We present results for the electrical conductivity (σ) of thin films of poly(benzo[1,2-b:4,5- b']dithiophene-4,8-diyl vinylene) (PBDV) and poly (dodecylthiophene) (PDDT) as a function of temperature in the range 15-295K. The polymers were doped with FeC13 and PF6 which resulted in electrical conductivities differing by two orders of magnitude at room temperature. We examine three sets of σ(T)-data by using the variable-range hopping (VRH) model that predicts a linear relationship between ln(T1/2σ) and T1/4. We observe a change in the slope of the ln(T1/2σ) vs T14 relationship in all three samples at low temperatures. We also analyze the temperature dependence of the resistivity of PBDV by using the thermal fluctuation-induced tunneling model.

Measurements of the barrier height by capacitance-voltage techniques and of the equilibrium exchange current density by current-voltage techniques are performed on the rectifying interface between n-InP and poly(pyrrole) (chemically polymerized and characterized by an electrochemical potential of ≈0.2V vs. SCE). The current-voltage data yielded a quality factor of 1.2±0.1 and an equilibrium exchange current density of (1.2±0.6) x 10−9. A cm−2. The capacitance-voltage data yielded a barrier height of 0.73 ± 0.02 V and measured dopant densities within 15% of the expected value. These data, taken together, are inconsistent with thermionic emission theories developed to describe inorganic semiconductor I metal interfaces and often applied to inorganic semiconductor I doped conjugated polymer interfaces. In particular, the ratio of the rate constant for majority carrier electron capture (surface recombination velocity) at the n-InP | poly(pyrrole) interface to that at n-InP | metal interfaces is found to be (6 ± 5) × 10−3.

We present optical measurements of 8-hydroxyquinoline aluminum (Alq3) a metal-chelate complex which is an important material used for multilayer light emitting diodes. Thin films of Alq3 produced by vacuum deposition were investigated by transmission and reflectance spectroscopy, and the dielectric coefficients in the near IR to UV-Vis energy range were calculated. Kramers-Kronig analysis was used to determine the real and imaginary dielectric spectral dependence of the thin films. Values obtained by internal field distribution measurements in organic double layer LED's are compared to those determined from optical data. A near-IR value of epsilon (real component) close to 3 was obtained from optical measurements.

Interfacial electronic structures related to organic electroluminescent (EL) devices were studied by UV photoemission spectroscopy (UPS). The two classes of interfaces studied were: (1) interfaces in a typical multilayer device AI/AIq3TPD/ITO, where Alq3 is tris(8-hydroxyquinolino)- aluminum, TPD is N,N×-diphenyl-NN×-(3-methylphenyl)- 1, 1‘-biphenyl-4,4’-diamine, and ITO is indium tin oxide, and (2) TTN/metals and TCNQ/metals interfaces, where TTN is tetrathianaphthacene and TCNQ is tetracyanoquinodimethane. The UPS studies of the specimen formed by the successive deposition of TPD, Alq3, and Al on ITO revealed interfacial energy diagrams, with the vacuum level shift of - 0.25 eV (downward) and - 0.1 eV (downward) at the TPD / ITO and the Alq3 / TPD interfaces, respectively. The deposition of TTN and TCNQ on metals showed opposite direction of the shift of the vacuum level, with the positive and negative charge at the vacuum side. This can be explained by considering the chargetransfer between the metal and the organic molecule, with these directions being consistent with the electron donating and accepting ability of these molecules.

Thermally-induced polymerization of 1,4-diphenyl-1,2,3-butatriene affords poly(1,4-diphenyl- 2-butyne-1,4-diyl) as a soluble high molecular weight material. Structure is characterized by 13C and vibrational spectroscopy. When treated with base, this material rearranges to a soluble red poly(acetylene) with a unique substitution pattern.

During the past few years there has been a strong interest in developing conducting polymers as an alternative to the traditional anticorrosion coatings. One of the driving forces for this research comes from the need for an environmentally friendly chromate-free anticorrosion coating for highstrength light weight aluminum alloys. The possibilities for a new scratch-tolerant paint for steel prompted the development of conductive polymer anticorrosion paints. By molecular engineering, we have synthesized a double-strand polymeric complex of polyaniline that is suitable as an anticorrosion paint on metals in low pH environments. In this article, we will discuss (1) the molecular design for solubility and adhesion, (2) the effectiveness of the electroactive coating under electrochemical impedance tests, and (3) a mechanistic study of the anticorrosion mechanism by examining the polymer/metal interfacial interactions.

