Florence Geneste

Versatile synthesis of various conjugated aromatic homo- and copolymers

In recent years, variously substituted derivatives of poly(1,4-phenylene vinylene)s have emerged as efficient candidates for the emissive layer in polymer light emitting diodes. The synthetic routes for these polymers divide between precursor routes and those leading to fully conjugated solvent-processible polymers. The Gilch dehydrohalogenation polycondensation has largely been used for the latter class. In this presentation, we describe a novel family of 2,3-disubstituted aromatic precursors, derived from catechol, and we report their efficient polymerisation as homo- and copolymers with, for example, silyl-substituted derivatives to give materials which are highly fluorescent and serve as interesting materials in polymer LEDs.

Efficient electroluminescent poly(p-phenylene vinylene) copolymers for application in LEDs

A new and efficient route for the synthesis of poly(p-phenylene vinylene)s (PPVs) containing dialkoxy substituents at the 2,3-positions of the phenylene ring of the polymer backbone has been developed. In comparison to the more classical 2,5-substitution pattern these PPV polymers show a significantly blue-shifted longest-wavelength absorption (lambda (max)) and emisson band (lambda (em)). Two statistical PPV copolymers comprising 2,3-dibutoxy and dimethyloctylsilyl- or 2,5-bis(dimethyloctylsilyl) side-chains were synthesized via the Gilch dehydrohalogenation route. Double-layer light-emitting devices (LEDs) of the configuration ITO/PEDOT/polymer/Ca were demonstrated to combine high electroluminescence efficiencies with low turn-on voltages.

Synthesis of conjugated polymers for application in light-emitting diodes (PLEDs)

Abstract In the field of electroluminescent organic materials, conjugated polymers have attracted much attention over recent years owing to their versatile synthesis, their relative ease of processing and the possibility of establishing predictive structure–function relationships between chemical structures and optical properties. This review article highlights the advances made in the synthesis of conjugated polymers for use in light-emitting devices (LEDs) covering the last two years. Research efforts were largely directed towards the improvement of the synthesis of monomers and polymers involving classical polymer structures such as poly( p -phenylene vinylene)s (PPVs), poly( p -phenylene)s (PPPs), poly(2,7-fluorene)s (PFs), or poly(2,5-thienylene)s (PTs). Control of the color of emission by modulation of the effective conjugation length, improving balanced charge injection and transport properties by introduction of electron-donating or -withdrawing moieties directly into the polymer backbone or enhancement of the emission efficiency by attempts to influence film morphology are some examples of recent research directions. All these investigations contributed to a significantly better understanding of the chemical and physical processes spanning topics from the manufacturing process to the operation of LEDs and leading to the announcement of the first commercial products. In addition to the classical π -conjugated polymers a few examples of rather unusual structures have also emerged.

The copolymer route to new luminescent materials for LEDs

The synthesis of the highly fluorescent mono- and bis-silylated poly(1,4-phenylene vinylene) derivatives 1 and 2 is reported. The Gilch dehydrohalogenation polycondensation and the Horner synthesis of strictly alternating copolymers have been used to prepare the copolymers 8-11 and 14, 16-18, respectively, in which the tunability of various optoelectonic properties may be examined systematically.

Efficient blue–green light emitting poly(1,4-phenylene vinylene) copolymers

2,3-Dialkoxy-substituted poly(1,4-phenylene vinylene) (PPV) homo- and co-polymers have been prepared by the Gilch dehydrohalogenation polycondensation of the corresponding bishalomethyl-substituted benzene monomers, and double layer light emitting devices fabricated with these materials exhibited high electroluminescence efficiencies with low turn-on voltages.

Ortho-Metallation as a key step for the synthesis of silyl substituted Poly(p-phenylenevinylene)s

A new synthetic pathway for the preparation of silyl substituted poly(p-phenylenevinylene) (PPV) precursors has been investigated. By using directed ortho-metallation, it has been possible to significantly improve the overall yields for the synthesis of mono- and disubstituted silyl monomers. We have also synthesised a new unsymmetrically substituted monomer. From these monomers we have synthesised the following polymers: DMOS-PPV 1 (DiMethylOctlylSilyl-PPV), BDMOS-PPV 2 (Bis-(DiMethylOctlylSilyl)-PPV)), BDMDS-PPV 3 (Bis-(DiMethylDecyllSilyl))-PPV and C8C10-PPV (2-(dimethyloctylsilyl)-5-(dimethyldecylsilyl))-PPV 4.

New routes to monomers and polymers for LEDs

The synthesis of poly(1,4-phenylene vinylene)s (PPVs) containing a 2,3-dialkoxy substitution pattern has been developed. Poly[2,3-bis(2-ethylhexyloxy)-1,4-phenylene vinylene] (BEH-PPV) 4 was prepared by Gilch polycondensation, and its optical properties were compared with the recently discussed poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV) 1. The precursors for the Gilch method have traditionally been prepared by methods which have certain disadvantages. These can be overcome by the use of directed metallation reactions which are illustrated in the synthesis of some poly(2,5-disilyl-substituted 1,4-arylene vinylene) derivatives.

Synthesis of New Building Blocks for Light Emitting Polymers

The synthesis of poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV) has allowed the study of this material as the active layer in a multiple layer device using a composite combination of polymer and Alq 3 with an oxadiazole as electron injection/transport layers. The luminous efficiency of the resulting device was significantly improved as a result of this combination of transport layers. An entirely new approach to the synthesis of monomers for PPV precursors is described in which the 2- and 5- substituents are introduced by directed metallation groups (DMGs) which ultimately become the bis(halomethyl) groups.

Versatile Syntheses of Various Homo- and Copolymers of Poly(1,4-Arylene Vinylene)S

The synthesis of poly(1,4-phenylene vinylene)s (PPVs) containing a 2,3-dialkoxy substitution pattern has been developed. Poly[2,3-bis(2-ethylhexyloxy)-1,4-phenylene vinylene)] (BEH-PPV, 4) was prepared and its optical properties compared with the recently discussed poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV, 1), which showed in contrast to classical 2,5-substituted PPV derivatives a notable blue-shift of the longest-wavelength absorption (λ max ) and a considerable increase of the solid-state photoluminescence (PL) efficiency. The two statistical PPV copolymers 5 and 6 comprising 2,3-dibutoxy and dimethyloctylsilyl- or 2,5-bis(dimethyloctylsilyl) side-chains, respectively, were synthesized via the Gilch dehydrohalogenation route. Double-layer light-emitting devices (LEDs) were demonstrated to combine high electroluminescence efficiencies with low turn-on voltages.

Design and synthesis of conjugated materials for efficient optoelectronic devices

Highly luminescent poly(arylene vinylene)s can be prepared by a range of polycondensation methods. In this paper we report the synthesis of useful monomers and their application in the Gilch dehydrohalogenation and Wittig polycondensation methods to prepare highly luminescent poly(1,4-phenylene vinylene) (PPV) homo- and copolymers for use in light emitting devices.