bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermally stimulated current studies of thermotropic polyesters with polymethylene spacers (I): The glass transition and relaxation behavior of anisotropic and isotropic glasses
Authors: Liu Shur‐Fen , Lee Yu‐Der
Published: April 2003

Thermally stimulated current (TSC) and relaxation map analysis (RMA) were used to study the glass transitions and relaxation phenomena of the anisotropic and isotropic glasses for the semiflexible polyesters with various polymethylene spacers (n = 7 ˜ 10). TSC analysis indicated that the glass transition temperatures (Tg) of polymers at around 40 ˜ 50°C exhibited an apparent even‐odd behavior not only for the anisotropic glasses but also for the isotropic glasses. The Tg of the isotropic glass for the polymer with even n value was observed to be higher than those for the two neighboring polymers with odd n values. The anisotropic glass for the polymer with even n value had a lower Tg than those for the two neighboring polymers with odd n values. The lower value was attributed to the configuration and orientation effects on the behavior of polarization. RMA revealed that the relaxation modes of the investigated polymers were also influenced by the configuration and orientation effects. The dipolar relaxation of the anisotropic glass for the polymer with odd n value occurred at a higher temperature and had a lower entropy (enthalpy) of activation than that of the isotropic glass for the same polymer due to the orientation effect. However, an inverse relation was found to occur for the polymer with even n value, which came from the trans configuration of the even polymethylene spacers. Finally, the thermokinetic properties evaluated by RMA (e.g., the final state after depolarization) correlated quite well with the results obtained by TSC. © 1995 John Wiley & Sons, Inc.
Influence of conformational asymmetry on the surface enrichment of polymer blends II
Authors: Donley James P. , Fredrickson Glenn H.
Published: April 2003

We reexamine the influence of statistical segment length asymmetry on the surface segregation of homopolymer blends in a mean field thread model of polymer melts. By developing numerical self‐consistent field solutions of the Edwards‐Helfand equations, we demonstrate that the component with the smaller value of the parameter β2 = a2/(6ν) (a is the statistical segment length and ν is the segment volume) is enriched at a neutral, impenetrable surface. Qualitatively, this finding is in agreement with our earlier analytical work and with experiment. However, in contrast to our earlier work, we find that the absolute magnitude of the segregation is a sensitive function of the chain lengths of the two species and of the compressibility of the system. © 1995 John Wiley & Sons, Inc.
Gas transport properties of polyarylates part II: Tetrabromination of the bisphenol
Authors: Pixton M. R. , Paul D. R.
Published: April 2003

The gas transport properties of a series of polyarylates based on isophthalic acid have been examined. The polyarylates were synthesized from the following bisphenol monomers with and without tetrabromo substitution: bisphenol A, hexafluorobisphenol A, phenolphthalein, and fluorene bisphenol, to study the effects of tetrabromination in combination with varying the bisphenol connector group size and shape. Substitution of a tertiary butyl group at position five on the isophthalate ring was used to increase polymer permeability. Tetrabromination of the bisphenol maintains or increases gas permeability and significantly increases permselectivity particularly for the O2/N2 gas pair as compared with the non‐brominated analog. The substitution of t‐butyl groups increases gas permeability by two‐to fourfold but lowers permselectivity. Most of the increase in permeability can be related to an increase in the diffusion coefficient for each gas. All the brominated polyarylates have gas transport properties superior to most known glassy materials for O2/N2 separation with several materials close to a proposed empirical “upper bound” between permeability and selectivity. © 1995 John Wiley & Sons, Inc.
A nuclear magnetic resonance study of toluene‐polyisobutylene solutions. 3. Spin‐lattice relaxation: Rotational and segmental motion
Authors: Bandis Athinodoros , Inglefield Paul T. , Jones Alan A. , Wen Wen‐Yang
Published: April 2003

The spin‐lattice relaxation times are determined for the methylene carbon of polyisobutylene (PIB), as well as for the ortho carbon of toluene in toluene‐polyisobutylene solutions. The Hall‐Helfand correlation function combined with restricted anisotropic rotational diffusion was used to treat theT1data of the methylene carbon of PIB. A simple exponential correlation function was used to describe the local motion of toluene in the solutions which falls in the extreme narrowing limit for the solutions studied. Both models described satisfactorily the temperature and field dependence of the spin‐lattice relation times. From the temperature dependence of the correlation times for the polymer segmental motion, the free volume of the solution at each concentration is extracted and compared with the values obtained from previous studies of the translational motion of the toluene penetrant. The free volume values extracted from theT1data for the methylene carbon of PIB and the self‐diffusion data for the toluene were found to be in substantial agreement. The interrelationship of the timescale of segmental motion of the polymer and the translational diffusion of the toluene was also examined and it was found that the two types of motion seem to be correlated in high polymer concentrated solutions. The toluene reorientational motion was found to be much faster than both the polymer segmental motion and the toluene translational diffusion leading to the conclusion that the toluene reorientational motion is uncoupled from these two motions. ©1995 John Wiley & Sons, Inc.
Revisit to the intrinsic viscosity‐molecular weight relationship of ionic polymers. 7. Examination of the Pals‐Hermans dilution method with reference to the viscosity behavior of dilute aqueous dispersion of ionic polymer latex
Authors: Yamanaka Junpei , Yamada Saiko , Ise Norio , Yamaguchi Takuji
Published: April 2003