Nanocomposites of phenoxy-substituted vanadyl phthalocyanine with a t-conjugated polymer, poly(benzimidazobenzophenanthroline ladder), have been prepared from their Lewis acid complexes in organic solvents. The resulting composite thin films obtained by spin-coating have excellent optical transparency and interesting composition-dependent morphology and photoelectronic properties. Enhanced photoconductivity, compared to the components, was observed in some composites with discrete nanoscale metallophthalocyanine aggregates.

We report the synthesis of a polymeric complex of polyaniline that is dispersed in water as a stable suspension. The polymer, PAN:PVME-MLA, is a molecular complex of polyaniline and poly(vinylmethylether-co-maleic acid). The synthetic process leads to a stable latex-like suspension in water. The water-borne conducting polymer, once dried as a thin film on a substrate, is not dissolvable by water or other solvents. An example of piece-dyeing process is presented to show its potential for electrostatic dissipation of textile products. Another example illustrates that the material may be used as electroactive thin-films for electrochromic windows and for rechargeable battery applications.

Multilayer organic light emitting devices based on tris-8-(hydroxyquinoline) aluminum (Alq3) and a naphthyl-substituted benzidine derivative (NPB) have demonstrated practical electroluminescence with a wide range of color. Trap states in these materials play an important role in the carrier transport as well as the light emission process. We report the first observation of thermally stimulated luminescence (TSL) from Alq3 and NPB. The TSL spectra from 8 K to 300 K were used to determine the trap states in Alq3 and NPB. The results for Alq3 show a significant trap distribution at 156 K, which corresponds to a mean trap depth ranging from 0.18 to 0.12 eV, whereas the trap states in NPB are centered from 0.15 eV to 0.01 eV. We have used TSL to study the trap state properties of thin metal layers in the Alq3 films. In addition, we report photoluminescence as a function of temperature for Alq3. TSL spectroscopy provides a technique to study the trap states in a specific layer of the device structure.

Poly(zinc-bisquinoline) synthesized via a reactive self-assembly technique has been used as an active transport and emitting layer in light emitting diodes. This small molecule self-assembly, pioneered in our laboratory, was shown for the first time to produce pinhole-free films as thin as 400 Å. The ellipsometric trajectory and the refractive index of zinc bisquinoline self-assembled films on silicon were determined using spectroscopic ellipsometry. Psi and Del values were extrapolated at 633nm and 70 deg incidence for films ranging in thicknesses from 0 nm to 125 nm and plotted with model trajectories of 1.65, 1.70, and 1.75 refractive indices. Thin films over 20 nm followed a trajectory having similiar refractive indices between 1.65 and 1.70, indicative of homogenous films. A refractive index of 1.68 ± 0.01 at 633 nm was found to be among the highest reported values for a self-assembled metallorganic multilayer. Atomic force microscopy of a 90 Å film on silicon substrates with mean square roughness of c.a. 12 Å showed an approximate roughness of 14 - 17 Å.

Dendritic macromolecules, called “dendrons,” having a branching structure modified with an electron donor/acceptor functionalized azobenzene chromophore have been synthesized. The structurally different dendrons possess different numbers, 1, 3, 7, and 15, of chromophore units. The second harmonic generation (SHG) of dendrons was measured in the molecular oriented thin films prepared by the Langmuir-Blodgett film transfer technique. In such structurally organized thin films, individual chromophores coherently contribute to the increase in the molecular hyperpolarizability of dendrons. The SHG activity became large as the numbers of branching units of dendrons increased. The highest molecular hyperpolarizability was found to be <8000×10−30 esu for dendron containing 15 chromophoric units. The SHG results suggest that the structure of dendrons synthesized is uniaxially dipolar, and that there is a particular merit in this structure for the generation of SHG.

Emissive behavior of dye molecules embedded in the systems with the size of visible wavelength were studied. The structures consisted of close-packed arrays of spherical dielectric particles with diameter of submicrometer were fabricated. Photoluminescence from selfassembled arrays of dye-doped polystyrene microspheres were examined. In this systems, partial suppression of spontaneous emission by ordered structures were observed. Electricallypumped emission from organic light emitting diodes with highly ordered arrays of silica microspheres were attempted.

Squarylium dye with two propyl and two hexyl groups forms a mono-molecular layer with domains of J-aggregates by spreading its chloroform solution at an air-water interface. Fluorescence microscopy and an absorbance evaluation which also considers the reflectance suggest that this Langmuir-film has a close packed two-dimensional structure with a complete Jaggregate formation of all dye molecules. Strong and ultrafast nonlinear optical responses, indicating delocalization of excitons over 30 molecules, have been observed at 5 °C from this ideal mono-molecular layer of J-aggregates.

