Electrophysical properties of latent tracks of heavy ions in polymers

Poly(ethylene terephthalate) films irradiated by high-energy ions without additional etching have been studied. It has been shown that tracks of heavy high-energy ions in poly(ethylene terephthalate) may be considered to be single through capillaries suitable for studying electrophysical properties. It has been revealed that the surface electrical conductivities of electrolyte solutions (KCl, LiCl, MgCl₂, and BaCl₂) in the tracks of nonetched membranes are substantially higher, while the surface charges are noticeably lower, than those of etched membranes.     

Radiofrequency-discharge plasma treatment of heavy ion-irradiated poly(ethylene terephthalate) films

The effects of treatment in a radiofrequency (RF) discharge plasma on the rate of chemical etching of the tracks made by xenon ions (with an energy of ~1 MeV/nucleon) in poly(ethylene terephthalate) (PETP) films were investigated. The influence of plasma treatment conditions on the structure and properties of nuclear track membranes formed by etching was studied. It was found that the RF plasma treatment of heavy ion-bombarded PETP films leads to a decrease in etchability of both tracks and the starting polymer matrix. The changes in track and matrix etchability due to crosslinking of the polymer surface layer were shown to be responsible for the asymmetry of the track membrane structure.     

Study of the mechanism of the polarographic reduction of N-acylsydnoneimines

The polarographic reduction of the N-phenylcarbamoyl derivative of 3-( -phenylisopropyl)-sydnoneimine (sidnokarb) in aqueous alcohol media was investigated. It is shown that, depending on the protonation rate of both the starting depolarizer and the intermediates in the reduction of sidnokarb, six or four electrons may be consumed to give, in the first case, a derivative of the amino acid amide and ammonium ions and, in the second case, the corresponding hydrazine derivative.Translated from Geterotsiklicheskikh Soedinenii, No. 1, pp. 33–38, January, 1977.     

In situ and Real-Time Monitoring of Plasma-Induced Etching of PET and Acrylic Films

Residual gas analysis (RGA) and optical emission spectroscopy have been evaluated as potential in situ techniques for the detection of plasma-induced polymer surface etching. The detection is based on the measurement of CO and CO₂ species formed in the gas phase following oxidation of the etching fragments released from the polymer surface. Experiments were performed on poly(ethylene terephthalate) and UV-cured acrylic (tripropylene glycol diacrylate) films exposed to O₂ RF (13.56 MHz) plasmas. A linear correlation is obtained between the formation of CO and the polymer etching rate over the entire experimental range, but discrepancies appear for the formation of CO₂ at high treatment powers (etching rate > 1.0 g/min.cm²). This behavior is attributed to a deficit of oxidizing agents relative to the generation of etching fragments. The results suggest that both RGA and optical emission spectroscopy can be used to monitor in situ and in real-time the etching of polymer surfaces during plasma treatment.     

Electrokinetic study of etching latent tracks of accelerated heavy ions in poly(ethylene terephthalate) and polyimide

The etching of latent tracks and pore formation in track membranes are studied. It is shown that the incorporation of K⁺ and Ba²⁺ ions into alkaline solutions accelerates the etching of poly(ethylene terephthalate) (PET) and latent tracks in it. The etching is accelerated due to a decrease in the negative surface charge of PET surface and the pores in track membranes. Isoelectric points are determined for PET and polyimide track membranes and it is established that they depend on pore diameter. As the pore diameter is enlarged from 30 to 70 nm, the magnitude of the negative surface charge rises seemingly due to the increase in the concentration of carboxyl groups on the pore surface. It is assumed that this effect is due to either a high mobility of carboxyl groups in a gel, which is formed on pore walls as a result of etching latent tracks, or a displacement of the slipping plane caused by a decrease in the thickness of the gel layer.     

Evaluation of the Distribution Depth of Charge Injected by Direct-Current Discharge Plasma into Thin Polyimide and Poly(ethylene terephthalate) Films

The dynamic capacitor method was proposed for determining the distribution depth of negative charge induced in the surface layers of thin polymer films under exposure to a dc discharge as a result of trapping plasma-injected electrons, and equations for calculation were obtained. Charge distribution in thin poly(pyromellitimide) and poly(ethylene terephthalate) films with different thickness (1–6 m) was experimentally studied, and the negative charge due to the injection of electrons from plasma was found penetrate to a depth greater than 0.5 m.     

