Photoinduced intramolecular charge transfer in porphyrin–viologen dyads has been investigated as a potential method leading to optical limiting in the nanosecond range. Solutions of these dyads in acetonitrile were studied by picosecond and nanosecond time-resolved fluorescence and absorption spectroscopy. Both methods give evidence of efficient photoinduced charge separation. Nonlinear transmission measurements around 600 nm with nanosecond laser pulses have shown that the dyad solution leads to a lower transmission at high incident fluences (>1 J/cm2) than the model porphyrin solution. Moreover, this dyad solution is more efficient than a solution of porphyrin with added viologen, both solutions having the same quenching efficiency.

Six homopolymers derived from the naphthalimide emitting moiety have been synthesized and characterized by UV-visible absorption and photoluminescence (PL). These polymers differ either by the nature of the backbone (polymethylmethacrylate PMA or polystyrene PS) or by the N-substituent. All the polymers show a green electroluminescence (EL). A bilayer diode emitted a maximum luminance as high as 7100 cd/m(2) and exhibited a maximum external quantum yield of 1%.

The influence of the introduction of a dopant molecule, namely DCM, in a matrix of a naphthalimide derived polymer (PNI) is studied by means of UV-visible absorption spectroscopy, photoluminescence emission and excitation spectrometry, and 2D photoluminescence spectrometry. We demonstrate that, contrary to previous observations on similar systems, energy transfer occurs between PNI and DCM. Moreover, photoluminescent (PL) and electroluminescent (EL) emissions are assigned to arise from the same excited state.

We used a side-chain polymer based on a high-electron affinity TEA) naphhalimide moiety (PNI), to fabricate single and double-layer light-emitting diodes (LEDs) with improved efficiency in the green spectral region. The chromophore is attached to a polymethacrylate backbone through a spacer and is characterised by a 30% photoluminescence quantum yield. In single-layer light-emitting diodes we find that the electroluminescence efficiency is not limited by Al cathodes a!, for poly(p-phenylene vinylene), PPV, as expected from consideration of the EA. We also report maximum internal quantum efficiencies of about 1.7% for Ca and 0.9% for Al in double-layer devices where PPV serves as both hole-injector and emitter. Tuning of emission in the red is possible by dye-doping (at high concentration) the PNI and causing the emission to happen in this layer. Unexpectedly, not only does the dye-doping of PNI red-shifts the emission spectrum, but also affects significantly the charge transport properties and in particular reduces the driving field necessary for electroluminescence in both single-and double-layer LEDs and we propose this effect as one of the factors for the lifetime increase upon doping recently reported in the literature [J. Shi, C.W. Tang, Appl. Phys. Lett. 70 (1997) 1665.]. (C) 1998 Elsevier Science B.V.

We report the fabrication of efficient green light-emitting diodes using a side-chain random polymer based on a high electron affinity (EA) naphthalimide moiety (PNI). The chromophore is attached to a polymethacrylate backbone through a spacer, and emits in the green with high efficiency (30% photoluminescence quantum yield). In single-layer light-emitting diodes (LEDs), we find that the electroluminescence quantum efficiency is not limited by Al cathodes as for poly(p-phenylene vinylene), PPV, and we attribute this to the increased EA. We also report maximum internal quantum efficiencies of about 1.7% for Ca and 0.9% for Al in double-layer devices where PPV serves as both hole injector and emitter. Compared to some oxadiazole based electron injection/transport layers, PNI gives higher efficiencies at high currents, and longer lifetimes. Tuning of emission in the red is possible by dye doping (at high concentration) the PNI and causing the emission to happen in this layer. We discuss the properties of the different device configurations from the viewpoint of the electronic structure of the materials and, in particular, the influence of the thickness of the individual layers on both quantum (photon/electron) and luminous (Lumen/W) efficiency and driving conditions. Unexpectedly, we find that not only does the dye doping of PNI redshift the emission spectrum, but also affects significantly the charge transport properties, and in particular reduces the driving field necessary for electroluminescence in both single and double-layer LEDs.

