bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on the Relations of Structure and the Ultrafast Optical Kerr Effect of Polynitriles
Authors: Wang Q. , Li Y. Y. , Pei W. W. , He Y. K. , Luo C. Q. , Chen H. Y. , Lin L. , Wang C. F. , Zou Y. H. 
Published: April 2011

AbstractA series of polybenzonitrile derivatives, prepared by plasma glow discharge processes or chemical polymerization, were characterized by FT-IR, UV-Vis, GPC and VPO etc. The secondorder nonlinear optical hyperpolarizability γ of various benzonitrile monomers and their, polymers were measured by the femtosecond time-resolved optical Kerr effect technique, and the structureproperty relationships were discussed. The power law dependence of γ on the averagepolymerization- degree of several polybenzonitrile derivatives were also reported.
Radiative Decay of Excitons in Model Aggregates of π-Conjugated Oligomers
Authors: Manas Eric S. , Spano Frank C. 
Published: April 2011

AbstractSpontaneous emission from exciton states in an aggregate of π-conjugated oligomers is studied theoretically. Each oligomer is taken as a ring of N carbon atoms and is treated using a PPP Hamiltonian. Coulombic interactions between rings are treated to first order. The radiative decay rate γ from an exciton state in an aggregate of M aligned oligomers is superradiant, being M times faster than the decay rate of an isolated oligomer exciton. Inter-oligomer interactions have little effect on the exciton size and energy when the oligomer size N is large compared to the interoligomer spacing. However, when N is small, both the exciton size and energy are strongly affected by these interactions, leading to a markedly different N dependence for γ.
An Emulsion Polymerization Process for Soluble and Electrically Conductive Polyaniline
Authors: Kinlen P. J. , Ding Y. , Graham C. R. , Liu J. , Remsen E. E. 
Published: April 2011

AbstractA new emulsion process has been developed for the direct synthesis of the emeraldine salt of polyaniline (PANI) that is soluble in organic solvents. The process entails forming an emulsion composed of water, a water soluble organic solvent (e.g., 2-butoxyethanol), a water insoluble organic acid (e.g., dinonylnaphthalene sulfonic acid) and aniline. Aniline is protonated by the organic acid to form a salt which partitions into the organic phase. As oxidant (ammonium peroxydisulfate) is added, PANI salt forms in the organic phase and remains soluble. As the reaction proceeds, the reaction mixture changes from an emulsion to a two phase system, the soluble PANI remaining in the organic phase. With dinonylnaphthalene sulfonic acid (DNNSA) as the organic acid, the resulting product is truly soluble in organic solvents such as xylene and toluene(not a dispersion), of high molecular weight (Mw >22,000), film forming and miscible with many polymers such as polyurethanes, epoxies and phenoxy resins. As cast, the polyaniline film is only moderately conductive, (10−5 S/cm), however treatment of the film with surfactants such as benzyltriethylammonium chloride (BTEAC) or low molecular weight alcohols and ketones such as methanol and acetone increases the conductivity 2–3 orders of magnitude.
Electrical Rectification by a Molecule of Hexadecylquinolinium Tricyanoquinodimethanide
Authors: Metzger R. M. , Chen B. , Vuillaume D. , Höpfner U. , Baldwin J. W. , Kawai T. , Tachibana H. , Sakurai H. , Lakshmikantham M. V. , Cava M. P. 
Published: April 2011

AbstractThe asymmetrical forward versus reverse - bias DC electrical conductivity (macroscopic and also nanoscopic) through Langmuir-Blodgett multilayers and monolayers of γ-(nhexadecyl) quinolinum tricyanoquinodimethanide, C16H33Q-3CNQ (1) is attributable to rectification of electrical current by a single molecule.
A Scanning Force Microscopy Study of Block Copolymers Containing a Conjugated Segment
Authors: Leclère Ph. , Lazzaroni R. , Parente V. , François B. , Brédas J. L. 
Published: April 2011

