Particle-plasmon decay-time determination by measuring the optical near-field’s autocorrelation: influence of inhomogeneous line broadening

A detailed analysis of the influence of inhomogeneous plasmon absorption band broadening on particle-plasmon decay-time determination by an interferometric autocorrelation method is reported. We present model calculations based on the representation of plasmons in an array of non-uniformly shaped particles by an ensemble of harmonic oscillators. Considering carefully the extent of the inhomogeneous broadening our theoretical treatment yields an unambiguous correlation between the autocorrelation function and the plasmon decay time. As an experimental example we find a plasmon decay time of 6 fs for a gold nanoparticle sample. Received: 24 November 1998 / Revised version: 12 March 1999 / Published online: 7 July 1999     

Time-resolved two-photon photoemission spectroscopy of HOPG and Ag nanoparticles on HOPG

Received: 6 November 1998     

Deconfinement transition: a three dimensional model

We present a three–dimensional model for quark matter with a density dependent quark–quark (confining) potential, which allows to describe a sort of deconfinement transition as the system evolves from a low density assembly of bound structures to a high density free Fermi gas of quarks. We consider different confining potentials, some of which successfully utilized in hadron spectroscopy. We find that a proper treatment of the many–body correlations induced by the medium is essential to disentangle the different nature of the two (hadronic and deconfined) phases of the system. For this purpose the ground state energy per particle and the pair correlation function are investigated. Received: 10 June 1998 / Revised version: 24 September 1998     

Synthesis of a new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxycarbonyl)aminobenzenesulfonamide and its copolymerization with N‐phenyl maleimide

The new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxy‐ carbonyl)aminobenzenesulfonamide (MPBAS) (M₁) is synthesized using sulfadiazine as parent compound. It could be homopolymerized and copolymerized with N‐phenyl maleimide (NPMI) (M₂) by radical mechanism using AIBN as initiator at 60 °C in dimethylformamide. The new monomer MPBAS and polymers were identified by IR, element analysis and ¹H NMR in detail. The monomer reactivity ratios in copolymerization were determined by YBR method, and r₁ (MPBAS) = 2.39 ± 0.05, r₂ (NPMI) = 0.33 ± 0.02. In the presence of ammonium formate, benzyloxycarbonyl groups could be broken fluently from MPBAS segments of copolymer by catalytic transfer hydrogenation, and the copolymer with sulfadiazine side groups are recovered. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2548–2554, 2000     

The kinetics of polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol using benzyltriethylammonium chloride as a phase‐transfer catalyst

The phase‐transfer catalyzed polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol was carried out using benzylethylammonium chloride in a two‐phase system of an aqueous alkaline solution and benzene at 60 °C under nitrogen atmosphere. The rate of polycondensation was expressed as the combined terms of quaternary onium cation and 4,4′‐isopropylidenediphenolate anion rather than the feed concentration of catalyst and 4,4′‐isopropylidenediphenol. The measured concentrations of hydroxide and chloride anion in the aqueous solution and α,α′‐dichloro‐p‐xylene in the organic phase were used to obtain the reaction rate constant with the integral method, and to analyze the polycondensation mechanism with a cyclic phase‐transfer initiation step in the heterogeneous liquid–liquid system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3059–3066, 2000     

The effect of hydrogen bonding on the physical and mechanical properties of rigid‐rod polymers

The idea of competing effects between intramolecular and intermolecular hydrogen bonding was investigated. Results indicate that the formation of one type of hydrogen bond does not preclude the formation of the other. The strength of the intermolecular association was measured by ab initio calculations for several polymer systems, including methyl pendant poly(p‐phenylene benzobisimidazole) and poly‐{2,6‐diimidazo[4,5‐b:4′5′‐e]pyridinylene‐1,4(2,5‐dihydroxy)phenylene} (PIPD). Fibers with strong intermolecular association have high compressive strength and torsional modulus. The influence of intermolecular hydrogen bonding on torsional modulus is discussed in light of the transverse texture present in poly(p‐phenylene terephthalamide) and some other high‐performance fibers. Enhanced intermolecular interaction not only influences the aforementioned properties but also results in higher fiber density. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3053–3061, 2000     

Current Density‐Voltage and Capacitance‐Voltage Characteristics of Local p‐n Junction Structures in CuInSe2 Single Crystals

Local p‐n junction were obtained under room temperature conditions in CuInSe2 by applying strong electric field through small indium and copper contacts. The current density voltage (J‐V) and the capacitance‐voltage (C‐V) of three different samples were measured at room temperature. The J‐V method shows that the current is dominated by the drift component of the injected carriers. The C‐V method gave a barrier height of 1.04 eV for all three samples which agrees with the reported energy gap of this material. Analysis of these results indicate that the p‐n junction structures formed by strong electric fields are hihgly compensated and the current transport is dominated by the space charge limited current effect.     

New electrochemically synthesized mixed polymers with very high electrochemical stability

The electrosynthesis of new mixed polymers is described, starting with the anodic oxidation of a mixture of 3,4‐ethylenedioxythiophene: EDOT and dicyanomethylenefluorene: DiCNFl. The resulting mixed polymer possesses a very high electrochemical stability and good electrochromic properties. Copyright © 2000 John Wiley & Sons, Ltd.     

Time‐resolved crystallization study of absorbable polymers by synchrotron small‐angle X‐ray scattering

Changes in the lamellar morphology that occurred during the quiescent isothermal crystallization of absorbable poly(p‐dioxanone) (PDS) and PDS/poly(glycolide) block copolymer were studied by synchrotron small‐angle X‐ray scattering. Important morphological parameters such as the lamellar long period, the thicknesses of the crystal and amorphous phases, and the scattering invariant were estimated as a function of time, and trends observed over a wide range of experimental conditions are discussed. Thicker but more perfect lamellae were detected at higher crystallization temperatures. The breadth of the normalized semilog Lorentz‐corrected intensity peak systematically decreased with increasing temperature. In addition, the values of the crystallization half‐time and the Avrami exponent (n = 2.5), determined from the real‐time changes in the lamellar development, showed superb agreement with the bulk crystallinity data generated from other experimental techniques, such as calorimetry and dielectric relaxation spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 153–167, 2001     

Calorimetric study of the solubilization of ethylenediamine,N,N-dimethylaminoethylamine and N,N,N′,N′-tetramethylethylenediamine by reversed AOT micelles

Distribution constants and standard enthalpies of transfer of ethylenediamine (en), N,N-dimethylaminoethylamine (dmen) and N,N,N,N-tetramethylethylenediamine (tmen) partitioned between n-heptane and water containing reversed sodium bis(2-ethylhexyl) sulfosuccinate (AOT) micelles as a function of the molar concentration ratio R (R=[water]/[AOT]) were evaluated by a calorimetric method. The results show that en, dmen and tmen molecules, solubilized in the reversed micelles, are distributed between the micellar aqueous core and the micellar palisade layer. An analysis of the thermodynamic parameters of the partition process demonstrates the peculiar solvent properties of the water containing reversed AOT micelles.