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  • Articles  (10,329)
  • Springer  (10,329)
  • American Meteorological Society
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  • 2010-2014
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  • 1999  (10,329)
  • Chemistry and Pharmacology  (10,329)
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  • Articles  (10,329)
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  • 2010-2014
  • 1995-1999  (10,329)
  • 1990-1994
  • 1955-1959
  • 1935-1939
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  • 1
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Synchrotron radiation has been used to record the diffraction patterns from Poly(ethylene terephthalate) for a range of draw rates (0.1 to 10sec−1) and temperatures (90 to 120°C). The patterns were analysed to derive the development of the 〈P 2(cosθ)〉 order parameter and the rates of crystallisation. The effects of temperature and draw rate can be unified with a WLF time-temperature shift factor. Comparison with estimates of chain relaxation processes show that, when the draw rate is faster than the chain retraction process, the onset of crystallisation is delayed until the end of drawing. Crystallisation is very sensitive to both temperature and orientation and has an approximate 4th power dependence on 〈P2(cosθ)〉.
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  • 2
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The glass transition temperatures of several blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene have been measured by DSC, and the T g -composition data have been described on the basis of a thermodynamic treatment. A negative enthalpy of mixing and a positive entropy of mixing have been found, in agreement with the well known miscibility of the blend. The presence of a singolarity point in the T g -composition plot has been evidenced and considered at the light of a theoretical treatment recently proposed.
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  • 3
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    Polymer bulletin 43 (1999), S. 157-163 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Two AB-type poly(ether imide)s were prepared by one-pot polyimidization in N-methyl-2-pyrrolidone(NMP)/pyridine or N,N-dimethylacetamide(DMAc)/Et3N solution in the presence of triphenylphosphite(TPP) activator. The polymers were obtained with inherent viscosities of 1.16(5a) and 0.54(5b) dL/g and were highly thermostable up to at least 552°C with 5% weight loss. The polymers showed chemical resistance against chloroform even at higher temperature but could readily be dissolved in m-cresol and concentrated sulfuric acid. Wide-angle X-ray diffractograms revealed that the polymers were semi-crystalline.
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  • 4
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Organocobalt poly(arylene-vinylene)s composed of 1,2- or 1,3- linkage at their cyclobutadiene moieties (3 and 4, respectively) were prepared by the Heck reaction of p-divinylbenzene with (cyclobutadiene)cobalt-containing monomers having two aryl bromide moieties (1 and 2, respectively). The number average molecular weights (M n) of the obtained organocobalt poly(arylene-vinylene)s (3 and 4) were 4,100 and 4,000, respectively (GPC, on the basis of polystyrene). UV-vis spectra of 3 and 4 exhibited main π-π* absorption peaks at 362 and 397 nm, respectively, which were ca. 60 nm bathochromically shifted from those of the corresponding monomeric units. Both polymers were found to show thermotropic liquid crystallinity in the range of room temperature to ca. 80 °C by employing differential scanning calorimetry (DSC) and the optical measurement using crossed polarizers.
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  • 5
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    Polymer bulletin 43 (1999), S. 171-175 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Copolymers containing vinyltrimethoxysilane (VTMOS) and 2-vinylpyridine (2VPy) at different compositions were synthesized and characterized. The monomer reactivity ratios r1 and r2 were estimated by using the classical Fineman-Ross and Kelen Tüdos linear fitting procedures. Moreover, these parameters were also estimated using a nonlinear computational fitting known as Reactivity Ratios Error in Variable Method (RREVM). Attempts to obtain the corresponding copolymer with vinyltrimethylsilane (VTMS) were performed but only hompolymerization 2VPy is observed due to the non-reactivity of VTMS under this conditions. The results were analysed in terms of the relative comonomeric structures and compared with similar related systems. The reactivities are interpreted in terms of the resonance and stabilization effects together with the chemical structure.
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  • 6
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymers having Fischer-type alkoxycarbenes in the side chain were synthesized by the reaction of pendant hydroxy groups with pentacarbonyltungsten acetoxyphenylcarbene [(CO)5W=C(Ph)O2CCH3, 2]. Namely, copolymers of methyl methacrylate with 4-hydroxybutyl methacrylate [poly(MMA-co-HBMA), 3b] were prepared and subjected to the reaction with 2 derived from tetramethylammonium salt of pentacarbonyltungsten hydroxyphenylcarbene [(CO)5W=C(Ph)ON(CH3)4, 1] with acetyl chloride. Soluble copolymers (4b) with pendant metal-carbene segments were obtained, and 1H NMR and UV spectroscopic analyses indicated that the metal-carbene moiety was introduced onto 20–70% of hydroxy groups of the copolymers. In contrast, the introduction of carbene moiety into a copolymer of MMA with 2-hydroxyethyl methacrylate [poly(MMA-co-HEMA), 3a] was unsuccessful because no reaction with 2 took place. The formed polymer (4b) served as a polymeric catalyst for the polymerization of phenylacetylene under the photo-irradiation.
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  • 7
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A novel polymer homolog of N,N-dimethylacetamide (DMAc) having amide groups on all main chain carbons, poly(N,N-dimethylcarbamoylmethylene) 1, was prepared by heating poly(di-t-butyl fumarate) 2 at 180 °C for 2 hours followed by treatment with hexamethylphosphoramide at 180 °C for 5 hours. The structure of the obtained polymer 1 was confirmed by 1H-, 13C-NMR and IR spectroscopy. The polymer 1 actually showed the properties based on its repeating structures. 1 had the amphiphilicity and was soluble both in protic and aprotic solvents. Furthermore, 1 showed the miscibility with commodity polymers such as poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(vinyl chloride). In comparison with another polymer homolog of DMAc, poly(2-methyl-2-oxazoline), the polymer 1 exhibited better miscibility with poly(N-vinylpyrrolidone).
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  • 8
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    Polymer bulletin 43 (1999), S. 191-198 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Biocompatible and potentially biodegradable polyamides (PAs) containing in the chain both peptide bonds and hydrophilic triethyleneoxide segments have been prepared by interfacial polycondensation of sebacoyl dichloride with amide-diamines derived from the 4,7,10-trioxa-1,13-tridecanediamine and α-aminoacids such as glycine, L-valine and L-phenylalanine. These PAs exhibit moderate inherent viscosity values and show limited solubilities in CHCl3, DMF and DMSO. 1H-NMR and FTIR spectroscopy analysis confirmed the expected structures. DSC and X-rays diffraction spectra indicated crystallinity degrees from 19 to 31%. The melting temperatures range between 135–238 °C. Liquid water absorption measurements indicate a high equilibrium weight-uptake when a glycine residue is present in the amide-diamine moiety. In vitro tests carried out using cultures of human fibroblasts showed the biocompatibility of the prepared PAs.
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  • 9
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    Polymer bulletin 43 (1999), S. 199-206 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary W(NO)2(O2CR)2 - Lewis acid (LA) catalysts (LA=TiCl4, SnCl4; R=-CH(C2H5)(CH2)3CH3) induce substituted acetylenes (phenylacetylene, propargyl ether, 1,6-heptadiyne, diphenylacetylene) to polymerize or oligomerize. Their catalytic ability strongly depends on the Lewis acid and solvent. The polymerization reactions of phenylacetylene always accompany the cycolotrimerization reactions. In the system with TiCl4 in CH2Cl2 the yield of polymer equals to 56% at 80% conversion of a monomer. However, in the system with SnCl4 in benzene, 42% cyclotrimers arise at 57% conversion of phenylacetylene. The mechanism of these reactions as well as the structure of the obtained polymers were determined.
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  • 10
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Transesterification reactions between bisphenol-A polycarbonate and polydimethylsiloxane-polycaprolactone block copolymers were studied in melt at 270°C. Influence of the composition of reaction mixture and the catalyst type on the formation and properties of the products obtained were investigated by spectroscopic, chromatographic and thermal methods. Both of the catalysts used, zinc acetate and lanthanum acetylacetonate are very efficient transesterification catalysts for the system studied. GPC and DSC results clearly show the formation of novel polymers displaying combined properties of the polycarbonate and the silicone-ester copolymer.
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  • 11
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new method for determining the dominant termination mechanism in radical polymerization based on ultrasonic scission of long chains is used to study the termination of polystyrene and polymethyl methacrylate. The method is extended to obtain the disproportionation/combination ratio. Long dead polymer chains in solution were broken by ultrasound. The chain radicals thus formed were then allowed to terminate in the presence and absence of a chain terminating agent (radical trap). The resulting molecular weights are compared to find the dominant termination mechanism. It is found that the dominant mechanism in polystyrene is combination and that in polymethyl methacrylate is disproportionation. These results are in accordance with those quoted in the literature and obtained by other methods.The effectiveness of the radical trap used (2-chloroethyl benzene) was tested by NMR and it was found that when the trapping agent is present it terminates 100% of the polymethyl methacrylate chains. The time evolution of the degree of polymerization was compared to simulations based on Schmid's model. The disproportionation/combination ratios were found for polymethyl methacrylate as 2 and for polystyrene as 1/7 respectively through simulation studies.
