bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energy migration in poly(N‐vinyl carbazole) and its copolymers with methyl methacrylate: Fluorescence polarization, quenching, and molecular dynamics
Authors: Gallego Javier , Mendicuti Francisco , Mattice Wayne L. 
Published: June 2003

AbstractFluorescence polarization and quenching measurements were used to examine intramolecular energy migration for poly(N‐vinyl carbazole) and copolymers of N‐vinyl carbazole with methyl methacrylate. Quenching measurements of the carbazole fluorescence by CCl4 were performed in dilute solution in toluene, and fluorescence anisotropy, r, was measured for the chains dispersed in a solid matrix of poly(methyl methacrylate) (PMMA). The results suggested that the chains with a high carbazole content, that is, a high content of excimer trapping sites, do not show the highest values of the singlet energy‐migration rate. Isotropies, r−1, of the samples in vitrified PMMA corroborated such conclusions. Molecular dynamics simulations on isotactic and syndiotactic trichromophoric copolymer fragments were used to obtain parameters related to the energy‐transfer process as a function of the methyl methacrylate content. The parameters from the simulations supported the interpretation of the experiments. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1615–1626, 2003
Study of the phase transition of poly(N,N‐diethylacrylamide) in water by rheology and dynamic light scattering
Authors: Lessard D. G. , Ousalem M. , Zhu X. X. , Eisenberg A. , Carreau P. J. 
Published: June 2003

AbstractPoly(N,N‐diethylacrylamide) (PDEA) possesses a lower critical solution temperature (LCST) in aqueous media. The solution properties of PDEA at various temperatures have been characterized with techniques such as rheology and dynamic light scattering. There is a decrease in the coil size before the phase transition due to a coil‐to‐globule transition. At the LCST, rheological and dynamic light scattering studies have also confirmed an aggregation phenomenon. This aggregation modifies the rheological properties of the polymer solutions. High frequencies hinder the phase‐transition process and reduce the LCST of the polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1627–1637, 2003
Effects of the oriented mesophase on the cold crystallization of syndiotactic polystyrene and its blend with poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Dikshit A. K. , Kaito A. 
Published: June 2003

AbstractThe effects of molecular orientation on the crystallization and polymorphic behaviors of syndiotactic polystyrene (sPS) and sPS/poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) blends were studied with wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry. The oriented amorphous films of sPS and sPS/PPO blends were crystallized under constraint at crystallization temperatures ranging from 140 to 240°C. The degree of crystallinity was lower in the cold‐crystallized oriented film than in the cold‐crystallized isotropic film. This was in contrast to the case of the cold crystallization of other polymers such as poly(ethylene terephthalate) and isotactic polystyrene, in which the molecular orientation induced crystallization and accelerated crystal growth. It was thought that the oriented mesophase was obtained in drawn films of sPS and that the crystallization of sPS was suppressed in that phase. The WAXD measurements showed that the crystal phase was more ordered in an sPS/PPO blend than in pure sPS under the same annealing conditions. The crystalline order recovered in the cold‐crystallized sPS/PPO blends in comparison with the cold‐crystallized pure sPS because of the decrease in the mesophase content. The crystal forms depended on the crystallization temperature, blend composition, and molecular orientation. Only the α′‐crystalline form was obtained in cold‐crystallized pure sPS, regardless of molecular orientation, whereas α′, α″, and β′ forms coexisted in the cold‐crystallized sPS/PPO blends prepared at higher crystallization temperatures (200–240°C). The β′‐form content was much lower in the oriented sPS/PPO blend than in the isotropic blend sample at the same temperature and composition. It was concluded that the oriented mesophase suppressed the crystallization of the stable β′ form more than that of the metastable α′ and α″ forms during the cold crystallization of sPS/PPO blends. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1665–1675, 2003
Thermal transitions of benzene in copolymers and interpenetrating polymer networks based on hydrophilic and hydrophobic components: Experimental evidence of hydrophobic interaction
Authors: Salmerón Sánchez M. , Monleón Pradas M. , Gómez Ribelles J. L. 
Published: June 2003

