Catalytic Activity Of Poly Research Articles

Poly(aniline-co-melamine)@MnFe2O4 nanocatalyst for the synthesis of 4,4'-(arylmethylene) bis (1H-pyrazole-5-ol) derivatives, and 1,4- dihydropyrano[2,3-c]pyrazoles and evaluation of their antioxidant, and anticancer activities.

In this work, magnetic poly(aniline-co-melamine) nanocomposite as an efficient heterogeneous polymer-based nanocatalyst was fabricated in two steps. First, poly(aniline-co-melamine) was synthesized through the chemical oxidation by ammonium persulfate, then the magnetic nanocatalyst was successfully prepared from the in-situ coprecipitation method in the presence of poly(aniline-co-melamine). The resulting poly(aniline-co-melamine)@MnFe2O4 was characterized by FTIR, FESEM, XRD, VSM, EDX, TGA, and UV-vis analyses. The catalytic activity of poly(aniline-co-melamine)@MnFe2O4 was investigated in the synthesis of 4,4'-(arylmethylene)bis(1H-pyrazole-5-ol) derivatives, and new alkylene bridging bis 4,4'-(arylmethylene)bis(1H-pyrazole-5-ol) derivatives in excellent yields. The yield of 1,4-dihydropyrano[2,3-c]pyrazoles, 4,4'-(arylmethylene)bis(1H-pyrazol-5-ol), yields, and new alkylene bridging bis 4,4'-(arylmethylene)bis(1H-pyrazol-5-ol) derivatives were obtained 89%-96%, 90%-96%, and 92%-96%, respectively. The poly(aniline-co-melamine)@MnFe2O4 nanocatalyst can be recycled without pre-activation and reloaded up to five consecutive runs without a significant decrease in its efficiency. In addition, the antioxidant activity of some derivatives was evaluated by DPPH assay. Results showed that the maximum antioxidant activity of 4,4'-(arylmethylene)bis(1H-pyrazole-5-ol) derivatives and 1,4-dihydropyrano[2,3-c]pyrazoles were 75% and 90%, respectively. Furthermore, 4,4'-(arylmethylene)bis(1H-pyrazole-5-ol) derivatives and 1,4-dihydropyrano[2,3-c]pyrazoles showed good potential for destroying colon cancer cell lines. Consequently, the poly(aniline-co-melamine)@MnFe2O4 nanocomposite is an excellent catalyst for green chemical processes owing to its high catalytic activity, stability, and reusability.

Poly(N-vinylimidazole): A biocompatible and biodegradable functional polymer, metal-free, and highly recyclable heterogeneous catalyst for the mechanochemical synthesis of oximes.

The catalytic activity of poly(N-vinylimidazole), a biocompatible and biodegradable synthetic functional polymer, was investigated for the synthesis of oximes as an efficient, halogen-free, and reusable heterogeneous catalyst. The corresponding oximes were afforded in high to excellent yields at room temperature and in short times using the planetary ball mill technique. Some merits, such as the short reaction times and good yields for poorly active carbonyl compounds, and avoiding toxic, expensive, metal-containing catalysts, and hazardous and flammable solvents, can be mentioned for the current catalytic synthesis of the oximes. Furthermore, the heterogeneous organocatalyst could be easily separated after the reaction, and the regenerated catalyst was reused several times with no significant loss of its catalytic activity.

Phase Transition Behavior and Catalytic Activity of Poly(N-acryloylglycinamide-co-methacrylic acid) Microgels.

Poly(N-acryloyl glycinamide) is a well-known thermoresponsive polymer possessing an upper critical solution temperature (UCST) in water. By copolymerizing N-acryloyl glycinamide (NAGA) with methacrylic acid (MAA) in the presence of a crosslinker, poly(N-acryloyl glycinamide-co-methacrylic acid) [P(NAGA–MAA)] copolymer microgels with an MAA molar fraction of 10–70 mol % were obtained. The polymerization kinetics suggests that the copolymer microgels have a random structure. The size of the microgels was between 60 and 120 nm in the non-aggregated swollen state in aqueous medium and depending on the solvent conditions, they show reversible swelling and shrinking upon temperature change. Their phase transition behavior was studied by a combination of methods to understand the process of the UCST-type behavior and interactions between NAGA and MAA. P(NAGA–MAA) microgels were loaded with silver nanoparticles (AgNPs) by the reduction of AgNO3 under UV light. Compared with the chemical reduction of AgNO3, the photoreduction results in smaller AgNPs and the amount and size of the AgNPs are dependent on the comonomer ratio. The catalytic activity of the AgNP-loaded microgels in 4-nitrophenol reduction was tested.

