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1.
Mustafa Özden Ergun Ekinci A. Ersin Karagözler 《Journal of Solid State Electrochemistry》1998,2(6):427-431
A polyindoline permselective polymer film was readily synthesized by an electrochemical polymerization of indoline in an
aqueous solution of KCl at a potential of 0.4 V vs Ag/AgCl. The amperometric responses of the polyindoline film-coated platinum
electrodes to electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and
urea) substances were measured at a potential of 0.7 V. Effects of various variables such as film thickness, concentrations
of monomer and electrolyte, and pH on the permselective behavior of the polymeric membrane were systematically investigated
and the optimal values were determined. It was found that permselective polyindoline-coated electrodes prepared in this one-step
procedure permitted hydrogen peroxide oxidation while it prevented interference due to oxidizable species such as ascorbic
acid and oxalic acid. As a result, it is believed that this polymeric membrane, owing to its permselective character, can
be used as the protective material in the construction of hydrogen peroxide-based biosensors.
Received: 10 November 1997 / Accepted: 27 January 1998 相似文献
2.
Following an approach to density functional theory calculations based on the matrix representation of operators, we implemented
a scheme as an alternative to traditional grid-based methods. These techniques allow integrals over exchange-correlation operators
to be evaluated through matrix manipulations. Both local and gradient-corrected functionals can be treated in a similar way.
After deriving all the required expressions, selected examples with various functionals are given.
Received: 7 March 1998 / Accepted: 21 May 1998 / Published on line: 6 August 1998 相似文献
3.
Michael E. G. Lyons Judith Murphy Thomas Bannon Serge Rebouillat 《Journal of Solid State Electrochemistry》1999,3(3):154-162
The processes of reaction, diffusion and electromigration of a charged substrate within an electronically conducting polymer
film deposited on an inert supporting electrode are examined in terms of a quantitative analysis and solution of the pertinent
differential equations. An analytical expression for the concentration profiles of substrate within the polymer layer is derived
and a theoretical expression for the corresponding steady-state amperometric current response is presented. The transport
and kinetics of the substrate are discussed in terms of a dimensionless reaction/diffusion parameter γ and a migration/diffusion
parameter β.
Received: 13 March 1998 / Accepted: 17 July 1998 相似文献
4.
Giuseppe Casalbore-Miceli Nadia Camaioni Giancardo Beggiato Alessandro Geri M. C. Gallazzi 《Journal of Solid State Electrochemistry》1998,3(1):15-24
The dark and photovoltaic characteristics of the Schottky junction between n-doped silicon and a conducting polymer in its
oxidised form, poly(4,4′-dipentoxy-2,2′-bithiophene), have been determined as a function of the nature of the electrical contact
on the polymer side. It was found that the dark and photovoltaic performances of the device depended strongly on this contact.
An aluminium contact is oxidised by the polymer and an aluminium oxide film forms between the polymer and the contact through
which the forward current is controlled by charge injection. The devices assembled with indium tin oxide, platinum and gold
contacts show better characteristics than the ones with aluminium contact; in the last three cases, however, a faradic charge
transfer reaction on the contact, probably the oxidation of some amount of water contained in the polymer, affects the characteristics
of the junction.
Received: 27 December 1997 / Accepted: 24 April 1998 相似文献
5.
Xinping Hou Kok Siong Siow Zhiqiang Gao 《Journal of Solid State Electrochemistry》1999,3(7-8):387-391
One of the approaches to improving the ionic conductivity and the mechanical strength of a solid polymer electrolyte is to
use polymers in modified forms, such as polymer blends, copolymers and cross-linked polymers. In this study, a new polymer
electrolyte based on the acrylonitrile-butadiene-styrene (ABS) copolymer has been prepared. The ionic conductivity, electrochemical
stability and interfacial characteristics of the polymer electrolyte in contact with a lithium electrode have been investigated.
The temperature dependence of the conductivity below 20 °C can be described by the Arrhenius equation, and above 20 °C by
the VTF equation. Lithium passivation appeared to have taken place in the system. The conductivity and electrochemical characteristics
of the system are somewhat similar to those of PAN-based polymer electrolytes.
Received: 9 December 1998 / Accepted: 9 March 1999 相似文献
6.
Celestino Angeli Renzo Cimiraglia Maurizio Persico 《Theoretical chemistry accounts》1998,100(5-6):324-328
Within the frame of multireference perturbation configuration interaction we have developed a fast algorithm, based on diagrammatic
techniques, for the calculation of the first-order correction to the one-particle density matrix. As an example of an application
we have chosen the evaluation of the dipole moment of the CO molecule, where utilization of the first-order density is shown
to corroborate the variational calculation.
