The nature of the field dependence of drift mobility in molecularly doped polymers

A direct experimental comparison is performed for the field dependences of drift and effective mobilities of holes in a polar molecularly doped polymer (polycarbonate containing 30 wt % p-diethylaminobenzaldehyde diphenylhydrazone), which are measured by the time-of-flight method during the bulk irradiation of polymer samples with a pulse of fast electrons. A numerical simulation of the time-of-flight experiments is conducted with the use of the multiple-trapping model with the Gaussian energy trap distribution. The parameters of the model are determined during independent measurements. It is shown that, because of the nonequilibrium state of the transport of holes under the conditions of the time-of-flight experiment, the true Poole–Frenkel constant (0.27 (μm/V)^1/2) makes up only a part of the experimentally measured value (0.39 (μm/V)^1/2).     

Study of the effect of organo-substituted trialkoxysilanes on the textural and structural properties of mesoporous silica

The effect of additives of organo-substituted trialkoxysilanes: (3-aminopropyl)triethoxysilane (APTES), (2-cyanoethyl)triethoxysilane (CNETES), and tris(trimethylsiloxy)silane (TTMSS) as cosources of silica on its textural and structural properties was studied. The influence of organo-substituted trialkoxysilane additives on the variation of porous structure parameters of mesoporous silica during the hydrothermal treatment was demonstrated. The synthesized mesoporous silica samples were characterized by low-temperature nitrogen adsorption, X-ray powder diffraction, scanning electron microscopy, thermal and elemental analysis, and Raman spectroscopy.     

Dynamics of three-component exchange on a cationite with lithium manganese spinel structure

The dynamics of the sorption of lithium ions on a cationite with lithium manganese spinel structure from neutral solutions against the background of a large amount of sodium ions was studied. It was demonstrated that the dynamics of the ion exchange of these ions from their mixed solutions differs significantly from that observed for their individual solutions. The experimental results can be explained by assuming that, at a large concentration of sodium ions in the solution, they saturate the surface of the cationite and that lithium ions are predominantly exchanged for sodium ions. This assumption is supported by the results of a mathematical modeling.     

Universal technique for studying electron transport in polymers

A universal technique was developed for studying electron transport in polymers, which consists in the combination of the time-of-flight technique in the surface and bulk carrier generation modes with measurement of transient radiation-induced conductivity. Central to the technique in question is the time-of-flight method with homogeneous irradiation. The procedure was implemented on the basis of an ELA-50 electron beam device with variable electron energy (3–50 keV). The practicability of the universal technique was demonstrated using the model polymers polyvinylcarbazole and molecularly doped polycarbonate as examples.     

Theoretical analysis of the Rose-Fowler-Vaisberg model: Dipolar conductivity

Results of numerical calculations on the kinetics of radiation-induced conductivity (current transients) in a case polymer in terms of the Rose-Fowler-Vaisberg model assuming dipolar carrier transport (irradiation times of 10⁴–10⁶ s) are reported. Unlike the case of unipolar transport, the pattern of current transients noticeably changes at times after passing a maximum in current. A steady-state value is still attained; however, its increase relative to the case of unipolar conductivity is disproportionately high with respect to a relatively small value of the parameter χ, which characterizes the relative contribution of minority carriers to the current. Allowance for the formation of radiation traps during irradiation somewhat mitigates this effect; however, the discrepancy between the conclusions of the theory for the two types of conduction strongly increases for the estimates of polymer recovery time after preliminary irradiation.     

Kinetics of wetting of a compacted powder by aqueous solutions of surface active agents

Summary The capillary rise of aqueous solutions of anionic wetting agents into a compacted powder of an organic chromium complex is discussed on the basis of the Washburn-Rideal equation expanded to account for the porous structure parameters.At the porosity 1 —/6, corresponding to the loosest packing of monodisperse spheres the penetration rate is found to be mostly governed by the effective tensions operative at the moving three phase line of contact in case no deflocculation intervenes.

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Zusammenfassung Der Kapillaraufstieg wässeriger Lösungen anionischer Netzmittel in gepreßtem Pulver eines organischen Chrom-Komplexes wird durch die erweiterte Gleichung vonWashburn-Rideal wiedergegeben, in der die Parameter der porösen Struktur mit einbezogen werden.Bei der Porosität 1 —/6, die der lockersten Anordnung gleichförmiger Kugeln entspricht, wird die Eindringgeschwindigkeit meistens durch die an der sich bewegenden Dreiphasengrenze wirkenden Grenzflächenspannungen bestimmt, wenn keine Peptisation eintritt.

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Paper presented at the XII Intern. Congr. Fat Research, Milan, September 1974.     

Generation of excess charge carriers in molecularly doped polymers by electron-beam irradiation

The processes of generation and transport of excess charge carriers in molecularly doped polycarbonate and polystyrene were experimentally studied at room temperature. The polymers were ionized by 7-and 50-keV electrons. The radiation-chemical yield of free ions was determined by means of the universal method based on the combination of the time-of-flight technique in two carrier generation modes (surface and bulk generation) with the measurement of nonsteady-state conductivity. It was shown that the radiation-chemical yield of free ions under irradiation by 7-keV electrons is almost the same as that in the case of 50-keV electrons, despite the substantially different values of the linear energy transfer for these electrons.     

Comparison of the properties of phospholipid surfaces formed on HPA and L1 biosensor chips for the binding of the coagulation factor VIII.

Binding of a coagulation factor VIII to phosphatidylserine-containing membranes is critical for exerting its cofactor activity. The use of surface plasmon resonance allows studying factor VIII interaction with immobilized phospholipids. In the present study we compared factor VIII-binding properties of phospholipid surfaces immobilized on L1 and HPA Biacore chips in the form of a flexible bilayer and rigid monolayer, respectively. We demonstrated that immobilized phospholipid surfaces with physiological contents of PS and PE formed on L1 but not on HPA chip closely mimic intact phospholipid vesicles in their factor VIII and thrombin-activated factor VIII (factor VIIIa) binding properties.     

Influence of the temperature-time conditions on the textural and structural properties of mesoporous silicon dioxide synthesized in an ammonia-alcohol medium

The conditions for the formation of mesostructural silica materials (MSMs) in the ammonia-alcohol media were determined. Mesoporous silicon dioxide was synthesized by the template liquid-phase condensation method at high concentrations of the surfactant. The effect exerted by temperature and time of the synthesis, autoclaving, and by organosilane additive [(trimethylsiloxy)silane] used in synthesis on the structural and textural properties of the mesoporous material was determined. The temperature-time conditions for the preparation of mesostructured silicon dioxide were optimized.     

The role played by a polymer matrix in the transfer of charge carriers in molecularly doped polumers

Transient current curves were recorded for polystyrene and polycarbonate doped with 15 wt % tritolylamine using both surface and volume charge carrier generation. The multiple trapping model was used to perform numerical calculations of time-of-flight curves for the published Gaussian disorder model parameters. The calculation results were compared with the experimental data. It was shown that the experimental and calculated curves satisfactorily coincided. The flat plateau observed in time-of-flight curves should not be associated with the establishment of a quasi-equilibrium transport regime.