bluuebunny/crossref_metadata_2025_split huggingface dataset:
Incompatibility of polymer solutions. II. Concentration and angle dependence of the light scattering in the system polystyrene + polyisobutylene + toluene
Authors: Van Den Esker M. W. J. , Laven J. , Broeckman A. , Vrij A. 
Published: April 2003

AbstractLight scattering experiments are described on the system polystyrene (PS) + polyisobutylene (PIB) + toluene at constant temperature. At a fixed concentration of the nearly “invisible” PIB the light scattering at various angles was measured as a function of varying PS concentration up to the region of incompatibility. For interpretation of the results use is made of an extension of the classical fluctuation theory for multicomponent systems to finite scattering angles. The experimental data can be described qualitatively with this theory. Addition of a second polymer has little influence on the size of the other polymer. The variation of the light scattering with the wavelength can be explained in terms of the (negative) adsorption of one polymer by the other.
Incompatibility of polymer solutions. III. Critical opalescence in the system polystyrene + polyisobutylene + toluene
Authors: Van Den Esker M. W. J. , Vrij A. 
Published: April 2003

AbstractThe angular dependence of light scattering from the homogeneous ternary system polystyrene + polyisobutylene + toluene was measured at a fixed (critical) concentration as a function of temperature. On approaching the critical temperature the scattering becomes very large and strongly angle‐dependent. The experiments show that the interaction range rG is of the same order of magnitude as the molecular radius of gyration of the polymer, but cannot be set equal to it as in the case of a binary system of one polymer in a single solvent. The temperature dependence of the various interaction parameters does not depend on the molecular weights of the polymers.
Lactone polymers. VIII. Dynamic mechanical properties of ϵ‐caprolactone and γ‐(tert‐butyl)‐ϵ‐caprolactone copolymers
Authors: Seefried C. G. , Koleske J. V. , Critchfield F. E. 
Published: April 2003

AbstractThe temperature dependencies of dynamic mechanical properties have been determined with a torsional pendulum for copolymers of ϵ‐caprolactone and γ‐(tert‐butyl)‐ϵ‐caprolactone over the entire composition range. Copolymers containing at least 25 mol % (33 wt %) of γ‐(tert‐butyl)‐ϵ‐caprolactone units are amorphous in nature. The experimentally obtained glass transition temperatures of the copolymers and poly(γ‐(tert‐butyl)‐ϵ‐caprolactone) were used to calculate the glass transition temperature of amorphous of poly(ϵ‐caprolactone) according to the Fox relation. This value of −70°C is in excellent agreement with values obtained from similar calculations based on compatible blends of poly(ϵ‐caprolactone) with other homopolymers.
The nature and origin of structural defects in polymeric sulfur nitride
Authors: Baughman R. H. , Chance R. R. 
Published: April 2003

AbstractDefect structures in (SN)x crystals obtained by solid‐state polymerization are so numerous and varied that they are likely to conceal inherent property aspects of the defect‐free polymer. In addition to frequent macroscopic twinning, three different kinds of defect sites are observed. These sites are related to the disruption of molecular orientational order about the chain axis direction and the sequencing of chain types in the periodic phase. The origin of these defects is explained by the nonuniqueness of solid‐state polymerization and recrystallization processes, which transform the initial dimer phase to the final polymer phase. The orientational relationship between the dimer and polymer phase is predicted from the observed twinning mode and the structural relationship between these phases. The change from dimer phase (at zero and at intermediate conversions involving solid solution formation) to polymer phase can be described by a shear transformation on the (001) dimer plane. This observation suggests an analogy with known martensitic reactions and a method for improving the perfection of (SN)x.
The hydrodynamic properties of the cellodextrin alditols
Authors: Tostevin James E. , Swenson Harold A. 
Published: April 2003