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  • 12
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly((3-hydroxypropyl β malate) has been synthesized starting from aspartic acid and benzyloxy-1-propanol as precursors. This new polymer was characterized by 1H and 13C NMR, size exclusion chromatography and differential scanning calorimetry. Homopolymer is soluble in water. Two kinds of amphiphilic copolymers were also prepared and characterized. Such polymers have been synthesized with a view to preparing non-charged degradable associating networks or drug carriers.
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  • 13
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    Polymer bulletin 43 (1999), S. 305-310 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymerization of phenylacetylenes containing imino groups with a variety of transition metal catalysts was investigated. The monomers employed were N-(4-ethynylbenzylidene)aniline (1), N-(3-ethynylbenzylidene)aniline (2), N-(4-ethynylbenzylidene)-2,6-diisopropylaniline (3), N-(4-ethynylbenzylidene)-4-hexylaniline (4), N-(4-ethynylbenzylidene)butylamine (5), and N-(4-ethynylbenzylidene)octylamine (6). All of the monomers smoothly polymerized with [(nbd)RhCl]2-Et3N to give polymers in excellent yields, whereas no polymerization took place with W, Mo, and Fe catalysts. The produced polymers were orange to red solids and soluble in common organic solvents except for poly(1). UV-vis spectra of the polymers indicated that the main chains possess a similar degree of conjugation to that of poly(phenylacetylene). However, the stability of polymer backbone toward oxidative cleavage in solution remarkably improved, which is contributed by the electron-withdrawing character of imino groups.
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  • 14
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The radical polymerization of methylmethacrylate and ethylacrylate was carried out in the presence of tris(4,4'-dimethyl-2,2'-bipyridine) copper(II) hexafluorophosphate complexes and aluminium isopropoxide. The molecular weight of the synthesized polyethylacrylates increased proportionally with conversion, whereas the polymerization of methylmethacrylate revealed a nonlinear behavior. The polydispersities of the molecular weight distributions observed were between 1.09 and 1.34. Poly(styrene-block-polymethylmethacrylate) was synthesized by sequential monomer addition.
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  • 15
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: ABSTRACT : We have investigated a novel monomer having two pendent phenyl imido groups for preparing new cycloaliphatic-aromatic polyamides. Novel polyamides were synthesized by direct polycondensation reaction of N,N'-diphenyl-2,3,5,6-diimido cyclohexane-1,4-dicarboxylic acid(PICA) and various aromatic diamines such as p-phenylene diamine, 4,4'-oxydianiline and 4,4'-methylene dianiline. A direct polycondensation was carried out by a Yamazaki method which is typical of using triphenyl phosphite, lithium chloride, and pyridine. Inherent viscosity of these resulting polyamides are ranged 0.20 ∼ 0.45 dl/g. A transparent flexible and tough film was casted. The glass transition temperature of the polyamide from the PICA and 4,4'-oxydianiline is 147 °C. The decomposition temperature of these polyamides are ranged from 350 ∼ 360 °C and the ash contents of them orders MDA 〉 p-PDA 〉 ODA according to kinds of the using diamines. And the solubilities of these polyamides are good in aprotic solvents such as DMAc, NMP, DMF.
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  • 16
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In order to investigate the polymerization behavior of allytrimethylsilane as a comonomer, ethylene was copolymerized with allyltrimethylsilane at 80°C in toluene using methylaluminoxane (MAO) activated metallocene catalysts. The catalytic activity of the polymerization strongly depended on both the type of the catalysts and the concentration of allyltrimethylsilane. End group analysis of the copolymers by means of 1H and 13C NMR spectroscopy revealed that allyltrimethylsilane rather act as a chain transfer agent in the copolymerization, even though considerable amount of allyltrimethylsilane was incorporated in the polymer chain with rac-Et(Ind)2ZrCl2 catalysts. The chain transfer reaction influence strongly the molecular weight and comonomer content of the copolymers.
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  • 17
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    Polymer bulletin 43 (1999), S. 341-347 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Five copolymers from N-(hydroxyethyl)ethyleneimine as nucleophilic monomer and phenylsuccinic anhydride (PhSAn) as electrophilic monomer, were synthesized according to the spontaneous copolymerization concept. These copolymers were characterized by elemental analysis, FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The copolymer composition determined from the 1H-NMR spectra showed that the copolymers are not alternating. According to all the data, it was suggested a copolymer structure which includes ester and anhydride bonds. The molecular weights determined by vapor pressure osmometry ranged between 5.100 and 6.100 g/mol.
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  • 18
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This work describes the kinetics of triethyleneglycol dimethacrylate (TEGDM) polymerization, photoinitiated by camphorquinone (CQ) / N-phenylglycine (NPG) and CQ /D,L α-phenylglycine (α-PG), in air and/or in N2. The rates of polymerization (Rp), double bond conversion (p), monomer conversion (pmax), at different concentration of NPG and α-PG were measured and analysed. It was found that CQ/NPG is much more effective photoinitiator system than CQ/α-PG, regarding to the different their chemical structure and H-atom donor ability.
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  • 19
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    Polymer bulletin 43 (1999), S. 395-402 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermal and mechanical properties of poly(methylmethacrylate-co-dodecylmethacrylate) nanocomposites based upon exfoliated organophilic layered silicates, were investigated as a function of the silicate and comonomer content. Layered silicates such as sodium bentonite were rendered organophilic by means of ion-exchanging sodium cations for N,N,N,N-dioctadecyl-dimethyl-ammonium cations. Silicate exfoliation was enhanced by means of 5 and 10 wt.-% dodecyl-methacrylate (LMA) addition to afford translucent reinforced acrylic nanocomposites. In contrast to conventional filled acrylic polymers, only 10 wt.-% organophilic silicate was sufficient to increase Young's modulus from 2200 to 4030 MPa, glass temperature from 72 to 80 °C and degradation temperature from 220 to 256 °C with respect to the neat MMA/LMA (90 wt.-%/10 wt.-%) copolymer. Flammability studies, performed on a cone calorimeter, revealed that the maximum heat release rate of MMA/LMA copolymer nanocomposite decreased from 837 kW/m2 to 566 kW/m2. The nanocomposite morphology was examined by means of transmission electron microscopy (TEM).
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  • 20
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    Polymer bulletin 42 (1999), S. 25-32 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The aim of this study was to investigate the bile salts adsorption behavior of the diethylaminoethyl (DEAE)-chitosan, in vitro. In order to prepare the DEAE-chitosan, where the DEAE groups are specifically introduced onto 6-OH groups of chitosan with minimal by-product, DEAE-chitin was prepared by reacting chitin with N,N-diethylaminoethyl chloride, and direct N-deacetylation of DEAE-chitin was carried out in 10% of an aqueous sodium hydroxide solution containing sodium borohydride. DEAE chitosan samples were incubated with cholic acid sodium salt and deoxycholic acid sodium salt in a tromethane buffer solution (pH 7.5) for 1 hour, and the bile salts adsorption performances of the samples were examined by HPLC. The modified chitosan samples showed improved bile salts adsorption performances compared to chitosan, and the absorption amount of bile salt to the samples increased with increase in the DEAE groups introduced. In most cases, the adsorption amount of deoxycholate to the samples was greater than that of cholate.
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  • 21
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    Polymer bulletin 42 (1999), S. 41-46 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Room temperature polymerization of three naturally occurring bile acids, cholic, lithocholic and deoxycholic, was carried out using a mixture of diisopropyl carbodiimide (DIPC), and a 1:1 salt of dimethyl amino pyridine and p-toluenesulfonic acid (DMAP/PTSA). The corresponding polymers were characterized by IR, NMR, Thermal Analysis and X-ray diffraction. Molecular weights were calculated by gel permeation chromatography in the range 50,000–60,000, using polystyrene standards. The polymers were also characterized by mass spectrometry, using matrix assisted laser desorption ionization-time of flight, MALDI-TOF.
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  • 22
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(phenylacetylene)s bearing dialkylamino groups were prepared by the polymerization of p-(N,N-dialkylamino)phenylacetylenes with [Rh(nbd)Cl]2, and their electrochemical behavior was examined. Rh-catalyzed polymerization of p-(N,N-diethylamino)phenylacetylene (DEAPA) and p-(N,N-di-n-butylamino)phenylacetylene (DBAPA) in toluene in the presence of triethylamine gave good yields of the polymers (86 and 90%, respectively). Poly(DEAPA) was soluble in chloroform and dichloromethane, and poly(DBAPA) dissolved in various solvents such as toluene, THF, dichloromethane and chloroform. Poly(DEAPA) and poly(DBAPA) showed onset temperatures at 248 and 190°C, respectively, and absorptions around 300–400 nm. Electrochemical doping of the polymer films resulted in the shift of the absorptions to a region around 680 nm, which accompanied a color change of the polymer films from green ocher to deep blue.