The isoionic dilution method, which was proposed by Pals and Hermans, for linear ionic polymer solutions, was examined for the viscosity behavior of dilute aqueous dispersion of ionic latex [particle diameter, (0.120 ± 0.003) × 10–6 m; surface charge density, 1.6 × 10–6 C/cm2] in the presence of sodium chloride (5 × 10–5 to 5 × 10–4 M). Linear relations were obtained between the reduced viscosity and the latex concentration, when a parameter m, which appeared in the effective ionic strength introduced by Pals and Hermans, was chosen to be about 0.1. This finding on the latex system does not support that, at the salt and polymer concentrations employed, the dimension of linear macroions varies with changing effective ionic strength and it is kept constant along the isoionic dilution line. Brief discussion on the m value is presented. ©1995 John Wiley & Sons, Inc.
Dilute solution properties, chain stiffness, and liquid crystalline properties of cellulose propionate
Authors: Casay G. A. , George A. , Hadjichristidis N. , Lindner J. S. , Mays J. W. , Peiffer D. G. , Wilson W. W.
Published: April 2003

The solution properties of cellulose derivatives are of interest from both technological and purely scientific aspects. At high concentrations these solutions form liquid crystalline structures. In dilute solution cellulosic chains can be described as semiflexible or wormlike with properties intermediate between random coils and rigid rods. A series of fractions of cellulose propionate have been examined by dilute solution viscometry, static and dynamic light scattering, and polarizing microscopy. Power law exponents are considerably larger than those observed for flexible chains and analysis of the intrinsic viscosity and hydrodynamic radii has yielded chain diameters and Kuhn statistical segment lengths. Corresponding aspect ratios from the hydrodynamic measurements are in good agreement with those obtained from polarizing microscopy, as analyzed in light of Flory's theory. Some aggregation and specific solvent effects have been observed, however separation of these effects has proven to be difficult. Results of these studies are compared to previous work for other cellulose derivatives. ©1995 John Wiley & Sons, Inc.
Analysis of polyurethanes using core excitation spectroscopy. Part II: Inner shell spectra of ether, urea and carbamate model compounds
Authors: Urquhart S. G. , Hitchcock A. P. , Priester R. D. , Rightor E. G.
Published: April 2003

Core excitation spectra of selected small molecule analogue species have been acquired to assist interpretation of the core excitation spectra of model methylenediphenyldiisocyanate (MDI) polyurethane polymers. Oscillator strength spectra for C 1s and O 1s core excitation of diethyl ether and diisopropyl ether; C 1s, N 1s, and O 1s core excitation of urea, N‐phenyl urea, N, N′‐diphenyl urea, ethyl carbamate, N‐phenyl carbamate, N‐phenyl N‐methyl carbamate, and benzyl carbamate have been derived from gas phase electron energy loss spectra (EELS). Extended Hückel Molecular Orbital (EHMO) calculations are used to assist assignment and to interpret the effect of π‐electron delocalization on the gas phase spectra. Functional group identification by core excitation is explored for the purpose of using core excitation spectra for microanalysis of polyurethane polymers. © 1995 John Wiley & Sons, Inc.
Fluorescence of perylene‐ and naphthalene‐containing polyimides: Evidence of molecular aggregation and chain coiling in chloroform solution
Authors: Ghassemi H. , Zhu J. H.
Published: April 2003

Fluorescence of several new polyimides in which neighboring imides are linked by a N‐N bond was examined in chloroform solutions. For the naphthalene‐containing polyimide 1, analysis of the emission, excitation, and absorption spectra at different concentrations showed the existence of a ground‐state intermolecular charge transfer (CT) complex due to chain association and aggregation. For the perylene‐containing polyimides 3‐6, the fluorescence was characterized by a low energy band superimposed on the normal perylenediimide bands. This was interpreted as arising from a CT interaction between electron donor‐acceptor pairs on the polymers backbone of the same chain, revealing certain degrees of chain coiling of these polymers in solution. © 1995 John Wiley & Sons, Inc.
Sorption, diffusion, and partial molar volumes of C4 hydrocarbons in rubbery polymers
Authors: Kamiya Yoshinori , Terada Katsuhiko , Naito Yasutoshi , Wang Jin‐Sheng
Published: April 2003

Sorption and dilation isotherms and diffusion coefficients for seven hydrocarbons (n‐butane, isobutane, 1‐butene, cis‐2‐butene, trans‐2‐butene, isobutylene, and 1,3‐butadiene) in two rubbery polymers, 1,2‐polybutadiene (PB) and poly(ethylene‐co‐vinyl acetate) (EVAc), were measured at 25°C. Dissolution parameters (Henry's law coefficient and Flory‐Huggins interaction parameter), partial molar volumes, and diffusion coefficients were determined. PB exhibited greater affinity and lower diffusivity than EVAc to the C4 gases, although the gases showed nearly the same partial molar volumes in the two polymers. The diffusivity of such elongated molecules as trans‐2‐butene in both polymers was higher than that of bulky molecules with similar partial molar volume, such as cis‐2‐butene and isobutylene. Pressure‐dependent permeabilities of PB and EVAc films to the hydrocarbons were predicted and discussed based on the dissolution parameters and the diffusivities. © 1995 John Wiley & Sons, Inc.
Fluorescence study on a thermotropic liquid‐crystalline polyester at high temperatures
Authors: Huang Hsu Wen , Horie Kazuyuki , Yamashita Takashi
Published: April 2003

