bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solubility and miscibility of poly(ethyl oxazoline)
Authors: Lin Pinyen , Clash C. , Pearce Eli M. , Kwei T. K. , Aponte M. A. 
Published: April 2003

AbstractThe solubility of poly(ethyl oxazoline) in aqueous solutions was studied. The cloud point temperatures decreased in the presence of sodium chloride but increased by the addition of tetrabutylammonium bromide or dioxane. Solution‐cast films of blends of the polymer and poly(acrylic acid) were miscible, but mutual precipitation occurred in water, methanol, and dioxane. The compositions of the complexes correspond in most cases to simple molar ratios of the interacting groups. The glass transition temperatures of the complexes are higher than the values for blends of the same compositions, and the high values are attributed to hydrogen bonds acting as physical crosslinks. Complex formation also occurs when the polymer is mixed with a styrene‐acrylic acid copolymer and with low weight polymers containing phenol groups.
Counterion selectivity in cationic polyelectrolytes
Authors: Boussouria B. , Ricard A. , Audebert R. 
Published: April 2003

AbstractChloride ion activity coefficients in aqueous solutions of several cationic copolymers have been determined using ion‐selective electrodes in both the absence and the presence of simple univalent and divalent salts. Without added salt, the activity coefficient depends on the polymer concentration. It increases with increasing concentration of the added salt. The extent of interaction between counterions and polyions at a given polymer concentration, as estimated form chloride anion activity, is greater for bivalent than for univalent anions. Experimental data are in good agreement with theory. Selective interaction of anions with the ammonium copolymers has also been evidenced by viscometry. The selectivity follows the orderFor organic anions, in addition to electrostatic interactions, hydrophobic effects, which depend on the structure of the copolymer, play a significant role.
Plastic deformation of polytetramethylene oxide. I. Influence of molecular weight distribution, crystallinity, and structure
Authors: Kretz M. , Meurer B. , Lotz B. , Weill G. 
Published: April 2003

AbstractPolytetramethylene oxide with a planar zig‐zag structure similar to polyethylene can be obtained with narrow molecular weight distributions. The plastic deformation of samples differing in molecular weight, molecular weight distribution, crystallinity, and structure has been studied. The degree of crystallinity of the undeformed annealed samples, as studied by NMR and DSC, leads to a value of the enthalpy of melting ΔHm = 167 J g−1, supporting the lower of two previously reported values. The low natural draw ratios and low Young's modulus of the drawn samples, together with the effect of blending a small amount of high molecular weight material into a low molecular weight sample, highlight the role of the flexibility and of the high molecular weight tail of the distribution in the plastic deformation process. The stress required for the propagation of the neck and the tensile strength are found to be linear functions of, respectively, the natural and maximum draw ratio.
Viscoelastic behavior and order‐disorder transition in mixtures of a block copolymer and a midblock‐associating resin
Authors: Kim Jinhwan , Han Chang Dae , Chu Sung Gun 
Published: April 2003

AbstractThe viscoelastic behavior and order‐disorder transition in mixtures of a block copolymer and a midblock‐associating resin were investigated. The block copolymers investigated were polystyrene‐block‐polysioprene‐block‐polystyrene (SIS) copolymers (Shell Development Company), specifically Kraton D‐1107, with the block molecular weights 10,000S‐120,000I‐10,000S, and Kraton D‐1111, with the block molecular weights 15,000S‐100,000I‐15,000S. The midblock‐associating resin investigated was a resin polymerized from C5 hydrocarbon, referred to as Piccotac 95BHT (Hercules Inc.), which is an aliphatic hydrocarbon containing considerable amounts of cyclic structures, with a weight‐average molecular weight of 1,100 and a glass transition temperature Tg of 43°C. In the investigation, mixtures of the block copolymer and Piccotac 95BHT were prepared with toluene as solvent. Temperature scans of the samples were made to obtain information on dynamic storage modulus G′, dynamic loss modulus G″, and loss tangent tan δ, using a Rheometrics dynamic mechanical spectrometer. It was found that Piccotac 95BHT decreased the plateau modulus G0N and increased the Tg of the polyisoprene midblock of the SIS block copolymer in the mixture. This experimental observation led to the conclusion that Piccotac 95BHT associates (or is compatible) with the rubbery polyisoprene midblock of the SIS block copolymer. The order‐disorder transition behavior of mixtures of SIS block copolymer and Piccotac 95BHT was also investigated by a rheological technique proposed by Han and Kim (Ref. 21). The order‐disorder transition temperature Tr (i.e., the temperature at which the ordered microdomain structure of the block copolymer completely disappears) of the SIS block copolymer decreased steadily with increasing amount of Piccotac 95BHT in the mixture. With the information determined on Tr, a phase diagram for the mixture was constructed, showing the boundary between the mesophase and homogeneous phase in the mixture. The phase diagram is in qualitative agreement with the theoretical predictions of Whitmore and Noolandi (Ref. 28).
Solubility parameters of poly(vinylidene fluoride)
Authors: Bottino A. , Capannelli G. , Munari S. , Turturro A. 
Published: April 2003