A series of 4-aminonaphthalimide functionalized polymers has been synthesized. They differ by the nature of their backbone: (either a polymethacrylate or a polystyrene) and by the nature of the substituent at the imide nitrogen atom. The absorption and emission properties of these polymers have been investigated. Photoluminescence quantum yields in the solid state up to 35% were observed. Cyclic voltammetry in conjunction with UV-visible spectrometry have been performed in order to determine the HOMO and LUMO energy levels of the different materials. Electroluminescent devices were fabricated with these polymers as emitting layers, and ITO and Ca (or Al) as anode and cathode, respectively. Monolayer devices showed a limited performance. Efficient green light emission was obtained with a bilayer device based on PVK as a hole transport material and a polystyrene derivative (PST-NI-BuP) as an emitting layer. A maximum luminance of 7100cd/m(2) was obtained under 16V. The device had a maximum external quantum efficiency of 1% and a maximum external energetic efficiency of 0.2%. Doping PST-NI-BuP with 20% DCM resulted in red-orange emission with a brightness as high as 1800cd/m(2). Moreover, this study showed a strong influence of the chemical environment of the naphthalimide moiety on the photoluminescent and electroluminescent properties of the polymers.

We report the fabrication of efficient green light-emitting diodes using a side-chain polymer based on a high-electron affinity (EA) naphtalimide moiety (PNI). The chromophore is attached to a polymethacrylate backbone through a spacer, and emits in the green with high efficiency (30% photoluminescence quantum yield). In single-layer light-emitting diodes LEDs), we find that the electroluminescence GEL) efficiency is not limited by Al cathodes as for poly(p-phenylene-vinylene), PPV, and we attribute this to the increased EA.We report maximum internal efficiencies of about 1.7% for Ca and 0.9% for Al in double-layer devices where PPV serves as both hole-injector and emitter. Compared to some oxadiazole based electron injection/ransport layer, PNI gives higher efficiencies at high currents, and longer lifetimes (time to reach 50% of the initial emission). Tuning of emission in the red is possible by dye-doping the PNI and causing the emission to happen in this layer.We discuss the properties of the different device configurations with a view to the electronic structure of the materials and in particular to the influence of the thickness of the individual layers on effciency and driving conditions.

A dual delay-line surface acoustic wave (SAW) sensor has been used to study the potentialities of fluoropolyol (FPOL) coatings for the detection of organophosphorus compounds. Thin films are sprayed on ST quartz substrates and experimental results as a function of vapor concentration and coating thickness are presented. Possible explanations of interactions between FPOL coatings and chemical agents are discussed.

In order to improve our understanding of the mechanisms involved in the electrooptical effects of liquid crystal—polymer composites, and to identify the relevant parameters of these complex systems, we have investigated the influence of the chemical nature of the polymer surface on the anchoring of the liquid crystal. Our method consists in removing the liquid crystal from the composite by dissolution followed by supercritical drying of the solvent. The surface of the polymer is then modified by different reagents and the liquid crystal is reintroduced to the cell.

Summary form only given. In conclusion we have demonstrated that optical limiting in the visible over at least 220 nm is achievable in four metal substituted phthalocyanines. The choice of a broadband criterion on the linear transmittance of the dye led us to impose a fixed integrated photopic transmission (70%), which determines the concentration of the solutions. MPc's with linear transmittance best adapted to the day vision response and good RSA properties (heavy metal substitution), as GaPc2, will then allow more efficient broadband optical limiting.

In order to eliminate problems linked to the use of small emitting molecules or conjugated polymers, a novel type of electroluminescent material is investigated. Side-chain polymers have been conceived, synthesized and tested. Blue, green and oragen diodes have been made. It is demonstrated that a hole-transporting layer increaess the light emission of the green diode. Doping of side-chain polymers has been studied to produce orange light.