AbstractThermal transitions of benzene in a hydrophobic polymer network have been explained by us in terms of the phase diagram of the polymer‐solvent system. In this work, we executed a similar study on copolymers and interpenetrating polymer networks (IPNs) with controllable hydrophilic/hydrophobic ratios. Copolymers and IPNs were swollen with different amounts of benzene and subjected to cooling and heating scans with differential scanning calorimetry (DSC). Synthesis of the IPNs was carried out in such a way that phase separation appeared, and three qualitatively different types of DSC thermograms were identified depending on the benzene content of IPN. Thermal transitions of benzene in the hydrophilic/hydrophobic copolymers can also be explained as a consequence of the phase diagram of the system, but an increase in the glass‐transition temperature of the system can be correlated with the interactions among the hydrophilic groups of the copolymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1713–1721, 2003
Chain dynamics in entangled polymers: Diffusion versus rheology and their comparison
Authors: Wang Shi‐Qing 
Published: June 2003

AbstractThis review article scrutinizes and reanalyzes the extensively available literature data on the tracer and self chain diffusion coefficients Dtr and Ds along with the corresponding zero‐shear viscosity η0 to show that Ds ∝ M−ν starts with ν > 2.0 and converges to the asymptotic scaling exhibited by Dtr ∝ M−2.0 as the molecular weight M increases beyond M/Me = 10–20, in contrast to the onset of the asymptotic scaling M3 for η0 taking place typically for M/Me ≫ 10–20. A coherent analysis of these observations leads to the suggestion that the observed crossover in Ds is due to the constraint release effect, which diminishes around M/Me = 10–20 and is negligible in measurements of Dtr when the matrix molecular weight P is much greater than M. The contour length fluctuation (CLF) effect, which is believed to cause the molecular weight scaling of η0 to deviate significantly from its limiting behavior of M3, has little direct influence on the chain diffusion. The absence of the CLF effect on Ds leads to a much stronger than linear dependence of the product η0Ds on M, which has been observed previously. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1589–1604, 2003
Effect of annealing on the structure and properties of poly(vinylidene fluoride) β‐form films
Authors: Nakamura Koh , Sawai Daisuke , Watanabe Yuuji , Taguchi Daisuke , Takahashi Yoshiyuki , Furukawa Takeo , Kanamoto Tetsuo 
Published: June 2003

AbstractOriented poly(vinylidene fluoride) (PVDF) films consisting of β crystals were prepared by the solid‐state coextrusion (SC) of a gel film near the melting temperature (Tm) and by conventional cold tensile drawing (TD) of a melt‐quenched film. These films were annealed over the temperature range of 75–190 °C (below and above the static Tm) while the sample length was kept constant or constant loads were applied. After annealing with the sample length kept constant, the dynamic Young's modulus markedly decreased because of the relaxation of oriented amorphous chains, as shown by infrared spectroscopy. In contrast, annealing under a constant load improved the chain orientation in both the crystalline and amorphous regions, resulting in an increase in the modulus from an initial 10.5 to 14.3 GPa for the SC and from an initial 3.3 to 4.8 GPa for the TD. The SC, annealed at 190 °C with a constant load corresponding to an initial tension of 200 MPa, exhibited an extreme crystalline‐chain orientation of 0.998 and a modulus of 14.3 GPa, among the highest values ever reported for PVDF. Although the remanent polarization (Pr) of the TD increased slightly from the initial 62 to 68 mC/m2, Pr of the SC stayed constant at 100 mC/m2 independently of the annealing conditions. This suggests that the Pr value of 100 mC/m2 approached the equilibrium value for this PVDF sample containing 3.5 mol % structural defects. Therefore, although the modulus and Pr of the TD increased slightly with annealing, the maximum values achieved by annealing were markedly lower than those of the SC and annealed SC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1701–1712, 2003
Infrared spectroscopic study of the interactions of nylon‐6 with water
Authors: Iwamoto Reikichi , Murase Hiroshi 
Published: June 2003