A thermotropic liquid‐crystalline (LC) polyester, poly[(ethylene terephthalate)‐co‐(p‐oxybenzoate)] (PET40/OBA60) (OBA content: 60 mol %), is investigated by fluorescence technique using two model compounds: dimethyl terephthalate (DMT) and methyl methoxybenzoate (MMB) and is demonstrated to form an intermolecular ground‐state complex between the terephthalate and OBA moieties. The change in fluorescence of PET40/OBA60 film is studied from 25°C to 450°C. The peak wavelength change for fluorescence of the intermolecular ground‐state complex from 394 to 430 nm was observed in the temperature range between Tg and the LC transition temperature (115∼ 250°C). This is attributed to the electronic distribution change between terephthalate and OBA moieties in the excited state, which play roles of acceptor and donor, respectively. The increase in the fluorescence intensity from the temperature near the annealing temperature to the temperature near the isotropic temperature (287∼370°C) is suggested to be the increase in LC configuration and the formation of a more stable excited state due to the electronic distribution change between terephthalate and OBA moieties. The lifetime of PET40/OBA60 film quenched from LC temperature (300°C) to room temperature is in agreement with that of the nonannealed one, which is due to the fact that the deactivation process of the sample quenched from LC temperature is in accord with that of the nonannealed one. © 1995 John Wiley & Sons, Inc.
Light scattering study of solubilization of organic molecules by block copolymer micelles in aqueous media
Authors: Tian Minmin , Arca Emin , Tuzar Zdenek , Webber Stephen E. , Munk Petr
Published: April 2003

Block copolymers, when dissolved in a selective solvent, form spherical micelles. These micelles can selectively solubilize organic molecules otherwise insoluble in the pure solvent. In this study, we report solubilization of organic molecules by styrene‐methacrylic acid block copolymer micelles in aqueous buffers. A light scattering technique was developed to determine the extent of micellar solubilization. Our results indicate that the extent of micellar solubilization depends on the chemical nature of organic molecules, specifically, on the interactions between the organic compound and polystyrene. A thermodynamic model has been developed to describe micellar solubilization. The theoretical calculation agrees reasonably well with the experimental results for two micellar samples examined. ©1995 John Wiley & Sons, Inc.
Effect of the structure of latex particles on adhesion. Part I: Synthesis and characterization of structured latex particles of acrylic copolymers and their peel adhesion behavior
Authors: Mayer André , Pith Tha , Hu Guo‐hua , Lambla Morand
Published: April 2003

This is a series of articles that deals with fundamental aspects of the effects of the structure of latex particles of acrylic copolymers on their adhesion behavior. Specifically, relationship or analogy between rheological properties and adhesion performance of the acrylic copolymers was demonstrated. The first part of this series concerns the synthesis and characterization of latex particles with desired structures and compositions, and the experimental results of peel adhesion. The second part develops an analogy between the peel adhesion performance of the adhesives and rheological properties of the corresponding copolymers. The third part addresses the generalities and particularities of three major tests for adhesion: peeling, blistering, and spontaneous peeling. Three types of structured latex particles were synthesized by three different emulsion polymerization processes: the first type had a uniform composition over the entire particles with a glass transition temperature (Tg) varying between −40°C and 0°C, depending upon the compositions of monomers involved in the copolymer; the second type was of core‐shell structure. As for the third type, the composition of monomers varied gradually across the particle radii. The glass transition behavior and the dynamic mechanical properties in the solid state of the copolymers confirmed the structures of the corresponding latex particles. On the other hand, the peel adhesion performance of the films of these latex particles varied with the dynamic mechanical properties of the corresponding copolymers. This implies that a correlation could be found between the structure of the latex particles, dynamic mechanical properties in the solid state of the corresponding copolymers, and the peel adhesion performance of the adhesive films. ©1995 John Wiley & Sons, Inc.
Effect of the structure of latex particles on adhesion. Part II: Analogy between peel adhesion and rheological properties of acrylic copolymers
Authors: Mayer André , Pith Tha , Hu Guo‐hua , Lambla Morand
Published: April 2003

This article, the second part of this series, concerns the development of an analogy between the peel behavior of pressure‐sensitive adhesives and the dynamic mechanical properties of the corresponding copolymers. The adhesive copolymers used were synthesized by emulsion polymerization processes. Their physical and dynamic mechanical properties were characterized and presented in Part I of this series. In this study, an analogy was built up between the force in a peel test as a function of peel velocity, Fp(vp), and the loss modulus of the adhesive as a function of the angular frequency in a dynamic mechanical experiment, G″(ω). This was done by superimposing the curves of Fp versus vp and those of G″ versus ωβ0/β, where β0/β is a shift factor with β being a parameter in the Kaelble theory and β0 being some reference value of the Kaelble parameter. When the curves of Fp ∼ vp and those of G″ ∼ ωβ0 were plotted together, they followed the same trend of variation. This analogy between G″(ωβ0/β) and Fp(vp) was further confirmed by the fact that the apparent activation energies of the primary glass transition for G″(ω) and Fp(vp) are virtually the same, suggesting that the analogy between G″(ω) and Fp(vp) is dictated by the glass transition. The existence of the above‐mentioned analogy between G″(ω) and Fp(vp) shows that the performance of an adhesive can be evaluated or predicted from the dynamical loss modulus of the corresponding (co)polymer. ©1995 John Wiley & Sons, Inc.
Low‐temperature elastic moduli and internal dilational and shear friction of polymethyl methacrylate
Authors: Fukuhara Mikio , Sampei Asao
Published: April 2003

Longitudinal and transverse wave velocity, five kinds of elastic parameters (young, shear and bulk moduli, Lamér; parameter. Poisson's ratio) and dilational and shear internal friction of polymethyl methacrylate were simultaneously measured over a temperature range 68–400K, using the ultrasonic pulse method. All elastic moduli decrease with increasing temperature, suggesting lowering of molecular bonding strength. From dilational and shear internal frictions, the 139, 382, and 385K peaks are interpreted as rotation of x‐methyl estel groups, micro Brownian motion of main chains and stress relaxation, and abrupt increases from 242 and 395K are regarded as free motion of side chains and glass transition, respectively. ©1995 John Wiley & Sons, Inc.
Network formation studied by temperature scanning Brillouin scattering and differential scanning calorimetry techniques. I. The cure of 1,4‐butanediol diglycidyl ether with cis‐1,2‐cyclohexanedicarboxylic anhydride initiated by triethylamine
Authors: Samios D. , Castiglia S. , Da Silveira N. Pesce , Stassen H.
Published: April 2003

