John F. Yanus

Hole transport in solid solutions of substituted triarylmethanes in bisphenol-A-polycarbonate

The time-of-flight and xerographic discharge techniques have been used to study electronic transport in films of dialkylamine-substituted triarylmethanes in bisphenol-A-polycarbonate binder. The hole mobility has been measured as a function of applied electric field, concentration of the molecules, and temperature. The results indicate that charge transport occurs by hopping among localized states associated with the molecule. In chemical terms, the hole transport involves a series of one-electron oxidation-reduction steps involving the organic molecules. The influence of some substituent groups on the electronic transport in these aromatic diamines has also been studied.

Electrical properties of a series of carbazole polymers

The electrical transport properties of three vinyl carbazole polymers have been examined to determine if the observed variations in NMR chemical shifts resulting from inter−ring shielding effects could be correlated with carrier mobilities in the polymers. Drift mobilities were measured in films of the polymers overcoated with thin layers of amorphous Se using a xerographic discharge technique. Under the conditions for observing trap free space charge limited currents the hole mobilities were calculated from Child’s law. The three polymers exhibited mobilities varying as the square of the electric field over the range of fields examined. P2VK which showed the overall largest upfield shift of the aromatic protons exhibited a mobility of 1.4×10−6 cm2/V⋅sec at a field of 4×105 V/cm. PVK which exhibit an intermediate degree of shielding had a mobility of 1.4×10−7 cm2/V⋅sec and P3VK which exhibits the smallest shielding effect had a mobility of 2.4×10−8 cm2/V⋅sec both at equivalent fields. Although P2VK showed...

Comparison of Hole Hopping Diffusion and Migration in a Triarylamine Containing Polymer

Abstract Electron hopping charge transport rates in a triarylamine containing polymer were investigated electrochemically in the presence of a contacting electrolyte and in the solid state (absence of liquid electrolyte). Electron hopping diffusion coefficients were measured by steady state voltammetry in thin polymer films on Au microelectrode interdigitated arrays. In addition, zero-field extrapolated electron hopping mobilities and zero-field mobility activation energies are obtained from time-of-flight (TOF) measurements. Electron hopping diffusion coefficients (Dh, cm2/s) and diffusion activation energies obtained in solid state electrochemical experiments can be correlated with zero-field hole mobilities (cm2/V-s) and activation energies via the Einstein relationship.

The Effect of Rapid Cooling and a Magnetic Field on the NMR Relaxations and Thermal Behavior of [N-(P-ethoxybenzylidene)-p-butylaniline] (EBBA)

Abstract Rapid cooling of EBBA from the nematic phase results in a mixture of amorphous and crystalline material. The presence of these two phases are detected in the nmr relaxation data by the occurrence of two separate relaxations for reorientation of the methyl/ethyl groups in each of these phases. Aligning of the molecules in the liquid crystalline state by a magnetic field prior to crystallization gives rise to morphological changes which are manifested by a melt temperature some two degrees higher than the normal crystal melt.