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  • 23
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    Polymer bulletin 42 (1999), S. 149-152 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Hydrogenation of poly(vinyl cinnamate) was performed with RhH(CO)(PPh3)3 catalyst with intent to clarify the photoalignment mechanism of liquid crystals on poly(vinyl cinnamate) alignment layer. The hydrogenated cinnamate side group shows the characteristic peaks at 2.9 ppm and 2.5 ppm in 1H-NMR spectrum, and a decreasing peak at 280 nm in UV spectrum. This reaction can reveal the role of dimerized or residual cinnamate groups in the applications of the polymeric layer for electronic devices.
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  • 24
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The reactions of α,ω-diyne, HC≡C(CH2)mC≡CH (m = 6 and 8), with 3,3'-diaminobenzidine and with 3,3'-diamino-4,4'-dihydroxybiphenyl in the presence of RU3(CO)12-PPh3 catalyst give the corresponding poly(alkylenebenzoxazole)s and poly(alkylenebenzimidazole)s, respectively. The former polymers obtained from the equimolar reaction of the monomers are partly soluble in polar organic solvents such as DMF, DMSO, and NMP, while the poly(benzimidazole)s are soluble in these solvents. GPC measurement shows the molecular weights of the polymers, M n of 4.8−14.1×103 and M w of 6.4−19.7×103.
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  • 25
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    Polymer bulletin 42 (1999), S. 159-166 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The procedures for the purification of commercial chitosan samples as hydrochlorides and in the neutralized form are described. Thermal analysis reveals that, independently of the purification method, all samples are highly pure. The agreement between values of degrees of acetylation determined by conductimetric titrations and by 1H nmr spectroscopy is very good. The aqueous solutions of both forms of purified chitosan were free of aggregation as evaluated by their Huggins constants. The potential use of solutions of chitosan hydrochloride in acid-free aqueous NaCl for the studies aiming to characterize the solution behavior of chitosan is demonstrated.
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  • 26
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Two nonlinear optical (NLO) methacrylate monomers, 2-methyl-acrylic acid 2-(ethyl-{4-[2-(6-nitro-quinolin-2-yl)-vinyl]-phenyl}-amino)-ethyl ester (5) and 2-methyl-acrylic acid 6-{3-[2-(6-nitro-quinolin-2-yl)-vinyl]-carbazol-9-yl}-hexyl ester (7) were newly synthesized and copolymerized with methylmethacrylate to give NLO polymers, P1 and P2. These polymers were well soluble in organic solvents and showed glass transition temperatures at 145 °C and 114 °C, respectively. The number average molecular weights (Mn) were 26,600 for P1 and 9,300 for P2. The SHG coefficients (d33) of corona-poled films of P1 and P2 measured with 1.064 μm Nd-YAG laser were 32.2 pm/V and 17.6 pm/V, respectively.
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  • 27
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: ABSTRACT: We have investigated a new 1,2-type aromatic dibromide monomer for preparing a modified π -conjugated poly(p-phenylenevinylene). A novel π -conjugated poly(p-phenylenevinylene) was prepared by dehalogenation polycondensation of a dibromoaromatic compound with a squaric unit as a monomer with zerovalent nickel [Ni(0)] complex. The monomer and the polymer were characterized by FT-IR, 1H-NMR, Elemental Anaylsis, TGA, DSC, GPC and UV-Visible. The resultant polymer had good solubility to polar aprotic, solvents, e.g. DMF, DMAc, DMSO and NMP and solvatochromism in DMAc.
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  • 28
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Mechanical degradation and mechanochemical reaction in heterogeneous systems of the solid poly(vinyl chloride)-poly(vinyl alcohol) aqueous solutions have been studied by ultrasonic irradiation at 30 °C. The rate of decrease in the viscosity-average degree of polymerization of the degraded poly(vinyl chloride) was much faster than that of the degraded poly(vinyl alcohol). Mechanochemical reaction occurred by free radicals produced from the chain scissions of both polymers by ultrasonic waves. The copolymer was obtained and the molar ratio of the vinyl chloride and the vinyl alcohol units in its copolymer can be determined. In addition, the changes in the composition of the total block copolymer, the unreacted poly(vinyl chloride), and the unreacted poly(vinyl alcohol) were obtained.
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    Polymer bulletin 42 (1999), S. 221-227 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: The fracture toughness of the semi-IPN's of crosslinked epoxy and linear polysulfone(PSf) having morphology spectrum was investigated. The epoxy resin was based on diglycidyl ether of bisphenol A(DGEBA) and diaminodiphenylsulfone(DDS). The morphology spectrum, which has the gradual change of the morphological feature resulting from the concentration gradient of PSf in the epoxy resin can be obtained by inserting a PSf film in DGEBA/DDS mixture before cure. The relative rate of the dissolution of the PSf in the epoxy oligomer and the rate of curing reaction determine the concentration gradient of the PSf. In the region where the PSf concentration is less then 5%, sea(epoxy)-island(PSf) morphology is observed. As the concentration of PSf increases, the morphology changes to nodular structure, inverted sea-island, and PSf/epoxy homogeneous phase. Up to overall 10wt% of PSf, the fracture toughness of the PSf modified epoxy with morphology spectrum was higher than that of the counterpart with uniform concentration of PSf. These results were ascribed to the plastic deformation of the continuous PSf rich phase which was present in the morphology spectrum.
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    Polymer bulletin 42 (1999), S. 265-272 
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    Notes: Summary Homopolymerization of allylbenzene was carried out with various metallocene/methylaluminoxane (MAO) catalysts. Different polymerization behavior was observed depending upon the catalysts empolyed. rac-Et(Ind)2ZrCl2 and rac-Me2Si(Ind)2ZrCl2 gave semicrystalline polyallylbenzenes while i-Pr(CpFlu)ZrCl2 and CpTiCl3 did not give any polymeric product. The Cp2ZrCl2 gave amorphous polyallylbenzene with low molecular weight. The effect of temperature on the polymerization was investigated with a constant Al/Zr ratio. The temperature showing maximum catalyst activity is higher for the ansa metallocene catalysts than Cp2ZrCl2 catalyst. The IR and NMR spectra indicated that the polyallylbenzene consisted of allylbenzene repeating unit and no isomerization occurred.
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    Polymer bulletin 42 (1999), S. 237-244 
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    Notes: Summary 5-Nitro-2-(2′-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 5-nitro-2-(2′-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3-nitro-4-(2′-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3-nitro-4-(2′-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of 5-nitro-2-(2′-vinyloxyethoxy)benzaldehyde (1) and 3-nitro-4-(2′-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Vinyl ether monomers 2a-b and 4a-b were polymerized with boron trifluoride etherate as a cationic initiator to yield poly(vinyl ethers) 5-6 having nitrooxybenzylidenemalononitrile and nitrooxycyanocinnamate, which is effective chromophore for second-order nonlinear optical applications. Polymers 5-6 were soluble in common organic solvents such as acetone and DMSO. T g values of the resulting polymer were in the range of 70–81°C. Electrooptic coefficient (r33) of the poled polymer films were in the range of 19–27 pm/V, which was improved by introducing of nitro group. Polymers 5–6 showed a thermal stability up to 300°C in TGA thermograms, which is acceptable for NLO device applications.
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    Polymer bulletin 42 (1999), S. 257-264 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Oligo(ɛ-caprolactone)s functionalised with acid groups were prepared by reacting hydroxyl terminated oligo(ɛ-caprolactone)s with succinic anhydride, maleic anhydride or glutaric anhydride. Quantitative conversion of the hydroxyl functionality was achieved in the melt at 130 °C. The resulting acid terminated oligo(ɛ-caprolactone)s were characterised by 1H and 13C NMR spectroscopy. The reactivity of these oligomers was enhanced by conversion of the acid functionality in an acid chloride functionality using thionyl chloride or an anhydride functionality using acetic anhydride. It was shown that these activated oligo(ɛ-caprolactone)s can be used for coupling reactions with compounds containing alcohol- or amino functionalities.
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    Keywords: Keywords: Nucleophilic and electrophilic monomers; spontaneous copolymerization; non-alternating copolymers.
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    Notes: Summary The copolymerization of p-chlorophenylmaleimide (1) as electrophilic monomer with 2-methyl-2-oxazoline (2) as nucleophilic monomer without initiator in solution under different experimental conditions was investigated. Copolymers were characterized by FT-IR and 1H-NMR spectroscopy. The copolymer composition was determined from 1H-NMR spectra. Molecular weights ranged between 1700 and 5400 g/mol by vapor pressure osmometry.
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    Notes: Summary The heat of base-catalyzed alcoholysis of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) as well as several related aromatic and aliphatic esters has been measured using a high-pressure calorimeter. The process is essentially thermoneutral, and heats of CH3ONa-catalyzed methanolysis of PET and PEN are +1.8±0.6 and +9.3±0.2 kJ/mol-carboxyl group, respectively. Furthermore, the heats of Zn(OCOCH3)2-catalyzed alcoholysis of PET with ethylene glycol and benzyl alcohol are also calculated as +5.8±0.2 and +6.6±0.8 kJ/mol-carboxyl group, respectively. These values are comparable to those for ethyl esters of p-substituted benzoic acids and propionic acid.
