The field dependence of mobility in molecularly doped polymers under the conditions of nonequilibrium transport

A multiple-trapping model has been used to numerically analyze the effects of the nonequilibrium transport of holes on the field dependence of drift mobility as obtained in a time-of-flight experiment. The intrinsic field dependence has been assigned to the frequency factor in the form of the Poole-Frenkel law. Strongly dispersive transport, as well as a nonequilibrium-charge-transfer regime given by the Gaussian disorder model, has been considered. It has been established that the currently accepted approach to the analysis of the field dependence of mobility needs to be reexamined.     

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.     

Radiation-induced conductivity in polymers during long-term irradiation

Radiation-induced conductivity (RIC) in polystyrene, poly(ethylene terephthalate), polyvinylcarbazole, and low-density polyethylene during long-term (to 3.6 × 10³ s) irradiation with 50-keV electrons (dose rate of 6–830 Gy/s) was experimentally and theoretically studied. It was shown that the nonmonotonic RIC kinetics in the polymers is a direct consequence of the generation and the subsequent transport of charge carriers in them in the presence of traps distributed over a broad energy range almost according to the exponential law. This phenomenon has no relation to degradation and crosslinking processes that occur in irradiated polymers. The nonmonotonic RIC kinetics in polymers is a universal phenomenon, and it is described satisfactorily in terms of the Rose-Fowler-Vaisberg model.     

The effect of temperature on carrier transport in molecularly doped polycarbonate

Hole transport in low-polarity polystyrene (PS) doped with 10 wt % tritolylamine was studied. The radiation-induced mode of the time-of-flight technique (TOF) with the carrier generation zone of a variable thickness was used. A theoretical treatment of the data in terms of the Gaussian disorder model has shown the mobility value to be fundamentally inconsistent with the flat shape of the plateau, a contradiction that cannot be resolved within the framework of this model. It has been shown that hole transport is actually dispersive, rather than quasi-equilibrium. The contribution of radiation conductivity of the polymer matrix to the TOF signal was evaluated.     

Predicting the solubility of xenon in n-hexane and n-perfluorohexane: a simulation and theoretical study

The solubility of xenon in n-hexane and n-perfluorohexane has been studied using both molecular simulation and a version of the SAFT approach (SAFT-VR). The calculations were performed close to the saturation line of each solvent, between 200 K and 450 K, which exceeds the smaller temperature range where experimental data are available in the literature. Molecular dynamics simulations, associated with Widom's test particle insertion method, were used to calculate the residual chemical potential of xenon in n-hexane and n-perfluorohexane and the corresponding Henry's law coefficients. The simulation results overestimate the solubility of xenon in both solvents when simple geometric combining rules are used, but are in good agreement if a binary interaction parameter is included. With the SAFT-VR approach we are able to reproduce the experimental solubility for xenon in n-hexane, using simple Lorentz-Berthelot rules to describe the unlike interaction. In the case of n-perfluorohexane as a solvent, a binary interaction parameter was introduced, taken from previous work on (xe + C₂F₆) mixtures. Overall, good agreement is obtained between the simulation, theoretical and experimental data.     

The influence of electric field on the mobility of holes in molecularly doped polycarbonate

The data on the influence of an applied electric field (field dependence) on the mobility of holes in molecularly doped polycarbonate samples prepared at Eastman Kodak laboratories and at the Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, were compared. The results were generally close (the dispersive transport and almost coinciding mobilities in medium fields), but, at high fields, substantial differences in the field dependence were observed. This is at variance with the almost universal applicability of the Pool-Frenkel law reported in the literature.     

Studying the Initial Stage of Nucleation and Growth of a New Phase during Cathodic Intercalation of Lithium into Aluminum

Kinetics of cathodic intercalation of lithium into aluminum from a 0.5 M LiCl solution in dimethylformamide at the stage of nucleation and growth of intermetallic compound -LiAl is studied by one- and two-pulse potentiostatic methods. If the length of the first potential pulse is short, the current at the beginning of the second pulse is proportional to the overvoltage squared. The experimental data point to a lamellar-spiral growth of -LiAl crystals at the initial stage of their development and to a change in the balance between different growth mechanisms as a function of the overvoltage and surface coverage by -LiAl.     

Absorption spectra of 3-OXO-2,3-dihydrothio-naphthene and its derivatives

Conditions have been found for the iodination of naphtho[1,8-bc]thiophen-2-one. A number of new thioindigoid dyes have been synthesized and their photochemical isomerization has been performed in benzene.For Communication XVI, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1034–1036, August, 1973.