The network formation process of the triethylamine‐initiated reaction of 1,4‐butanediol diglycidyl ether with cis‐1,2‐cyclohexanedicarboxylic anhydride has been investigated by conventional differential scanning calorimetry and temperature scanning Brillouin light scattering as a new experimental method for the estimation of the reaction's conversion factor. The time‐temperature evolution of the observed quantities (reaction enthalpy in the calorimetric measurements and hypersound velocity in the light scattering) reflects in both sets of experimental data, but results in different kinetic parameters obtained by the assumption of an Arrhenius behavior. These differences are ascribed to the relation of the observed properties with respect to the evolution of the reaction. The enthalpy production of the system observed in the calorimetric experiment is shown to be connected directly to the chemical reaction, whereas the change in the hypersound velocity measured by the light scattering method is sensitive to the solidification of the system. © 1995 John Wiley & Sons, Inc.
Intermolecular interactions in substituted phenols. Investigation of model compounds
Authors: Teegarden D. M. , Landry C. J. T.
Published: April 2003

The results of heats of mixing experiments on a series of ortho‐substituted phenols with an amide or an ester are described. Substituents were chosen to span a wide range of electronic and steric character. Enthalpy of mixing results do not correlate solely with the acid strength of the phenol, or with a Hammett linear free‐energy analysis. Rather, interactions are favored by the presence of groups with the ability to weaken the base strength of the proton donor while simultaneously increasing its acid strength. Such groups share a combination of electron‐withdrawing ability and/or steric bulk that causes an effective decrease in the electron density about the phenolic oxygen. Trifluoromethyl and tert‐butyl, and to a lesser extent halogen and hydroxy substituents ortho to the phenolic OH, give the highest exothermic enthalpies of mixing and are thus the most effective at promoting intermolecular interactions with weak bases such as amides and esters. These results should be useful in designing miscible or compatible polymer blends in which specific interactions such as hydrogen bonding are important. © 1995 John Wiley & Sons, Inc.
Phase transitions in two polyesters containing a smectic diol
Authors: Khan Nazir , Patel Vijya L. , Bashir Zahir , Price Duncan M.
Published: April 2003

This work reports the phase behavior of the polyesters made from the condensation of isophthalic acid (IA) and terephthalic acid (TA) with the mesogenic diol 4,4′‐bis (6‐hydroxy hexoxy) biphenyl (BHHBP). The latter monomer forms a smectic mesophase in the interval 98‐179°C. Fischer et al., who investigated the room temperature x‐ray patterns of the oriented polyesters of BHHBP and IA, as well as BHHBP and TA, claimed that both polymers also showed smectic mesophases. However, they showed no other evidence to support their interpretation. In the present work, examination of these polyesters under the optical microscope revealed focal conic textures for the IA polyester, but spherulitic textures for the TA polyester. DSC studies revealed thermograms with two peaks in the cooling scan for the IA polyester, at different cooling rates, which supported the view that there were two phase transitions. The heating scans of the TA polyester showed multiple peaks that depended on heating rate whereas on cooling, only a single exothermic peak was observed at all cooling rates. Thus, the current results definitely support the case for a smectic A mesophase in the IA polyester but, contrary to Fischer et al.'s opinion, do not suggest any mesophase formation in the TA polyester. © 1995 John Wiley & Sons, Inc.
Effects of solvent treatment on crystallization kinetics of poly(p‐phenylene sulfide)
Authors: Woo E. M. , Chen J.‐M.
Published: April 2003

Isothermal melt crystallization kinetics were investigated by differential scanning calorimetry (DSC) for virgin and α‐chloronaphthalene solvent‐treated poly(phenylene sulfide) (PPS) systems. The overall crystallization rates were found to be much faster for the solvent‐treated PPS than for the virgin neat PPS. Additionally, the Avrami crystallization plot for the solvent‐treated PPS samples appeared as two straight portions with an apparent discontinuity, but as a continuous straight line for the virgin PPS system. After the treatment of solvent dissolution and subsequent drying, the residual trace α‐chloronaphthalene, upon being quenched to the crystallization temperatures, initiated some localized solvent‐induced nuclei‐like crystals in PPS. It was the nuclei that enhanced secondary crystallization in treated PPS during the second stage, and the higher extents of secondary crystallization in the solvent‐treated PPS caused the apparent discontinuous break in the Avrami plots. The causes for the difference were explained and the mechanism of the sequential primary/secondary crystallization kinetics for the solvent‐treated PPS was satisfactorily described with a proposed series‐parallel crystallization model. ©1995 John Wiley & Sons, Inc.
Water sorption in poly(zwitterions) of the ammonioalkoxydicyanoethenolate type
Authors: Galin J. C. , Galin M.
Published: April 2003