AbstractAtomic Force Microscopy (AFM) and related techniques are used to investigate the morphology of diblock copolymers. We focus on compounds containing a conjugated segment, polyparaphenylene, associated to a polymethylmethacrylate or a polystyrene block. The influence of the presence of the conjugated segment on the microdomain morphology is analyzed as a function of chain composition. Separate microdomains are observed on the surface of thin films by means of phase-detection imaging tapping-mode AFM. Their shape and size are interpreted in terms of molecular aggregation, with the help of molecular dynamics calculations.
Double-strand Polyaniline as a Molecular Quasi-Memory to Chemical Stimuli
Authors: Kota Gowri P. , Sun Linfeng , Liu Huaibing , Yang Sze C. 
Published: April 2011

AbstractWe report the apparent hysteresis cycles in the protonation/deprotonation induced conductor-insulator transition for a water-soluble double-strand polyaniline. Experimental evidences show that the polymeric complexes of polyaniline and poly(styrene sulfonic acid) are soluble in water as non-aggregated single molecules. Although the hysteresis loop becomes narrower within 40 hours and the bistability is not permanent, the rate of collapse of the hysteresis loop is extremely slow for a solvated polymer in water. The water soluble polyaniline was compared with solid state samples of PAN:HCl. It was found that, under thermodynamically identical conditions, the memory effect is stronger for the water-soluble polyaniline than the water-insoluble solid of PAN:HCI.
Synthesis and Photophysical Properties of Some Conjugated Polymers Functionalized with Ruthenium Polypyridine Complexes
Authors: Ng Po King , Ng Wai Yue , Gong Xiong , Chan Wai Kin 
Published: April 2011

AbstractA series of conjugated polymers functionalized with different ruthenium polypyridine metal complexes were synthesized by the palladium catalyzed reaction. Two conjugated polymer systems have been studied: 1. poly(phenylenevinylene) with bis(2,2':6',2”-terpyridine) ruthenium (II) on the mainchain and 2. quinoxaline based polymers with tris(2,2'-bipyridine) ruthenium (II). The ruthenium polypyridine complexes exhibit a long-lived metal to ligand charge transfer excited state which can enhance the photosensitivity of the resulting polymers. Different physical properties such as the photoconductivity and charge mobility in these polymers are also studied.
Electrochemically Based Light Emitting Devices from Sequentially Adsorbed Multilayers of a Polymeric Ruthenium (II) Complex and Poly(Acrylic Acid)
Authors: Wu Aiping , Lee Jin-Kyu , Rubner Michael F. 
Published: April 2011

AbstractWe have investigated a new light emitting material, Ru(bpy)3 2+ polyester for fabricating electrochemically based solid state light emitting devices using the layer-by-layer sequential adsorption processing technique. By controlling the deposition conditions such as the pH of the Ru(bpy)32+ polyester and poly(acrylic acid) (PAA) solutions, we systematically altered the layer thickness and bilayer composition to obtain multilayers that contain different amounts of Ru(bpy)32+ polyester (from 46% to 70%). Differences in the Ru(bpy)32+ polyester composition, in turn, influence the device performance dramatically.
Synthesis, Characterization and Properties of Conjugated Poly(1-Alkyl-2,5-Pyrrylene Vinylene)
Authors: Kim In Tae , Elsenbaumer Ronald L. 
Published: April 2011

AbstractA series of poly(N-alkylpyrrylene vinylenes)( alkyl = methyl(l), hexyl(2), dodecyl(3)) have been synthesized from the monomer, N-alkyl-2,5-bis(thiophenylmethylene)pyrrole, by base induced elimination and polymerization. The resulting deep purple conjugated polymers (2,3) were soluble in a variety organic solvents. The electrical conductivities of the polymers lie in the range, 10−2to 2.5 S/cm. The highest yield was obtained when the polymers were synthesized in refluxing THF with a monomer/ base mole ratio of 1/4. The optical band gap of the undoped polymers were 1.89 eV(1), 1.69 eV(2) and 1.65 eV(3). Characterization of the polymers includes IR, CV,1H and13C NMR, UV-vis spectroscopy, TGA and molecular weight studies.
Conjugated Polymers Containing Pendant Terpyridine Complexes as Photoactive Sensors
Authors: Jiang Biwang , Sahay Shailesh , Jones Wayne E. 
Published: April 2011