AbstractThe solubility behavior of poly(vinylidene fluoride) (PVDF) in about 50 liquids was investigated. The results were input to a computer program to obtain a three‐dimensional representation of the polymer solubility region in the Hansen space; the values of dispersion, hydrogen bonding, and polar components of the total solubility parameter δt,P were evaluated. The latter was also estimated from limiting viscosity number data in the eight solvents found. Both experimental methods gave δt,P values in very good agreement. Comparisons among our findings, the literature, and calculated results are discussed.
The role of differential scanning calorimetry and X‐ray diffraction in identifying crystal continuity in highly oriented samples of die‐drawn polypropylene
Authors: Taraiya A. K. , Unwin A. P. , Ward I. M. 
Published: April 2003

AbstractX‐ray diffraction and differential scanning calorimetry studies of die‐drawn polypropylene have indicated the presence of a crystalline structure which does not identify with any of the usual crystallographic forms and has a melting point slightly below that of the monoclinic a form. The melting of this structure is stress sensitive and shows the superheating effect expected from the melting of an extended chain structure, whose chain ends are physically constrained. It is postulated that this structure bridges the gaps between adjacent monoclinic crystal blocks and provides the framework necessary to maintain mechanical stability at temperatures well above that of the glass transition. Moreover, together with taut tie molecules, this structure is considered to be the main source of the high material stiffness.
Rheology of a miscible polymer blend
Authors: Roland C. M. 
Published: April 2003

AbstractDifference spectra of blends of cis‐1,4‐polyisoprene and atactic poly(vinylethylene), obtained from the measured FTIR spectra of the pure components and the blends, indicate that mixing of these polymers is not accompanied by any specific chemical interactions. Miscibility in this system arises solely due to the small combinatorial entropy of mixing. The conformation and configuration of the polymer chains in the blends are, therefore, identical to those in the pure melts. As a consequence it was found that the entanglement density of the blends varied monotonically with composition. This variation, however, was not in accordance with predictions based simply on the mechanical interaction density. The principle rheological effect of miscible blending was a large change in the monomeric friction coefficient, which arises from the strong dependence of free volume on composition. The zero shear viscosity and the terminal relaxation time of the blends reflected this change in local chain mobility. Empirical relations, which have previously been proposed for the properties of miscible polymer mixtures, were found to be without merit in describing the obtained experimental results.
Theoretical stress–strain isotherms for elastin model networks
Authors: Debolt L. C. , Mark J. E. 
Published: April 2003

AbstractA theoretical analysis was carried out for polypeptides composed exclusively of one of the three highly conserved repeat sequences present in the bioelastomer elastin. Conformational energy maps of the relevant amino acids were generated and a standard matrix method used. Various levels of intramolecular hydrogen bonding were studied, ranging from none to the inclusion of longer‐range hydrogen bonds implicated in stabilizing β‐bend conformations considered of importance owing to a Pro‐Gly pair present in each of the three repeat peptides. Monte Carlo techniques were used to evaluate the distribution functions of the end‐to‐end distance vector r, from which the modulus as a function of elongation was calculated. With minor exception, the resulting stress–strain isotherms for chains having degree of polymerization 5 and 10 showed little deviation from Gaussian behavior for elongation ratios up to 2.
T∥ from the temperature dependence of carbon‐13 NMR correlation times τc
Authors: Boyer Raymond F. 
Published: April 2003