AbstractDiffusion coefficients of cellodextrin alditols from DP 1 to 5 in 0.32 molar NaOH are found to be 22% less than in water. Slightly lower diffusion rates and higher friction coefficients and Einstein–Stokes hydrodynamic radii are also reported for the alditols as compared to cellodextrins in water. Considered as ellipsoids based on diffusion rates, the length‐to‐width ratio for the alditols, only slightly greater than for the cellodextrins in water, increase by about 100% in alkali. A similar increase in axial ratio is shown for cellodextrins in the highly alkaline solvent cadoxene as for the alditols in alkali. It is suggested that creation of the large frictional envelope occurs in alkali prior to complexing with the common cellulose solvents in which complexing with copper, cadmium, and iron in divalent from are involved. The possible nature of the enlarged frictional domain is discussed.
Surface energies of chain molecules from homogeneous nucleation
Authors: Calvert P. D. 
Published: April 2003

AbstractA model for the interpretation of homogeneous nucleation data for chain molecules is presented. The two surface energies σs and σe are related to interchain and intrachain bonding. Surface energies calculated from experimental data on n‐alkanes from octane to dotriacontane and polyethylene agree with estimated values. The results are discussed in relation to surface energies measured from spherulite growth rates in polymers but these values are not known with sufficient reliability to provide a good basis for comparison.
Mechanical relaxations in some ionene polymers. I. Effect of Ion concentration
Authors: Tsutsui Tetsuo , Tanaka Ryuichi , Tanaka Takehide 
Published: April 2003

AbstractDynamic mechanical properties of m,n‐ionenes, the structure of which are shown in Figure 1, were examined by torsional braid analysis. Three relaxations designated as α,β and γ were found. The α relaxation, ascribed to the primary relaxation due to an amorphous phase, was observed at 70–130°C, the temperature increasing with an increase of the ion concentration along the polymer chains. The β relaxation at around 0°C was related to the ionic portions of the polymers. The γ relaxation at around–120°C was a so‐called local mode relaxation. The γ relaxation peak was split into two peaks in the very slowly cooled 12,10‐ionene sample and the formation of an inhomogeneous structure in the amorphous phase is proposed.
Dielectric relaxations in a series of vinyl aromatic polymers: Poly(2‐vinyl‐N‐ethylcarbazole), poly(3‐vinyl‐N‐ethylcarbazole), poly(2‐vinylanthracene), and poly(α‐methyl‐2‐vinylanthracene)
Authors: Pochan J. M. , Hinman D. F. 
Published: April 2003

AbstractTwo dielectric relaxations have been studied on poly(2‐vinyl‐N‐ethylcarbazole) (P2VK) and poly(3‐vinyl‐N‐ethylcarbazole)(P3VK), poly(2‐vinylanthracene) (P2VA) and poly(α‐methyl‐2‐vinylanthracene) (PMe2VA). The relaxations in P2VK and P3VK occur in the temperature regions 220°C and −150°C. Evidence for a third relaxation in both polymers at ca. 120°C has been found; and, for this reason, the relaxations studied (220°C and −150°C) are labeled α and β, respectively, and have been attributed toTgand carbazole rotational libration about the bond connecting the carbazole moiety to the polymer backbone. Additionally β (ca. 20°C) and γ(ca. −150°C) relaxations in P2VA and MeP2VA have been observed and assigned, respectively, to wagging motion and rotational libration of the pendant anthracene moiety.
Dynamics of macromolecular chains. V. Interpretation of the dielectric relaxation data
Authors: Gény F. , Monnerie L. 
Published: April 2003

AbstractThe autocorrelation function of orientations, derived for the model of conformational jumps in a chain described in a tetrahedral lattice, has been tentatively applied to dielectric relaxation data. The complex dielectric relaxation of polymers can be interpreted by the aid of only two relaxation processes. In the case of poly(p‐chlorostyrene) in solution, the characteristic times that we have calculated agree favorably with the fluorescence‐depolarization results. The model has been shown to be consistent with the empirical decay function exp[− (t/τ)β] proposed by Williams.
The study of domain structure in polyurethanes by nuclear magnetic resonance
Authors: Assink R. A. 
Published: April 2003