Water sorption by amorphous (meth)acrylic poly(zwitterions)‐bearing quaternary ammonioalkoxydicyanoethenolate side groups , dipole moment μ(D) = 25.9 and 30.8 for p = 2 and 3, respectively was studied at 23°C over a broad range of water activity a (0.14–0.98). Water diffusion is nearly Fickian (Ds = 5.9 10−7 cm2.s−1 for a = 0.63) and the sorption isotherms may be quantitatively analyzed according to the Guggenheim‐Anderson‐De Boer equation for a multilayer process characterized by a number of site‐bound water molecules per monomeric unit, nm ⋑ 0.7. The Flory χ interaction parameter is a strongly increasing function of the water content in the glassy hydrated systems and it always remains higher than 0.75. Clustering of water molecules (Zimm‐Lundberg theory) is never observed. Differential scanning calorimetry allows to quantify nonfreezable bound water (type I) of strong plasticization efficiency, n(I) = 2.8 mol. of water per monomeric unit, and it points out the quasisimultaneous emergence of low amounts of freezable bound water (type II) crystallizing at −40°C and melting at −1°C and of bulkfree water (type III, n(II)/n(III) ⋑ 0.1). All these typical features distinguish these rather hydrophobic poly(zwitterions) from their hydrophilic homologues of the quaternary ammoniopropanesulfonate type . © 1995 John Wiley & Sons, Inc.
Structural data and thermal studies on nylon‐12,10
Authors: Franco Lourdes , Puiggalí Jordi
Published: April 2003

The structure and morphology of Nylon‐12, 10 lamellar crystals has been investigated using transmission electron microscopy, selected area electron diffraction, and x‐ray diffraction. Additional data have been obtained from uniaxially oriented fibers. The unit cell parameters of two crystalline structures have been determined. They are similar to those usually found in other polyamides (α and β form). Calorimetric (DSC) studies on nylon 12, 10 were also carried out. Melting curves indicate that changes in the internal structure occur when scanning speeds less than 80°C min−1 are used. ©1995 John Wiley & Sons, Inc.
Rodlike/flexible polyimide composite films prepared from soluble poly(amic diethyl ester) precursors: Miscibility, structure, and properties
Authors: Kim Y. , Ree M. , Chang T. , Ha C. S. , Nunes T. L. , Lin J. S.
Published: April 2003

Homogeneous precursor/precursor solutions with various compositions were obtained with appreciably high solid contents in N‐methyl‐2‐pyrrolidone from soluble poly(amic diethyl ester) precursors of rodlike poly(p‐phenylene biphenyltetracarboximide) (BPDA‐PDA) and flexible poly(4,4′‐oxydiphenylene biphenyltetracarboximide) (BPDA‐ODA), which are hydrolytically more stable as well as more soluble than the corresponding poly(amic acid)s being equilibrated with the constituent monomers. Both optical microscopic and light scattering measurements showed that the dried precursor blend films and resultant polyimide composite films were optically transparent, regardless of compositions and process conditions. The composite films showed a single Tg behavior. However, for the composite of 30 wt % BPDA‐PDA dispersed in the matrix of 70 wt % BPDA‐ODA, a smectic crystalline‐like aggregation of the BPDA‐PDA component was detected on wide‐angle x‐ray diffraction patterns, indicative of microscopic phase separation between the two components. This phase separation was not detected on the optical microscopy, light scattering, and dynamic mechanical thermal analysis because of their resolution limits: Optical microscopy has a resolution of submicrometers, whereas dynamic mechanical thermal analysis and light scattering have a resolution of ca. 50 Å. Therefore, it is speculated that in the composite films BPDA‐PDA and BPDA‐ODA polyimide molecules have demixed on the scale of a few nanometers. The mean long periodicity, which was estimated from the small‐angle x‐ray scattering pattern, varied from 134 to 170 Å as the content of BPDA‐ODA component increased. In addition, mechanical properties of the composite films were characterized. ©1995 John Wiley & Sons, Inc.
Cellulose‐polyamide 66 blends. Part II: Mechanical behavior
Authors: Ramirez M. Garcia , Cavaillé J. Y. , Dufresne A. , Tékély P.
Published: April 2003

Blends of the natural polymer cellulose with a synthetic polymer, polyamide 66, are studied in order to determine if the expected strong interaction between them, due to hydrogen bonds, could improve their mechanical properties such as strength and elongation at break. In a previous work {Part I, J. Polym. Sci. Polym. Phys., 32, 1437 (1994)}, the preparation technique and the characterization of cellulose‐polyamide 66 (PA66) blends were described in detail. Several samples in the composition range between 0 to 70 wt % of PA66 were carefully dried and examined using dynamic mechanical and tensile tests. Based on previous work a new percolation model has been developed. It takes both linear and nonlinear mechanical behaviors into account and allows for the effect of adhesion between material domains. From comparison between experimental and predicted data, it is concluded that a partial miscibility between the amorphous phases of cellulose and PA66 exists and is responsible for a strong adhesion at their interface. Solid‐state 13C nuclear magnetic resonance has also been used to study these samples and supports the existence of strong interactions between both homopolymers. © 1995 John Wiley & Sons, Inc.
A detailed study of the viscoelastic nature of vapor sorption and transport in a cellulosic polymer. II. Sorption and longitudinal swelling kinetic correlations
Authors: Sanopoulou M. , Roussis P. P. , Petropoulos J. H.
Published: April 2003

Longitudinal swelling kinetics of cellulose acetate films sorbing acetone vapor at 30°C were studied under various conditions and correlated with the corresponding sorption kinetic measurements reported in Part I. The results were analyzed in the light of (1) previous theoretical studies of simple viscoelastic polymer‐penetrant model systems and (2) mechanical stress‐strain data on the cellulose acetate‐acetone system, which are also reported here. The conclusions drawn from this analysis confirm and/or amplify (particularly as regards the effect of longitudinal differential swelling stresses) our previous interpretations based on sorption kinetic analysis, concerning the physical nature and causes of various features of the non‐Fickian kinetic behavior of cellulosic polymer‐micromolecular penetrant systems. History‐dependent long‐term aging effects were also observed and investigated. © 1995 John Wiley & Sons, Inc.
Mechanical properties of dual‐phase polymer electrolytes prepared from poly(styrene‐co‐butadiene) rubber/poly(acrylonitrile‐co‐butadiene) rubber mixed latices
Authors: Ichino Toshihiro , Takeshita Yukitoshi , Nishi Shiro
Published: April 2003