AbstractWe studied the interactions of nylon‐6 with water by following the Fourier transform infrared spectra of a hydrated thin film during dehydration. Very small changes in the spectra caused by the interactions were clearly revealed by the application of spectral subtraction. The water was found to interact with amide groups to form hydrogen bonds with non‐hydrogen‐bonded or free CO and NH groups in the amorphous portion in the first hydration sphere. This was deduced from an analysis of minus and plus peaks appearing around the absorptions of the NH stretching, amide I band, and amide II bands in the difference spectra between the spectra during dehydration and the one at the most dehydration. The interactions of the amide groups with water were significantly stronger than the hydrogen bond between CO and NH in the crystalline portion, according to the magnitude of the frequency shift of relevant bands. Water, as the interacting counterpart, showed a distorted OH stretching absorption with two close peaks at about 3450 cm−1. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1722–1729, 2003
Effect of the premelting temperature and sample thickness on the polymorphic behavior of syndiotactic polystyrene/clay nanocomposites
Authors: Wu Tzong‐Ming , Hsu Sung‐Fu , Wu Jeng‐Yue 
Published: June 2003

AbstractX‐ray diffraction methods and differential scanning calorimetry thermal analysis have been used to investigate the structural changes of syndiotactic polystyrene (sPS)/clay nanocomposites. sPS/clay nanocomposites have been prepared by the mixing of sPS polymer solutions with organically modified montmorillonite. X‐ray diffraction data and differential scanning calorimetry results indicate that the dominating crystal forms and their relative fractions in sPS and sPS/clay nanocomposites are different for various premelting temperatures (Tmax's). Higher Tmax's favor the formation of the thermodynamically more stable β‐crystalline form, and its relative fraction has been obtained from the X‐ray diffraction data in the range of 11.5–13°. The intensity of the X‐ray diffraction data in the range of 11.5–13° decreases as the thickness of sPS/clay nanocomposites decreases from 150 to 20 μm. At the same time, the intensity of the X‐ray data in the range of 6–7° becomes sharper as the thickness of sPS/clay nanocomposites decreases. The calculation ratio based on the peak intensities at 6.2 and 6.8° for sPS/clay nanocomposites of equal thickness and crystallinity in the pure β and α forms has also been determined in this study. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1730–1738, 2003
Electrical and optical properties of ceramic–polymer nanocomposite coatings
Authors: Sun Jiakuan , Gerberich William W. , Francis Lorraine F. 
Published: June 2003

AbstractTransparent, conductive composite coatings were fabricated from suspensions of poly(vinyl acetate‐acrylic) (PVAc‐co‐acrylic) copolymer latices (50–600 nm) and nanosized antimony‐doped tin oxide (ATO) particles (∼15 nm). The suspensions were deposited as coatings onto poly(ethylene terephthalate) substrates and dried at 50 °C. Microstructure studies using field emission scanning electron microscopy and tapping‐mode atomic force microscopy (TMAFM) indicated that the latex particles coalesced during drying and forced the ATO particles to segregate into the boundaries between the latex particles. Low phase contrast was observed with TMAFM; this result was consistent with the presence of PVAc‐co‐acrylic in the ATO‐rich phase of the composite. The conductivity of the composite coatings followed a percolation power‐law equation, with the percolation threshold between 0.05 and 0.075 volume fractions of ATO and the critical conductivity exponent ranging from 1.34 to 2.32. The highest direct‐current conductivity of the composite coatings was around 10−2 S/cm. The optical transmittance and scattering behavior of the coatings were also investigated. Compared with the PVAc‐co‐acrylic coating, the composite coatings had lower transparency because of the Rayleigh scattering. The transparency of the composite coatings was improved by a reduction in the coating thickness. The best transparency for the coatings with a direct‐current conductivity of approximately 10−2 S/cm was around 85% at a wavelength of 600 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1744–1761, 2003
Effect of operation parameters on temperature rising elution fractionation and crystallization analysis fractionation
Authors: Anantawaraskul Siripon , Soares João B. P. , Wood‐Adams Paula M. 
Published: June 2003