AbstractPolyurethanes are block copolymers composed of hard and soft segments which often undergo microphase separation with the resultant formation of hard and soft domains. The nuclear‐magnetic‐free induction decay of such systems is shown to consist of a fast Gaussian component corresponding to glassy domains and a slow exponential component corresponding to rubbery domains. Thus, by being sensitive to the microscopic mobility of a material, nuclear magnetic resonance (NMR) has the potential to determine when a polyurethane has separated into domains and the relative amounts of material in each domain. After annealing the free‐induction decay of a linear polyurethane showed a distribution of relaxation times indicating that mixing of the domains had taken place and a continuum of compositions exist in the material. The free‐induction decay of a cross‐linked polyurethane was unaffected by annealing, confirming the results of an earlier study.
On‐line viscometry combined with gel permeation chromatography. I. Instrumental calibration and testing with linear polymers
Authors: Park Won S. , Graessley William W. 
Published: April 2003

AbstractGel permeation chromatography (GPC) was combined with flow time measurements on the eluent to provide both the distribution of hydrodynamic volumes and the distribution of intrinsic viscosities in linear polymers. Standard polystyrene samples were used to establish a universal hydrodynamic volume calibration as well as the zone spreading and viscometer transfer line tailing parameters. Viscometry data are particularly helpful in establishing the zone spreading parameters and the calibration curve at very high molecular weights. The results were applied to measurements on samples of linear polybutadiene and polyvinyl acetate. Agreement between values of Mw from GPC with those obtained by light scattering confirmed the universal calibration principle.
Inhomogeneous polymer solutions: Theory of the interfacial free energy and the composition profile near the consolute point
Authors: Vrij A. , Roebersen G. J. 
Published: April 2003

AbstractThe Flory–Huggins formulation of the combinatorial entropy, supplemented with residual free energy, is applied locally to obtain the interfacial free energy and the concentration profile of polymer in the interface between two demixed polymer solution phases. Two choices were investigated for the residual free energy: a “regular solution” formulation and an empirical formulation of Koningsveld for polystyrene in cyclohexane. Asymptotic, analytical solutions of the equations near the critical solution point and solutions obtained by numerical calculations are given as a function of temperature for several molecular weights. At temperatures farther below the critical temperature the equations have no solutions. The reason for this is not entirely clear. The local formulation of the free energy used here is an improved version of a previous one, which gave wrong results for asymmetric systems (polymer in a low molecular weight solvent). This newer version is consistent with our theory of critical opalescence and gives a relation between the interface “thickness” and the correlation range of the concentration fluctuations. The calculated correlation ranges were in good accord with those found experimentally by Debye, Chu, and Woerman. That the newer version of our equations for an interface gives no acceptable solutions at lower temperatures could be caused by a “collapse” of a diffuse to a sharp interface as suggested by Nose.
Studies of the polymerization of diallyl compounds. XXV. Gel point in the polymerization of diallyl esters of aromatic dicarboxylic acids
Authors: Matsumoto Akira , Yokoyama Shigeyuki , Khono Tetsuro , Oiwa Masayoshi 
Published: April 2003

AbstractStudies on gelation in the radical polymerization of diallyl dicarboxylates have been conducted by Simpson,9,11 Gordon,10 and Oiwa.13 However, the results obtained have not always been consistent and are still far from full elucidations. In this paper, the gel point in the polymerization of diallyl aromatic dicarboxylates, including diallyl phthalate (DAP), diallyl isophthalate (DAI), and diallyl terephthalate (DAT) is experimentally reexamined in detail and discussed according to Gordon's theory; the discrepancy between actual and theoretical gel point conversion was quite large and was enhanced in the order DAT > DAI > DAP. Moreover, from detailed inquiry into the primary chain length of the prepolymer it is suggested that the intramolecular chain transfer reaction plays an important role in the polymerization of diallyl ester accompanying the intramolecular cyclization reaction. The polydispersity coefficient (Pw,0/Pn,0) of the initial prepolymer of DAP is also estimated to be 2.0 from the extrapolation of Pw/Pn to zero conversion.
Phase‐separation phenomena in solutions of poly(2,6‐dimethyl‐1,4 phenylene oxide). II. Differential scanning calorimetry of solutions in toluene
Authors: Koenhen D. M. , Smolders C. A. 
Published: April 2003