Selective assembly of cyclodextrins on poly(ethylene oxide)–poly(propylene oxide) block copolymers

This paper presents a computational study on the formation of a molecular necklace formed by specific threading of cyclodextrins (CDs) on block copolymers. Structural as well as energetic principles for the selective complexation of - and -cyclodextrin with poly(ethylene oxide)–poly(propylene oxide) block copolymers (PEO–PPO) are elucidated considering a diblock copolymer of equimolecular composition (PEO)4–(PPO)4 as guest. A non-statistical distribution of CDs, i.e. -CDs primarily located on the PEO chain and -CDs on PPO blocks of the polymer, is based on a variety of structural features and energetic preferences considering both potential as well as solvation energies. This selectivity becomes already obvious considering 1:1 complexes between PEO and PPO monomers and the two CDs, but is increasingly evident when calculating higher order ensembles. Besides the host–guest interaction, docking between CDs themselves is an important, also non-statistical, prerequisite for the self-assembly of highly ordered tubes. The formation of intermolecular hydrogen bonds between adjacent CDs in a tubular aggregate gives an important contribution to the overall stability of the molecular necklace. The net effect, based on the preferential interaction between host and guest as well as between the host molecules themselves, results in the formation of a stable, highly ordered macromolecular, multicomponent aggregate.     

Etching of tracks of accelerated heavy ions in poly(ethylene terephthalate) and some physicochemical properties of track membranes

The features of etching of latent tracks of heavy ions in poly(ethylene terephthalate) up to pore formation were investigated. It was found that the etching process included the following stages: (1) electrolyte penetration into the pores due to capillary forces and removal of monomeric radiolysis products; (2) swelling of the cross-linked (due to secondary electrons) polymer areas around the tracks to give the gel layer; (3) removal of the gel layer and the formation of track membranes with a pore radius of 40–50 Å. The radiation-chemical processes in polymers influence the physicochemical properties of the obtained membranes. The microrelief of the membrane surface was studied by atomic-force microscopy.     

Plutonium-244 and strange xenon components in the solar system

A number of strange xenon components have been reported in the literature during the past three decades; for example, AVCC (average carbonaceous chondrite), CCF (carbonaceous chondrite fission) xenon, xenon-X, xenon-H, xenon-L, xenon-S, xenon-U, SUCOR (surface correlated xenon), BEOC (Bern Oberflächen-Correliert) xenon, and so on. It is often assumed that they reprsent the isotopic compositions of more or less pure or primordial components of xenon. If one attempts to interpret the existing xenon isotope data for meteorites and lunar samples, assuming that they are pure or primordial, however, one encounters all sorts of problems and no coherent theory concerning the variation of the isotopic composition of xenon in the solar system emerges. We have therefore re-examined over 4,000 sets of existing xenon isotope data for meteorites and lunar samples. The results indicate that these strange xenon components are mixtures of²⁴⁴Pu fission xenon and atmospheric xenon, whose isotopic compositions have been altered by the processes of a) mass-fractionation, b) spallation and c) neutron-capture reactions.     

Acid-base and catalytic properties of iron-antimony oxide catalysts

Iron antimonate, whose strongest acidic sites (Fe³⁺) are blocked by weak acidic aprotic centers Sb³⁺, is an active and selective catalyst for the ammoxidation of propylene.

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, (Fe⁺³) Sb⁺³, .

     

Factors determining pore shape in polycarbonate track membranes

The formation of pores in polycarbonate films irradiated by accelerated ions upon their treatment with alkali solution containing a surfactant was studied. It was found that the pore shape is determined by both the structure of the initial film and the peculiarities of interaction of a surfactant with a polymer surface and its transfer to a track. Because of the inhomogeneity of the initial material, the track pore cross section varies along the pore length. The presence of a surfactant leads to an additional effect. Being adsorbed onto the film surface and at the entrances of etched tracks of heavy ions, surfactant molecules tend to decrease the etching rate, thus leading to the formation of spindle-shaped pores. Thus, the use of a surfactant as a component of the chemical etching solution makes it possible to vary the pore shape of track membranes in a directional manner, optimizing their efficiency and selectivity.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 725–732.Original Russian Text Copyright © 2004 by Apel, Blonskaya, Orelovich, Akimenko, Sartowska, Dmitriev.     