AbstractWe have synthesized a novel conjugated polymer containing terpyridine receptors. This conjugated, polymer-based fluorescent chemosensory system exhibits unusually high sensitivity toward transition metal ions (∼-10−9 M). The fluorescence quenching response of the terpyridine containing conjugated polymer to transition metal ions is related to a facile energy migration in which energy from absorption of a photon, can migrate through the conjugated polymer system and be quenched by trapping sites. Terpyridine receptors can readily bind to transition metal ions and create a low lying Metal to Ligand Charge Transfer (MLCT) state which can act as an excitation trap.
Self-Assembling Functionalizable Polydiacetylenes and their Optical Properties
Authors: Sukwattanasinitt M. , Wang X. , Lee D-C. , Li L. , Kumar J. , Tripathy S. K. , Sandman D. J. 
Published: April 2011

AbstractThe alkoxycarbonylmethylurethanes of 9-(N-methyl-N-phenylamino)-5,7-nonadiyn-l-ol were synthesized and polymerized by 60Co gamma radiation. The resulting polydiacetylenes (PDA) are soluble, processable, and self-assemble into an acentric array. These PDAs are susceptible to postpolymerization functionalization via its dialkylaniline and ester groups, and hence comprise the most versatile PDA system for systematic chemical modification reported to date. Dialkylaniline functionalization via tetracyanoethylene and diazonium salt coupling led, respectively, to materials with interesting second order nonlinear optical properties and that exhibit directly photofabricated regular surface relief gratings. The latter materials provide the first example of a rigid rod polymer (lacking a detectable glass transition) to exhibit such phenomena. Moreover, these PDAs can form self-assembled multilayer structure in water by ester hydrolysis.
Investigation of Organic-Organic Interfaces by Time-Resolved Photocurrent, Electrochemical, And Photoemission Techniques
Authors: Lin Liang-Bih , Mason M. Gary , Young Ralph H. , Schildkraut Deniz E. , Borsenberger Paul M. , Jenekhe Samson A. 
Published: April 2011

AbstractHole transporting properties and energy barriers at organic-organic interfaces relevant to electrophotographic and organic electroluminescent (EL) devices are described. Three wellknown hole transporting molecules, 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC), N,N′- diphenyl-N,N′-bis(1 -naphthyl)-(1,1 ′-biphenyl)-4,4′-diamine (NPB), and N,N,N′,N′-tetrakis(4- tolyl)-(1,1 ′-biphenyl)-4,4′-diamine (TTB) are used in this study. The ionization potentials (IP) and oxidation potentials (Eox) of these materials are determined by photoemission spectroscopy and electrochemical measurements, from which a conversion formula is obtained (IP ∼ 4.5 eV + eEox). Hole transport across organic-organic interfaces is investigated by time-of-flight transient photocurrent techniques. The efficiencies of hole injection are consistent with the energy barriers, when present, at these interfaces.
Polymeric Complexes of Polyaniline as Anticorrosion Coatings
Authors: Racicot R. J. , Yang S. C. , Brown R. 
Published: April 2011

AbstractDuring 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.
Very Large Second Order Non-Linear Optical Activity Shown by Heterocycle-Based Dicyanomethanide Zwitterions
Authors: Abbotto A. , Bradamante S. , Facchetti A. , Pagani G. A. , Ledoux I. , Zyss J. 
Published: April 2011

AbstractThe 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 × 10−48esu), in comparison with some of the best recently reported neutral systems 7 and 8.
Ab Initio Calculations on Porphyrins in the Condensed Phase
Authors: Day P.N. , Wang Z. , Pachter R. 
Published: April 2011

AbstractPorphyrins 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.
Morphology Dependence of the Optical Properties of Dalm Related Materials
Authors: Wagner-Brown K. B. , Ferris K. F. , Kiel J. L. , Albanese R. A. 
Published: April 2011

AbstractDiazoluminomelanin (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.
Infrared Studies on C60 Polymers
Authors: Kamarás K. , Forró L. , Iwasa Y. 
Published: April 2011

AbstractWe 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.
Formation of Ultra Smooth Bi-Based Ferroelectric Films and their size effect on Dielectric Constant
Authors: Tabata H. , Yanagita T. , Hamada M. , Kawai T. 
Published: April 2011