AbstractThe phase‐separation phenomena observed in solutions of poly(2,6 dimethyl‐1,4 phenylene oxide) in toluene have been investigated by differential scanning calorimetry. These measurements supplement the experimental evidence in favor of the concept that the phase transitions observed are crystallization and melting phenomena. The experiments suggest that two kinds of crystals can develop and that a seeded crystallization is possible.
Four‐center photopolymerization in the crystalline state. VIII. X‐ray crystallographic study of the polymerization of some diolefinic compounds
Authors: Nakanishi Hachiro , Hasegawa Masaki , Sasada Yoshio 
Published: April 2003

AbstractThe four‐center photopolymerization of five diolefinic compounds has been investigated by x‐ray crystal analysis. A common packing feature is found for the photopolymerizable crystals and all polymers are three‐dimensionally oriented. Topotaxies observed are classified according to the coincidence of space group and the three crystal axes, between monomer and polymer. The polymerization mechanism is discussed on the basis of the topotaxies and it is concluded that the polymerization is lattice controlled over the whole reaction process.
Thermally stimulated discharge current studies on the effect of thermal treatment on the strength of polycarbonate
Authors: Aoki Y. , Brittain J. O. 
Published: April 2003

AbstractIt is well known that polycarbonate annealed at 80–130°C undergoes gradual changes in mechanical properties. Annealing below Tg (ca. 150°C) results in a decrease in impact resistance and an increase in strength. Polycarbonate has three single relaxation processes and some distributed relaxation processes in the temperature range between 100 and 250°K (the β transition region). The effect of thermal pretreatment on the relaxation has been investigated by the thermally stimulated discharge current technique. Partial heating, peak cleaning, and theoretical fitting have also been performed and the activation parameters associated with the relaxation processes have also been calculated to assist in the analysis of the relationship between effects of annealing and structural motions in polycarbonate.
Analysis of anomalous X‐ray diffraction effects of isotactic polystyrene gels and its implications for chain conformation and isomeric homogeneity
Authors: Atkins E. D. T. , Isaac D. H. , Keller A. , Miyasaka K. 
Published: April 2003

AbstractOriented gels, obtained by high supercoolings of isotactic polystyrene solutions, exhibit unexpected “fiber‐type” x‐ray diffraction patterns. In particular a pronounced meridional reflection at a spacing of 0.51 nm, together with its successive orders, requires an extended, or nearly extended, chain conformation which appears irreconcilable with the stereochemistry of isotactic polystyrene. Furthermore, the value of 0.51 nm correlates directly with the axial projected repeat expected for two styrene monomer units. Two possible stereosequences merit atention: syndiotactic and syncephalic (head‐to‐head, tail‐to‐tail). In addition to the 0.51 nm meridional reflection, layer lines are observed with spacing 3.06 nm (6 × 0.51) which equate with 24 carbon–carbon bonds in the backbone. Cylindrically averaged Fourier transform calculations for the various models are compared with the observed x‐ray results and the best fit is obtained for a 24/11 helix of isolactic polystyrene with the syncephalic stereosequence. This conclusion, however, clashes with the 13CNMR evidence which indicates that the polymer is essentially isotactic. The implications of these novel results in relation to gel crystallization are discussed.
Acoustic absorption and dynamic compressibility studies of dilute and concentrated solutions of polystyrene in toluene and cyclohexane
Authors: Dunbar Janice I. , North Alastair M. , Pethrick Richard A. , Steinhauer Daniel B. 
Published: April 2003

AbstractAcoustic absorption and adiabatic compressibility measurements are reported on solutions of polystyrene (Mn = 89,000) in toluene and cyclohexane. The data in toluene cover a temperature range from 293 to 343°K and a concentration range of 10–400 Kg m−3 (1–40 wt%). The dependence of acoustic absorption on concentration was found to be linear up to 100 kg m−3, which corresponds to the concentration at which polymer–polymer interactions cause significant changes in the specific viscosity‐concentration relationship. Up to 200 kg m−3 the data could be fitted to computations based on an artificial separation of the dispersion into contributions from viscoelastic and segmental processes, using parameters obtained from a study of narrow molecular weight distribution samples at 25 kg m−3. However, neither approach was capable of describing dispersions in the 300, 400 kg m−3 solutions. The modification of the relaxation spectrum observed at the highest concentrations is ascribed to volume and entropy changes associated with alterations of the local environment around a segment of the polymer chain. These changes have their origin in interchain penetration and polymer–polymer contacts, and indicate that ‘entanglement’ is primarily entropic in effect.The adiabatic compressibility exhibited similar deviations from a simple concentration dependence, and allowed estimation of an incompressible volume increment associated with polymer–polymer interactions in the high‐concentration entangled matrix. However, the adiabatic compressibilities of solutions of polystyrene, 10–15 kg m−3, in cyclohexane showed no deviations from simple behavior in the region of the theta temperature. Measurements of the adiabatic compressibility of polystyrene in mixtures of cyclohexane‐toluene have been used to obtain the relative magnitude of solvent and polymer contributions to the excess compressibility.
Automated light‐scattering apparatus for studying polymer films
Authors: Chu W. H. , Horne D. E. 
Published: April 2003