Received: 4 August 1998 / Accepted: 21 September 1998 / Published online: 16 November 1998 相似文献
7.
Ursula Rammelt Sven Bischoff Mohamed El-Dessouki Renate Schulze Waldfried Plieth Lother Dunsch 《Journal of Solid State Electrochemistry》1999,3(7-8):406-411
The influence of the nature of the anions on the conductivity of polypyrrole films in aqueous solution was investigated by
photocurrent spectroscopy combined with electrochemical impedance spectroscopy in dependence on the potential. As demonstrated,
the conductivity of polypyrrole films at negative potentials can vary from a semiconducting to an ionic conducting state,
depending on the size of the charge-compensating counter-anion incorporated during the electropolymerization. The reduced
polypyrrole shows semiconducting properties when small anions are inserted, releasing the polymer matrix during the reduction
process. The polymer can than be considered as a two-layer system, consisting of a semiconducting layer and a porous layer.
Measurements at different thickness of polypyrrole films have shown that the position of the semiconducting layer is in the
electrode/polymer interface. The ohmic resistance of the semiconducting layer is in the range 1–5 kΩ, the capacitance approaches
a value of 100–500 nF and the flatband potential is −0.62 VSCE. If large anions are incorporated, cation insertion takes place during reduction, the electrolyte content in the polymer
then is relatively high and the polymer's behaviour is similar to that of an ionic conductor. The results are presented and
discussed together with the example of methylsulfonate as a relatively small anion and polystyrenesulfonate as a large anion.
Received: 28 July 1998 / Accepted: 22 February 1999 相似文献
8.
The surface diffusion of physical-vapour-deposited metal atoms on thermoplastic polymer substrates was investigated. In accordance
with the hypothesis of the “classical” atomistic diffusion model, diffusion coefficients are derived from a Monte Carlo simulation.
Because the “classical” atomistic diffusion model neglects the desorption of the metal atoms, the absolute diffusion data
obtained in our investigations should only be considered as rough estimates. It is more the intention of our work to present
relative values in order to correlate the metal surface diffusion on polymer substrates with their physical states (morphologies
and surface dynamics). As expected, the diffusivity of metal atoms is strongly influenced by the chemical affinity (“reactivity”)
between the metal atoms and the polymer substrate. Furthermore, the diffusivity strongly depends on the physical state of
the polymer substrate. On polymer surfaces above the glass-transition temperature the surface diffusivity of metal atoms is
1 order of magnitude higher than the diffusivity below the glass-transition temperature.
Received: 9 April 1999/Accepted in revised form: 21 October 1999 相似文献
9.
Renato Colle Raffaele Montagnani Oriano Salvetti 《Theoretical chemistry accounts》1999,101(4):262-268
A molecular fragment approach is used to compute ionization potentials, transition energies and electron affinities of pyrrole
oligomers. The calculations of these quantities include correlation energy contributions evaluated by integrating a functional
of the two-particle Hartree-Fock density matrix. Pyrrole oligomers with chains of up to 16 rings are explicitly treated and
the calculated quantities extrapolated to the limit of an infinitely long chain, to predict polymer properties. The theoretical
results compare favorably with data on gas-phase ionization potentials deduced from experimental oxidation potentials, and
with optical absorption peaks recorded in solution or on solid films. The large discrepancy between electron affinities obtained
from the eigenvalues of an independent-particle frozen-orbital calculation and those obtained from separate, correlated calculations
on the neutral system and the negative ion in shown.
Received: 24 March 1998 / Accepted: 2 September 1998 / Published online: 7 December 1998 相似文献
10.
Temperature-sensitive micron-sized monodispersed composite polymer particles were prepared by seeded copolymerization of
dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 1.77 μm-sized monodispersed polystyrene seed particles.
The change in surface property at temperature above and below 35 °C was examined by differential scanning calorimetry, trypsin
activity and the adsorption/ desorption behaviors of low molecular weight cationic emulsifier as well as biomolecules.
Received: 6 August 1997 Accepted: 16 January 1998 相似文献
11.
J. Andrés M. Oliva V. S. Safont V. Moliner O. Tapia 《Theoretical chemistry accounts》1999,101(1-3):234-240
The carboxylation and oxygenation processes of a model substrate, 3,4-dihydroxy-2-pentanone, have been theoreticaly characterized
as a set of steps, mimicking the corresponding reactions of D-ribulose-1,5-bisphosphate catalyzed by rubisco. A theoretical characterization is carried out of transition-state structures
and possible molecular intermediates represented as saddle points of index 1 and minimum energy structures, respectively.
