesized from tetraethylenepentamine (TEPA) and glycidol acrylate. The obtained polycation was abbreviated as PTGA. The structure and protonation property of PTGA was characterized by ¹H NMR, FTIR, GPC and acid-base titration. ¹H NMR of PTGA indicated that there were not only Michael addition and ring-opening but also high degree of amidation during polymerization. Only 12% ester group was left after polymerization. So PTGA is a kind of poly(hydroxyl-β-amino amide). Acid base titration indicated that the protonation of PTGA has wide protonation range and shows obvious proton sponge effect. The complexation of PTGA with polyanion was studied by using poly(acrylic acid) (PAA) as a model polyanion. The complex was characterized by dynamic light scattering and UV-Vis spectroscopy. It was found that the size of complex particle size first increased and then decreased as the charge ratio of PTGA to PAA.