AbstractCrystallization analysis fractionation and temperature rising elution fractionation are two techniques used to estimate the chemical composition distributions of semicrystalline copolymers. This study investigates the cooling rate and cocrystallization effects for both techniques with a series of ethylene/1‐olefin copolymers and their blends. Ideally, both techniques should operate in the vicinity of thermodynamic equilibrium so that crystallization kinetic effects are avoided. The results show that, in fact, crystallization kinetic effects play an important role at the typical cooling rate used with both techniques. Cocrystallization is significant when fast cooling rates are used. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1762–1778, 2003
Heats of Combustion and Formation of New Energetic Thermoplastic Elastomers Based on GAP, PolyNIMMO and PolyGLYN
Authors: Diaz Emmanuela , Brousseau Patrick , Ampleman Guy , Prud'homme Robert Emery 
Published: June 2003

AbstractHeats of combustion and formation of various energetic thermoplastic elastomers (ETPE), corresponding to linear copolyurethanes based on an energetic prepolymer and a diisocyanate, were measured by a calorimetric method. These ETPEs were synthesized from three different molecular weights of glycidyl azide polymer, from poly(3‐nitratomethyl‐3‐methyloxetane) and from poly glycidyl nitrate. The prepolymers were also analyzed for comparison with the corresponding ETPEs. A significant difference of the heats of formation was observed between the prepolymers and their ETPEs, while the heats of combustion were similar.
An Investigation of Composite Propellant Accelerated Ageing Mechanisms and Kinetics
Authors: Judge Michael D. 
Published: June 2003

AbstractThe ageing kinetics and mechanisms of a composite solid rocket propellant were investigated by monitoring unstressed propellant samples during prolonged storage at elevated temperatures. For samples confined under air during ageing, it was determined that oxidative cross‐linking of the propellant binder was the main degradation mechanism over time. Plasticizer loss was a significant ageing mechanism only for those samples aged unconfined. In addition, there was an indication that ambient humidity had a significant but reversible effect on propellant mechanical properties. Arrhenius mathematical relationships were derived in order to ascertain the extent to which ageing was accelerated by increased propellant temperature. An activation energy for binder oxidation of between 71 and 74 kJ/mol was determined.
Effect of Porosity on the Burn Rate of a Gas‐Generating Composition
Authors: Lessard Pierre , Beaupré France 
Published: June 2003

AbstractIn the course of the development of an oxidizer‐based extruded composite propellant for use as gas generant, a simple model to describe and evaluate the actual porosity using simple methods was developed. It is briefly described and used to assess the influence of porosity on the burn rate of propellants produced. For the formulation studied the presence of microporosities does not seem to significantly influence the burn rate. On the other hand, volume fraction of porosities in extruded composition grains can exert a large influence and can increase considerably under thermal treatment with a resulting augmentation in burn rate.
Multivariate Calibration of Semi‐Synthetic Data Sets: Gun Powder Analysis
Authors: Ouellet Nathalie , Lussier Louis‐Simon , Beaupré France 
Published: June 2003

AbstractQuantitative analysis of multi‐component mixtures such as propellant powders is not trivial since it usually requires separation of the mixture constituents. Multivariate calibration combined to the use of semi‐synthetic data sets can eliminate the need for standard solutions preparation, and therefore allow the rapid determination of mixtures provided no intermolecular interactions occur in the systems. Multivariate compositional analyses of FTIR spectra of low‐vulnerability (LOVA), high‐energy low‐vulnerability (HELOVA) and energetic thermoplastic elastomer (ETPE) propellant powder systems were performed using the partial least‐squares (PLS) regression algorithm. All constituents except ethyl centralite (EC) were quantified. Concentrations were predicted within 1% error for the major component (1,3,5‐trinitro‐1,3,5‐triazacyclohexane or RDX), and within 5% error for the minor components (between 12 and 2% nominally by weight). LOVA, HELOVA, and ETPE gun powder samples concentrations were estimated and compared to expected compositions.
Synthesis of a functionalized high affinity mannose receptor ligand and its application in the construction of peptide‐, polyamide‐ and PNA‐conjugates
Authors: Kinzel Olaf , Fattori Daniela , Ingallinella Paolo , Bianchi Elisabetta , Pessi Antonello 
Published: June 2003