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    Polymer bulletin 42 (1999), S. 301-307 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: Summary Allylbenzene was polymerized in the presence of two types of homogeneous zirconocene catalysts (co-catalyst methylaluiminoxane). Selective chain termination through β-hydride elimination or chain transfer to aluminum was observed depending upon the catalysts employed. The rac-Et(Ind)2ZrCl2, and rac-Me2Si(Ind)2ZrCl2, catalysts gave the polyallylbenzenes with saturated end groups due to chain transfer to aluminum, while the Cp2ZrCl2 catalyst gave the polyallylbenzenes with vinylidene end groups due to β-hydride elimination.
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    Polymer bulletin 42 (1999), S. 373-378 
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    Notes: Summary Radical polymerization of the methacryloyl isocyanate containing 1-adamantanol (Ad-MAI) with AIBN in different solvents at 60°C was investigated. It is observed that polymerization is slower in polar solvents than in nonpolar ones. The rate of polymerization for Ad-MAI was found to be slower than those of Adph-MAI and MMA both in photopolymerization and in thermal polymerization. Copolymerization of Ad-MAI (M1) with styrene (M2) in benzene was studied at 60°C. The monomer reactivity ratio was calculated to be r1=1.53 and r2=0.76 according to the method of Fineman-Ross. The prominent glass transition temperature for poly(Ad-MAI) was observed at 142°C from global TSC spectrum.
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    Notes: Summary Monoaldehydes have been synthesized from tri- and tetra(ethylene glycol) monosubstituted derivatives and introduced into chitosan by the reductive alkylation technique to give comb-shaped polysaccharide hybrids. The reaction of chitosan with the aldehydes in the presence of sodium cyanoborohydride proceeded efficiently to give chitosan derivatives having oligo(ethylene glycol) side chains at the amino groups. The products were characterized by high affinity for organic solvents as well as water in sharp contrast to the original chitin and chitosan. They showed significant adsorption capacity toward metal cations.
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    Notes: Summary : Nonlinear optical poly(ether imides) with an adequate thermal stability has been synthesized by direct coupling of hydroxy poly(ether imides) and NLO chromophores with a quantitative yield. The resultant amorphous NLO poly(ether imides) exhibited good solubility in common organic solvents, providing optical-quality thin films by spin coating. The glass transition temperatures of the polymers are at around 180 °C. The electrooptic coefficients (r33, @1.3μm) of PEI-DR1 was 12.3 pm/V with an electrical poling field of 100 V/μm and it decayed about 10 % over 10 months at 90 °C under atmospheric conditions.
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    Notes: Summary Crystalline polymers, such as poly(ɛ-caprolactone) (PCL), poly(ethylene adipate) (PEA), and polyethylene (PE), were successfully grafted onto carbon black surface by direct condensation of terminal groups of these polymers with carboxyl groups on the surface using N,N'-dicyclohexylcarbodiimide as a condensing agent. The electric resistance of a composite prepared from these crystalline polymer-grafted carbon black drastically increased to 104–105 times of initial resistance in good solvent vapor of grafted polymer and returned to initial resistance when it was transferred into dry air. However, the change of electric resistance of the composite hardly observed in poor solvent vapor. These results suggest that these composite can be applied as a novel gas sensor.
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    Polymer bulletin 42 (1999), S. 575-578 
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    Notes: Summary The orientational behavior of liquid crystalline polymers with para-nitro azobenzene as side chains under electric field was studied by UV-visible spectroscopy. The results showed that λmax of the poled polymer films was around 394nm, compared to that of the unpoled films, the absorption decreased due to poling. The orientational parameters increased linearly with the increase of the electric field. The temporal stability of the poled polymer film is good at room temperature. This kind of materials showed promise application as nonlinear optical component in photorefractive polymers
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    Polymer bulletin 42 (1999), S. 579-586 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The molecular orientation behaviour of epoxy networks on the basis of the diglycidyl ether of bisphenol-A (DGEBA) and various linear aliphatic diols was studied by rheo-optical FTIR spectroscopy. Uniaxial deformation was performed above and below the glass transition temperature. The influence of diol chain length and molar ratio on the mechanical properties and the orientation parameter will be discussed.
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    Notes: Summary The electro-optical response of two novel side chain liquid crystalline polysiloxane copolymers containing chiral pendant groups was investigated. It was found that both copolymers possessed N* phase with a long pitch and therefore the origin of the electro-optical response detected in this phase was considered to be the electroclinic effect.
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    Polymer bulletin 42 (1999), S. 611-618 
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    Notes: Summary Alternating propene-carbon monoxide copolymers (P-CO) were melt-blended with polystyrene, poly(styrene-co-acrylonitrile) (SAN), and with poly(styrene-co-maleic anhydride) (SMA). P-CO forms homogeneously miscible blends with SAN containing 25 wt% AN at the investigated blend compositions. The transparent blends have single, intermediate glass transition temperatures that fit the Fox equation. The elastic properties of P-CO at room temperature disappear upon blending with SAN because the T g is driven above RT. Polystyrene and SMA are not miscible with P-CO and form heterogeneous blends with two glass transitions. This demonstrates that both the polarity of the styrenic copolymer and the nature of the comonomer govern its phase behavior.
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    Polymer bulletin 42 (1999), S. 635-639 
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    Notes: Summary We have studied the polymerization of methyl methacrylate (MMA) using biscyclopentadienylcalcium (Cp2Ca) and bis(pentamethylcyclopentadienyl)calcium (Cp2 *Ca) as initiators. Polymerizations initiated with CP2Ca produced poly(methyl methacrylate), PMMA, with %rr = 80. This polymerization was conducted in 1,2-dimethoxyethane at 0°C; monomer conversion was 57% after 19 h. Lindsell and co-workers reported a much higher syndiotacticity for the same initiator. While 80%rr is higher than a free radical polymerization of MMA at the same temperature, the broad polydispersity and low conversions make this polymerization method unattractive. Use of the more soluble initiator Cp2 *Ca significantly increases monomer conversion but produces PMMA with lower syndiotacticity.
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    Notes: Summary Diethyleneglycoldivinylether (DVE2) and triethyleneglycoldivinylether (DVE3) were photopolymerised together with monovinylethers and hydroxyalkylvinylethers, in order to study the curing reaction and to evaluate the properties of the films obtained. In the presence of the monovinylethers, the flexibility of the cured films increased and the Tg values decreased. In the presence of a hydroxyalkylvinyl ether, a stronger plasticisation effect was obtained and attributed to a chain transfer reaction involving -OH groups.
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    Polymer bulletin 42 (1999), S. 655-660 
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    Notes: Summary The synthesis and metal ion responsive properties of Congo Red-based polyamide are reported. The polymer was prepared by simple interfacial polymerization between Congo Red and sebacoyl chloride. The polymer showed decrease in electronic absorption when exposed to metal ions. The absorbance tends to decrease linearly in a measurable range according to metal ion concentration. It is found that the polymer showed high sensitivity toward Ca2+ and Fe3+.
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    Notes: Summary Poly(amide-imide)s(PAIs) with different microstructures were prepared based on trimellitimide and 4,4'-diphenylether with varying the reaction conditions. The microstructures of PAIs were examined by 500MHz 1H-NMR spectroscopy. The head-to tail (HT-) PAI showed a sharp peak in WAXD curve, a large shift at around 1670 cm−1 for −C=O stretching in FT-IR spectra, and poor solubility in organic solvents, high density, Tg, tensile strength and modulus compared to head-to-head (HH-) PAI and copolymers of HT and HH. These results might be due to the higher packing tendency of the HT PAI than HH PAI or copolymers.
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    Polymer bulletin 42 (1999), S. 683-688 
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    Notes: Summary Metathesis polymerization has been employed for the synthesis of polyphenylacetylene (PPA) containing redox-active ferrocene groups at both ends. Two reversible one electron oxidation waves were detected in CV. The ΔE values decreased with increase in chain length of the polymer, indicating that the metal-metal interaction decreases by increasing the chain length.
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    Polymer bulletin 42 (1999), S. 693-699 
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    Keywords: Key Words: poly(o-toluidine); enzyme electrode; amperometric biosensor
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An amperometric biosensor for glucose was constructed in a one-step procedure by the electropolymerization of o-toluidine in the presence of glucose oxidase on Pt substrates in KCl aqueous electrolyte at a potential of 0.5 V vs Ag / AgCl. The amperometric responses of the prepared polymeric biosensor to the glucose were measured at a potential of 0.7 V in PBS solution. Results showed that this polymeric sensor exhibited a fast amperometric response time (4–5 s) and a linear range up to 6 mM glucose with poor stability. Also, it was seen that biosensor responded successfully to glucose injections in the presence of some interfering species such as lactose, sucrose and urea.
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    Notes: Summary The miscibility of a series of poly(ethyl methacrylate-co-4-vinylpyridine) with poly(styrene-co-cinnamic acid), is investigated by differential scanning calorimetry. The results show that each blend is miscible as ascertained by a single composition dependent glass transition temperature. The Tg's of the blends exhibit positive deviations from the weight average Tg's of the blend components. The thermograms data exploited according to the Kwei and Schneider approaches suggest the occurrence of strong specific intermolecular attractive interactions within the binary systems. The strength of these interactions, as estimated from the Kwei q-values, increases with the proton donor and proton acceptor contents in the copolymers.