ABSTACTWe have formed Bi-based ferroelectric films, such as Bi2WO6, Bi2VO5.5(n=1), Bi2SrTa2O9, Bi3TiNbO9(n=2) and Bi4Ti3O12(n=3) using a pulsed laser deposition technique. Especially, the Bi2VO5.5 film shows an atomically smooth surface with a flat 2000-3000Å wide terrace and steps of 8 Å and 16Å which correspond to a half and one unit cell, respectively. The dielectric constant, remanent polarization and coercive field of the Bi2VO5.5 thin films formed on Nb-SrTiO3(100) are 8, 3.0 μ C/cm2 and 16.0 kV/cm, respectively. The Bi2VO5.5 film formed on SiO2/Si(100) shows memory windows of 0.35V against a±2V gate bias during C-V measurements‥
MOCVD of SrBi2Ta2O9 for Integrated Ferroelectric Capacitors
Authors: Hendrix Bryan C. , Hintermaier Frank , Desrocherst Debra A. , Roedert Jeffrey F. , Bhandarit Gautam , Chappuist Maggie , Baumt Thomas H. , Van Buskirkt Peter C. , Dehm Christine , Fritsch Elke , Nagel Nikolas , Honlein Wolfgang , Mazure Carlos 
Published: April 2011

ABSTRACTSrBi2Ta2O9 (SBT) is a promising material for ferroelectric random access memories (FERAM's) because it has high resistance to fatigue and imprint combined with low coercive field. Metalorganic chemical vapor deposition (MOCVD) offers the ability to produce high quality, conformai SBT films for both high and low density memory applications. An MOCVD process based on liquid delivery and flash vaporization has been developed which allows precise delivery of low vapor pressure precursors to the process. Precursor decomposition has been examined over a wide temperature range and the effects of process pressure have been examined. It is shown that Bi(thdb is superior to Bi(Ph)3 as a source of Bi, offering a wide decomposition window with compatible Sr and Ta precursors so that a simple, well-controlled, and repeatable process is achieved at low temperatures. Films with 90% conformallity have been grown on 0.6 μm structures with a 1:1 aspect ratio. The MOCVD process yields the fluorite phase, which is transformed to the ferroelectric layered perovskite phase upon annealing in oxygen. Dielectric constants (ε) of 200 and remanent polarization (2Pr)up to 16 μC/cm2 have been achieved on 150 mm wafers.
Reversible and Irreversible Contributions to the Polarization in SrBi2Ta2O9 Ferroelectric Capacitors
Authors: Lohse O. , Bolten D. , Grossmann M. , Waser R. , Hartner W. , Schindler G. 
Published: April 2011

ABSTRACTThis work presents a survey of the mechanisms of the polarization in ferroelectric thin films which are relevant for application in non-volatile ferroelectric memories (FeRAM). Since the integration of these materials in new memory generations requires small structures and therefore a maximum utilization of the switchable polarization, the distinction between the several polarization mechanisms is of specific interest. Standard characterization methods, such as hysteresis loops, C-V measurements and fast pulse switching tests are evaluated and used to distinguish between the reversible and irreversible contributions to the total polarization. The respective contributions are described qualitatively and demonstrated at spin-coated SrBiTa2O9 thin films and compared with Pb(Zr,Ti)O3 films. Additionally, a method is described to obtain the static hysteresis curve, a precise characterization of the polarization which does not depend on the measuring frequency. These data are compared with C-V measurements. It is shown that the standard dynamic hysteresis curve reveals misleading statements about the remanent polarization and the coercive voltage.
Thickness Dependence of the Electrical Properties of Sol-Gel Derived Lead Zirconate Titanate Thin Films with (111) and (100) Texture
Authors: Chu F. , Xu F. , Shepard J. , Trolier-McKinstry S. 
Published: April 2011

