Magnetic properties of a binary mixture of mesogenic tetraphenylporphyrin Cu(II) and VO(IV) complexes are reported. These mesogens show two lamellar mesophases (DL and DLC) and a binary phase diagram revealed that each mesophase is miscible. The magnetic properties were investigated by magnetization measurements using SQUID. It was found that the magnetization of 1:1 mixture (mole% base) was larger than those of the pure compounds below ca. 190 K, whilst 1:3 and 3:1 mixtures showed the decrease of magnetization in the full range of temperature in which the measurements were carried out. It was shown that χ−1 vs. T plots did not obey Curie-Weiss law. For the VO(IV) complex and 1:1 mixture, stepwise changes could be recognized at the temperatures corresponding to the phase transitions. 1:1 mixture as well as Cu(II) and VO(IV) complexes totally involve antiferromagnetic interaction. However, ferromagnetic behavior in χ−1 vs. T plots was seen about DL - DLC phase transition.

The photoluminescence properties of thiophene-based polymers obtained by the random copolymerization of 3,4-dibutylthiophene and 3-butylthiophene are reported. Optical absorption spectra, cw photolumninescence (PL) spectra, PL quantum efficiencies and PL decays have been measured in dilute solutions. By varying the copolymer chemical composition it is possible to tune the intensity and the color of the luminescence spectra in the whole visible range. We evidence the role of disorder, controlled by interring rotations, as the tuning factor for the disexcitation pathway of the photoexcitations in these materials.

Well-defined poly(2,7-fluorene) derivatives have been prepared through palladium-catalyzed couplings; using this versatile synthetic method, processable polyfluorenes have been obtained in good yields. In solution, these yellow polymers exhibit blue emission around 410 nm with high quantum yields. Moreover, novel acidic polyfluorene derivatives have been synthesized (e.g. poly(2,7'-(pentyl 9,9-dioctyl-7,2'-bifluorene-9'-carbonyl))) which show, upon base-doping, electrical conductivities of 10−2 − 10−3 S/cm. This new doping method for conjugated polymers could open the way to the preparation of air-stable electron-injecting electrodes. Polyfluorene derivatives show their potential to play a double function in the fabrication of LEDs, i.e. as ntype electrode and luminescent polymeric materials.

The magnetization of novel tetranuclear supramolecular grid structures and their mononuclear analogues was measured. In the tetranuclear complexes with Co2+ or Ni2+ ions an intramolecular antiferromagnetic coupling of the four metal centers is observed. The isotropic coupling strength was determined to be J = -8 K for the Ni2+ grids, and J = -2 K for the Co2+ grids.

We have previously demonstrated that a self-assembled monolayer (SAM) of alkyltrichlorosilane molecules, covalently bonded to the native oxide of a silicon substrate, allows the fabrication of MIS (Metal-Insulator-Semiconductor) devices with excellent electrical properties [1]. Here we demonstrate that we can functionalize, with π-electron moieties, the end-groups of the molecules, once grafted to the substrate, without disturbing the low conductivity through the SAM (σ⊥), while strongly increasing the in-plane conductivity (σ//). The functionalization of the monolayer is monitored by FTIR, ellipsometry and X ray reflectivity. Conductivity, photoconductivity and capacitance measurements are carried out to study the effect of these chemical functionalizations on the electrical properties of the monolayers. We demonstrate that the low perpendicular conductivity (σ⊥≈10−15 S/cm) is not altered by the end-group functionalities while high anisotropic conductivities (σ///σ⊥ ≈ 107-108) are obtained at a monolayer level. Interfacial (Si/SAM and SAM/metal) energy barriers are investigated as a function of the end-group functionalities. We also show that conducting monomers substituted by alkyl chains (3,6- dibromocarbazole-N-octyltrimethoxysilane), directly grafted to the substrate, exhibit similar behavior.

Porphyrins are a promising class of materials for optical limiting applications, and in the condensed phase solvent effects have been shown to be significant. We report results with a method designed to simulate the effects of discrete solvent molecules, namely the effective fragment potential (EFP) approach which has been implemented for use in ab initio calculations. Further, a simulated annealing (SA) method has been implemented with the EFP solvation model in an attempt to solve the problem of multiple minima in clusters of molecules. The results with this method indicate some success on models of aqueous formamide and aqueous glutamic acid. Ab initio calculations can now be carried out on porphyrins, and the solvation methods are being updated for their use on these systems.