Fast DSC applied to the crystallization of polypropylene

In an effort to find the limit of crystallization of polypropylene, a series of quantitative and semiquantitative DSC experiments at rates up to 10,000 deg/min are described. Even at these fast rates polypropylene crystallized on cooling between 350±15 K and 280±6 K. No fully amorphous polypropylene was produced. No initial stage crystallization to the condis state could be proven by quenching after partial crystallization.

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Zusammenfassung Eine Reihe von quantitativen und semiquentitativen DSC-Versuchen mit Aufheizgeschwindigkeiten bis 10000 K/min wurden ausgeführt, um die Grenze der Kristallisation von Polypropylen festzustellen. Sogar bei diesen schnellen Aufheizgeschwindigkeiten kristallisiert Polypropylen beim Abkühlen zwischen 350±15 K und 280±6 K. Kein völlig amorphes Polypropylen wurde erhalten.

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, 10 000 /. 350±15 280±6 . « » . .

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This work was supported in part by a grant of Hercules, Inc. to the ATHAS effort and in part by the Polymers Program of the National Science Foundation (Grant number DMR 8317097). The experimentation was helped by an instrument gift by the Celanese Company.     

Simultaneous oxidation of CH4 and SO2 over vanadium and palladium containing catalysts

The kinetics of deep oxidation of CH₄ and SO₂ over complex vanadium catalysts with and without palladium additives and over silica-supported palladium has been studied. Sulfur dioxide increases the rate of CH₄ oxidation, not affecting the reaction mechanism, whereas CH₄ does not effect SO₂ oxidation on the catalysts studied.

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Peculiarities of the formation of track-etched membranes by the data of atomic force microscopy and X-ray scattering

Atomic force microscopy (AFM) is employed to obtain information on the main stages of the preparation of ultrafiltration track-etched membranes based on poly(ethylene terephthalate) (PET). The surface structure of initial commercial samples of PET films and the same films irradiated with various fluxes of accelerated heavy ions and subsequently treated with alkaline that results in the formation of pores owing to track etching is studied. It is shown that the order of the aforementioned stages of the formation of track-etched membranes with various porosities (from 0.02 to 6%) at a typical pore size of about 50 nm leads only to slight changes in surface structural parameters and does not fundamentally affect the polymer structure formed by spherulites with sizes that are comparable with the pore sizes. In this case, nearly the same content of the crystalline phase in the initial film and track-etched membrane are identified by large-angle X-ray scattering. The picture of X-ray scattering by track-etched membranes at small angles fully corresponds to the scattering on cylindrical pores with a diameter of about 50 nm. The analysis of the set of roughness profiles of the surfaces of initial films and track-etched membranes obtained by the AFM technique makes it possible to determine and introduce—in addition to standard parameters of the surface, the mean value of roughness and its standard deviation the correlation length characterizing the mean distance at which the memory of the roughness value is lost. It is shown that treatments resulting in the formation of track-etched membranes favor an increase in the values of roughness and practically do not affect the mean correlation length, thus supporting the conclusion of the invariance of the main structural parameters of the PET surface.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 2, 2005, pp. 248–258.Original Russian Text Copyright © 2005 by Solovieva, Timofeeva, Erina, Vstovsky, Krivandin, Shatalova, Apel, Mchedlishvili, Timashev.     

The effect of surfactant concentration on the geometry of pores resulting from etching of poly(ethylene naphthalate) films irradiated by high-energy ions

The influence of temperature and concentrations of an alkali and a surfactant in etching solutions on the structural and transport characteristics of membranes produced by etching latent tracks of high-energy heavy ions in poly(ethylene naphthalate) films has been studied. The presence of a surfactant provides the formation of spindle-shaped pores narrowing in the direction toward the film surfaces. A procedure has been developed for the quantitative assessment of the degree of widening of spindle-shaped pores in their central part. The transport properties of track membranes with spindle-shaped and cylindrical pores have been compared.     

Study of pore formation during etching of latent tracks of accelerated heavy ions in poly(ethylene terephthalate) by atomic force microscopy

The process of transformation of latent tacks of accelerated heavy ions of poly(ethylene terephthalate) into pores and the formation of a porous structure of track membranes was studied by atomic force microscopy. It was shown that on initial etching, 10-nm high knolls with an average diameter of 800–1000 Å are formed in place of tracks. Based on the knolls, through channels are formed, which emerge on the surface as conical cavities. It was shown that further etching gives first cylindrical channels of diameter 800–1000 Å, which then undergo radial etching.     

