Edsko Enno Havinga

The X-ray structure and MNDO calculations of α-terthienyl: A model for polythiophenes

Abstract The X-ray structure of α-terthienyl reveals two identical, crystallographically-independent molecules in the unit cell. Neighbouring thiophene moieties in α-terthienyl are placed antiparallel, while the molecule is almost planar, with torsional angles between the rings of about 6 – 9°. MNDO calculations of α-terthienyl show that great care should be taken in using calculations of this type for geometrical optimizations of polythiophenes.

PRECURSOR ROUTE PENTACENE METAL-INSULATOR-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS

Metal‐insulator‐semiconductor field‐effect transistors have been constructed with pentacene as the active semiconductor. The pentacene is processed by spin coating from a soluble precursor. A simple thermal conversion yields transistors with carrier mobilities as high as 9×10−3 cm2 V−1 s−1 and current modulations of the order of 105. Depletion of charge is essential to the device operation. Data for an invertor exhibiting voltage amplification are presented.

Spectra and electrical properties of soluble partially alkyl-substituted oligomers of thiophene up to 11 rings

Abstract A series of strictly α, α′-coupled oligomers of thiophene containing 3,4,5,6,7,9, and 11 rings and provided with 0 to 5 side groups (n-butyl, n-dodecyl or tert-butyl) have been prepared and their melting points, solubilities in chloroform, UV-vis absorption and emission spectra of both solutions and solids, and conductivities after doping with iodine have been measured. The dependence of the conjugation length on the number of rings, and on the number, length, and position of side groups is discussed.

Correlation between the superconducting transition temperature and crystal structure of high-Tc cuprate compounds

Abstract For the various p-type cuprate superconductors we have calculated the formal valence for the copper and the oxygen ions in the central CuO 2 planes from bond lengths according to Zachariasen rules. It is shown that in all structures these values correlate remarkably well with the maximum critical temperature. The correlation found shows that T c, max increases the more the holes in the CuO 2 planes prefer the oxygen sites over the copper sites. In a correlated electron picture this implies a higher value for U − Δ + W 2 .

Poly-1,4-diketones obtained by the Stetter reaction: a new route to conducting heterocyclic polymers

The electrically conducting, alternating copolymers para-phenylene-2,5-pyrrole and para-phenylene-2,5-thiophene were prepared by the Stetter reaction followed by ring closure and subsequent doping with I2 or AsF5.

Polymers for Electronics and Photonics

Recently, polymers show promising prospects as active constituents of optical and electronic devices, especially polymers for nonlinear optics and conducting polymers. In a remote future even organic ferromagnets and molecular electronics may become more than wishful thinking. For this reason several fundamental aspects of these materials are the subject of intensive research. In this paper we will review the present state of the art in these new fields of polymers for electronics and photonics. Special emphasis will be laid on recent results from our laboratories.

Poly-1,2-Azepines by the Photopolymerization of Phenyl Azides: A New Route to Processible Conducting Polymers

Processibility of conjugated and conducting polymers is one of the major topics in the chemistry and applications of these polymers. In this paper we describe the gasphase photopolymerization of phenyl azides, that yield thin films of poly-1,2-azepines on a variety of substrates. The photochemistry occurs at the interface of substrate and gas-phase and the polymer is grown at the surface of the substrate. High resolution patterns of poly-1,2-azepines are formed when a photomask is used in this gasphase photopolymerization. Upon oxidative doping with iodine or arsenic pentafluoride these polymers exhibit conductivities up to 0.01 S/cm. Mechanism, kinetics and versatility of the photopolymerization of phenyl azide and a series of substituted phenyl azides is discussed.

The effect of molecular orientation on the conductivity of iodine intercalates of 1,4-trans-polybutadiene

Of three polybutadienes, 1,4-cis-PB, 1,2-syndio-PB and 1,4-tarns-PB, only the latter forms an intercalate with iodine. Maximum conductivity of 1,4-trans-PB/I2 is 0.9.102 cm 1 in ambient atmosphere. Intercalation in stretch-oriented samples, obtained via calendering or solid state coextrusion is impaired leading to markedly lower conductivities. The effect of enhanced molecular orientation with respect to conductivity is adverse. These results undermine a conclusion reached by A.J. Thakur in a study of iodine intercalates of polydienes, implying that a conjugated backbone is not a necessary prerequisite for an effective organic conductor.