The considerable interest in the possibility of fabricating efficient optical limiters based on solid-state materials have led us to develop an easy method for producing RSA compound doped in PMMA. The choosen RSA dye was a soluble silicon phthalocyanine (SiPc(OC7H15)). By comparing the non linear absorption of this compound in solution in THF and in PMMA, we show that broadband solid-state limiters can be made with such a dye for visible nanosecond-pulse excitation. The importance of broadband criterion such as the photopic transmission to adjust the transmission at low incident energy in conjonction with the color neutrality are also stressed.

P(VF2-TrFE) copolymers are ferroelectric polymers. After Poling with electric fields of 100 V/mum they present pyroelectric properties which lead to the fabrication of IR uncooled detectors. Their low pyroelectric coefficient (4 10(-5)C/m) is associated to a low dielectric constant. Therefore, their voltage responsivity is similar to the one of the ceramic materials. Easy to process by the standard technique of CDD silicon circuit, they have allowed Thomson-CSF to fabricate a new IR uncooled 128 x 128 detectors matrix. The Noise Equivalent Temperature Difference is equal to 0.6 K for an optical aperture of f/1 and an image frequency of 50 Hz.

Amorphous polymeric films including active NLO moieties frozen in an acentric alignment have proved to be the most promising candidates for electro-optic application. However, these systems generally suffer from a low stability of their NLO properties. Until now, the best results in terms of stability and efficiency have been obtained by forming epoxy-amine networks. Following this concept, two new types of epoxy-ended NLO compounds, among which are two different NLO units, have been synthesized at THOMSON. Corresponding poled and crosslinked films have been elaborated and their EO properties characterized. The realization of good quality films possessing a thickness ranging from 1 to 1.5 μm required a formulation optimization work. The curing process was characterized by Tg measurements and IR spectroscopy, therefore allowing for each system the determination of the best curing/poling procedure. The r33 coefficients were determined for each system before and after a thermal aging treatment. A long-term thermal stability of the EO properties at elevated temperatures (ranging from 80 to 130 °C) was demonstrated for these systems. A high Tg associated with the fixation of the chromophores by both end has proved to be a major factor of stability.

Comb-like liquid-crystalline polymers exhibit many unique properties that challenge not only basic research but also numerous technological opportunities. They combine (partly) the properties of orientation of low molecular weight liquid crystals with the rigidity of polymers. For example, they can be oriented in the mesomorphic state and the structure frozen in a glassy state. These polymers with functionalized pendent groups lead to potential applications in the field of nonlinear optics, or in the domain of electro-optical displays. Other polymers like polysilanes show interesting properties such as photo-conductivity. This paper describes the properties and applications of some new side chain liquid-crystalline polyacrylates and their amorphous copolymers. It also describes the photoconductive properties of polysilanes and their applications in spatial light modulators with liquid crystals. In the first part of this paper, we describe the properties of liquid crystal copolymers and amorphous polyacrylate copolymers with cyanobiphenyls and/or pendent groups with a large hyperpolarizability. Their different properties are compared with some recent results from the literature. These amorphous copolymers allow one to obtain, after poling in an electric field, high optical non-linear coefficients. We have used these copolymers for the manufacture of an electro-optic modulator working at 1.3 mum in the frequency range of 1 GHz. Applications to second harmonic generation at 1.06 mum are also discussed. In the second part of this paper we describe the photo-conductive properties of polysilanes and the realization and performance of an organic spatial light modulator for optical correlation.

It is of interest to use nonlinear optical materials in a wavelength domain close to the absorption band, in order to increase the nonlinear coefficient value of the material [1]. However, this absorption should appear at a multiphoton level, because single photon absorption gives rise to high optical attenuation of the pump beam. This concept is mainly applied in third order nonlinear experiments [2], for which working near half the band gap leads to high χ(3) coefficient without strong absorption of the pump beam.

The synthesis, structure, electrochemical properties and second harmonic generation from the title compounds are presented.