Egbert Willem Meijer

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.

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.

Colourless nonlinear optical D-π-A polymers with sulphones as electron acceptors

Novel colourless side-chain methacrylate copolymers exhibiting relatively narrow charge-transfer bands at 335 nm and second-order optical nonlinearities up to d33= 4.3 pm V–1(at 1064 nm) have been synthesized and characterized.

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.

Poled Polymer For Frequency Doubling Of Diode Lasers

Aligning polar molecules imbedded in a polymer matrix by means of a high electric field, as demonstrated by Havinga and van Pelt,’ can introduce a significant polar orientation. This makes these materials suitable for secondorder nonlinear optical (NLO) effects, like electro-optical modulation2’3 and second-harmonic generation (SHG) .3,4 Especially for this last purpose polymeric materials are very promising, as they can easily be applied in optical waveguide geometries, thereby transforming low powers like those emitted by diode lasers into high intensities and consequently giving high conversion efficiencies. However, up to now no poled polymer has been reported that can be used to double the frequency of the emission of the common AlGaAs-GaAs laser diodes (/2 820 nm) . In this letter we describe polymers that were specifically designed for this purpose and present the optical properties that affect their performance in this specific application. The major requirements for the NLO moiety are a high first-order hyperpolarizability /3( 2w;w,o) and complete transparency at both the fundamental and the second-harmonic wavelength. As a small separation between the charge transfer (CT) band and the second harmonic gives a large resonant enhancement to fi (Ref. 3) a narrow CT band is obviously advantageous. After having screened a large number of chromophores for their linear and nonlinear optical properties,5 we have selected some stilbene compounds containing an alkylsulfone group as electron acceptor and an alkoxy group as electron donor, as favorable candidates. Some relevant properties of these molecules are listed in Table I.