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    Polymer bulletin 42 (1999), S. 709-716 
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    Notes: Summary γ- and UV-irradiation was successfully used for the preparation of mixed networks on the basis of high molecular weight polyoxyethylene (POE) and/or N-isopropylacrylamide and poly(N-isopropylacrylamide) (PNIPAAm). These gels preserve the swelling transition temperature of the pure PNIPAAm and shrink faster above this temperature due to the hydrophilic POE chains. It was found that in a collapsed state these gels retain alkaline organic salts from aqueous solutions.
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    Polymer bulletin 42 (1999), S. 717-724 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Jet erosion tests of outdoor insulating silicone and EPDM rubbers were carried out by means of a modified sandblasting equipment. The presence of relatively large, non-reinforcing filler particles increased the erosion rate of the silicone rubber compounds. The erosive wear of highly filled compounds strongly depended on the incident angle of the eroding particles. Rubbers with low amount or very finely dispersed reinforcing filler showed a good resistance to solid particle erosion. The mechanisms of material removal were studied by scanning electron microscopy and discussed.
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    Notes: Summary 6,6-Diethyl- (1a) and 6-methyl-6-propyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1b) were synthesized by the acetalization of 2-vinylcyclopropane-1,1-dicarboxylic acid with 2- or 3-pentanone. The new monomers were characterized by IR, 1H NMR and 13C NMR spectroscopy. The radical polymerization of the monomers 1a and 1b, in addition of 6,6-methyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1c) and (exo/endo)-7-ethoxycarbonyl-2-oxo-7-vinyl-bicyclo[4.1.0]heptane (1d), was carried out in bulk with 2,2`-azoisobutyronitrile (AIBN) as the initiator. The polymer yield with 1d was only low. The polymerization of the monomers 1a and 1c resulted in cross-linked polymers, whereas in case of the polymerization of monomer 1b soluble polymers in a high yield were obtained.
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    Notes: Summary The Ru(II)-centered star-shaped polymer was prepared by coordination of 2,2'-bipyridyl-terminated poly(propylene glycol) with ruthenium ion. The structure was confirmed by GPC analysis and UV/Vis spectrum. The resulting polymer complex was well-soluble in various organic solvents and water.
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    Notes: Summary Novel class of p-phenylenevinylene copolymer with sulfonylene group in the main chain (PPVS) was synthesized through the Wittig reaction of bis(bromomethyl-p-phenyl)-sulfone triphenylphosphonium salt with terephthaldehyde. PPVS was highly soluble in common organic solvents and showed strong blue-shifted fluorescence because the polar sulfonylene group provided better solubility and limited π-conjugation in polymer chain. A single layer device with PPVS sandwiched between indium-tin-oxide (ITO) and aluminum electrodes showed a blue electroluminescence (EL) peaked at 470 nm under the threshold voltage of 14 V. HOMO and LUMO levels of PPVS were found to be 0.46 and 0.28 eV, respectively, lower than those of poly(p-phenylenevinylene) (PPV).
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    Notes: Summary A new polyelectrolyte complex between chitosan and poly(2-acryloylamido-2-methylpropanesulfonic acid) (PAMPS) was prepared by mixing aqueous solutions of its components or by free radical polymerization on chitosan template. The complex formation was sensitive to the ionic strength of the medium. The complex was stable in acidic and neutral medium and dissociated at pH 〉 8. Its composition did not depend on pH values of the medium and the way of preparation. The mixing dilute aqueous solutions of chitosan and PAMPS resulted in the formation of nanoparticles with mean particle diameter 250 nm and monomodal distribution.
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    Polymer bulletin 43 (1999), S. 75-80 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SUMMARY Heterogeneous nucleation is not only a commonly encountered phenomenon of polymer crystallization, but also a fundamentally important research topic for understanding polymer crystallization. Both, polymer epitaxy and transcrystallization are well known mechanisms for surface induced oriented nucleation, but they only have been studied separately with respect to the nucleation abilities of one polymer to another. A new experimental procedure is established to combine transcrystallization and heteroepitaxy of one polymer on two different polymeric substrates. This provides a new way for comparing the relative nucleation onset of one polymer nucleated simultaneously onto two different substrates.
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    Notes: Summary The chemical shift in the 13C NMR spectra of copolymers of 2-chloroethyl vinyl ether (CEVE) and maleic anhydride (MA), and of n-butyl vinyl ether (BVE) and MA is assigned. It is found that both copolymers are made of completely alternating monomer unit sequences and that the proportion of cis linkage configuration at the cyclic MA units is 45 % and 47 % in the CEVE-MA copolymer and in the BVE-MA copolymer, respectively. Depending on the relative orientation of the cyclic anhydride group, quasi “isotactic” and quasi “syndiotactic” tacticity are considered, with quasi “syndiotactic” diads shielding the vinyl ether carbons more effectively.
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Lewis acidic sites (LAS) of silica, modified with TMA and MAO samples differed by TMA content, have been characterized by IR spectroscopy (CO adsorption as probe molecule at 77 K). Two types of LAS were found on the surface of silica modified with MAO and TMA: M LAS of moderate strength (νCO= 2204−2212 cm−1) and weak W LAS (νCO= 2194 cm−1). The concentration of these acidic sites has been estimated. It was shown by IRS study Cp2ZrMe2 interacts both with W LAS and M LAS. Correlation between the amount of M LAS and the activity of ethylene polymerization has been found.
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  • 60
    ISSN: 1436-2449
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    Notes: Summary A new family of random copolymers composed of chloromethylstyrene and a silicon based styrenic monomer was prepared using living radical polymerization. The lithographic efficiency of the resulting electron beam resists was examined. A pronounced improvement on the lithographic resolution and image quality of resists with a narrow molecular mass distribution was observed and is described.
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  • 61
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary It is shown that chitosan gel beads are suitable carriers of 8-hydroxy-7-iodoquinoline-5-sulfonic acid (SQ) and 2,5-dihydroxybenzenesulfonic acid (DHBSA) - substances applied in medicine. Drug release has been investigated with respect to the nature of the crosslinking agent (epichlorohydrin or glutaraldehyde) and pH of the medium. Considerable differences in the release rate of DHBSA and SQ have been found. The total amount of the desorbed SQ, as well as the release rate of the drug depends on pH of the medium - they decrease from alkaline to acidic medium. The antimicrobial and antimycotic activity of the loaded with SQ beads is demonstrated.
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  • 62
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    Polymer bulletin 43 (1999), S. 117-120 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Alternating boration copolymerization between 1,4-diallenylbenzene (2) and 2,7-diethynylfluorene (3) was examined using diphenylbromoborane (1) to give the corresponding copolymer (4). The organoboron copolymer obtained was characterized by 1H-, 11B-NMR, IR, and UV-vis absorption spectra.
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  • 63
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The radical polymerization of styrene was investigated in the presence of diphenyl ditelluride (DPDTe) under varied conditions. In the polymerization without any radical initiator at higher temperature (125°C), the addition of DPDTe surely decreased the polymer molecular weight (M n) while the polydispersity (M w/M n) was rather broad. The polymerization with benzoyl peroxide (BPO) as the initiator was also uncontrollable to afford polymers with broad M w/M n probably due to the redox side reaction of BPO with DPDTe. On the contrary, the precision control of M n and the initiating end structure could be achieved by the polymerization with 2,2'-azobisisobutyronitrile (AIBN), that is, M n increased in proportion to the molar ratio of monomer to initiator suggesting the suppression of bimolecular chain termination reactions by the excellent radical capturing ability of DPDTe.
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  • 64
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Ionized networks of copolymers of N-vinylcaprolactam with charged comonomer, sodium itaconate (mole fraction of ionic comonomer xs= 0−0.1) and of a crosslinker, 3,3'-(ethane-1,1-diyl)bis(1-vinyl-2-pyrrolidone) were prepared by radiation polymerization in water/ethanol mixture (H2O/Et = 0.3/0.7 by vol.) and their swelling; mechanical behaviour in water was investigated as a function of temperature. On heating, a decrease in the swelling degree was observed. Increasing xs shifts the volume transition temperature Ttr from the swollen to shrinked state to higher temperatures; in all cases, this transition is continuous. The observed decrease in swelling with temperature is accompanied by an increase in equilibrium modulus, so that mechanical behaviour is predominantly determined by swelling. The swelling of hydrogels can be in the first approximation described by the theory of polyelectrolyte networks in which repulsion of charges on the chain and finite chain extensibility were considered. In accord with this theory, as the Flory-Huggins interaction parameter χ= 0.522 for the uncharged network swollen in water, no jumpwise change in volume with increasing temperature was observed.
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  • 65
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    Polymer bulletin 43 (1999), S. 129-134 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Living polymerization of hexaethylcyclotrisiloxane was achieved with nBuLi-(nBuO)3PO at room temperature to produce living poly(diethylsiloxane). The molecular weight of the polymer increased in direct proportion to monomer conversion and to the reciprocal to the initial nBuLi concentration. Molecular weight distribution remained 1.1–1.2 during the polymerization. The polymerization was completed only after 1 day despite no solvent was used. When a compound containing SiOH groups was added to the polymerization system, the number of polymer chain agreed with a sum of nBuLi and SiOH groups.