Evaluation of physicochemical properties and catalytic activity of poly(PMDAH-co-ODA/PPDA) nanocomposites towards the removal of toxic pollutants

Synthesis of Polyimides (PIs) between pyromellitic dianhydride (PMDAH) and oxydianiline (ODA) or p-phenylenediamine (PPDA) in the presence and absence of V2O5 and Ag nanoparticles (NPs) were carried out under N2 atmosphere at 160 °C for 5 h with vigorous stirring in N-methylpyrrolidone (NMP) solvent. The prepared PI and its nanocomposites were analyzed by FT-IR spectroscopy, 1H NMR spectroscopy, FE-SEM, SEM, DSC and TGA like analytical instruments. The FE-SEM showed various surface morphologies for different PI nanocomposites. The particle size of the prepared nanoparticles was calculated as less than 60 nm for Ag and 15 nm for V2O5 nanoparticles by HR-TEM. The PI nanocomposites embedded with Ag nanoparticles (P2 and P5) showed a higher thermal stability than the pristine PIs (P1 and P4) and PI/V2O5 nanocomposites (P3 and P6). Further, the possible application of metal (Ag) and metal oxide (V2O5) NPs embedded PI nanocomposites was assessed on the catalytic reduction of highly toxic Cr(VI), Rhodamine 6G (R6G) dye and p-nitrophenol (NiP) pollutants with the help of a reducing agent (NaBH4). The apparent rate constant (kapp) values were calculated to assess the catalytic efficiency of the prepared PI and its nanocomposites. The PI/Ag nanocomposite (P2) system showed an efficient catalytic reduction than the other systems.

Synthesis, spectral analysis, and catalytic activity of poly(aniline‐co‐congored)–metal oxide nanocomposites

ABSTRACTElectrically conducting, water‐soluble fluorescent copolymer nanocomposites were synthesized by a solution polymerization method under different experimental conditions in the presence of CuO and V2O5 nanoparticles. The prepared copolymer nanocomposites were characterized with analytical tools, including Fourier transform infrared spectroscopy, ultraviolet–visible (UV–vis) spectroscopy, and fluorescence emission spectroscopy. The order of copolymerization was determined on the basis of the UV–vis absorption spectra and fluorescence emission spectra. The copolymer–CuO nanocomposite system exhibited the highest electrical conductivity. The scanning electron microscopy image showed the presence of more CuO nanoparticles on the surface of the copolymer. Furthermore, the catalytic activity of the copolymer nanocomposites was tested for the reduction of p‐nitrophenol. All three types of polymer systems exhibited almost the same apparent rate constant values. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46469.

Synthesis, characterization and catalytic activity of poly(Schiff base)

The poly(ethylene glycol) (PEG) based Schiff base was prepared at 80 °C under oxygen atmosphere, further the poly(Schiff base) was characterized by various analytical methods like FTIR spectroscopy, UV–visible spectroscopy, GPC. The thermal stability of the Schiff base was determined by DSC and TGA. The hydrophilic nature of samples was determined by water contact angle measurement. The surface morphology was followed by SEM. The application of the PEG-Schiff base was extended to catalytic reduction of the nitro phenol and hexavalent Cr mixture. The highly toxic hexavalent Cr was reduced to trivalent Cr, similarly the nitro phenol was reduced to aminophenol. The rate constants were determined and compared with the literature value. Suitable reaction scheme was proposed.

The Impact of the Polymer Chain Length on the Catalytic Activity of Poly(N-vinyl-2-pyrrolidone)-supported Gold Nanoclusters

Poly(N-vinyl-2-pyrrolidone) (PVP) of varying molecular weight (Mw = 40-360 kDa) were employed to stabilize gold nanoclusters of varying size. The resulting Au:PVP clusters were subsequently used as catalysts for a kinetic study on the sized-dependent aerobic oxidation of 1-indanol, which was monitored by time-resolved in situ infrared spectroscopy. The obtained results suggest that the catalytic behaviour is intimately correlated to the size of the clusters, which in turn depends on the molecular weight of the PVPs. The highest catalytic activity was observed for clusters with a core size of ~7 nm, and the size of the cluster should increase with the molecular weight of the polymer in order to maintain optimal catalytic activity. Studies on the electronic and colloid structure of these clusters revealed that the negative charge density on the cluster surface also strongly depends on the molecular weight of the stabilizing polymers.