Optically addressed spatial light modulators (OASLMs) based on deformed helix ferroelectric liquid crystals (DHFLC) with high tilt angles on order of 40° and helical pitches less than 0.2μm were developed. The diffraction efficiency reached the order of 20%. The light induced deviation of the optical axis of the DHFLC layer was measured in sandwich structures consisting of photoconductors and liquid crystals. The photoelectric parameters of photoconductive amorphous silicon carbide a-SiC:H and a photoconductive polymeric films were measured with and without light blocking and reflecting layers. The application of the developed OASLMs in a holographic image corrector was demonstrated.

We present X-ray and Raman studies of the conjugated oligomer, hexaphenyl, which forms polycrystalline layers. The Raman studies have been carried out under hydrostatic pressures up to 70 kbar. The relative intensity of the two modes at 1220 cm−1 and 1280 cm−1 shows the influence of planarization under hydrostatic pressure. These results are interpreted within the framework of theoretical calculations and compared with X-ray studies.

We have studied the photoluminescence emission spectra of polycrystalline and amorphous powder samples of phenylene-type polymers and oligomers. In order to modulate both intrachain and interchain interactions these investigations were performed at hydrostatic pressures up to 70 kbar and in a tOmperature range of 20 to 300 K. We report characteristic changes of the emission spectrum which depend on both the molecular environment as well as the intramolecular bond configuration.

It is well known that conductive polyaniline (PANI) films are usually doped by immersing dedoped PANI films in HCI solution. This paper shows that a corona discharge can be successfully employed to dope thin films of polyaniline coated on poly (ethylene terephthalate) films. Similarly to the conventional doping with aqueous HCl the process is accompanied by a color change from blue to green and the conductivity can be tuned in the range from 10−10 up to 0.3 Scm−1. Such new doping method presents several advantages over the conventional one namely, dry process, use of no chemicals, rapidity and no dopant migration. Measurements also showed that the conductivity persists for a long time as observed for films prepared in chemical solution doping. It is believed that this novel technique could be employed in a continuous doping process aiming to produce films with large area for anti electrostatic packing applications.

The anisotropy induced in a series of methacrylate polymers doped with Disperse Orange 3 (DO3, NO2-phenyl-N=N-phenyl-NH2) was investigated by polarized FTIR spectroscopy. Three kinds of methacrylate polymers with different glass transition temperature (Tg), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA), were used as polymer matrices. Observed infrared absorption bands of DO3 in the polymer films were assigned to symmetric (NO2s) and antisymmetric (NO2as) stretching modes of NO2, and the C-N stretching mode of C-NH2 (C-N). The infrared dichroism was observed in these bands under the irradiation. The orientation factors, Kzfn, (f=x, y, z, n=trans, cis), for both isomers of DO3 were determined in the photostationary stite for every polymer matrix. The factors indicate that it is difficult for NO2 group to move in the PMMA during trans-cis-trans isomerization and that it is difficult for NH2 group to move in the PBMA. The dynamical behavior of DO3 molecules which depends on the kind of polymers could be interpreted from orientation factors. This study shows that polarized FTIR spectroscopy is one of the most powerful methods available to analyze the physical mechanisms of photoinduced anisotropy.

N-(3-nitrobenzylidene)-p-phenylenediamine (NBPDA) was used as ultrahigh density data storage medium by scanning tunneling microscope (STM) technique. Data marks of 1.4nm in diameter were written by applying voltage pulses between the STM tip and the substrate. Structures of single crystal and thin films were characterized by IR, UV–Vis, XRD, STM and verified by DFT quantum chemical calculation.

We report on the nature of emitting states in two different quaterthiophenes: the unsubstituted quaterthiophenes (T4) and a bridged T4 (T4B), where the bridging have been realized by introducing a second bond between the two central thiophene rings. The effect of the chemical bridging on the photophysics of these compounds have been studied via photoluminescence measurements under hydrostatic pressure, which permit to clarify the influence of interchain coupling, conformational effects and intrachain structural changes on the optical properties.