ABSTRACTCrack-free (111) and (100)-textured Pb(Zr0.52Ti0.48)O3 films with thicknesses ranging from 0.25 to 2.5 μm were prepared using a methoxyethanol-based precursor solution, multiple spin-coating and multiple crystallization steps. The thickness dependence of the dielectric, ferroelectric and piezoelectric properties were investigated on both (111) and (100) oriented PZT films. In both cases, the degree of preferred orientation did not change with thickness. It is found that the dielectric constant, remanent polarization and piezoelectric coefficients (d33 and d31) increase with increasing film thickness. The (100)-textured film showed higher dielectric constant but lower remanent polarization relative to (111) textured film. 1 μm was identified to be a critical thickness that marks the change of dielectric, ferroelectric and piezoelectric behaviors as a function of thickness.
Sol-Gel Derived Pb(Zn1/3Nb2/3)O3-PbTiO3 Thin Films
Authors: Teowee G. , McCarthy K. C. , McCarthy F. S. , Davis D. G. , Dawley J. T. , Zelinski B.J.J. , Uhlmann D. R. 
Published: April 2011

ABSTRACTA series of sol-gel derived PB(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) films, with various PbTiO3 contents, have been prepared on platinized Si wafers. The (l-x)PZN - xPT films fired to 700C became single phase perovskite for x > 0.7. In the PZN-0.1PT films, the films still contain pyrochlore phase at a firing temperature of 850C; the perovskite phase appeared at a firing temperature of 800C. The dielectric constant increased with increasing PT content, with a peak in dielectric constant at x = 0.8. PZN-PT films with x = 0.8 exhibited dielectric constant, dissipation factor, remanent polarization and coercive field values of 600, 0.10, 6 and 45 kV/cm respectively.
Silicon Nitride Films Deposited by Atmospheric Pressure Chemical Vapor Deposition
Authors: Lin Xian , Endisch Denis , Chen Xiaomeng , Kaloyeros Alain 
Published: April 2011

ABSTRACTFilms of silicon nitride are widely used in semiconductor technologies for very large scale integration (VLSI), thin film transistor (TFT), and solar cell applications. Current production technologies for silicon nitride use low pressure chemical vapor deposition (LPCVD) at temperatures > 700 °C or plasma enhanced chemical vapor deposition (PECVD) at temperatures below 450 °C. In this report, successful deposition of silicon nitride films by the low temperature thermal atmospheric pressure chemical vapor deposition (APCVD) method is described. Using a novel precursor tetraiodosilane (SiI4), deposition of silicon nitride has been achieved at temperature as low as 400 °C. Data pertaining to the dependence of film properties on deposition temperature are presented, along with a evaluation of the deposition rate, composition, chemical structure, and conformality of the resulting films.
Growth of Highly Transparent Nano-Crystalline Diamond Films by Microwave CVD
Authors: Bhusari D. M. , Chen K. H. , Yang J. R. , Lin S. T. , Wang T. Y. , Chen L. C. 
Published: April 2011

ABSTRACTWe report here growth of highly transparent nano-crystallinc diamond films on quartz substrates by microwave plasma enhanced CVD. Optical transmittancc of greater than 84% beyond 700 nm has been obtained for films as thick as 1 μm. Such high optical transparency of these films is primarily attributed to the high smoothness of their surface (average roughness of about 60–65 À) as well as the high content of sp3 bonded carbon therein. The effects of methane fraction in the source gas, substrate temperature and grain size of the diamond powder used for substrate pretreatment on the structural and optical properties of these films arc also studied.
Temperature-Dependent Studies of a-SiC:H Growth by Remote Plasma CVD Using Methylsilanes
Authors: Lee Moon-Sook , Lal Pratik , Bent Stacey F. 
Published: April 2011

ABSTRACTThin hydrogenated amorphous silicon carbide (a-SiC:H) films were grown at substrate temperatures ranging from 200 K to 600 K by remote ECR plasma-enhanced CVD. Mono- and trimethylsilane were used as single source precursors. The films grown using both precursors were compared as a function of temperature by in situ multiple internal reflection Fourier transform infrared (MIR-FTIR) spectroscopy. The difference in growth temperature leads to changes in both the hydrogen content and the composition of the film. At low growth temperature, films incorporate high concentrations of intact methyl group and a mixture of SiHx (x=1–3) groups, with a polysilane-like structure. At higher temperatures, the hydrogen content decreases. This decrease is observed in two different ways: (1) a loss of highly hydrogenated SiHx groups (SiH3 or SiH2); and (2) a shift from methyl groups to CH2 and CH bonding. However, the temperature dependence of each functional group is found to be different for the two precursors.