Structure and Catalytic Activity of Poly(Titanium Oxide) Doped by Gold Nanoparticles in Organic Polymeric Matrix

The nanocomposite copolymers of poly(titanium oxide) (PTO) in an organic matrix of poly(hydroxyethyl methacrylate) (HEMA) doped by the Au nanoparticles (NPs) were synthesized in one-pot reaction. The composites were characterized as high optical transparence. It was proved by the SIMS, SAXS, and X-ray diffraction that PTO forms the 6 nm clusters uniformly distributed inside the organic polymer and chemically bonded to it. The AuNPs were formed by the UV irradiation of the copolymers containing the HAuCl4 embedded into the reaction mixture before the synthesis. The primary structure of the PTO clusters is close to the anatase modification of crystalline TiO2. This conclusion is made on the basis of agreement between the experimental FTIR spectra of the synthesized copolymers and the calculated IR spectra of the PTO/HEMA fragments calculated by the DFT quantum chemical methods and also by XPA-analysis. The synthesized materials have high photocatalytic activity. It has been shown by methylene orange decomposition under UV irradiation.

Differences in Catalytic Activity of Poly(vinylamine) Introduced on Surface of Mesoporous SBA-15 by Grafting from and Grafting onto Methods in Knoevenagel Condensation

Various amounts of poly(vinylamine) (PVAm) were deposited on the surface of SBA-15 mesoporous silicas, prefunctionalized with suitable organosilanes, by two different grafting techniques: “grafting...

Catalytic activity of poly(N-vinylpyrrolidone) protected gold nanoparticles deposited on ZnO

Gold (AuNPs) nanoparticles protected by poly(N-vinylpyrrolidone) (PVP) were prepared by «one-pot» synthetic protocol. Absorption spectra, size, morphology, structure and thermal properties of AuNPs were studied by UV-Vis spectroscopy, DLS, TEM and SAXS. According to DLS and SAXS measurement the average size of AuNPs stabilized by PVP in aqueous solution is varied from 6 to 15 nm. PVP protected AuNPs were deposited on zinc oxide by impregnation method. TEM images reveal that the average size of AuNPs-PVP deposited on the surface of ZnO is arranged between 6 and 10 nm and coincides well with DLS and SAXS measurements. The catalytic activity of polymer-protected AuNPs supported on the surface of ZnO was evaluated with respect to decomposition of hydrogen peroxide. The optimal conditions H2O2 decomposition in dependence of catalysts amount, concentration of substrate and temperature was found.

Conjugated polyelectrolytes-initiated chemiluminescence: A biosensing platform for label-free and homogeneous DNA detection

In this study, it was found that conjugated polyelectrolytes (CPEs) would initiate the strong chemiluminescence (CL) emission of luminol–H2O2 in weak basic media. Using CL spectra, ultraviolet visible light spectra, fluorescence spectra and electron spin resonance (ESR) spectra, the catalytic mechanism of CPEs on luminol–H2O2 CL was discussed in detail. Furthermore, it was found that the catalytic activity of poly [3-(3′-N,N,N-triethylamino-1′-propyloxy)-4-methyl-2,5-thiophene hydro chloride] (PMNT) (a kind of cationic CPEs) on the luminol–H2O2 CL system was closely relevant to the conformation of PMNT. The CL intensity of luminol–H2O2–PMNT system in the presence of single-stranded DNA was much larger than that in the presence of double-stranded DNA. By taking advantage of this phenomenon, a label-free and homogeneous CL detection of DNA hybridization is proposed. The detection limit of target DNA (3σ) was estimated to be as low as 3.7×10−13M. The present CL method for DNA hybridization detection offers the advantages of being simple, cheap, rapid and sensitive.

Electrocatalytic properties of poly(3,4-ethylenedioxythiophene) (PEDOT) in Li-O2 battery

The catalytic activity of poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated during oxygen reduction/evolution reactions in Li–O2 batteries. PEDOT was prepared by in situ chemical polymerization of 3,4-ethylenedioxythiophene monomer in carbon matrix. PEDOT significantly reduces the overvoltage of the charging process in a Li–O2 battery. The electrocatalytic effect of PEDOT can be attributed to its redox activity. Apparently, PEDOT acts as a mediator in electron transfer during discharge and charge processes.

Catalytic activity of poly[(methacrylato)aluminum(III)] obtained at different gamma-radiation doses

A novel coordination polymer was obtained throughout the polymerization of aluminum(III) methacrylate at different doses (10, 20, 30, 40, 50 and 80 kGy) using gamma-radiation as initiator. The materials were characterized by electronic paramagnetic resonance (EPR), thermogravimetric analyses (TGA) and scanning electron microscopy/electron dispersive X-ray analyses (SEM/EDAX) techniques; particle size distribution and surface areas were also determined. The samples of poly[(methacrylato)aluminum(III)] obtained at different γ-doses were found to catalyze 2-propanol dehydrogenation and dehydration to acetone and propene. A noticeable activity was observed with Poly[(methacrylato)aluminum(III)] obtained at 50 kGy, which has higher conversion of 2-propanol and the highest selectivity to acetone (∼90%). Results suggest that the decomposition of 2-propanol is correlated with the effect of gamma-radiation on the structure and surface area of the catalysts.

Research on poly(styrene-acrylic acid)-supported neodymium complex in catalytic copolymerization of styrene and 4-vinylpyridine

The catalytic activity of poly(styrene-acrylic acid) (PSAA) supported neodymium chloride (NdCl 3) complex for the copolymerization of styrene and 4-Vinylpyridine was studied. The influence of various factors, such as Al/Nd molar ratio, reaction time, macromolecular carrier (PSAA), and ratio of styrene to 4-vinypyridine (g/g), on the copolymerization yield of styrene and 4-Vinylpyridine was investigated. The results showed that the copolymerization of polar monomers with olefins occurred efficiently and the catalytic activity of polymer-supported catalyst was higher than that of the similar small molecular catalysts. The activity of PSAA·Nd complex increased with increasing Al/Nd molar ratios and decreased with increasing polymerization time. The highest activity of PSAA · Nd was observed at 120 min, and the highest yield was found at the ratio of styrene to 4-vinylpyridine of 4:2. DSC analysis presented that the resulted polymer had only one glass transition temperature, and showed very good thermal stability.

Oxidation of organic sulfides with atmospheric oxygen in the presence of phthalocyanine complexes as catalysts

Catalytic oxidation of a mixture of low-molecular-weight sulfides with atmospheric oxygen was studied. The catalytic activity of poly(cobalt phthalocyanine) in this process is higher than that of monomeric cobalt phthalocyanine.

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The catalytic activity of poly(3-qunuclidinyl methacrylate) (PQM) and its copolymer (PQM-StX) with styrene was investigated in the reaction of phenyl isocyanate with 1-butanol. Their catalytic activity was compared with those of poly[4-(N,N-dimethylamino)butyl methacrylate] (PDBM) and 1,4-diazabicyclo[2.2.2]octane (DABCO) and proved to be superior to that of PDBM, but inferior to that of DABCO. The catalytic activity of PQM-StX was higher than that of PQM. This would be caused by interaction of styrene component of PQM-StX with phenyl isocyanate.

EFFECTS OF NICARAVEN ON NITRIC OXIDE-RELATED PATHWAYS AND IN SHOCK AND INFLAMMATION

Expression of the inducible isoform of nitric oxide (NO) synthase, and the formation of peroxynitrite from NO and superoxide are responsible for some of the pathophysiological alterations seen during reperfusion injury and in various inflammatory conditions. Some of the effects of peroxynitrite are related to DNA single-strand breakage, and activation of poly (ADP-ribose) synthetase. Here we investigated the effect of nicaraven (2(R,S)-1,2-bis(nicotinamido)propane), a known hydroxyl radical scavenger compound and neuroprotective agent, on several NO- and peroxynitrite related pathways in vitro, and in shock and inflammation in vivo. Nicaraven, at 10 microM-10 mM, failed to inhibit the peroxynitrite-induced oxidation of dihydrorhodamine 123, indicating that the agent does not act as a scavenger of peroxynitrite. In RAW murine macrophages stimulated with peroxynitrite, nicaraven caused a dose-dependent, slight inhibition of poly (ADP-ribose) synthetase activation, possibly due to a direct inhibitory effect on the catalytic activity of poly (ADP-ribose) synthetase. Nicaraven partially protected against the peroxynitrite-induced suppression of mitochondrial respiration in RAW macrophages and caused a slight, dose-dependent inhibition of nitrite production in RAW macrophages stimulated with bacterial lipopolysaccharide. We next investigated the effect of nicaraven treatment in a variety of models of inflammation and reperfusion injury. Nicaraven (at 10-100 microg/paw) exerted significant protective effects in the carrageenan-induced paw edema model and (at 100 mg/kg i.v.) reduced neutrophil infiltration and histological damage in splanchnic artery occlusion-reperfusion injury. However, nicaraven failed to alter the course of hemorrhagic and endotoxic shock and arthritis in rodent models. The current data indicate the limited role of hydroxyl radicals in the pathogenesis of the inflammatory conditions tested.

The catalytic activity of poly(siloxane)-supported metalloporphyrins in olefin oxidation reactions: the effect of the support on the catalytic activity and selectivity

Supported tetra(-4-pyridyl)porphyrinato-manganese(III) [Mn III(TPyP)] + and -tin(IV) [Sn IV(TPyP)] 2+ have been prepared. The solid support was iodonated poly(siloxane) surface prepared by condensation reactions of (EtO) 4Si with (MeO) 3Si(CH 2) 3I. The supported metalloporphyrins were employed as catalysts for the oxidation reactions of 1-octene and of cyclohexene. NaBH 4 was used to reduce [Mn III(TPyP)] + and [Sn IV(TPyP)] 2+ back to their catalytically active Mn II and Sn II forms, respectively. Contrary to their homogeneous counterparts, both of the supported metalloporphyrins catalysed the cyclohexene oxidation reaction to yield only 2-cyclohexen-1-one with no other products over a reaction time of 10 h. In addition to cyclohexene oxidation, the supported [Mn III(TPyP)] + catalysed 1-octene oxidation as well, whereas the supported [Sn IV(TPyP)] 2+ was inactive for the oxidation of 1-octene.

Catalytic activity of poly(ADP-ribose) polymerase is necessary for repair of N-methylpurines in nontranscribed, but not in transcribed, nuclear DNA sequences.

The role of poly(ADP-ribose) polymerase (PADPRP) in nuclear DNA repair and other nuclear processes has been intensely studied and debated for decades. Recent studies have begun to shed new light on these arguments with firm experimental data for its role, primarily, as a remodeler of chromatin structure. Those studies imply that PADPRP plays an indirect role in DNA repair, serving to expose DNA to repair enzymes through chromatin remodeling. Only DNA that is tightly packaged would require PADPRP activity for its repair; while DNA in an open conformation would be accessible to DNA repair enzymes and not require PADPRP activity. The purpose of the current studies was to address the above hypothesis directly. Using quantitative Southern blot analysis, we studied repair in transcribed and nontranscribed nuclear DNA sequences in ADPRT 351 cells 95% deficient in PADPRP activity. Cells were exposed to methylnitrosourea (MNU) for 1 h and allowed to repair for 8 or 24 h. Densitometric scans of autoradiographs revealed that, when compared to their parental V79 cell line, ADPRT 351 cells 95% deficient in PADPRP activity were equally as efficient in repair of N-methylpurines in the transcribed sequence containing the dihydrofolate reductase gene. However, the ADPRT 351 cells were deficient in the ability to repair these lesions in the nontranscribed sequence containing the IgE gene compared to repair of the same sequence in the parental V79 cells. Nucleoid sedimentation assays demonstrated that the ADPRT 351 cells are deficient in repair across the entire genome when compared to the parental V79 cells. These studies indicate that PADPRP activity is not required for repair of N-methylpurines in transcribed nuclear DNA sequences but is necessary for the repair of these lesions in nontranscribed nuclear DNA sequences as well as across the entire genome since the DNA in a given cell is predominantly nontranscribed.

Catalytic Activity of Poly(α-sulfoundecenoic acid)

Poly(α-sulfoundecenoic acid), poly(SUA-H), was prepared from poly(undecenoic acid), poly(UA-H). The critical micelle concentration, CMC, and pre-CMC of poly(SUA-H), estimated with measurement of electric conductivity of the aqueous solution, were slightly higher than those of poly(sodium undecenoate), poly(UA-Na), and benzene was solubilized into aqueous solution of poly(SUA-H) at the concentrations above the pre-CMC. Catalytic activity of poly(SUA-H) on the acid hydrolyses of sucrose and p-nitrophenyl acetate, PNPA, was examined. For the hydrolysis of sucrose in water, the catalytic activity of poly(SUA-H) was slightly lower than that of hydrochloric acid and the catalysis followed an ordinary second-order kinetics. For the hydrolysis of PNPA in ethanol-water mixture (1:1 in vol.), the catalytic activity was slightly higher than that of hydrochloric acid, although the catalysis seemed to follow an ordinary second-order kinetics. For the hydrolysis of PNPA in water, however, catalytic activity was found to be considerably higher than those of hydrochloric acid and low molecular weight analog of poly(SUA-H). The reaction rate showed a saturation phenomenon with increasing concentration of poly(SUA-H), although it increased proportionally with increasing concentration of PNPA in the examined range. Lineweaver-Burk plots of the kinetic data showed good straight lines, which indicated that the catalysis followed a Michaelis-Menten type kinetics. These results can be explained by hydrophobic interactions of the catalyst with the substrate.