We studied the sub-picosecond dynamics of photoexcitations in methyl-substituted poly(para--phenylene)-type ladder polymer (m-LPPP) films in a wide excitation density range up to values typical for the regime of narrow band emission by pump-probe spectroscopy. The singlet excitons relaxation dynamics, monitored at the stimulated emission (SE) peak at 2.53 eV, showed an intensity dependent ultrafast decay component, which occurs on a sub-picosecond time scale, ascribed to the onset of amplified spontaneous emission (ASE). In addition we identified photoinduced absorption (PA) bands of singlet excitons at 1.48 eV and polarons at 1.9 eV respectively. At high excitation density an additional absorption band becomes evident at 2.63 eV.

We report on the magnetic field effect (MFE) on the photoluminescence in films of a highly fluorescent conjugated laddertype poly(paraphenylene) (LPPP). We observe no MFE for the pure material, however, the introduction of a very small content of chemical defects via photo-oxidation leads to a MFE proportional to the amount of defects. The chemically induced increase in MFE is correlated with a change in other properties of the LPPP films, such as photoluminescence emission and excitation spectra, transient photoluminescence and infrared spectra.

One-pot post-polymerization modification reactions such as azo-coupling and tricyanovinylation reactions were employed to synthesize a series of polymers containing different nonlinear optical (NLO) chromophoric as well as ionic functionalities. We have extended and established the versatility of our earlier reported post-modification strategy to incorporate various heteroaromatic chromophores as well as ionic functionalities in the polymers, at the final stage of synthesis. The correlation between different heteroaromatic chromophore structures and the NLO properties of the polymers was extensively studied. Polymers containing heteroaromatic chromophores exhibit improved temporal stability and enhanced NLO activity. Polymers with ionic chromophores were employed to fabricate NLO active ultra-thin films using electrostatic selfassembling (ESA) technique. Attempts were also made to synthesize second order NLO active polydiacetylene derivatives using post azo-coupling reaction.

The dispersion of third-order nonlinear coefficients and of three different NLO(nonlinear optical) polymer films were determined by electroabsorption spectroscopy. The first material investigated is an epoxy-based polymer BP-2A-NT, with azobenzene NLO chromophore 4-[((4-nitrophenyl)(azo)phenyl)azo)]aniline in its side chain. The other materials are two polydiacetylenes, poly(BPOD) and poly(4-BCMU), in which the( 3de)localized polymer chains contribute to the third-order nonlinearity. The complex spectrum of of each material is very similar in shape to corresponding spectrum. The ratio of to is 3.2 for BP-2ANT, 1.5 for both poly(BPOD) and poly(4-BCMU). These ratios indicate that the distribution of the side-chain NLO chromophores of BP-2A-NT is very close to three-dimensional isotropy, and the distribution of the main-chain chromophores of poly(BPOD) and poly(4-BCMU) is concentrated on the film plane.

Directed lithiation of a polyethersulfone and the reactions of the lithiated species have been investigated. This method provides a new route to second-order nonlinear optical polymers.

A new material for second-order nonlinear optics was synthesized, which was a copolymer of N-phenylmaleimide, 4-isopropenylphenol and 4'-[N-ethyl-N-(4-isopropenylphenoxyethyl) amino]-4”-nitroazobenzene (PMPD). PMPD films were poled by corona-poling technique. The optical nonlinearity of poled PMPD was measured by second harmonic generation (SHG) and electro-optic (EO) effect, and it was demonstrated that this polymer had large optical nonlinearity and a very long-time stability, as was expected. These properties were thought to be sufficient enough for practical EO devices. On the other hand, from the viewpoint of the sample preparation technique, poling conditions were investigated in order to achieve the highest possible dipolar orientation. As a result, it was found that the relationship between the electric resistance of polymer film and substrate was a critical factor for corona-poling efficiency. From a simple model, it was suggested that the poled PMPD film prepared onto the glass substrate with a resistance of ˜0.8 GΩ (at 160 °C) exhibits large SHG and EO coefficients, more than ˜500 × 10−9 e.s.u (d33 at λ = 1.064 μm) and ˜70 pm/V(r33 at λ = 632.8 nm), respectively. It should be noted that this expected values are approximately twice as much as obtained under conventional corona-poling conditions.

The new series of recently synthesized chromophores 2 - 6 in which a positively charged N-alkylpyridinium acceptor and a negatively charged dicyanomethanide donor are spaced by thiophene-based and/or ethylenic bridging units show dramatically enhanced first molecular hyperpolarizabilities (μβ as high as 27000 × 10−48 esu), in comparison with some of the best recently reported neutral systems 7 and 8.