Berthold Winkler

Blue electroluminescence devices based on parahexaphenyl

Abstract Homogeneous thin films of the organic oligomer parahexaphenyl (PHP) allow the application of this material as a stable emitting layer in blue electroluminescence (EL) devices. We used oligoazomethine (OAM) and diaminoctofluorobiphenyl (DOB) as charge transport layers, which allowed us to achieve excellent EL performance with enhanced EL quantum efficiencies above 1%, improved brightness up to 2000 cd/m2 Luminance and increased rectification ratio in excess of 103 compared to single layer devices.

Electroluminescent nanostructures in new polystyrene-oligo (phenylene-vinylene) graft copolymer

Abstract We present a new electroactive polymer, the polystyrene-oligo(phenylene-vinylene) (PS-OPV), in which nanostructured photoactive conjugated phenylene-vinylene segments are attached as sidechains to the polystyrene backbone. The number of phenylene-rings of the OPV segments is very homogeneous (2–4 rings), as the UV/vis absorption and photoluminescence (λ max =430nm) spectra compared to OPV oligomer spectra show. The photoluminescence quantum yield is very high. Electrochemical measurements were used to determine the electronic structure of the conjugated polymer. The PS-OPV was successfully used as a blue light emitting layer in single and multilayer electroluminescence devices

Novel fluorinated π-conjugated oligomers as electron transport materials in organic light emitting diodes

New partially fluorinated π-conjugated oligomers have been synthesised by transition metal catalysed coupling reactions. These electron deficient arenes were applied as electron transport materials in organic light emitting devices using the blue luminescing p-hexaphenyl as active material. The threshold voltage is affected by lower or higher values compared to the single layer device, while quantum efficiency increases with all prepared charge transport materials reaching values up to 3.4%. A multilayer device using a partially fluorinated trimer with poly(azomethine) as hole transport material showed a turn-on voltage of approximately 3.4 V.

Synthesis and characterization of a novel side-chain liquid crystalline poly(p-phenylenevinylene)

Abstract We describe the synthesis of soluble liquid crystalline poly( p -phenylenevinylene)s with cyanobiphenyl as the mesogenic group linked to the vinylene group via a flexible alkyl chain. The polymers were well characterized by spectroscopic methods (NMR, IR, UV—Vis, photoluminescence (PL)) and showed PL emission of green light with a maximum around 540 nm. Polarized UV—Vis spectroscopy of polymer films prepared on oriented substrates indicated a high orientation of the backbone and mesogenic units.

Synthesis and optical properties of highly fluorescent meta-para oligo-phenylenevinylenes

Abstract The synthesis of unsubstituted meta – para oligo-phenylenevinylene ( mp -OPV) was carried out via metathesis polycondensation (acyclic diene metathesis polymerisation ADMET) of commercially available divinylbenzene (55% in ethylvinylbenzene). A stable molybdenum carbene complex of the Schrock type served as initiator. The obtained mp -OPV, which is an intensively yellow powder, with a degree of polymerisation of 2–6 is soluble in CHCl 3 . This oligomer shows a photoluminescence quantum efficiency >50% and λ em lies in the blue-green range.

New transport layers for highly efficient organic electroluminescence devices

Multiheterostructure electroluminescence (EL) devices with blue emission color based on parahexaphenyl (PHP) as the emitting layer and various new organic materials as hole and/or electron transport layers (HTL, ETL) were fabricated to improve the EL efficiency. We present new ETLs, which were prepared via different metal-catalyzed coupling reactions of brominated educts in high yields. Utilizing these new organic materials enables us to obtain high performance of blue PHP EL devices with low threshold fields (0.3 MV/cm) and high external EL quantum efficiencies up to 3.4%.

Group IV Metallocene Bis(trimethylsilyl)acetylene Complexes as Catalysts in the Dehydrocoupling Polymerization of 1,2-Disubstituted Hydrodisilanes

Summary. The catalytic activities of five bis(trimethylsilyl)acetylene complexes of group IV metallocenes in the dehydrocoupling reaction of various 1,2-disubstituted hydrodisilanes were investigated. The reactions were monitored by GC/MS analysis in the early stages, and the polymers were characterized by NMR spectroscopy and gel permeation chromatography.Zusammenfassung. Die katalytische Aktivität von fünf Bis(trimethylsilyl)acetylen-Komplexen von Metallocenen der 4. Nebengruppe bei der dehydrierenden Polymerisation von verschiedenen 1,2-disubstituierten Disilanen wurde untersucht. Zu Beginn (während der Bildung von Oligomeren) wurden die Reaktionen mittels GC/MS verfolgt. Die erhaltenen Polymere wurden mittels NMR-Spektroskopie und Gelpermeationschromatographie charakterisiert.

A novel precursor route to poly(p-phenylene-1,3-butadiene-1,4-ylene)

Abstract Bifunctional esters containing terminal bromo aryl and vinyl groups were polymerized with Pd(0) catalyst to soluble precursor polymers, which could be easily converted to poly(p-phenylene-1,3-butadiene-1,4-ylene). The transformation into the conjugated polymer was investigated with DSC, TGA, FT-IR, UV/vis, PL and DI-MS. Resulting polymer shows a bathochromic shift of absorbance and photoluminescence spectra in comparison to PPP and PPV. The experimentally determined value for the bandgap energy E g is 2.25 eV, which was predicted due to theoretical calculations (E g = 2.06 eV).

Synthesis and optical properties of highly fluorescent oligo-(phenylene vinylene)

Abstract Oligo-and poly- mp -phenylene vinylenes were synthesized via metathesis and Heck coupling chemistry using (a) unsubstituted m and p -divinylbenzenes, (b) unsubstituted m and p -divinylbenzenes copolymerised with norbornene diacetate and (c) unsubstituted p divinylbenzene and 4-alkoxy-1,3-dibromobenzene (alkoxy = pentyloxy and decyloxy). For (a) it could be observed that there is a shift to the blue in the photoluminescence if the concentration of incorporated m -units in the oligomers is increased, for (b) that the quantum efficiency is > 50% and for (c) that the substituents have little influence on the photoluminescence.

Side Chain Liquid Crystalline Polymers Via ROMP

First we would like to give a brief introduction to the basic topics of this field which has become of great interest the past two decades. The liquid crystalline state in general can be seen as an intermediate state between the solid 3-dimensional perfectly ordered state and the liquid state. In the case of a classical solid to liquid phase transition the position and the orientation order is immediately lost. When a liquid crystalline phase is formed starting from the solid state, the order is lost stepwise. Therefore the different LC phases can be classified.