bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isomorphous replacement in nylon 6 by 4‐aminomethylcyclohexanecarboxylic acid
Authors: Prince Frank R. , Pearce Eli M. , Fredericks Robert J. 
Published: April 2003

AbstractIt was desired to determine the effect of geometric configuration on the ability of 4‐aminomethylcyclohexanecarboxylic acid (AMCC) to “isomorphously” replace ε‐aminocaproic acid residues in nylon 6. However, we found that cis‐AMCC isomerized to the more thermodynamically stable trans isomer during copolymerization with caprolactam (CL) and also during homopolymerization. A 20/80 cis/trans ratio of AMCC residues was found in the 50:50 copolyamides regardless of whether a high‐cis (72/28) or high‐trans (15/85) AMCC was used. Powder x‐ray diagrams showed similar interplanar spacings for the copolyamides made from both high‐cis and high‐trans AMCC. The x‐ray study also showed that the nylon 6 lattice can accommodate less than 30 mole‐% AMCC residues before a new structure appears. DTA and TGA data of the CL:AMCC copolyamide showed that AMCC raised the melting point, Tg, Tc, and stability of nylon 6.
Polymerization studies on allylic compounds. V. 2‐chloropropenes
Authors: Reed Samuel F. 
Published: April 2003

AbstractThe free‐radical polymerization of three 2‐chloro‐3‐substituted propenes have been investigated. Compounds studied were 2,3‐dichloropropane, 2‐chloro‐3‐hydroxypropene, and 2‐chloro‐3‐acetoxypropene. These compounds were found to homopolymerize with difficulty to give low molecular weight polymers. Their effect upon the polymerization of methyl methacrylate and styrene was investigated by rate and viscosity measurements. Copolymerization occurred with a retarding action attributed to significant chain transfer processes and differences in monomer reactivities.
Gel permeation chromatography and cellulose. II. Application of universal calibration
Authors: Segal L. , Timpa J. D. , Wadsworth J. I. 
Published: April 2003

AbstractIn previously reported work concerning the chain‐length distributions obtained by gel permeation chromatography (GPC) in celluloses, degrees of polymerization (DP) of unusually high magnitude were reported. Later work in GPC has shown that the concept of relating extended nolecular chain length of different polymers to elution volume for obtaining molecular weight is not theoretically sound. Correlation of molecular hydrodynamic volume (indicated by the product of intrinsic viscosity and molecular weight) with elution volume has been found to place polymers of vastly different natures on a single curve, such is now designated universal calibration. Application of universal calibration to the determination of DP distributions in celluloses required a different method of converting counts to DP. This new procedure is described in detail. Weight‐average DP's given by the procedure for samples of cellulose I, II, III, and IV were 5190, 4520, 4795, and 3390, respectively. These are decreases of 74–75% from the results obtained by the extended‐chain procedure. The results compare favorably with the viscosity‐DP's of the samples. Number‐average DP's were 1580, 1040, 1140, and 490 for the four samples, respectively, these being decreases of 87–93% from the values formerly reported. The polymolecularity ratios for the samples are now unusually large, being 3.4, 4.7, 4.2, and 7.1, respectively.
Extension of elastic liquids: Polyisobutylene
Authors: Vinogradov G. V. , Radushkevich B. V. , Fikhman V. D. 
Published: April 2003

AbstractAn apparatus is described and a method discussed for determining the rheological characteristics of elastic liquids during extension at constant rates of deformation and extension. The material studied was polyisobutylene of molecular weight 7 × 104. At low constant deformation rates steady‐flow regimes were achieved, with corresponding equilibrium high elastic strains. A detailed study has been made of the process of attainment of steady‐flow regimes and it is shown that before steady flow is reached the curve of longitudinal viscosity versus strain passes through a maximum. As the rate of deformation rises, the strains at which steady–state flow regimes are achieved increase, and the time required to reach these regimes decreases. Qualitatively this occurs in the same way as upon shear. The dependence of equilibrium high‐elastic strains (under steady‐flow regimes) on the rate of deformation has been determined. At steady‐flow regimes the stress depends linearly on the rate of deformation at low values of the stress. Under such conditions Trouton's formula is valid. At constant rates of extension the stress versus time curve passes through a maximum which becomes higher with increasing extension rates.
Determination of the molecular weight spread of narrow peaks in the gel‐permeation chromatograms of nitric acid‐degraded polyethylene
Authors: Williams T. , Udagawa Y. , Keller A. , Ward I. M. 
Published: April 2003