AbstractWe demonstrate that carbon‐13 NMR average correlation times τc published by Dekmezian et al. as plots of log τc against reduced temperature, T/Tg, reach a visibly apparent asymptotic limit, (T/Tg)as, at about 1.21 for 9 amorphous polymers and 4 semicrystalline polymers; PIB and ethylene copolymers are exceptions. The average value of Tc/Tg is 1.21, where Tc is the carbon‐13 NMR collapse temperature reported by Axelson and Mandelkern. Log τc − T data can be linearized by the WLF equation or by the Vogel equation using a reference temperature, Tr ≡ Tc. Log f, versus T/Tg data can also be linearized by a hyperbolic equation method. All three methods yield an asymptotic frequency of 1 Hz or less, rationalizing why Tc (about 106 Hz) ≡ T‖ (f ≤ 1 Hz). Dielectric loss data analyzed by the Lobanov–Frenkel method confirm and define a T* (K) at a frequency of about 105−107 Hz at T‖ associated with local chain motion. A plot of Tc or T* against Tg (static) is linear, suggesting that Tc ≡ T* ≡ T‖. It is demonstrated that values of log f versus 1/T with f = 1/2πτc help to define the high‐frequency locus in relaxation maps for cis‐PI, PIB, and at‐PP.The T‖ transition thus manifests itself in any of three ways: motion of the entire macromolecule in low frequency (1–1000 Hz) dynamic mechanical tests, an increase with temperature in Cp and in the coefficient of expansion in static measurements, and a high‐frequency local response in NMR and dielectric loss data. All three aspects are associated with the disappearance of interchain segment‐segment contacts at T‖, i.e., the “segmental melting” of Lobanov and Frenkel. Carbon‐13 NMR is a powerful tool for investigating T‖ dependence on structure in amorphous and crystalline polymers but is less satisfactory with ethylene copolymers. A linear correlation of Tc or Tas against Tg is demonstrated, where Tas is the asymptotic temperature from log τc versus T plots. This correlation can be used to define Tg in crystalline polymers if their Tc is known.
Dependence of the glass transition temperature of poly[N‐(n‐alkyloxy‐carbonyl‐methyl) Maleimides] and poly[N‐(5‐n‐alkyloxycarbonyl‐n‐pentyl) Maleimides] on n‐alkyl side‐chain length
Authors: Barrales‐Rienda J. M. , Mazón‐Arechederra J. M. 
Published: April 2003

AbstractThe glass transition temperature has been determined by a refractometric technique for two homologous series of poly[N‐(n‐alkyloxycarbonyl‐methyl) maleimides] (PEMIS 1) and poly[N‐(5‐n‐alkyloxycarbonyl‐n‐pentyl) maleimides] (PEMIS 5) with the outer part of the n‐alkyl side‐chain ranging in length from ethyl to decosyl for PEMIS 1 and from ethyl to decyl for PEMIS 5 and including only the even members of the series. The glass transition temperature is directly related to the number of methylene groups in the outer part of the n‐alkyl side‐chain (including terminal methyl) of the repeating unit. A semiempirical equation is presented that affords estimates of Tg that are in good agreement with the experimental data.
Effects of bond‐angle inversion on the statistical properties of poly(dimethylsiloxane)
Authors: Debolt L. C. , Mark J. E. 
Published: April 2003

AbstractEvidence of only a low barrier to inversion in SiOSi sequences could be important with regard to the interpretation of the statistical properties of silicone polymers. The effects are estimated for the temperature coefficients of the unperturbed dimensions, dipole moments, and optical‐configuration parameter for poly(dimethylsiloxane).
Electron spin resonance studies of manganese(II) and copper(II) salts of poly(ethylene‐co‐methacrylic acid)s
Authors: Takei Miyuki , Tsujita Yoshiharu , Shimada Shigetaka , Ichihara Hisakatsu , Enokida Motohiro , Takizawa Akira , Kinoshita Takatoshi 
Published: April 2003

AbstractThe ionic interaction of poly(ethylene‐co‐methacrylic acid) ionomer neutralized with Mn2+ or Cu2+ was studied by ESR spectroscopy to explore the local structure in the ionic aggregate. ESR spectra of the ethylene ionomer were obtained as functions of degree of neutralization and temperature. The existence of both isolated and aggregated cations in the ionomer was confirmed by ESR. In addition, the formation of a Cu2+−Cu2+ dimer structure similar to the crystal structure of copper acetate monohydrate was found in ethylene ionomer containing the Cu2+. Cation‐cation interactions changed markedly around 70°C with increasing temperature, representing the onset of the motion of cations in the aggregated ionic structure.
On the dual mode gas transport model for glassy polymers
Authors: Petropoulos J. H. 
Published: April 2003