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  • 66
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    Polymer bulletin 43 (1999), S. 121-128 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reactions of living polyisobutylene (PIB+) with different allylsilanes, as potential linking and coupling agents, have been studied. Quantitative monoaddition of 2-Phenylallyltrimethylsilane to living PIB+ yielded macromonomer (I), however coupling was absent. Rapid and quantitative coupling has been observed with 1,3-bis[2-(3-trimethylsilyl)-propenyl]benzene (bTPB). Using 1-(2-propenyl)-3-[2-(3-trimethylsilyl)-propenyl]benzene (PTPB) star polymers with an average of four arms have been prepared with high efficiency. The study of this linking reaction revealed that star formation takes place in two well separated steps. In the first step a macromonomer is formed in situ by the rapid reaction of PIB+ with the allyltrimethylsilyl functionality. Subsequent reaction of this macromonomer with the remaining electrophilic PIB+ ends followed by interchain reactions results in the formation of star polymers.
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  • 67
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    Polymer bulletin 43 (1999), S. 151-155 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Hydroboration polymerizaton of dicyano compounds was examined by using tripylborane, which is known as a fairly stable hydroborating agent, to give the corresponding poly(cyclodiborazane)s in good yields. The number average molecular weights of the obtained polymers were in the range of several thousands. These polymers exhibited high stability toward air and moisture.
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  • 68
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A novel difunctionalized 5,5'-dibromomethylene-2,2' bipyridine ligand was prepared and covalently bound with concurrent crosslinking by a post-polymer modification method to (N-vinylcarbazole-vinylalcohol) copolymer. The electrochemistry and UV-vis spectroscopy results both confirm the covalent attachment of ruthenium transition metal complex to the polymer backbone. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicate high thermal stability of the copolymer. The copolymer is also highly phosphorescent making it a potential polymeric material for transition metal based electroluminescent devices.
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  • 69
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SUMMARY The crosslinked poly([2-(methacryloyloxy)ethyl]trimethyl ammonium chloride-co-acrylic acid) was tested as adsorbent for Cd(II), Hg(II), Zn(II), Pb(II), Cr(III), and U(VI) by batch equilibrium procedure. At pH 5.0 the adsorbent retained 74% (1.865 meq/g) of U(VI) with a maximum capacity of load of 2.7 meq/g (108 mg/g). The resin-U(VI) equilibrium was achieved around of 1 h which is considered adequate for a heterogeneous reaction. It showed a high selectivity for U(VI) respect to all the other metal ions both from competitive and non-competitive conditions. The recovery of the resin was over 65% by H2SO4 and Na2CO3.
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  • 70
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this study, isothermal crystallization in blends of isotactic polypropylene (i-PP) with polyethylene-b-poly(ethylene-co-butylene)-b-polyethylene block copolymer (CEBC) was investigated using a polarized photometer, polarized microscope and differential scanning calorimeter. Half time of crystallizaiton (τ1/2) is increasing with increasing CEBC content in i-PP/CEBC blends. Avrami index and rate constant of crystal growth decrease with increasing CEBC content in i-PP/CEBC blends. On the contrary, heat of fusion of i-PP crystal in the blends is almost constant against the variation of CEBC content in i-PP/CEBC blends. Hence, it is pointed out that blending i-PP with CEBC caused only retardation of rate of crystalline growth and change in mechanism of crystalline growth from three dimensional to two dimensional growth.
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  • 71
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    Notes: Summary Polyisoprene (PI) was pre-polymerized by using benzyl diethyldithiocarbamate (BDC) as an iniferter. The obtained PI was subsequently used to react with methyl methacrylate (MMA) in order to investigate whether the relevant block copolymers can be achieved. Results from 1H-NMR and GPC reveal that the PI-PMMA block copolymers were formed. This suggests that polymerization of isoprene through the use of BDC proceeded via a (psuedo) “living” mechanism.
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  • 72
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    Notes: Summary Phase diagram obtained from small angle light scattering (SALS) and differential scanning calorimetry (DSC) of polypropylene/liquid paraffin blend system indicates that the melts undergo solid-liquid phase separation upon cooling and liquid paraffin is expelled out of crystalline region of polypropylene. Fibers spun under high take-up draw ratio are found to be hard-elastic. Long periods in the meridional direction are observed on the curves of small angle X-ray scattering (SAXS), and the yield point of fibers decreases with the increase in liquid paraffin content, which indicates such fibers have row-nucleated lamellar structure perpendicular to the fiber direction. The feasibility of preparing microporous membranes by stretching such fibers is investigated.
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  • 73
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    Notes: Summary The molecular mobility of deoxycholic acid (DCA) / ferrocene inclusion compound has been investigated by high resolution solid state 13C NMR spectroscopy. Compared to the single crystal of ferrocene, the molecular mobility of the ferrocene in the inclusion compound is enhanced because it is included in the large cavity of DCA. It is found that the relaxation time measurement by solid state 13C NMR can provide powerful evidence to confirm the formation of the inclusion compound.
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  • 74
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    Notes: Abstract In order to study the nature of interaction of arylbutadiynes with transient free radicals, polymerization and copolymerization of some vinyl monomers such as methyl methacrylate (MMA), styrene (ST), methacrylonitrile (MAN), vinylidene chloride (VCl2), ethyl acrylate (EA) and acrylonitrile (AN), were carried out in the presence of diphenylbutadiyne (DPB), 4,4'-butadiynylene-N,N,N',N'-tetra-n-butyl-dibenzamide (BBA), and 4,4'-dibromodiphenylbutadiyne (BPB). MMA gave an intense ESR signal at the polymerization temperature when the polymerization system became viscous, and the number of radicals increased with polymerization time. Strong signals of polyEA and polyMAN radicals were also observed in the presence of DPB when the polymerization system became almost solid. This is a unique case where active transient propagating radicals such as that of polyEA can be detected at polymerization temperature. The rates of polymerization decreased by the presence of the diacetylenes, but the molecular weights did not change with the diacetylene concentrations. UV spectroscopy revealed that there was no diacetylene unit bonded to the obtained polymers, indicating that degradative chain transfer is not the case. The monomer reactivity ratios for MMA-ST and MMA-AN systems did not vary significantly in the presence of the diacetylenes, although some difference was observed. It seems that some arylbutadiynes interact with free radicals but do not form bonds.
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  • 75
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    Notes: Summary Deuterium nmr has been employed to determine the average orientation of chain segment in poly(butadiene) networks. The nmr spectrum lineshape reveals the orientation distribution of network vectors due to the crosslinks, whereas the observed splitting gives information about the orientation due to segmental interactions. Both the lineshape and the splitting have been fitted simultaneously for a range of deformed poly(butadiene) networks varied in crosslink density and precursor chain length. From the fitting parameters the separate contribution to the average orientation arising from network constraints and interaction are calculated. These are used to estimate the effective molecular weight between topological constraints and the size of the segmental interaction. It could be shown that the latter remains constant as the crosslink density is varied. This is a strong evidence of the recently published theoretical framework.
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  • 76
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    Notes: Summary MALDI-TOF mass spectral analysis was used to characterize the novel unimolecular micelles that result from functionalization of the chain ends of poly(propylene imine) dendrimers with C10 alkanoyl or C12 alkyl groups.
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    Polymer bulletin 43 (1999), S. 387-394 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Fluorescence techniques have been used to study the interactions of poly(methacrylic acid) (PMAA) with chitosan(CS) in aqueous solution. These studies show that PMAA and CS form complexes within a pH range of 3 to 10 and along with complexing with CS, the conformation of PMAA at pH 4 changed from a hypercoiled to a loose coiled form. However, this conformational change is not complete since the optimal ratio for the complex formation is 0.5:1(CS:PMAA, in residue unit). PMAA/CS complexes at pH 4 were largely disrupted with the addition of NaCl, most likely due to screening of the electrostatic attraction between ionized carboxyl groups of PMAA and protonated amino groups of CS.
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  • 78
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Radiation-induced graft polymerization of N,N-dimethylaminoethylmethacrylate (DMAEMA) from solutions in carbon tetrachloride or in chloroform onto bisphenol A-derived polycarbonate (PC-1) and allyl diglycol carbonate (PC-2), respectively, was carried out by method of preirradiation in air. It has been found essential difference in transparency and durability of the modified PC-1 and PC-2. Effects of preirradiation dose as well as temperature and time of graft polymerization on effectiveness of DMAEMA grafting onto PC-2 were investigated, the optimal values of dose and temperature are 500 kGy and 55°C, respectively.
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  • 79
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary High fluorine content macromolecular layers were deposited on polyethylene (PE) film surfaces under an originally designed, continuos-flow-system plasma reactor conditions. Survey and angle resolution, ESCA data and ATR-FTIR results indicate that the plasma-created films are thin and have a fairly uniform structure. The fluorinated layers have a 60% relative fluorine atomic concentration, and are mainly composed of CF2-CF, and C-CF3 groups. AFM images collected from virgin and plasma-exposed PE surfaces show a significantly rougher surface of the plasma-treated substrates. Applications can be envisaged for creating Teflon-like coatings on various polymeric film surfaces using a continuous plasma process.
