bluuebunny/crossref_metadata_2025_split 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

AbstractThermally 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

AbstractWe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractCore 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

AbstractFluorescence 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

AbstractSorption 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

AbstractA 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

AbstractBlock 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

AbstractThis 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

AbstractThis 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

AbstractLongitudinal 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

AbstractThe 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

AbstractThe 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

AbstractThis 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.