The quantum chemical characterization, at the HF/3-21G calculation level, of these stationary points is used to rationalize
and to discuss both catalyzed sequences. The reported set of these stationary points maps out most experimental aspects of
the reaction pathways for the real system.
Received: 24 March 1998 / Accepted: 3 September 1998 / Published online: 10 December 1998 相似文献
12.
S. L. Koontz R. V. Devivar W. J. Peltier J. E. Pearson T. A. Guillory J. D. Fabricant 《Colloid and polymer science》1999,277(6):557-562
We report synthesis and characterization of a macroporous polymeric material containing a covalently immobilized pore-surface
phase of well-defined thickness, gel-phase porosity and organic functional group content. The pore surfaces of otherwise inert
macroporous (32 μm mean pore size) ultrahigh-molecular-weight polyethylene (UHMWPE) are aminated throughout using a low-pressure
flowing-discharge process to enable covalent immobilization of lightly cross-linked polymer colloid particles on all pore
surfaces in the monolith. Solvent swelling and chemical derivitization of the covalently immobilized polymer colloid particles
produce a pore-surface gel phase of well-defined thickness, organic amine content, and gel-phase porosity. The low degree
of cross-linking in the polymer colloid particles prevents dissolution of the immobilized colloid in good solvents and enables
the formation of pore-surface gel phases having high gel porosity on swelling in good solvents. The pore-surface amination
introduced by the flowing discharge process varies by less than 17% through 5-mm thickness of the macroporous UHMWPE material.
The properties of the pore-surface gel phase also vary by less than 17% through the cross section. The pore-surface immobilized
polymer colloid particles swell by a factor of 10 in water and tetrahydrofuran after derivitization with polyethylene glycol.
Received: 20 November 1998 Accepted in revised form: 21 January 1999 相似文献
13.
The repulsive ground electronic state X2Σ+ of HeH is strongly coupled to the Rydberg states at small interatomic distances. Such large couplings also occur between
some of the Rydberg states. HeH+ ions that capture an electron in a Rydberg state end up in separated He and H atoms by indirect predissociation. This paper
presents a study of potential functions and pertinent matrix elements involving the lowest electronic states: the 2Σ+ states, X, A, C, and D, and the 2Π states B and E. Individual transition rates as well as total radiative and non-radiative lifetimes have been computed for
the lowest vibrational and rotational levels.
Received: 22 June 1998 / Accepted: 21 August 1998 / Published online: 12 October 1998 相似文献
14.
Rheology of an aqueous solution of an end-capped poly(ethylene glycol) polymer at high concentration
Generally it is observed that the viscosity of an aqueous solution of a hydrophobically modified polymer increases with concentration;
however, here it is shown that the viscosity profile of an end-capped poly(ethylene glycol) polymer passes through a maximum.
Thus, a substantial decrease in viscosity is observed at high concentrations (≥50 wt%). The observation is suggested to be
due to a gradual change, on the molecular level, from a structure containing micellelike structures that are interconnected
via polymer bridges to a more meltlike state, where micro segregation in hydrophilic and hydrophobic regions is less pronounced.
Received: 23 October 1998 Accepted in revised form: 10 March 1999 相似文献
15.
Frank Jensen 《Theoretical chemistry accounts》1998,99(5):295-300
A total of 36 stationary points have been located on the H2CO potential energy surface by means of gradient extremal following. These 36 points are believed to represent all the important
stationary points on this surface. There is no indication that the structure of the surface becomes less complicated as the
size of the basis set is enlarged at the Hartree-Fock level of theory, but many of the second- and third-order saddle points
disappear when electron correlation is introduced. Of the ten first-order saddle points (transition structures) located, the
majority have reaction paths entering the associated minima in a side-on approach, i.e. these cannot be located by uphill
walking from the minimum.
Received: 5 February 1998 / Accepted: 21 May 1998 / Published online: 29 July 1998 相似文献
16.
Micron-sized, monodispersed highly styrene-“adsorbed” particles having snow-man shape were prepared by the dynamic swelling
method (DSM) with tightly cross-linked polymer seed particles as follows. First, 3.8 μm-sized monodispersed polystyrene (PS)/
poly(divinylbenzene) (PDVB) (PS/PDVB = 1/10 wt. ratio) composite particles produced by seeded polymerization utilizing DSM
were dispersed in an ethanol/water (6/4, w/w) solution dissolving styrene monomer, and poly(vinyl alcohol) as a stabilizer.
