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1.
Guoqin Liu Chunlong Guan Wenjun Zou He Zhu Jin peng Linqi Zhang Xiaoqin Bi 《Journal of Polymer Research》2007,14(6):461-465
The contraction of poly(acrylic acid-co-butyl methacrylate) (P(AA-co-BMA)) gel induced by complexation with linear Poly(N-vinyl-2-pyrrolidone) (PVP) is quite different from that of poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMAA) gel.
The dynamic mechanic properties vary greatly between complexed and uncomplexed networks. It was found that the concentration
of PVP has a strong effect on the complexation with P(AA-co-BMA) gel and the dynamic mechanic properties of the P(AA-co-BMA)/PVP
complexes. 相似文献
2.
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
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.
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
5.
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
6.
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
7.
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8.
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
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.
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
11.
12.
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
13.
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
14.
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.
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
17.
Ramón Coronado Sara Pekerar Arnaldo T. Lorenzo Marcos A. Sabino 《Polymer Bulletin》2011,67(1):101-124
In this study, an hydrogel was synthesized from the monomer N-isopropylacrylamide (NIPA), generating the poly(N-isopropylacrylamide) (PNIPA) and other formulations were synthesized in the presence of 1, 2, and 3% hyaluronic acid (HA) for obtain an interpenetrating polymer network. For all the obtained hydrogels, the thermo-sensitive response was studied since the lower critical solution temperature (LCST) and was analyzed by differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), and oscillatory rheology at constant frequency as a function of temperature. The LCST transition temperature (Tt onset) was found between 34.4 and 35.5 °C. By scanning electron microscopy (SEM) PNIPA-HA formulations showed a porous morphology. The applicability of the hydrogels as injectable and non-toxic materials was verified, respectively, by rheology results and by cytotoxicity studies through an in vitro test of cell hemolysis on blood agar. 相似文献
18.
Summary Ionized networks of random copolymers of acrylamide (AAm) and N,N’-diethylacrylamide (DEAAm) (mole ratios of xAAm/xDEAAm=1/0,0.75/0.25,0.5/0.5,0.30/70,0.15/0.85,0/1) with various amounts of ionic comonomer-sodium methacrylate (MNa) (mole ratios
to all monomers xMNa=0.0,0.025,0.05) and crosslinker – N,N’-methylenbisacrylamide (MBAAm) were prepared at high dilution in water. Their swelling
and mechanical behavior was investigated in water at various temperatures (from 10 to 90 °C) and in water/acetone (w/a) mixtures at room temperature. For some copolymers the transition region from expanded to collapsed state was observed at
critical concentration of acetone, ac, in w/a mixtures or at critical temperature, Tc, in water. It was found that with increasing content of DEAAm component in copolymers the ac values increase; the similar increase was observed with increasing xMNa. Neat PDEAAm and copolymers with the highest DEAAm content exhibit temperature transition; both increasing amount of AAm
and charges bound on the chains (xMNa) in copolymers shifts the Tc temperatures to higher values very efficiently (for more than 20 °C). 相似文献
19.
Hong-Wei Wang In Hae Kim Chang-Su Park Jae-Hwa Lee 《Korean Journal of Chemical Engineering》2008,25(4):801-803
α-amylase from Bacillus licheniformis was successfully immobilized on developed support, which was prepared by coating a chitosan-casein film on silica, at 20
°C, pH 6.0 for 5 hr with microbial transglutaminase (MTG) as the cross-linking factor. The optimal support was obtained when
1% chitosan and 1% casein were used in the coating mixture. The optimal condition for immobilization catalyzed by MTG was
confined to be at MTG concentration of 15 U/mL, pH 6.0, reacting for 6 hr at 20 °C. The highest specific activity of immobilized
α-amylase was achieved as 236 U/g. After immobilization, the obtained enzyme showed broader pH profile and maintained more
than 70% of the original activity after 20 reuses. 相似文献