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    Polymer bulletin 43 (1999), S. 417-424 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The fine emulsion polymerizations of styrene initiated by a redox system ammonium peroxodisulfate/sodium thiosulfite stabilized by a non-ionic emulsifier were kinetically investigated. The dependence of the rate of polymerization on conversion or the emulsifier concentration was described by a curve with maximum at medium conversion. The maximum rate of polymerization is proportional to the − 0.45th and 1.5th power of initiator and emulsifier concentration, the number of particles to the 0.32nd and 1.3rd power of initiator and emulsifier concentration and the molecular weight to the − 0.62th and −0.97th power of initiator and emulsifier concentration, respectively. The results show a strong decrease in turbidity at around 20% conversion when emulsion turns into translucent latex. Deviation from the micellar nucleation model was attributed to the solubility of emulsifier in monomer, high level of nonmicellar aggregates, thick interfacial layer and transfer emulsion to microemulsion. The strong decrease of molecular weight with increasing emulsifier concentration is attributed to chain transfer events promoted by the high level of emulsifier at the reaction loci.
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  • 81
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    Notes: Summary In situ fluorescence and light scattering techniques were used to study the formation of heterogeneities during the free-radical crosslinking polymerization of sodium acrylate (NaAc) in the presence of N,N'-methylene(bisacrylamide) (BAAm) as a crosslinker. Pyranine was used as a fluorescence probe in the experiments. The reactions were carried out at room temperature and at a monomer concentration of 20.6 w/v% in water. It was found that the gel forming system became turbid at the start of the reaction; continuing polymerization and crosslinking reactions turned the opaque gels into slightly opaque and finally transparent gels. Two peaks were observed both in the scattered and emitted light intensities versus the reaction time plots. The first peak corresponds to the formation and growth of the phase separated domains whereas the second peak reflects the macrogelation point in the reaction system.
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  • 82
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Bilayer films composed of a wheat gluten layer and a functionalized polyolefin film were performed by hot press process with the aim to improve the moisture barrier property of hydrophilic gluten films. An ethylene/acrylic ester/maleic anhydride terpolymer (Lotader 3410) and an ethylene/glycidyl methacrylate copolymer (Lotader GMA) were used. The use of both Lotader products had no incidence on film opacity, and was effective to reduce dispersion in water and water vapor permeability. In the presence of the terpolymer, the mechanical properties were enhanced and the wide range selectivity of gluten films was preserved.
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  • 83
    ISSN: 1572-8838
    Keywords: lead acid battery ; grid alloy ; silver ; electrochemical behaviour ; corrosion behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The influence of silver, in the range of 0.02 wt% to 0.07 wt%, on the electrochemical and corrosion properties of Pb–Ca–Sn–Al grid alloy in sulphuric acid solutions at room temperature was investigated by potentiodynamic and potentiostatic methods. The introduction of Ag into a common grid alloy of Pb–Ca–Sn–Al confers some important features on the alloy. Potentiodynamic anodic polarisation measurements provided a qualitative overview of the activating, passivating and transpassivating processes which correspond to Pb → PbSO4, PbSO4 → PbO2 reactions respectively. Cyclic voltammetric measurements provided information on the effect of Ag on the oxidation of PbSO4 to PbO2. The addition of Ag refined the grains and enhanced the passivation of the electrode and its corrosion resistance. A decrease in the oxygen evolution overpotential and an increase in the hydrogen evolution overpotential with the additions of Ag were also observed during the experiments.
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    Journal of applied electrochemistry 29 (1999), S. 27-34 
    ISSN: 1572-8838
    Keywords: natural convection ; turbulence k–π model ; current density ; Butler–Volmer law ; electrical potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A mathematical model proposed by Bark and Alavyoon for modelling laminar natural convection in electrochemical cells, with binary electrolytes, is extended to simulation of two-dimensional turbulent flows. The turbulence was modelled by a standard k–π model. The constants used in the model are the same as those used by Henkes and Hoogendoorn. Steady state calculations were carried out in a square, differentially heated enclosure for Gr=7×1010 and Pr=0.71. The turbulence model used could not predict the transition effect on the Nusselt number along the hot wall. Transient calculations performed in an enclosure with an aspect ratio of 35, for Gr=6.4×1011 and Sc=2763, revealed large scale fluctuations in the boundary layers near the vertical walls. The model was able to predict qualitatively the velocity field for transitional flow for air induced by buoyancy at Grh=8100 and Grh=22 500. The correlation between the Sherwood and Rayleigh numbers was studied by modelling the mass transfer at the electrodes using a Butler–Volmer law. The computed Sherwood number was found to be approximately proportional to the Rayleigh number to the power of 0.2 in the range of Rah between 5×108 and 1010, and with an order of magnitude of 105.
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    Journal of applied electrochemistry 29 (1999), S. 93-100 
    ISSN: 1572-8838
    Keywords: oxygen sensors ; thick film ; zirconia ; amperometric sensors ; cracks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Thick film amperometric oxygen sensors have been constructed using an ink prepared from a powder of yttria-stabilized cubic zirconia with 150nm particle size printed onto an alumina substrate. At a fixed temperature these sensors display characteristics typical of an amperometric sensor. However, the limiting current varies with operating temperature (T) according to a T−3.1 dependence. This indicates that the diffusion barrier (electrolyte) becomes more restrictive as the temperature is raised. Cracks in the zirconia film (detected by SEM) arise from the differential thermal expansion coefficient of the thick film and the substrate. Diffusion of oxygen to the cathode occurs through the cracks which open and close as the temperature is, respectively, lowered and raised. Measurements at total gas pressures in the range 1–1000mbar indicate that the mode of diffusion is of the Knudsen-type up to 120mbar then tending towards mainly a bulk- type at 1000mbar. Crack dimensions and their relation to the variation of limiting current and temperature dependence for the region of bulk diffusion are treated theoretically. A good correlation with theory is obtained using the results from the two sources, namely, crack dimensions at room temperature and sensor characteristics in the bulk diffusion regime. This provides evidence for the mechanism proposed to explain both the magnitude and sign of the observed temperature coefficient. The value determined by microscopy for the differential coefficient of thermal expansion between the thick film and the substrate (α) was 1.1×10−6K−1. Also, characteristics of the sensor in the bulk diffusion region give a value for α/θ2 of 0.70×10−6K−1, where θ is the tortuosity factor of the slots. Hence, θ=1.2. This value is in agreement with the value determined by microscopy within the bounds of experimental uncertainty.
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    Journal of applied electrochemistry 29 (1999), S. 123-128 
    ISSN: 1572-8838
    Keywords: tin ; perchlorate ; citric acid ; pitting ; inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Potentiostatic and potentiodynamic studies were carried out to establish the inhibiting effects of citric acid on the pitting corrosion of tin. The critical potential (Ecrit), which leads to pitting or general corrosion, was determined in sodium perchlorate solution in the pH range 1.0 to 4.0. Pit nucleation and growth, at pH4.0, can be described by instantaneous nucleation followed by progressive nucleation. The results show that the minimum acid concentration needed to inhibit pitting of tin is 10−2m. Pitting occurrence by direct interaction between metal and perchlorate anions was observed.
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    Journal of applied electrochemistry 29 (1999), S. 51-57 
    ISSN: 1572-8838
    Keywords: codeposition Ni ; Mn ; S ; X-ray analysis ; structure ; texture ; properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Microstructural parameters such as coherent domain size, microstrain, dislocation density and texture of electrolytically plated Ni–Mn–S layers were investigated by X-ray analysis. Structural parameters, layer composition and the macroproperties are discussed and explained. With the help of a statistical regression analysis the correlation coefficient r2 and its relationship with the investigated parameters is determined. It is shown that the microstructural parameters play an important role in determining the macroscopic properties. The manganese concentration is shown to influence the structural parameters, but no influence of sulphur is found. It seems that a relationship of the structural parameters with the macroscopic properties is valid in general and is not a special case. There structural correlations can be used in general for processing electrolytic deposits for required applications.
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    Journal of applied electrochemistry 29 (1999), S. 59-63 
    ISSN: 1572-8838
    Keywords: CoxByHz nanoparticles ; borohydride reduction ; metal hydride electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The performance of electrodes, prepared from amorphous CoxByHz nanoparticles without additives, in 20% KOH solution was tested by means of cyclic voltammetry and chronopotentiometry. Peaks, assigned to hydrogen adsorption and desorption, are observed in the cyclic voltammograms. After charging, hydrogen atoms occupy different types of sites in the substrate, from which electrochemical desorption occurs. An increase in hydrogen content as a result of repeated cycling was established. Discharge capacity of the electrodes, estimated from the chronopotentiometric discharge curves obtained, is about 250mAhg−1. The observed changes in hydrogen and boron content, due to electrochemical treatment, indicate that the electrode material is an active participant in the whole electrochemical process. Hypotheses for the reaction mechanism are proposed.