Second, water was subsequently added to the dispersion with a micro-feeder at a rate of 2.88 ml/h at room temperature. The
cross-linked seed particles adsorbed a large amount of styrene onto the surfaces and resulted in mono-dispersed highly styrene-“adsorbed”
snow-man shape particles having about 10 μm in diameter.
Received: 16 April 1998 Accepted: 9 June 1998 相似文献
17.
Production of soft core/hard shell composite polymer particles by the stepwise heterocoagulation method with heat treatment 总被引:1,自引:0,他引:1
Soft core/hard shell composite polymer particle was prepared by the stepwise heterocoagulation, which was proposed by authors
in 1990, of many cationic hard small polymer particles (SPs) onto an anionic soft large polymer particle (LP). The powder
was obtained by freeze-drying at 0 °C which was higher than glass transition temperature of LP (−7 °C) and lower than that of SP (90 °C).
Received: 9 December 1997 Accepted: 12 May 1998 相似文献
18.
V. Tirtaatmadja K. C. Tam R. D. Jenkins D. R. Bassett 《Colloid and polymer science》1999,277(2-3):276-281
Hydrophobically modified alkali-soluble emulsion (HASE) polymer is solubilized by the addition of a base. When the pH is
increased to greater than 6.5, methacrylic acids on the polymer backbone are neutralized and the carboxylated latex polymer
goes into solution causing a large increase in the viscosity due to inter-molecular associations of the hydrophobes. The stability
of the viscosity of the polymer solution at pH in the range 9–10 was studied in the presence of a strong (NaOH) and a weak
[1-amino-1-methylpropanol (AMP)] base. No change in the viscosity or the moduli was observed for the polymer in AMP. Reduction
in the viscous and elastic properties of the polymer solution in NaOH was observed after 4 weeks. Such small changes are detectable
using the superposition of oscillation on the steady shear technique. The decrease in the viscoelastic properties is attributed
to the hydrolysis reaction of the urethane groups of the macromonomer, which resulted in a decrease in the number of hydrophobes
per polymer chain. It is recommended that a weak base be used to neutralise the HASE polymer in order to avoid the possibility
of compositional changes in the polymer after neutralisation for more than 6 weeks.
Received: 19 May 1998 Accepted in revised form: 26 October 1998 相似文献
19.
Highly hydrophobically modified (with n-dodecylamide chain) linear poly(acrylic acid)s (HHMPAAH) and poly(sodium acrylate)s (HHMPAANa) with various degrees of grafting
(τ) were synthesized and used as emulsifiers of the n-dodecane/water system. The type of emulsion, oil in water (O/W) or water in oil (W/O), was investigated as a function of
the polymer chemical structure (τ, salt or acid form of the copolymer) and aqueous phase electrolyte concentration (NaNO3). Increasing τ and/or salt concentration was found to favor the formation of inverse emulsions. Direct liquid–liquid dispersions
are more likely to form with poly(sodium acrylate)s than with poly(acrylic acid)s. Hence, field variables such as τ, pH and
ionic strength are relevant parameters to control emulsion type. Moreover, a balanced polyelectrolyte neither soluble in oil
nor in water was synthesized for the first time. With this original emulsifier, the dispersion type was found to change from
O/W to W/O with polymer salting out. The work provides convenient model system for fundamental studies of polymer conformation
at liquid–liquid interfaces.
Received: 31 March 1998 Accepted: 30 April 1998 相似文献
20.
Immobilized metal-ion affinity chromatography of peptides on metalloporphyrin stationary phases 总被引:1,自引:0,他引:1
Magdalena Biesaga Jowita Orska Dariusz Fiertek J. Izdebski M. Trojanowicz 《Analytical and bioanalytical chemistry》1999,364(1-2):160-164
The retention of selected dipeptides and tripeptides containing tyrosine was examined. As stationary phase an aminopropylated
silica gel loaded with covalently linked tetraphenylporphyrin was used. The effect of metalization of porphyrin with Cu(II)
and Zn(II) on retention was investigated. The observed separation is based on a mixed mechanism involving π-π and hydrophobic
interactions as well as complex formation between immobilized metal ions and peptides. A satisfactory separation was demonstrated
for C-peptide and bovine insulin. The possibility of separation of various insulins was also investigated.
Received: 10 August 1998 / Revised: 21 December 1998 / Accepted: 28 December 1998 相似文献