AbstractThe synthesis of a high affinity mannose receptor ligand, appropriately functionalized for chemoselective ligation with an antigen or DNA‐binding moieties is described. By a combination of solid‐ and solution‐phase chemistry a versatile synthesis of the target structure was accomplished. Examples of subsequent ligation reactions are described. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
The chemistry of the opioid receptor binding sites
Authors: Medzihradszky Kálmán 
Published: June 2003

AbstractSince the discovery of the opioid receptors and their endogenous ligands an immense research work has been devoted to the exploration of their specificity, the mechanism of ligand binding and ligand–receptor interactions. One of the main goals has been the location and characterization of the binding sites. The present review compiles the results achieved in this field in the last quarter of a century, and puts some questions concerning the success of these efforts. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
Analogues of a potent oxytocin antagonist with truncated c‐terminus or shorter amino acid side chain of the basic amino acid at position 8
Authors: Flouret George , Chaloin Olivier , Slaninová Jirina 
Published: June 2003

AbstractTwelve analogues were synthesized, their structure derived from modifications of [(S)Pmp1, D‐Trp2, Pen6, Arg8]oxytocin, PA, in which (S)Pmp = β,β‐(3‐thiapentamethylene‐β‐mercaptopropionic acid). PA is a potent antagonist of the uterotonic effect of oxytocin in the rat (uterotonic test in vitro, pA2 = 8.86) and in the baboon. Truncated analogues of PA from the C‐terminus were systematically prepared ending in either the free acid or the amide, i.e. PA1–9 acid, PA1–8 acid, PA1–7 acid, PA1–6 acid, PA1–8 amide, PA1–7 amide and PA1–6 amide. PA1–8 amide was roughly as potent as PA in the rat uterotonic assay in vitro, and the shorter amides were only somewhat weaker antagonists. All four acid analogues were weaker antagonists than PA but still maintained rather high antagonistic potency. These findings suggest that, if these truncated acids form as metabolites in vivo, they may contribute to the overall biological effect of PA and their contribution should be taken into account. Furthermore, using these analogues, the radioimmunoassay measurements of PA may be standardized, as they may cross react with PA antibodies and interfere with the determination. In addition, five analogues were made by substituting Arg8 of PA with Lys8, Orn8, Dab8, Dap8 and Cit8. All of these analogues maintained high potency as OTAs in the uterotonic assay, although their activity was only about 1.5–3 times lower than PA. The most potent analogue in the uterotonic assay, [Dap8]PA, pA2 = 8.53, had weak pressor activity (pA2 = 6.90) and no antidiuretic effect. The pressor activity was lower for all tested acids, and for PA1–6 acid it was even below the detection limit. Additionally, PA1–9 acid, PA1–7 acid and PA1–6 acid showed no antidiuretic activity. Hence, the PA1–6 acid is a potent OTA with pA2 = 8.27 and no measurable effect in the pressor or antidiuretic tests and thus it is a pure oxytocin antagonist. This fact makes it an attractive candidate for further studies on inhibition of OT biological effects and on preterm labour. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
Modelling covariance structure in ascending dose studies of isolated tissues and organs
Authors: Brammer Richard John 
Published: June 2003

AbstractThis paper describes the analysis of two pharmacology assays: the guinea pig papillary muscle assay (an example of an isolated tissue assay) and an assay looking at pressure changes in isolated rat lungs. Both assays use an ascending dose design to minimize carryover effects. This is often necessary in these studies, due to the limited life span of the tissues. Various mixed models, with different covariance structures, are fitted to find the most appropriate model. These are then compared to two other possible methods of analysis: paired t‐tests and two‐way analysis of variance. For both assays, the mixed model was found to be the best approach. These examples illustrate the importance of modelling covariance structure correctly in any ascending dose study, whether in isolated organs/tissues, in animals or phase I volunteers. Copyright © 2003 John Wiley & Sons, Ltd.