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    Journal of applied electrochemistry 29 (1999), S. 1285-1289 
    ISSN: 1572-8838
    Keywords: AB2 alloy ; cell discharge capacity ; hydrogen storage alloy ; impedance ; silver/metal–hydride cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Silver/metal hydride (Ag/MH) cells of about 1 Ah capacity have been fabricated and their discharge characteristics at different rates of discharge, faradaic efficiency, cycle life and a.c. impedance have been evaluated. These cells comprise metal–hydride electrodes prepared by employing ∼60 μm powder of an AB2-Laves phase alloy of nominal composition Zr0.5Ti0.5V0.6Cr0.2Ni1.2 with PTFE binder on a nickel-mesh substrate as the negative plates and commercial-grade silver electrodes as the positive plates. The cells are positive limited and exhibit two distinct voltage plateaus characteristic of two-step reduction of AgO to Ag during their low rates of discharge between C/20 and C/10. This feature is, however, absent when the cells are discharged at C/5 rate. On charging the cells to 100% of their capacity, the faradaic efficiency is found to be 100%. The impedance of the Ag/MH cell is essentially due to the impedance of the silver electrodes, since MH electrodes offer negligible impedance. The cells may be subjected to a large number of charge–discharge cycles with little deterioration.
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  • 90
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    Journal of applied electrochemistry 29 (1999), S. 1171-1176 
    ISSN: 1572-8838
    Keywords: alloys ; cyclic voltammetry ; electrodeposition ; electroless deposition ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy deposition from a sulphate bath, containing sodium hypophosphite as reducer, was investigated. To increase the plating rate, the deposition parameters were optimized. The effect of process parameters (T, pH and [Zn2+]) on the plating rate and deposit composition was examined and it was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition. As a consequence, the percentage of zinc in the electroless Ni–Zn–P alloys never reaches high values. Using cyclic voltammetry the electrodeposition mechanism of Ni–Zn–P alloys was investigated. It was observed that the zinc deposition inhibits the nickel discharge and, as a consequence, its catalytic activity on hypophosphite oxidation. It was also found that increase in temperature or pH leads to the deposition of nickel rich alloys.
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  • 91
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    Journal of applied electrochemistry 29 (1999), S. 1217-1227 
    ISSN: 1572-8838
    Keywords: copper deposition ; copper foil ; copper nucleation ; electrocrystallization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Copper nucleation and growth on titanium substrates from concentrated acidic copper sulfate solutions was studied at 45 and 65∘C and high cathodic potentials. Electrochemical experiments allied to SEM examination were performed to characterize the mechanism of nucleation and its evolution with time. Particular emphasis was given to the influence of potential and agitation on the initial stages of nucleation and growth. Results indicated that most of copper nucleation on titanium from a 83 g dm−3 Cu2+ solution, at 65 ∘ C, is achieved in a matter of milliseconds. As expected, the initial stages of the copper nucleation and growth is strongly dependent of potential and temperature, and the influence of agitation is only evident at very high potentials. The calculated diffusion coefficients for Cu2+ at 45 and 65 ∘ C, under the experimental conditions, were found to be 9.16 × 10−6 and 1.62 × 10−5cm2 s−1, respectively.
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  • 92
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    Journal of applied electrochemistry 29 (1999), S. 1185-1190 
    ISSN: 1572-8838
    Keywords: carbon monoxide ; hydrogen ; infrared spectroscopy ; palladium ; poisoning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The oxidation of CO adsorbed on the surface of palladium electrodes loaded with different amounts of hydrogen was studied by single potential alteration infrared reflectance spectroscopy (SPAIRS). In the absence of hydrogen, only CO2 was detected during anodic oxidation of CO. Adsorption of CO in the presence of hydrogen in palladium led to a more negative onset of its electrooxidation, and the formation of other products, such as ethanol and formaldehyde, as well as CO_2. The results indicate that hydrogen occluded in palladium contributes to the displacement of carbon monoxide from the interface; this may assist in the continual electrooxidation of organic compounds at palladium electrodes.
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  • 93
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    Journal of applied electrochemistry 29 (1999), S. 1351-1354 
    ISSN: 1572-8838
    Keywords: electrocatalysts ; oxygen evolution/reduction ; spinel oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
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  • 94
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    Journal of applied electrochemistry 29 (1999), S. 137-145 
    ISSN: 1572-8838
    Keywords: aluminium electrolysis ; anode effect ; fluid dynamics ; gas evolution ; wettability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The so-called anode effect, particularly important in industrial alumina electrolysis, has mostly been interpreted as the consequence of altered wettability of the electrode surface by the melt. By means of a mathematical model assuming isolated large bubbles in contact with the electrode it is shown that the anode effect is the result of the combined action of fluid dynamics and wettability. The interpretation of the incipience of the anode effect obtained by means of a previous, completely different mathematical model is confirmed. The theoretical results are compared with experimental data by various authors.
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  • 95
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    Journal of applied electrochemistry 29 (1999), S. 221-227 
    ISSN: 1572-8838
    Keywords: electrohydrogenation ; electroreduction ; ethylpicolinate ; 2-hydroxymethylpyridine ; lead cathode ; pyridine nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electrolyses of ethylpicolinate in aqueous sulfuric acid solutions were performed on a lead cathode in galvanostatic mode. The reduction of the ester function was in competition with that of the pyridine nucleus. Study of the change in solution composition with time during electrolysis allowed evaluation of the influence of parameters such as acidity, current density, initial concentration of ethylpicolinate and temperature, on the competing formation of the different electrolysis products. Parameter values were chosen for synthesis of 2-hydroxymethylpyridine.
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  • 96
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    Journal of applied electrochemistry 29 (1999), S. 265-270 
    ISSN: 1572-8838
    Keywords: constant current ; electrosynthesis ; filter press ; p-hydroxybenzaldehyde ; sodium p-hydroxymandelate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrosynthesis of p-hydroxybenzaldehyde (PHB) from sodium p-hydroxymandelate (SPHM) was investigated and good synthesis conditions were obtained. The electrochemical reactor was a divided filter-press with carbon felt electrodes (anode and cathode). Two different anolytes were used depending on the membrane employed. Thus, a 0.6m SPHM 2.7m NaOH solution was used in conjunction with a cationic Nafion® 117 membrane while a 0.6m SPHM in 1.8m NaOH solution was employed with an anionic Ionac® MA-3475 membrane. The electrolysis was carried out at a constant current density of 100mAcm−2. A material yield of approximately 90% was obtained at an energy cost of 1.4–1.5kWhkg−1 PHB and a production of 49kg PHBm−2 day−1.
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  • 97
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    Journal of applied electrochemistry 29 (1999), S. 185-190 
    ISSN: 1572-8838
    Keywords: heat/mass transfer ; impinging jet ; limiting current technique ; shear stress ; turbulent jets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The surface local shear stress values were measured for a round submerged jet, with a fully developed turbulent velocity profile, impinging on a flat surface, using the electrochemical limiting current technique with the electrolyte consisting of potassium ferri- and ferrocyanide supported by aqueous sodium hydroxide. Experimental parameters were in the Reynolds number range 9200–73500, and in␣the nozzle-to-plate distance range 2–10. The measurements of local shear stress values on the impingement surface in the radial direction were taken, and the effect of the experimental parameters on the behaviour of the shear stress values was discussed.
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  • 98
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    Journal of applied electrochemistry 29 (1999), S. 165-170 
    ISSN: 1572-8838
    Keywords: active layer ; cermet anode ; diffusion layer ; substrate anode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract An approximate description of the SOFC cermet structure was performed on the basis of a combined optical and porosimetric structure analysis of the SOFC cermet anode and the results are described using the example of the SOFC substrate anode (anode with increased layer thickness). The electrode assembly consists of two layers. The electrochemically active layer of 70–90 μm corresponding the penetration depth of the electric field is located near the ZrO2 electrolyte. This layer thickness is also a function of porosity and pore radius distribution. The remaining electrode up to a layer thickness of about 2 mm basically acts only as a current and mass distributor. The corresponding diffusion overvoltage as a function of the structural properties was calculated.
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    Journal of applied electrochemistry 29 (1999), S. 1339-1345 
    ISSN: 1572-8838
    Keywords: copper corrosion inhibition ; EQCM ; STM ; 5-mercapto-1-phenyl-tetrazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The mechanism of copper corrosion and its inhibition were studied using electrochemical techniques, in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM) methods. The morphological changes of Cu (111) were followed in 0.1 M Na2SO4 solution at pH 2.95. The adsorption of 5-mercapto-1-phenyl-tetrazole (5-McPhTT) at different concentrations was studied. The anodic dissolution of copper in 0.1 M Na2SO4 was clearly modified and hindered by the addition of 5-McPhTT. The anodic current density was reduced sharply due to the adsorption of the inhibitor on the metal surface thus providing protection. EQCM data revealed that the addition of the inhibitor to the aggressive solution did not cause a continuous increase in the electrode mass. This fact indicates that the inhibitor effect in hindering copper corrosion was due to the adsorption of a monolayer or even a submonolayer.
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    Journal of applied electrochemistry 29 (1999), S. 1357-1358 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
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