In 1991, we reported a normal isotope effect in organic superconductor κ-(BEDT–TTF)2Cu[N(CN)2]Br, when all the hydrogen atoms of BEDT – TTF were replaced with deuterium. In other words, Tc was depressed by as much as 0.9 K, in contrast to the “inverse isotope effect” commonly observed in 10K-class organic superconductors. Recently, it was reported that the deuterated κ-(BEDT–TTF)2Cu[N(CN)2]Br shows an insulating nature when cooled very rapidly. Therefore, it is necessary for us to reexamine the superconducting transition of both deuterated and undeuterated κ- (BEDT – TTF)2Cu[N(CN)2]Br by SQUID measurements with special attention to the cooling speed. We studied the effect of cooling rate ranging from 10 K/min down to as slow as 0.02 K/min, and observed a significant effect not only on the superconducting transition temperature Tc but also on the superconducting volume fraction.

Diazoluminomelanin (DALM) is an electroluminescent polymer which has shown significant optical activity in response to perturbing fields. The current model for this process features optical excitation of a polymer backbone containing conducting conjugation, with subsequent energy transfer to a luminescent group. In this paper we have performed electronic structure calculations using the AM1 Hamiltonian with configuration interaction to estimate the electronic properties of two potential models for the DALM backbone. Contrary to the conventional picture of conjugation, the phenyl groups in the DALM backbone show significant twist angles (42° –55°) depending on substitutional group, resulting in localized electronic excitations.

We synthesized a series of new di-cholesteryl esters of several diacids. One of the compounds containing both of a diyne unit and long alkylene units, in the form of a thin solid film, showed stable iridescent colours in the visible region after rapid cooling process from the temperature of the cholesteric liquid crystalline phase. Measurement of selective reflectance of visible light, X-ray diffraction, optical rotation dispersion of the solid films proved that the films remained the cholesteric ordering of the molecules. The cholesteric structure in the solid films were completely stable at room temperature. The colour of the solid film was totally, partially or in imagewise manner changed into selected colours by adjusting the temperature of the surface just before the rapid cooling process. The property of this compound can be applicable to memory media with high density using the spectrum of light, or to thermosensitive full-colour recording materials.

Charge-transfer salts of EDT-TTF with tetrahedral anions MX4 (M=Fe, Ga ; X=Cl, Br) were prepared. They are isostructural to each other (monoclinic P21/m) with the stoichiometry of 2:1. All of them are semiconductors having the conductivity at room temperature of 5 to 9 Scm−1 and activation energy of 40 to 170 meV. Since the calculated band structure of them indicate that they should be quasi one-dimensional metals, they were discussed from the point of structural deformation and strong electron correlation.

We report on the organization of different disperse red dye derivatized methacrylate homo- and copolymers as Langmuir monolayers at the air-water interface. The monolayers were investigated using surface pressure and surface potential isotherms. Methacrylic homopolymers containing disperse red-1 (HPDR1) and disperse red-13 (HPDR13) and methacrylic copolymers with different mole percentages of the dye and hydroxyethyl spacer groups were synthesized and characterized. A comparison of the monolayer characteristics of HPDR1 and HPDR13 revealed the influence of the chlorine substitution in the aromatic ring of the dye. Studies with copolymers indicated a clear transition in the monolayer behavior with the change of mole percentage of the dye incorporated in the polymer. While copolymers with low dye content (up to about 5 mole%) presented an expanded monolayer, the copolymers containing higher dye content (12% and above) formed a condensed monolayer similar to that of the homopolymer. These results indicated the critical role of the dye component in the polymer chain in forming the monolayer at the air-water interface.

Preparation and characterization either by optical absorption, photoluminescence and micro-Raman spectroscopy of individual components as well as bilayers consisting of organic dye semiconductor Zinc Phthalocyanine (ZnPc) and fullerene, C60, thin films are reported. The layers and structures were deposited in vacuum and some fullerene films were also prepared by casting the C60 solution in benzene. The optical absorption and photoluminescence dependencies on film thickness in bilayers C60/ZnPc were observed and may be discussed in a context of interface induced simmetry reduction of C60 molecules.

We present infrared spectra of linear and planar polymeric structures consisting of C60 balls. The splittings of infrared lines can be explained fairly well on the basis of symmetry reduction, indicating that the structures are ordered. Increasing the temperature results in breaking of intermolecular bonds. This process is reversible in the alkali salts but irreversible in the neutral rh-C60 polymer; we conclude that charged C60 balls are more stable in polymer form than as monomers, while for neutral C60 the situation is reversed.