AbstractA method for the determination of the molecular weight spread in the narrow peaks in the GPC chromatograms of nitric acid‐degraded polyethylene is presented. It is found that polar endgroups added to the polymer chains during scission cause the peaks to be broader than those of paraffins with the same molecular weight spread. After allowing for this extra instrumental broadening, estimates are made of the molecular weight spread for unannealed and annealed single crystals of polyethylene and bulk polyethylene as a function of degradation time. It is proposed that after long degradation times the molecular weight spread is a measure of fluctuations in the original crystalline lamellar thickness.
Single crystals of high polymers by film formation
Authors: Patel G. N. , Patel R. D. 
Published: April 2003

AbstractA simple method of preparing thin uniform films of high polymers has been examined for growing single crystals from solution. Single crystals of polyethylene, polypropylene, polybutene‐1, polyacrylonitrile, and cellulose triacetate have been obtained by this method. Different stages of growth reveal different growth features that are also obtained from solutions of these polymers by changing temperature and concentration.
Adsorption of toluene‐soluble polymers at the toluene–water interface
Authors: Huber Hans F. , Thies Curt 
Published: April 2003

AbstractThe adsorption of several toluene‐soluble polymers at the toluene–water interface has been investigated by using the duNouy ring method of measuring interfacial tension γT/W. Polystyrene and poly(ethylene‐co‐vinyl acetate) (11.1 mole‐% vinyl acetate) have little affinity for this interface at 29°C, but poly(methyl methacrylate) (PMMA) (M̄n = 420,000) and ethyl cellulose (EC) (M̄n = 50,100; 49.1% ethoxyl) adsorb significantly at concentrations as low as 1.0 × 10−4 g/100ml. A plot of interfacial tension lowering versus initial logarithm of initial bulk phase polymer concentration is linear from 1.0 × 10−4 to 1.0 × 10−1 g/100 ml for EC and 1.0 × 10−4 to 1.0 × 10−2 g/100 ml for PMMA. When the PMMA concentration increases to 1.15 × 10−1 g/100 ml, its adsorption behavior changes markedly. Prolonged time effects occur and adsorption becomes dependent upon dissolved water content of the toluene prior to formation of the toluene/water interface. Such effects are not observed with the other solutions studied. Increasing temperatures have variable effects on values of γT/W for the polymer solutions studied. Experiments with various polymer mixtures indicate that the polymer lowering T/W the most is preferentially adsorbed at the toluene–water interface and rapidly displaces less strongly adsorbed polymers.
Universal calibration in GPC: A study of polystyrene, poly‐α‐methylstyrene, and polypropylene
Authors: Coll H. , Gilding D. K. 
Published: April 2003

AbstractThe theoretical justification for using M[η], or a similar quantity, as a universal calibration parameter in GPC is reviewed. The equation based on this parameter is applied to transform the primary calibration curve, obtained by means of polystyrene samples, into calibration curves for poly‐α‐methylstyrene, polypropylene, and linear polyethylene. The Mark–Houwink equations for these polymers, as they are used in the transformation, are discussed. The resulting GPC calibration curves are compared with molecular weights and peak elution volumes of fractionated poly‐α‐methylstyrene and polypropylene. The same comparison is made with samples of polypropylene and polyethylene having very broad molecular weight distributions. The agreement lies within experimental error.
Lamellar and interlamellar structure in melt‐crystallized polyethylene. I. Degree of crystallinity, atomic positions, particle size, and lattice disorder of the first and second kinds
Authors: Kavesh S. , Schultz J. M. 
Published: April 2003

AbstractAn x‐ray diffraction method for the simultaneous determination of crystallinity (including intracrystalline defects), effective Debye‐Waller factors, and atomic positions has been developed and applied to semicrystalline polyethylene. It was found that this material unambiguously constitutes a two‐phase system. Measurements of intracrystalline lattice disorder in the chain direction and perpendicular to the chain direction show these to be in the ratio 1:2.5. Lattice disorder was principally of the first kind. Paracrystalline disorder in the [110] direction was less than 2.4% at all experimental conditions. Results include measurements of degree of crystallinity, particle size, space group, and unit cell parameters and variation of these quantities with crystallization temperature, ambient temperature, and time.
General dynamic theory of macromolecular networks. II. Dynamics of network deformation
Authors: Takserman‐Krozer R. , Ziabicki Andrzej 
Published: April 2003

