Triplet Excitation Scavenging in Films of Conjugated Polymers

Nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time using 1,3,5,7‐cyclooctatetraene, a compound that can efficiently quench the phosphorescence of polyfluorene without affecting its fluorescence (see spectra). The results suggest that nonvertical triplet scavengers might be promising candidates for controlling the triplet concentration in fluorescent high‐brightness organic devices.

     

The influence of pressure on the lower critical solution temperature miscibility behavior of aqueous solutions of poly(vinyl methyl ether) and the relation to the compositional curvature of the volume of mixing

In mixtures of PVME and water, the influence of pressure on the LCST miscibility gap is determined covering the whole composition range and pressures from atmospheric pressure up to 900 MPa. The cloud point curve at atmospheric pressure has the characteristic bimodal shape in agreement with literature data. Upon increasing pressure the cloud point curve at the low concentration side decreases with pressure, whereas at the high concentrations the cloud point curve increases with pressure. The overall influence of pressure results in a less pronounced bimodality and ultimately the bimodal shape disappears. In addition to the pressure dependence of the miscibility behavior, the density of mixtures of water and PVME are determined at atmospheric pressure. The experimental excess specific volumes are negative for all measured compositions, but the compositional curvature varies with composition. The curvature of the excess specific volume is positive for the higher concentrations but it is negative in the lower composition range. The density measurements are linked to the pressure dependence of the LCST miscibility behavior using exact thermodynamic relationships. The excess specific volume and miscibility results are shown to be in good agreement. Moreover, it is shown that the Clapeyron equation, which is exact for pure components and also frequently assumed to apply to mixtures, is not valid in the system PVME/water. The system PVME/water is an example where the usual approximation of one-to-one correspondence between curvature and excess volume does not apply. Finally, the molecular origins for the observed excess volume and miscibility behavior are briefly discussed from theoretical and molecular simulation points of view.     

Thermoelectric properties of a dilute graphite donor intercalation compound

Data on the in-plane thermal conductivity and thermoelectric power of a stage-5 potassium donor graphite intercalation compound are reported in the temperature range 3 < T < 300 K. In the lowest temperature range the electronic contribution dominates the thermal conductivity, while at higher temperature there is a dominant lattice contribution, which is much smaller than pristine graphite. The thermopower is negative in the whole temperature range.     

Two connected inverse spectral transforms

We establish a transformation which connects the potentials of the one-dimensional Dirac and Klein-Gordon operators. This transformation links the solutions of the nonlinear evolution equations solvable by means of the two inverse spectral transforms which use the Dirac and Klein-Gordon direct and inverse spectral problems.     

The effect of pressure on the oxidation of benzhydrol by alkaline permanganate

The rate of oxidation of benzhydrol and benzhydrol-d to benzophenone by alkaline permanganate has been measured over a pH range 10 to 12.5 and pressures from 1 to 1000 bar. The pressure effect on the rate is small, Δ$\text{V}$^≠ = ?6 to ?8 cm³mol^?1. This is held to support a hydrogen atom transfer in the rate-determining step.     

Hydrodynamic effects in interacting Fermi electron jets

We theoretically study hydrodynamic phenomena originating from electron-electron collisions in a two-dimensional Fermi system. We demonstrate that an electron beam sweeping past an aperture creates a pumping effect, attracting carriers from this aperture. This pumping effect originates from the specific electric potential distribution induced by the injected electrons. In the regions near the main stream of injected electrons, a positive potential is induced by the injected electrons. Thus, the normally repulsive Coulomb interaction leads to an attractive force in the Fermi system. This quantum pumping mechanism in a Fermi system differs qualitatively from the Bernoulli pumping effect in classical liquids. We also discuss possible experimental realizations.