AbstractThe present paper is concerned with a detailed examination of the formalism and the physical basis of the dual mode mobility model used for the theoretical description of gaseous transport in glassy polymers in the light of recent theoretical and experimental work. It is shown that there are no really major differences among the original formulation of the model and later variants. A major modification becomes necessary, however, if the Langmuir sorption mode is assumed to exist in the form of patches or domains extensive enough to constitute a macroscopically recognizable phase rather than in the commonly accepted from of scattered individual adsorption sites. It is shown that the proper treatment of this case reduces to the familiar dual mode mobility formalism only under certain conditions. The interpretation of the experimental results thus far available is considered in some detail, and the usefulness of each of the aforesaid approaches in this respect is discussed.
Effect of tacticity on permeation properties of poly(methyl methacrylate)
Authors: Min K. E. , Paul D. R. 
Published: April 2003

AbstractThe effect of stereoregularity on gas permeation properties of poly(methyl methacrylate) (PMMA) was investigated. The gas permeability coefficients for He, H2, O2, N2, Ar, CH4, and CO2 at 35°C near atmospheric pressure have been measured for three different PMMAs. Apparent diffusion and solubility coefficients were obtained from time lag data, and these were compared with data for a commercial PMMA previously reported. The permeability, solubility, and diffusion coefficients increase as the content of syndiotactic sequences increases. These observations are consistent with more dense packing of the isotactic form in the glassy state that stems in part from its lower glass transition temperature. The transport behavior for a 50:50 isotactic/syndiotactic blend was also studied. These so‐called stereocomplexes exhibit permeation behavior comparable to other weakly interacting miscible blend systems.
Deformation of semicrystalline polymers via crystal–crystal phase transition
Authors: Saraf Ravi F. , Porter Roger S. 
Published: April 2003

AbstractA classification is given of flexible, semicrystalline polymers based on the early stage deformation behavior in the solid state. The criteria of each category are discussed with experimental evidence from the literature on 17 polymers. The central aim of this classification is to point out the possibility of ductility induced during deformation. The understanding of the induced ductility in a given semicrystalline polymer suggests a systematic route to optimize solid‐state deformation processes for achieving high draw ratios.
Influence of the glass transition on solvent self‐diffusion in amorphous polymers
Authors: Vrentas J. S. , Duda J. L. , Ling H.‐C. 
Published: April 2003

AbstractThe free‐volume theory of diffusion is used to analyze the temperature dependence of solvent self‐diffusion coefficients both above and below the glass transition temperature at concentrations removed from the pure polymer limit. The glass transition can have a pronounced effect on the temperature dependence of solvent self‐diffusion coefficients at small solvent concentrations, but the theory predicts a decreased effect of the transition on the diffusion process with increasing solvent concentration.
The entropy of inhomogeneous polymer–solvent systems
Authors: Balsara Nitash P. , Nauman E. B. 
Published: April 2003

AbstractThe entropy of inhomogeneous polymer solutions has been evaluated using a lattice model. Previous models for polymer solutions considered only the enthalpic contributions, and a more complete expression for the free energy is obtained by adding the entropic term. The resulting expression is used to predict the characteristics of spinodal decomposition of polymer solutions and the interfacial tension between demixed polymer solutions. There is general improvement in the agreement between theory and experiment when the entropic effects are included.
Test of a model of stress‐dependent diffusion by means of combined colored tracer and birefringence profile measurements
Authors: Petropoulos J. H. , Sanopoulou M. 
Published: April 2003

AbstractIn the present paper we further test a model of stress‐dependent diffusion previously used with success to simulate the variation from Case I to Case II penetration kinetics in the system liquid methylene chloride‐uniaxially oriented cellulose acetate film, according to whether penetration occurs across or along the axis of preferred macromolecular orientation. Data on penetration rates, optical density profiles (using a colored tracer), and the corresponding birefringence profiles, characteristics of these penetration modes in the aforesaid system, are presented and compared with appropriate model uptake kinetic curves and penetrant concentration and compressive differential swelling stress profiles. It is shown that the salient features of the observed experimental behavior are in general accord with model predictions based on physically realistic assumptions.
Thermotropic polyesters of 4'‐hydroxyphenyl‐4‐hydroxybenzoate: A study of the transition temperatures
Authors: Kotek R. , Krigbaum W. R. 
Published: April 2003

