Semiconducting polymers based on charge-transfer complexes. IV. Electrical properties and structure of polymeric charge-transfer complexes

Model electron donor molecules, 10-methylphenothiazine and 4-(methylthio)anisole, and polymeric electron donors which contained these molecules on the side chains of N-acyl-substituted polyethylenimines, were complexed with the electron acceptors, dichlorodicyanoquinone (DDQ), tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), and tetranitrofluorenone (TNF). The model donors formed 1:1 complexes with all the acceptors except TCNE. The polymeric donors formed amorphous complexes with DDQ, TCNQ, and TCNE. Crystalline complexes were formed with TNF which had low melting points (lower than the model complexes and the pure polymer). This is apparently due to poor lateral packing of the polymer chains. Electrical resistivities were lower for all the polymer complexes than for the corresponding model complexes. Electrical resistivity also decreased with increase in complex crystallinity. In the best case the polymer complex was two hundred times as conducting as the model. The concentration of unpaired electrons measured by EPR was nearly independent of temperature. Most of the electrons seen are trapped and do not participate in conduction. Thermal activation energies for conduction were in the range of 0.5–1.8 eV and were nearly equal for the model and corresponding polymeric complexes. Elongation of polymer complex with TCNQ by rolling produces a decrease in resistivity in the roll direction, although the complex is amorphous. This reinforces the hypothesis that conduction is parallel to the polymer backbone. A polymer–tetranitrofluorenone complex was photoconducting, though the photoconductivity was smaller than the dark conductivity at the level of illumination used. Dember and Seebeck effects indicated that the major carrier in the complex was holes.     

Trefoil Knots without Tritangent Planes

A quick proof is given that trefoil knots constructed explicitlyas (3,2) curves on a torus by stereographic projection fromS³ have no tritangent planes.     

Island models and the catalytic oxidation of carbon monoxide and carbon monoxide-olefin mixtures

Simple kinetic models which take account of the formation of islands of adsorbate on a catalyst surface are proposed, and are compared with an elementary step model for CO oxidation and oxidation of a CO-butene or CO-propylene mixture. The island models give fits to data from step change transient experiments which are comparable with the elementary step model, and give better fits to steady-state and continuously oscillating data (the latter with hydrocarbon present). Theoretical predictions of chaotic behaviour in CO oxidation can be obtained with the island models. Comparisons between island models suggest that islands of CO have the most significant effect on simulations at the experimental conditions.     

On wave propagation in inextensible elastic bodies

In this paper we study the propagation of acceleration waves in inextensible elastic bodies. ¹ While the computations are but an exercise, the results are interesting and quite unlike the corresponding results for unconstrained bodies. Indeed, a wave travelling in the direction of inextensibility must necessarily be transverse, and, when the reaction stress is compressive and sufficiently large, the corresponding speed of propagation becomes non-real, so that even transverse waves fail to exist.We also study (infinitesimal) progressive waves and we find the corresponding propagation condition to be the same as that for acceleration waves. Here, however, non-real speeds of propagation have a definite physical meaning: they imply exponential growth of the wave. Thus, in particular, when the reaction stress is compressive and sufficiently large, a transverse progressive wave travelling in the direction of inextensibility grows without bound. We conjecture that this indicates the presence of local buckling. ²     

The ESR spectrum of arsenic tetrafluoride

The ESR spectrum of AsF₄, generated by γ-radiolysis of a solid solution of AsF₃ in SF₆, is reported. The ⁷⁵As hyperfine interaction is 1576 G, and the two kinds of ¹⁹F nuclei have interactions of 49 G (equatorial) and 238 G (apical). These data are compared with those from the well-known PF₄ radical.     

Cyclisation reactions of alkenyl β-ketoesters involving a novel phenylseleno group migration

A number of alkenyl-substituted α-phenylseleno β-ketoesters can be cyclised in the presence of acidic catalysts in which a novel migration of phenylseleno moiety occurs.     

Core models for form factors and Drell-Yan-West relations

Expressions are derived for the vector and axial form factors of nucleons in the covariant parton model. Using core models their asymptotic behaviors are obtained and related to the spin averaged and polarized structure functions of electroproduction, giving rise to relations of the Drell-Yan-West type. It is found that the model is gauge invariant and has no second-class axial currents. For the polarized structure functions, the Drell-Yan-West relation depends on the core spin.