Mechanical properties of two dual‐phase polymer electrolytes (DPEs), prepared from poly(styrene‐co‐butadiene) rubber (SBR) and poly(acrylonitrile‐co‐butadiene) rubber (NBR) latices, are studied. Both DPEs are composed of an SBR supporting phase and an ionconductive phase of NBR/lithium salt solution. The first DPE maintains a tensile strength of 0.5 MPa and elongation of 280% with an ionic conductivity of 10−3 S/cm. Although the glass transition relaxations based on the dual‐phase structure are not resolved in this DPE because of the proximity of the glass transition temperatures of the SBR and NBR, the glass transition shifts to a lower temperature due to the plasticization by the lithium salt solution. In the second DPE, two distinctive glass transition relaxations, corresponding to the SBR and NBR phases, are observed in the viscoelasticity versus temperature measurement, indicating the dual‐phase structure. A simple equivalent mechanical model, which is modified from the Takayanagi model, is introduced to elucidate the mechanical behavior of the dual‐phase structure in the second DPE. According to this model, 8% of DPE is a mechanically continuous SBR phase in the tensile direction, which effectively gives mechanical support to the DPE. © 1995 John Wiley & Sons, Inc.
Hysteresis loss as a measure of metal–rubber adhesion
Authors: Bhattacharya Tinku , De S. K.
Published: April 2003

As in the case of reinforcing filler‐induced increase in hysteresis in rubbers, placement of aluminum (A1) foil to the surface of a rubber blend of epichlorohydrin rubber and carboxylated nitrile base induces increased hysteresis of the rubber due to adhesion between Al and the rubber blend. Changes in hysteresis loss due to Al foil can be correlated with the peel strength of Al‐rubber‐Al joints. © 1995 John Wiley & Sons, Inc.
High‐quality polythiophene films prepared by electropolymerization of thiophene in BF3‐ethyl ether solution
Authors: Li Cun , Shi Gaoquan , Xue Gi , Jin Shi , Yu Bo , Yang Sijun
Published: April 2003

Polythiophene films have been deposited on a platinum electrode surface by direct oxidation of thiophene in BF3‐ethyl ether solution containing a controlled amount of water (5 mM). The electric and mechanical properties of the films were studied. Experimental results demonstrated that the films prepared at low applied potentials were semiconductors with conductivities in the order of 10−1 s cm−1. The strengths of these films were high and comparable to those of some widely used engineering plastics such as poly(propylene) and poly(vinyl acetate). The conductivities of the PT films varied with the value of applied potential used for electrolysis and passed through a maximum of 19.13 s cm−1 at +1.6 V. At a given applied potential, low experimental temperature, and monomer concentration led to formation of films with high quality. © 1995 John Wiley & Sons, Inc.
Excitation energy transfer in poly(p‐phenylphenylenevinylene) determined by polarized fluorescence spectroscopy
Authors: Damerau T. , Hennecke M.
Published: April 2003

Polarized fluorescence spectroscopy is used to investigate the photophysical behavior of poly(p‐phenylphenylenevinylene) (PPPV) in polystyrene matrix in comparison with oligomeric model compounds. For this purpose PPPV is modeled by a chain consisting of a distribution of independent oligomeric segments. Excitation energy transfer (EET) between the segments depends on the wavelength of excitation, not only for transfer along an isolated polymer chain, but also for intermolecular transfer at high concentration of PPPV. The spatial range of EET, as indicated by fluorescence depolarization, is reduced for excitation at the long wavelength edge of the absorption spectrum (“red‐edge‐effect”). © 1995 John Wiley & Sons, Inc.
Osmotic deswelling of weakly charged poly(acrylic acid) solutions and gels
Authors: Silberberg‐Bouhnik Myriam , Ramon Ory , Ladyzhinski Ilya , Mizrahi Shimon , Cohen Yachin
Published: April 2003

The osmotic pressure of weakly charged aqueous poly(acrylic acid) (PAA) solutions and the swelling pressure PAA gels were studied by osmotic deswelling at different degrees of ionization (α). In solution, the osmotic pressure was found to scale linearly with concentration, whereas the scaling power of the swelling pressure of gels was higher (1.66). The effect of the ionization degree on the osmotic coefficient in PAA solutions was in agreement with the theory of Borue and Erukhimovich [Macromolecules, 21, 3240 (1988)]. Ionization increases the swelling capacity of the PAA gels until a plateau is reached at about 35% neutralization. The concentration at equilibrium swelling scales as Ce ∼ α−0.6. The contribution of the network to the gel swelling pressure is evaluated by subtracting the osmotic pressure of the polymer solution at the same concentration and degree of ionization. In swollen gels the extended network opposes swelling. As the gel is osmotically deswelled, a state of zero network pressure exists at a certain concentration, below which the network elasticity favors swelling. The crossover concentration shifts to lower values as the degrees of ionization increases. © 1995 John Wiley & Sons, Inc.
Small‐angle X‐ray scattering study of liquid crystalline polycarbonates based on α‐methyl stilbene mesogen and methylene‐containing flexible spacer
Authors: Cheng Yao‐Yi , Cebe Peggy , Capel Malcolm , Schreuder‐Gibson Heidi , Bluhm Aaron , Yeomans Walter
Published: April 2003