AbstractPolyesters based on 4'‐hydroxyphenyl‐4‐hydroxybenzoate and dichlorides of dibasic acids, prepared using a high‐temperature solution polycondensation in 1‐chloronaphthalene, exhibit enantiotropic nematic mesomorphism. The range of temperatures for the nematic phase Δ tN can be controlled by changing the number of methylene units in the repeating polymer unit. For n = 4, Δ tN = 97°C is the largest that can be obtained. Higher n leads to smaller values of Δ tN. When n = 12, the polyester exhibits only one single C‐I transition. For n > 12 a smectic mesophase can be expected in this system. Strezlecki and Liébert reported a wide range of temperatures of Δ tN (70–160°C) for the Sn polymers made by the transesterification of 4'‐acetoxyphenyl‐4‐acetoxybenzoate and the dicarboxylic acids. We believe the latter reaction occasionally involves the internal ester linkage in the monomer unit, producing a copolyester having a random distribution of hard segment lengths and changed polymer mesomorphic properties.
Calorimetric determination of head‐to‐head defect in poly(vinylidene fluoride)
Authors: Millich F. , Hauber B. F. 
Published: April 2003

AbstractDifferential scanning calorimetric analyses were conducted on samples of poly(vinylidene fluoride) polymerized in an autoclave by tributylborane‐oxygen by free‐radical initiation at low temperature (‐70‐0°C). The peak melting points and the percent head‐to‐head defect in each polymer sample were determined by a reported calorimetric method. A commercial sample showed a melting temperature in the range 157–162°C and a percent head‐to‐head defect of 7.7%; whereas two experimental samples showed melting temperatures in the range 172–179°C with a percent head‐to‐head defect of 4.4 and 4.9%. The calorimetric procedure was modified by reducing annealing times to only 2 h, which saves time and, as shown in this study, avoids thermal polymer degradation.
Crystallinities of copolymers of ethylene and 1‐alkenes
Authors: Clas S.‐D. , Heyding R. D. , McFaddin D. C. , Russell K. E. , Scammell‐Bullock M. V. , Kelusky E. C. , St‐Cyr D. 
Published: April 2003

AbstractRandom copolymers of ethylene with 1‐butene, 1‐octene, and 1‐octadecene have been prepared using a homogeneous vanadium‐based catalyst system. Comonomer contents determined by 13C‐NMR analysis of polymer solutions are in the range 1–10 mol%. Crystallinities were estimated by means of density measurements, x‐ray diffraction, differential scanning calorimetry, laser Raman spectroscopy, and CPMAS 13C‐NMR spectroscopy. The results are compared with those obtained for heterogeneous copolymers of ethylene containing 1–4 mol% 1‐butene. As the comonomer content is increased, the crystallinity decreases. The dimension perpendicular to the 110 plane in orthorhombic crystallites decreases linearly with crystallinity. This decrease in crystallite size is accompanied by an increase in the size of the orthorhombic unit cell. For copolymers containing large amounts of 1‐octene and 1‐octadecene, a second crystalline form appears. Differences in estimates of crystallinity are discussed in terms of looser packing in highly branched copolymers and the extent to which the second crystalline form participates in the phase structure.
Composition of vinylidene chloride/phenylacetylene (VDC/PA) copolymers and vinylidene chloride/methyl acrylate/phenylacetylene (VDC/MA/PA) terpolymers from analysis by 13C‐NMR spectroscopy
Authors: Howell B. A. , Smith P. B. 
Published: April 2003

Abstract13C‐NMR spectroscopy has been utilized to characterize Saran polymers containing polyene segments generated by incorporating phenylacetylene (PA) units into either poly(vinylidene chloride) (PVDC) or a typical Saran copolymer of 91% vinylidene chloride (VDC) and 9% methyl acrylate (MA). The incorporation of PA could not be defined in the usual statistical way because the presence of the PA double bond in the polymer backbone appeared to cause the dehydrohalogenation of units next to it. Thus, sequences of PA next to VDC were not observed. Rather, sequences of olefinic units next to VDC units were present at a level equal to the level of PA incorporation. The level of unsaturation in the PA copolymers is approximately four times the level of PA incorporation. These observations are consistent with the random incorporation into the copolymer of PA which then initiates the dehydrohalogenation in adjacent VDC units. This dehydrohalogenation reaction appears to propagate from one unit to the next along the backbone of the polymer such that polyene segments containing the PA unit are formed.