AbstractOn the basis of the general concepts of a macromolecular network as defined in the preceding paper, a detailed analysis of forces acting on a network chain is given. In all types of networks the chain tension involves elastic, diffusional, contact friction and internal viscosity terms; in entanglement networks there appears also an additional term associated with chain–chain friction at entanglement junctions. The force balance equation for a tetrafunctional network junction is derived. It is shown that exact formulation of this equation requires knowledge of the simultaneous configurations of all the network chains in the system. For energetic networks, solution of the force balance equation is not required for the determination of the distribution function; and the dynamics of such networks can be discussed in terms of a distribution function for a single chain. On the other hand, for entanglement and contact networks, where the force balance equation is a source of information about sliding rates, some simplified equations can be formulated and solved, by using a 4(N + 1)‐dimensional distribution function for a single macromolecule with N network junctions. It is shown that for both network classes with nonlocalized junctions the position of a network chain within the macromolecule plays an essential role and is a source of the effects of molecular weight on the physical behavior of the system.The analysis of forces acting on a network chain reveals also some essential differences in the dynamic behavior of energetic, entanglement and contact networks and thus confirms the significance of the classification proposed in the preceding paper.
General description of orientation factors in terms of expansion of orientation distribution function in a series of spherical harmonics
Authors: Nomura Shunji , Kawai Hiromichi , Kimura Itsuro , Kagiyama Mitsuyasu 
Published: April 2003

AbstractA mathematical representation of orientation distribution of structural units within the bulk polymer is given in terms of an expansion of the distribution function in a series of spherical harmonics. Each coefficient of the expanded series is discussed in general relation to the orientation factors, average degrees of orientation distribution, defined by several different authors independently. Several optical techniques to evaluate the orientation factors, the second and fourth moments of orientation distribution of crystalline and noncrystalline structural units from optical dichroic quantities, are discussed. Some graphical representations of the state of orientation are proposed, and the estimation of orientation distribution from the orientation factors of different orders is discussed quantitatively.
Determination of the width of a narrow molecular weight distribution by gel‐permeation chromatography
Authors: Waters J. L. 
Published: April 2003

AbstractA recycle gel‐permeation chromatography (GPC) method for extrapolating to infinite resolution is proposed. From the GPC calibration curve, the extrapolated elution peak width volume can be converted into peak width in decades of molecular weight. For an essentially Gaussian distribution, the weight‐average/number‐average molecular weight ratio can be determined from a calculated conversion table.
A dynamic approach to diffusion and permeation measurements
Authors: Pasternak R. A. , Schimscheimer J. F. , Heller J. 
Published: April 2003

AbstractA dynamic method for investigating the mechanism of permeation and diffusion through polymers has been explored. The permeation cell consists of two compartments separated by the membrane. The permeant (gas, vapor, or liquid) is introduced into one compartment; a carrier gas (helium) flows at constant rate through the other and sweeps the permeant which diffuses through the membrane to the thermal conductivity detector. Both compartments are at atmospheric pressure; thus no or little membrane support is required, and leakage problems are minimal. Moreover, the same membrane can be used over a wide temperature range and for diverse permeants. The detector signal is at any instant proportional to the permeation rate. A simple mathematical formalism for deriving the diffusion coefficient from the transient permeation rates has been developed. The measured diffusion and permeability coefficients of CO2, O2, and N2 through low‐density polyethylene closely agree with literature values. Permeation of hexane and benzene through polyethylene follows a complex diffusion law, and the rate depends on the thermal history of the system. The dynamic method is particularly suited to the study of transitions in polymers. Changes in permeation rates, usually occurring at transition points, can easily be discovered by slow temperature scanning of the system.
Multiple melting transitions in fractions of partially isotactic poly(propylene oxide)
Authors: Booth C. , Devoy C. J. , Dodgson D. V. , Hillier I. H. 
Published: April 2003

AbstractThree transitions are detected dilatometrically when partially isotactic poly(propylene oxide) melts. One transition, the temperature of which is independent of the crystallization temperature over a wide range below 60°C, is ascribed to the melting of lamellar crystallites which are limited in thickness by the average isotactic sequence length alone. The other two transitions, the temperatures of which vary with the crystallization temperature, are ascribed to the melting of lamellar crystallites with thickness determined predominantly by three‐ and two‐dimensional primary nucleation acts. The theory of Flory is adapted and applied quantitatively to the melting points of three crystalline fractions of poly(propylene oxide), obtained from a polymer produced via the zinc diethyl and water catalyst system. This method leads to a thermodynamic melting point of isotactic poly(propylene oxide) near 82°C.
Dilute solution parameters of polymethylphenylsiloxamers
Authors: Buch Robert R. , Klimisch Helen M. , Johannson O. K. 
Published: April 2003