Micropatterning of Inorganic-Organic Hybrid Coating Films from Various Tri-Functional Silicon Alkoxides with a Double Bond in Their Organic Components

Inorganic-organic hybrid coating films were prepared from various trifunctional silicon alkoxides with a C=C double bond in their organic components, such as vinyltriethoxysilane (VTES), allyltriethoxysilane (ATES) or trimethoxysilylpropylmethacrylate (TMSPM), and zirconium n-tetrapropoxide modified with methacrylic acid. UV light from a high-pressure mercury lamp was irradiated through a photomask on the hybrid films, and this irradiation increased refractive index and microhardness of the films and decreased solubility of the films in alcohol or alkaline solution. IR spectra of the coating films have shown that C=C bonds in these trifunctional silicon alkoxides were polymerized with the UV irradiation. Patterns with a width of about 10 m and thickness of about 5–15 m were formed by the etching of unirradiated region of the films. Since VTES and ATES have a shorter organic chain than TMSPM, the hybrid films prepared from VTES or ATES are expected to show small optical loss in the near-infrared region due to C—H bonds in their use as waveguides.     

TEM investigation of TiNx-PACVD-coatings

The wear resistance of cermet cutting tools can be remarkably increased by TiN_x coatings. These layers are deposited at substrate temperatures of 723 K, 773 K and 973 K using a plasma-assisted chemical vapour deposition (PACVD) process. TEM investigations combined with EDXS analysis and electron diffraction gave information on structure and composition of the TiN_x layers and the interface range. X-ray structure investigations were performed additionally.The structure and the chlorine content of layers and interfaces change in dependence on the deposition temperature. All coatings show a columnar structure, but the fibre diameter increases with temperature. The fine-grained TiN_x layer deposited at 723 K has the highest chlorine content, a low-developed columnar structure and a 111 texture. The coatings deposited at 773 K and 973 K contain less chlorine impurities and have a 100 preferred orientation. The fibre structures at 723 K and 773 K can be resolved into single crystallites. By TEM investigations the fibres formed at 773 K are proved to be an accumulation of neighbouring and similarly oriented crystallites. Grain size determined by X-ray analysis and fibre diameter agree with each other. Grain sizes determined more exactly from TEM images are 6 nm at 723 K, 10 nm at 773 K and 30 nm at 973 K. In the interface region the thickness and the chlorine content of this zone decreases with increasing deposition temperature and simultaneously the layer adhesion increases.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Electroreduction Kinetics of Palladium(II) Complexes with α-Alanine: A Polarographic Study

The kinetics of the electroreduction of palladium(II) complexes with -alanine are studied on a dropping mercury electrode in solutions containing various supporting electrolytes (NaF, Na₂SO₄, NaClO₄). The study is carried out at variable concentrations of palladium(II) alaninate complexes, the ligand, and the supporting electrolyte, in the pH interval extending from 3 to 11. The obtained values of the half-wave potential for the electroreduction of palladium(II) complexes with -alanine and the diffusion coefficient for palladium(II) alaninate complexes suggest that, in the acidic and alkaline solutions studied, the slow electrochemical stage involves chelate dialaninate palladium complexes Pd(ala)₂. Palladium(II) complexes underwent reduction on the positively-charged surface of DME without any preceding chemical stages. This process was hindered by anions of the supporting electrolyte adsorbed on DME, and in alkaline solutions, by the alaninate ions as well.     

Modification of the Surfaces of Polymer Films Irradiated by Heavy Ions and Nucleopore Nanofilters by XeF2 Vapors

The effect of xenon difluoride (XeF₂) vapors on the surface properties of the polymer films irradiated by heavy ions and of the nucleopore nanofilters produced from these films is studied. The procedure for modifying nucleopore membranes made of poly(ethylene terephthalate) and polyimide in XeF₂ vapors is developed. The hydrophilicity, electrosurface properties, and selectivity of modified membranes are investigated. It is shown that the water contact angle on the membrane surface decreases as a result of modification, and the extent of its change depends on the duration and temperature of membrane treatment. Electrokinetic measurements did not reveal any changes in the surface charge during the modification of the membranes prepared from poly(ethylene terephthalate), but their ion selectivity increased twofold. It is shown that the hydrodynamic diameter of the pores of modified membranes reversibly decreases with an increase in transmembrane pressure. The dislosed effects are explained by the presence of an elastoplastic gel-layer on the surfaces of the membrane and its pores. The gel-layer accumulates considerable surface and bulk charges and is characterized by the high hydraulic resistance hindering the convective ion transport.