Crystallization and melting behavior are studied by small‐angle X‐ray scattering (SAXS) for a series of recently synthesized monotropic liquid crystalline polycarbonates based on α‐methyl stilbene mesogen and methylene flexible spacer. The one‐dimensional electron density correlation function is used to obtain long period, crystal thickness, and linear crystallinity from the Lorentz‐corrected SAXS intensity. Changes in these parameters during nonisothermal crystallization and melting are explained by a model of dual crystal populations. The primary crystals form first using the liquid crystalline phase as crystal nuclei, while smaller and less perfect crystals form later from the isotropic phase at low temperature. The results of the real‐time SAXS study of isothermal crystallization also support the view that the nematic phase serves as crystal nuclei for fast crystallization. An odd‐even effect in crystal thickness and linear crystallinity is observed in all the SAXS experiments mentioned above. The results of this study and our complementary wide‐angle X‐ray scattering (WAXS) investigation show clearly that the difference in the position of the neighboring carbonate dipoles on a chain affects structural organization both at the unit cell level and at the level of the crystal in these monotropic LCPs. © 1995 John Wiley & Sons, Inc.
Distribution of chain ends at the surface of a polymer melt: Compensation effects and surface tension
Authors: Wu David T. , Fredrickson Glenn H. , Carton Jean‐Pierre , Ajdari Armand , Leibler Ludwik
Published: April 2003

We consider the surface of a nearly incompressible polymer melt, extending the usual ground‐state analysis of self‐consistent field theory to describe finite length polymers in the ground‐state potential. To maintain self‐consistency, further corrections to the potential are calculated within linear response theory. From this, we find an excess of ends near the surface, followed by a compensating depletion on the Rg length scale, which relies crucially on the finite compressibility of the melt. The attraction of ends to the surface can be described as resulting from a surface potential for ends with a strength on the order of kBT. Our results address the long‐standing controversies of the distribution of chain ends, the chain‐length dependence of the surface tension, and the interaction between objects immersed in a melt. © 1995 John Wiley & Sons, Inc.
Investigation of dielectric relaxations associated with the glass transition of vinylidene fluoride and trifluoroethylene copolymers by thermally stimulated current
Authors: Teyssèdre G. , Bernès A. , Lacabanne C.
Published: April 2003

Thermostimulated current (TSC) spectroscopy was applied to the characterization of dielectric relaxations associated with the glass transition of a series of P(VDF/TrFE) copolymers. The maximum temperature of the β‐mode increases slightly as the TrFE unit content is increased, in the same manner as the glass transition temperature. By using the technique of fractional polarizations to the resolution of this relaxation mode, we have isolated, for all the polymers investigated, a series of elementary relaxation times that obey a compensation law. This behavior is characteristic of the free amorphous phase of polymers. The mean activation energy of this mode increases as the TrFE unit content is increased, due to a stiffening of molecular chains. Annealing of the copolymers above their ferroelectric‐to‐paraelectric transition induces a strong crystallinity increase of the materials. As a matter of fact, the amorphous phase is squeezed in to dimensions lower than the characteristic length scale associated with the glass transition. © 1995 John Wiley & Sons, Inc.
PMMA adsorption over previously adsorbed PS studied by polarized FTIR‐ATR
Authors: Enriquez Erwin P. , Schneider Hildegard M. , Granick Steve
Published: April 2003

Polarized infrared spectroscopy in attenuated total reflection was used to investigate the adsorption of PMMA (polymethylmethacrylate) onto PS (polystyrene) that was previously adsorbed onto oxidized silicon from dilute solution in carbon tetrachloride at 30°C. The carbonyl group of PMMA forms hydrogen bonds with surface silanol groups, giving segment‐surface interaction energy of 4 kT as against 1 kT for PS (k is the Boltzmann constant, T the absolute temperature). The formation of hydrogen‐bonding by PMMA was unaffected, in rate or amount, by preadsorbed PS, but a lesser total amount of PMMA adsorbed onto PS, resulting in a higher average bound fraction. The histogram of the mass adsorbed, attributable to subpopulations of chains with different bound fractions, was inferred by subtracting infrared spectra acquired at successive times. Whereas this histogram was broad and bimodal for adsorption onto bare surface, it was narrower and unimodal for adsorption onto preadsorbed PS. © 1995 John Wiley & Sons, Inc.
Terbinafine is More Effective Than Itraconazole in Treating Toenail Onychomycosis: Results from a Meta-analysis of Randomized Controlled Trials
Authors: Krob H. Alexander , Fleischer Alan B. , D'Agostino Ralph , Feldman Steven R.
Published: April 2003

Background:

Toenail onychomycosis is a challenge for clinicians to treat, and this challenge is compounded by conflicting information in the medical literature concerning the efficacy of the two principal agents used in its treatment: Terbinafine and itraconazole.

Objective:

The purpose of this meta-analysis is to compare the efficacy of terbinafine with that of itraconazole in the treatment of toenail onychomycosis caused by dermatophytes.

Methods:

A Medline search was performed for all English language publications from 1966 to June 1999 on the use of terbinafine and itraconazole in the treatment of toenail onychomycosis. Included were randomized studies in which subjects received no less than 3 months (or cycles) and no more than 4 months (or cycles) of either terbinafine or itraconazole. Data were abstracted and statistical analyses (random effects model, fixed effects model, and Peto's method) were applied.