AbstractDilute solution parameters were determined for polymethylphenylsiloxamer fractions (5 × 104 < M < 1.5 × 106) in toluene, cyclohexane, and diisobutylamine (θ ≈ 30.4°C). The data are interpreted by the procedure suggested by Flory and Fox. Minor deviations from theory are noted. Polymers from both cis‐ and trans‐cyclotrisiloxanes were investigated. The major portion of the work, however, was concentrated on fractions derived from the trans form. From the data obtained, a characteristic ratio of dimensions (r/r)½ of 1.56 was determined. The hydrodynamic parameter Φ was determined to be (2.0 ± 0.3) × 1021. The appropriate model for the polymer is indicated to be the impermeable random coil with slight hindrance to rotation about backbone skeletal bonds.
Viscoelastic and relaxation properties of a polystyrene melt in axial extension
Authors: Vinogradov G. V. , Fikhman V. D. , Radushkevich B. V. , Ya. Malkin A. 
Published: April 2003

AbstractOn axial extension of polymer melts at constant deformation rates, the development of high‐elastic deformation is of predominant importance during the initial period. High‐elastic deformation is accompanied by a rise in viscosity and in the modulus of high‐elasticity and by retardation of the relaxation processes in the region of large relaxation times. At relatively low deformation rates, the rise in viscosity and high‐elasticity modulus and the retardation of relaxation processes may give way to a decrease in viscosity and high‐elasticity modulus and acceleration of relaxation processes, so that stationary flow regimes are attained. The transition from strain regimes with increasing viscosity and modulus of high elasticity to those with a decrease of these quantities corresponds to an increase in the rate of accumulation of irreversible deformation. Accordingly, a competing influence due to the orientation effect and to destruction of the network of intermolecular bonds becomes evident while stationary flow is being attained. The orientation effect must be responsible for the retardation of the relaxation processes, whereas rupture of the intermolecular network bonds results in structural relaxation accelerating relaxation processes. In contrast to shearing, during extension the orientation effect is of predominant importance. Hence in stationary flow regimes the viscosity may not only remain independent of the rate of strain, but even increase with it. In this case the contribution of the large relaxation times to the relaxation spectrum increases with increasing stress in stationary flow regimes. The fact that the longitudinal viscosity and the modulus of high elasticity are independent of the stress in stationary flow regimes does not guarantee linearity of the mechanical properties of the polymer in the prestationary stage of deformation when complex changes occur in its relaxation characteristics. At high deformation rates the viscosity and the modulus of high elasticity keep rising with increasing deformation until rupture occurs. Determination of the strength of polystyrene samples vitrified after extension showed that it is due not to the entire degree of extension, but only to the value of accumulated high‐elastic deformation. The strength of the vitrified samples is to a first approximation independent of the rate at which the melt was extended.
Conformation of poly(methacrylic acid) in alcohol–water mixtures. I. Effect of concentration, temperature, pH, and ionic strength
Authors: Priel Z. , Silberberg A. 
Published: April 2003

AbstractThe reduced specific viscosity of poly(methacrylic acid) has been studied in ethanol–0.002N HCI solvent mixtures as a function of polymer concentration, alcohol concentration, and temperature. In addition, experiments were performed at different HCI concentrations and with KCI instead of HCI. Both intrinsic viscosity and Huggins coefficient were shown to undergo unusually strong variations. Two minima and two maxima could be demonstrated in intrinsic viscosity. The Huggins coefficient seems to show corresponding variations. The first minimum in intrinsic viscosity indicates that the coil volume has collapsed almost to an Einstein sphere. In this region the Huggins coefficient is extremely large (of order 102) and is controlled by coil association. It was shown that several forms of intramolecular interaction must be assumed to be competing to account for this behavior. The presence of HCI, particularly in the preponderantly aqueous phase, is required to suppress the polyelectrolyte effect. It is found, however, that the behavior of the solutions at relatively high ethanol concentrations is more sensitive to HCI content than is that of highly aqueous solutions. KCI can be used to replace HCI over most of the range. Increase in temperature shifts the turning points of the curves to lower alcohol concentrations. Some evidence has been found that the association constant giving rise to dimers increase with rate of shear. The importance of poly(methacrylic acid) as a chemically simple model substance for various biopolymer effects is stressed.
Conformation of poly(methacrylic acid) in alcohol–water mixtures. II. