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1.
Waheed A. Badawy Khaled M. Ismail Ziad M. Khalifa 《Journal of Applied Electrochemistry》2007,37(5):593-604
Uniform conducting polymer films of poly(N-(1-Naphthyl) ethylene-diamine dihydrochloride), PNED, were prepared conveniently and reproducibly by the anodic oxidation
of the monomer, N-(1-Naphthyl) ethylene-diamine dihydrochloride, NED, in an acidic aqueous solution using the conventional potentiodynamic
technique. The different parameters influencing the preparation conditions like monomer concentration, solvent constitution,
scan range, scan rate, scan repetition, rotation speed of the working electrode and the type of the substrate were investigated
and the optimum preparation conditions are specified. The stability of the prepared films was tested in both aqueous and non-aqueous
media. The characteristics of the polymer films and their electrochemical activity towards catalyzing some technologically
promising redox reactions were also examined. The films were found to be very stable in aqueous solutions and in some organic
solvents like acetone, acetonitrile, and chloroform and dimethyl sulfoxide. The film stability was found to depend on the
solution pH. The polymer films were capable of catalyzing the redox processes of several natural products and amino acids
e.g. vitamin C and glycine. The polymer film possesses electrochromic properties and the color of the film changes from purple
to violet to dark blue and then to brown according to the preparation and/or polarization conditions. The electrochromic properties
are related to polaron formation, which subsequently oxidizes to diimine species followed by the oxidation of the aromatic
ring. The mechanism of the polymerization process was investigated and discussed. The process involves deprotonation reactions
and a head-to-tail coupling of the oxidized monomer with cation radicals.
An erratum to this article can be found at 相似文献
2.
The structures of gels polymerized using a mixed solvent that induces cononsolvency during the free
radical polymerization were investigated.N,N -isopropylacrylamide (NIPA)
gels were polymerized in water and N,N-dimethylformamide (DMF) mixtures.
The NIPA gels can have homogeneous/heterogeneous structures depending on the mole fraction of DMF, xD.
The NIPA gel synthesized at xD = ca. 0.25 was opaque in appearance, and its
porous structure was observed by the SEM micrograph; the porous structure is formed as the aggregates
of microgels phase-separated due to the cononsolvency. The porous NIPA gels achieve a very rapid shrinking
rate in response to the temperature jump, which are desirable for their applications. 相似文献
3.
Summary Swelling and mechanical behavior of negatively (ionic comonomer-sodium methacrylate) and positively (ionic comonomer-(2-acrylamidoethyl)trimethyl
ammonium chloride) charged networks of poly(N-isopropylmethacrylamide) (PIPMAm) and poly(N-isopropylacrylamide) (PIPAAm) was investigated in water/ethanol mixtures at room temperature. Strong cononsolvency effect
was observed for uncharged and negatively charged gels of both systems; while for neat solvents high degree of swelling Q was observed, for solvent mixtures pronounced minima in swelling were found. Swelling minima are connected with the coil-to-globule
transition of network chains and their characteristic parameters-concentration of ethanol at the minimum, ceth,m, and corresponding swelling degree, Qm, were determined. With increasing amount of negatively charged ionic comonomer the minimum in swelling shifts to higher ceth,m values and Qm increase. On the other hand, positively charged networks of both systems exhibit roughly constant Q values practically independent of solvent mixtures compositions. For all four systems it was found that mechanical behavior
is predominantly determined by the degree of swelling regardless of charge concentration. 相似文献
4.
Francisco López-Carrasquero Giuseppe Giammanco Angélica Díaz Johanna Dávila Carlos Torres Estrella Laredo 《Polymer Bulletin》2009,63(1):69-78
A series of comb like poly(p-n-alkylstyrene)s with linear alkyl groups, containing even numbers of carbon atoms from 12 up to 22 were synthesized by radical
polymerization and characterized by FTIR, 1H NMR, TGA, TVA DSC, and WAXS. All polymers were obtained in good yields and were soluble in organic solvents as chloroform,
dichloromethane or tetrahydrofuran and insoluble in methanol; they are stable up to temperatures near 300 °C. On the other
hand, the alkylic side chains of all series are able to crystallize in a paraffinic phase in which the melting temperature
and enthalpy increase with the methylene number of the n-alkyl chain. 相似文献
5.
Copolymer hydrogels of N-isopropylacrylamide and itaconic acid (IA), crosslinked with N,N′-methylenebisacrylamide, were prepared by radical copolymerization. These hydrogels were investigated with regard to their
composition to find materials with satisfactory swelling and drug release properties. A paracetamol is used as a model drug
to investigate drug release profile of the hydrogels. It was found that the investigated hydrogels exhibited pH- and temperature-dependent
swelling behaviour with restricted swelling and lower equilibrium degree of swelling at lower pH values and temperatures above
the LCST value of PNIPAM (around 34 °C). The diffusion exponent for paracetamol release indicate that the mechanism of paracetamol
release are governed by Fickian diffusion, while in all release media initial diffusion coefficient was lower than late time
diffusion coefficient. Furthermore, the paracetamol release rate depends on the hydrogel degree of swelling and it increased
in the first stage of diffusion process, whereas was no significant difference thereafter. The presence of the IA moieties
incorporated into the network weakened the shear resistance of the hydrogels. In order to calculate the pore size the characteristic
ratio for PNIPAM, C
n
= 11.7, was calculated. Based on the pore size, the investigated hydrogels can be regarded as microporous. According to the
obtained results swelling behaviour, mechanical properties, drug-loading capacity and the drug release rate could be controlled
by hydrogel composition and crosslinking density, which is important for application of the investigated hydrogels as drug
delivery systems. 相似文献
6.
Summary A new fluorescent initiator fluorescein 2-bromoisobutyrate (Flu-Br) was synthesized. The use of Flu-Br as initiator, Me6TREN as ligand and CuCl as catalyst by atom transfer radical polymerization allowed for chain-end fluoresceined poly(N-isopropylacrylamide) (Flu-PNIPAM) in one step. The polymerization reached high conversion (65%) and low polydispersity (PDI)
(1.15∼1.28). The linearity plot of the Mn,GPC and Mn,NMR against conversion and the low PDI revealed the well-controlled polymerization by ATRP. In addition, N-isopropylacrylamide (NIPAM) was copolymerized with hydrophilic N,N-dimethylacrylamide (DMAM) using Flu-Br initiator by ATRP. By changing the feed ratio of NIPAM to DMAM, it was very easy to
obtain thermo-sensitive fluorescent copolymers with proper lower critical solution temperature (36.0±0.2 °C, 38.0±0.2 °C).
The pH dependence on fluorescence intensity of Flu-PNIPAM displayed a similar behavior to the parent fluorescein. 相似文献
7.
In this study, a novel semi-interpenetrating network (semi-IPN’s) hydrogel, composed of acrylamide (AAm) with N-vinylimidazole (NVI) as comonomer, with poly (ethylene glycol)(PEG) and a multifunctional crosslinker such as trimethylolpropane
triacrylate (TMPTA) was prepared. Highly swollen poly (AAm/NVI) hydrogels and semi-IPN’s were synthesized by free radical
solution polymerization. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of NVI and PEG
content in hydrogels were examined. Poly (AAm/NVI) and poly (AAm/NVI/PEG) hydrogels showed large extents of swelling in aqueous
media the swelling being highly dependent on the chemical composition of the hydrogels. Swelling ratio of poly (AAm/NVI) hydrogels
and poly (AAm/NVI/PEG) hydrogels was shown 7.16–39.85. Diffusion behavior was investigated. Water diffusion into hydrogels
was found to be non-Fickian in character. This study has given the quantitative information on the swelling characteristic of poly (AAm/NVI) hydrogel
and semi-IPN’s as water absorbent in many potential applications. 相似文献
8.
M. R. Ganjali P. Norouzi F. Faridbod S. Riahi M. R. Yaftian A. Zamani D. Matt 《Journal of Applied Electrochemistry》2007,37(7):827-833
A Th4+ ion-selective membrane sensor was fabricated from poly (vinyl chloride) (PVC) matrix membrane containing 2-(diphenylphosphorothioyl)-N′,N′-diphenyl acetamide (DPTD) as a neutral carrier, potassium tetrakis (p-chlorophenyl) borate (KTpClPB) as anionic excluder and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH and additive
anionic influence on the response properties were investigated. The sensor, comprising 30% PVC, 63% solvent mediator, 4% ionophore
and 3% anionic additive demonstrates the best potentiometric response characteristics. It displays Nernstian behavior (15.2 ± 0.5 mV
per decade) over the concentration range 1.0 × 10−2–1.0 × 10−6 M. The detection limit of the electrode is 6.3 × 10−7 M (∼140 ng/ml). The response time of the electrode is 30 s .The sensor can be used in the pH range 3.0–9.0 for about 6 weeks.
The membrane sensor was used as an indicator electrode in the potentiometric titration of Th4+ ions with EDTA. It was successfully applied to the determination of thorium ions in binary mixture. 相似文献
9.
Metal complexes of poly(2-N,N-dimethylaminoethyl) methacrylate
were prepared by complex-forming with aqueous solutions of salts of FeSO4.2H2O;
CoCl2.6H2O; CuCl2.2H2O;
VOSO4.5H2O; Na2MoO4.2H2O
and Na2WO4.2H2O. The catalytic activity
of the complexes was studied in the oxidation of cyclohexene as a model reaction. The activities of
the complexes synthesized towards the reaction of cyclohexene epoxidation can be arranged by the following
order: PDMAEM-MoO2
2+> PDMAEM-VO2+
> PDMAEM-WO2
2+> PDMAEM-Co2+
> PDMAEM-Fe3+> PDMAEM-Cu2+. The complexes
catalyzing the homolytic decomposition of tert-butylhydroperoxide increased
the maximum yield of 2-cyclohexene-1-ol and 2-cyclohexene-1-on. The yield of cyclohexene oxide and 2-cyclohexene-1-ol
were 58% and 13%, respectively. 相似文献
10.
Gökhan Demirel 《Journal of Polymer Research》2007,14(1):23-30
In the present study, a series of ionic poly(N-t-butylacrylamide-co-acrylamide) [P(NTBA-co-AAm)] hydrogels were synthesized by free-radical crosslinking copolymerization
of N-t-butylacrylamide (NTBA) and acrylamide (AAm) monomers in fixed amount, but changing amount of maleic acid (MA) comonomer in
methanol using N,N-methylene-bis-acrylamide (BAAm) as the crosslinker, ammonium persulfate (APS) as the initiator, and N,N,N′,N′-tetramethylethylenediamine (TEMED) as the activator. The swelling behavior of these hydrogels was analyzed in buffer solutions
at various pHs. The prepared hydrogels also were investigated swelling-deswelling transition in water depending on the temperature.
For the bovine serum albumin (BSA) adsorption, the effect of pH, temperature, initial protein concentration and adsorption
rate were investigated. Maximum BSA adsorption was observed at pH 5.0 which is close to the isoelectric pH of BSA (pH 4.8).
The highest adsorption rate was achieved in about 12 h. and also, maximum BSA adsorption was found at +5°C. 相似文献
11.
Silver Catalyzed Bromination of Aromatics with <Emphasis Type="Italic">N</Emphasis>-bromosuccinimide
Rui Zhang Lei Huang Yanfang Zhang Xiaorong Chen Weihong Xing Jun Huang 《Catalysis Letters》2012,142(3):378-383
Abstract
A heterogeneous silver catalyst was prepared and applied efficiently for the selective bromination of aromatics with NBS. The silver nanoparticles combined with the acidic support HMB can activate both the aromatic ring and NBS, and the synergistic effects between the silver nanoparticles and the HMB highly enhanced the efficiency of the bromination reaction. 相似文献12.
13.
The electrochemical synthesis of poly(o -phenylenediamine) (PoPD) from an aqueous medium was suitably modified by controlling the switching potential to enhance the growth of the polymer. The charge–discharge data for the cell Zn/1 M ZnSO4 (pH 4)/PoPD are presented. The polymer was modified by incorporating Pt microparticles into its matrix during electropolymerization. The PoPD-Pt composite electrode was also characterized as a cathode active material in aqueous cells. 相似文献
14.
Kirsten A. Leiss Young H. Choi Ibrahim B. Abdel-Farid Robert Verpoorte Peter G. L. Klinkhamer 《Journal of chemical ecology》2009,35(2):219-229
Western flower thrips (Frankliniella occidentalis) has become a key insect pest of agricultural and horticultural crops worldwide. Little is known about host plant resistance
to thrips. In this study, we investigated thrips resistance in F
2 hybrids of Senecio jacobaea and Senecio aquaticus. We identified thrips-resistant hybrids applying three different bioassays. Subsequently, we compared the metabolomic profiles
of these hybrids applying nuclear magnetic resonance spectroscopy (NMR). The new developments of NMR facilitate a wide range
coverage of the metabolome. This makes NMR especially suitable if there is no a priori knowledge of the compounds related
to herbivore resistance and allows a holistic approach analyzing different chemical compounds simultaneously. We show that
the metabolomes of thrips-resistant and -susceptible hybrids differed considerably. Thrips-resistant hybrids contained higher
amounts of the pyrrolizidine alkaloids (PA), jacobine, and jaconine, especially in younger leaves. Also, a flavanoid, kaempferol
glucoside, accumulated in the resistant plants. Both PAs and kaempferol are known for their inhibitory effect on herbivores.
In resistant and susceptible F
2 hybrids, young leaves showed less thrips damage than old leaves. Consistent with the optimal plant defense theory, young
leaves contained increased levels of primary metabolites such as sucrose, raffinose, and stachyose, but also accumulated jacaranone
as a secondary plant defense compound. Our results prove NMR as a promising tool to identify different metabolites involved
in herbivore resistance. It constitutes a significant advance in the study of plant–insect relationships, providing key information
on the implementation of herbivore resistance breeding strategies in plants.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
The effects of key parameters on the preparation and regeneration of protoplast from the β-carotene-producing fungus Blakeslea trispora were discussed in this paper, including the combination of various enzymes, mycelial age, digesting time and temperature,
pH value, osmotic stabilizers, pretreatment, culture medium and culture method. Under the condition of mixed enzymes in osmotic
stabilizer (0.6 M NaCl) combined with 2% lysozyme, 3% cellulase and 3% snailase, the highest protoplast yield, as high as
7.48×106 protoplasts/mL, was obtained when mycelial age was 60 h at pH 5.0–6.0 with digesting for 14–16 h at 28 °C. After
purification of the obtained protoplasts, they were regenerated in PDA regenerative medium using bilayer plate culture method.
To validate the usability of the protoplasts, a novel plasmid with green fluorescent protein (GFP) was used in transformation
for easy visual observation. The results showed that the protoplasts prepared by the optimized method were active and applicable
in further gene manipulation experiments.
This work was presented at 13
th
YABEC symposium held at Seoul, Korea, October 20–22, 2007. 相似文献
16.
17.
Nikola Drenchev Tony Spassov Ivan Kanazirski 《Journal of Applied Electrochemistry》2008,38(2):197-202
The electrochemical hydriding/dehydriding under galvanostatic conditions of nanostructured Mg2-x
Sn
x
Ni (x = 0,0.1,0.3) were studied at different temperatures in the range 28–45 °C. The discharge capacity, cycle life and electrochemical
impedance of the alloys were found to depend on the presence of Sn. Tin decreases the maximum electrochemical capacity, but
essentially improves the cycle life of Mg2Ni. Intensive corrosion of surface Mg was found to take place during the first 2–3 charge/discharge cycles to a much larger
extent for Mg2Ni, compared to the tin containing alloys. Sn decreases the electron density around the Mg atoms and therefore impedes magnesium
oxidation. It was also found that Sn hampers charge transfer but reduces the hydrogen diffusion resistance in Mg2Ni based alloys. 相似文献
18.
Dhanapalan Karthikeyan Nachiappan Lingappan Bommasamudram Sivasankar 《Korean Journal of Chemical Engineering》2008,25(5):987-997
Bifunctional catalysts containing (0.1–0.5 wt%) Nickel and 0.1 wt% of Pd supported on H-β zeolite were synthesized by incipient wetness impregnation method and characterized by XRD, TEM, XPS, TPD and TPR techniques.
The catalytic activity of Ni containing and Ni free Pd/H-β Catalysts was studied, and it was found that Ni up to a threshold value (0.3 wt% on β) produced increased the n-decane conversion and isomerization selectivity. When Ni content exceeds the threshold value, the
conversion increases but isomerized products decrease. Moreover, Ni containing Pd/H-β showed increased sustainability and favored the protonated cyclopropane (PCP) intermediate mechanism in n-decane isomerization.
The catalyst containing 0.3 wt% Ni 0.1 wt% Pd is adjudged as one performing better than other catalysts studied because of
the isomerized mixture from it shows better octane number. 相似文献
19.
David R. Hall Dudley I. Farman Jerry V. Cross Tom W. Pope Tetsu Ando Masanobu Yamamoto 《Journal of chemical ecology》2009,35(2):230-242
The raspberry cane midge, Resseliella theobaldi, is a widespread pest of cultivated red raspberry in Europe. Pheromone-baited traps could provide a much-needed, accurate
means to monitor the pest. Volatiles collected separately from virgin female and male midges were analyzed by gas chromatography
(GC) coupled to mass spectrometry (MS) to reveal four female-specific components. In analyses by GC coupled to electroantennographic
(EAG) recording from the antennae of a male midge, at least three of these components elicited responses. Based on its GC
retention indices and mass spectrum, we propose that the major component is 2-acetoxy-5-undecanone and confirm this by synthesis
of the racemic compound in seven steps and 63% yield from 4-pentenoic acid. The three minor components were each present at
approximately 30% of the major component and were identified as 2-undecanone, (S)-2-acetoxyundecane, and (S)-2-undecanol by comparison of GC retention times and mass spectra with those of synthetic standards. GC analyses of the female-produced
volatiles on an enantioselective column showed that only one enantiomer of 2-acetoxy-5-undecanone was present, and this was
found to be the S-enantiomer by hydrolytic kinetic resolution of an epoxide intermediate in the synthesis and also by enantioselective hydrolysis
of the racemic acetate with a lipase enzyme. The two enantiomers were also separated by high-performance liquid chromatography
on an enantioselective column for field tests. In two field trapping tests, (S)-2-acetoxy-5-undecanone was highly attractive to male R. theobaldi; the R-enantiomer was not attractive. The racemic compound was just as attractive as the S-enantiomer, and addition of the three minor components in racemic form at two different loads did not affect catches. The
pheromone could be dispensed from both rubber septa and polyethylene vials for at least 1 month under field conditions, but
the former was preferred as it gave more uniform release. 2-Acetoxy-5-undecanone belongs to a new group of pheromone structures
in the Cecidomyiidae, most others being mono- or diesters. 相似文献