AbstractThe design and operation of an automated light‐scattering apparatus for studying structures in polymer films are described. The apparatus has angular resolution of 0.02 and 1.0° in radial and azimuthal angles, respectively. The radial scan can be made over the range of 0.5 (or less) to 90° and the azimuthal scan covers 180°. Time resolution is in the order of milliseconds. The operation, data collection, and reduction are fully automatic. Illustrative data on the crystallization of a low density polyethylene are described.
Photoelectret state in poly(vinylcarbazole)
Authors: Pillai P. K. C. , Agarwal S. K. , Nair P. K. 
Published: April 2003

AbstractThe photoelectret charge in the aluminum–poly(vinylcarbazole) (PVK) conducting‐glass (NESA), sandwich cell configuration has been observed to decrease with voltage above some critical voltage, depending on the intensity of illumination. This critical voltage corresponds to the value at which a time‐independent photocurrent is observed and also to the “knee‐point” voltage in the current voltage plot. The results are explained on the basis of field‐assisted detrapping setting in at high field.
Diffusion in polymer–solvent systems. III. Construction of Deborah number diagrams
Authors: Vrentas J. S. , Duda J. L. 
Published: April 2003

AbstractA method is presented for anticipating condition under which anomalous diffusion effects can be expected for amorphous polymer–solvent systems. The diffusion process is characterized by a dimensionless group called the diffusion Deborah number, and a method for calculating this dimensionless number is presented. Deborah number diagrams are constructed for the unsteady diffusion of ethylbenzene and polystyrene in thin films, and observed diffusion phenomena are discussed on the basis of these diagrams.
Properties of cellulose acetate in solution. II. Light scattering and elasticity measurements on gels in benzyl alcohol
Authors: Goebel K. D. , Berry G. C. 
Published: April 2003

AbstractKinetic studies are reported for the light scattering and elasticity of thermally reversible gels of cellulose acetate in benzyl alcohol over a range of temperature and polymer concentration. The small‐angle light scattering data are found to be described by exponential correlation functions, and it is concluded that the scattering has its origin in the nonrandom character of the crosslinking in the gels studied. The elasticity is discussed in terms of the density of crosslinks in the gels. Thus, the kinetics studied by light scattering and elasticity measurements are independently related to temperature and polymer concentration.
Dielectric relaxations in linear aliphatic polyesters
Authors: Ito M. , Nakatani S. , Gokan A. , Tanaka K. 
Published: April 2003

AbstractMolecular motions in a series of linear aliphatic polyesters [poly(ethylene adipate), poly(ethylene sebacate), poly(hexamethylene sebacate), and poly(decamethylene 1,16‐hexadecanedicarboxylate)] were studied by dielectric measurements. Two loss maxima were observed for each polymer in the temperature range from −196 to about 60°C and in the frequency range from 110 to 105 Hz. The loss maxima of these polyesters, lying between −17 and −38°C at 110 Hz (β‐relaxation), are due to the micro‐Brownian motions of amorphous main chains. It was found that these β‐relaxations are well described by the WLF equation. The loss maxima in the range from −88 to −109°C at 110 Hz (γ‐relaxation), are attributed both to local mode motions of main chains in the amorphous region and to motions of the polar groups involved at the chain ends. For the β‐relaxation, no simple relation between the methylene sequence length and the loss peak temperature was found. Furthermore, as the methylene sequence length decreased, the effective dipole moment of the polyesters increased gradually. These facts were explained in terms of interchain dipole attraction.