Results:

Thirteen studies were included from the original literature review of 1636 total referenced reports; four studies did not fulfill our inclusion or exclusion criteria. The primary analysis of six studies directly comparing terbinafine to itraconazole resulted in an odds ratio ranging from 1.8 (95% CI = 1.8, 2.8) to 2.9 (1.9, 4.1). The secondary analysis of three studies comparing either itraconazole or terbinafine to placebo estimated an odds ratio of 1.1–1.7. The former shows that terbinafine is 80%–190% more likely to result in mycologic cure than is itraconazole; the latter demonstrates a 10%–70% greater likelihood. The difference between the relative efficacies of terbinafine and itraconazole was highly statistically significant ( p < 0.0001).

Conclusion:

Meta-analysis of the published worldwide literature finds that terbinafine is significantly more effective than itraconazole at achieving mycologic cure of toenail onychomycosis.
Ärger und Aggression
Authors: Weber Hannelore
Published: April 2003

Zusammenfassung: Der Beitrag stellt das verbreitete Stereotyp in Frage, demzufolge ein enger Zusammenhang zwischen Ärger und Aggression besteht. In dem ersten Teil des Beitrags werden emotions- und aggressionstheoretische Annahmen zum Zusammenhang zwischen Ärger und Aggression zusammengestellt. Aus dieser Analyse folgt, daß aggressives Verhalten den theoretischen Annahmen zufolge nicht allein durch Ärger, sondern auch durch andere Emotionen begünstigt werden kann. Ob es infolge affektiver Erregung zu aggressiven Reaktionen kommt, so eine weitere wichtige Differenzierung, hängt entscheidend von der gelernten Regulation affektiver Erregung ab. In einem zweiten Teil des Beitrags werden daher Studien zur Regulation von Ärger vorgestellt, aus denen hervorgeht, daß neben verbal-aggressiven Reaktionen in hohem Maße nicht-aggressive, auch konstruktive Verhaltensformen verbreitet sind. Im dritten Teil werden Aspekte der sozialen Konstruktion angemessener Ärgerregulation diskutiert, um dem angenommenen starken Einfluß von kollektiven Konstruktionen und normativen Überzeugungen auf das individuelle Verhalten Rechnung zu tragen.
Sexuelle Aggression zwischen Jugendlichen: Eine Prävalenzerhebung mit Ost-West-Vergleich
Authors: Krahé Barbara , Scheinberger-Olwig Renate , Waizenhöfer Eva
Published: April 2003

Zusammenfassung: Die vorliegende Studie untersucht die Prävalenz unfreiwilliger Sexualkontakte bei älteren Jugendlichen in Ost- und Westdeutschland. 560 männlichen und weiblichen Befragten im Altersbereich zwischen 17 und 20 Jahren mit ost- bzw. westdeutschem Sozialisationshintergrund wurde eine deutsche Fassung der «Sexual Experiences Survey» vorgelegt, in der sexuelle Gewalterfahrungen weiblicher Opfer und sexuelle Aggression männlicher Täter in Abhängigkeit von verschiedenen Beziehungskonstellationen erfaßt wurden. Die Ergebnisse zeigen, daß auch in Deutschland sexuelle Gewalt in den Beziehungen Jugendlicher und junger Erwachsener ein verbreitetes Problem darstellt. 25 % der befragten Frauen berichteten unfreiwillige sexuelle Kontakte, die sich strafrechtlich definierten Tatbeständen zuordnen lassen. Bei den männlichen Befragten liegt die Prävalenzrate für die juristisch definierten Tatbestände zwar deutlich niedriger, doch steigt die Prävalenz stark an, wenn man den Einsatz von verbalem Druck, falschen Versprechungen oder Alkohol bzw. Drogen zur Überwindung weiblichen Widerstandes hinzunimmt. Ost-West-Unterschiede ließen sich weder für die sexuelle Viktimisierung noch für die sexuelle Gewaltanwendung feststellen.
Zu brav oder zu böse? Mobbing-Opfer und Abgelehnte im Prisoner's Dilemma-Paradigma
Authors: Schuster Beate
Published: April 2003

Zusammenfassung: Der soziometrische Status und der Viktimisierungsstatus von 5. bis 11. Klässlern wurde ermittelt, der Status hypothetischer InteraktionspartnerInnen sowie deren angebliche Wahlen variiert, und die Reaktionen im Gefangenendilemma erfaßt. Die Reaktionen wurden sowohl durch die experimentell vorgegebenen als auch durch die erwarteten Wahlen der InteraktionspartnerInnen bestimmt: Kooperative Zuege wurden eher kooperativ, und kompetitive Zuege eher kompetitiv beantwortet. Darüber hinaus vermieden Mobbingopfer kompetitive Züge, während zwei Untergruppen der Abgelehnten gegensätzliche Strategiepräferenzen aufwiesen: Versuchspersonen, die sowohl Ablehnung als auch Mobbing erfahren («Viktimisiert-Abgelehnte») verhielten sich besonders kooperativ; abgelehnte ProbandInnen, die nicht viktimisiert werden («Nicht-viktimisiert-Abgelehnte») dagegen vergleichsweise kompetitiv. Die kooperativen Wahlen viktimisierter Versuchspersonen wurden nicht erwidert: Die Versuchspersonen reagierten gegenüber den Viktimisierten kompetitiver als sich die Viktimisierten ihrerseits gegenüber ihren InteraktionspartnerInnen verhielten. Diese Befunde bestätigen die Notwendigkeit, bei «Abgelehnten» zwei Untergruppen auf der Basis der Viktimisierungsdimension zu unterscheiden. Die Befunde werden ferner vor dem Hintergrund der Hypothese diskutiert, daß die Submissivität potentieller Opfer mit zu ihrer Viktimisierungs-Erfahrung beiträgt.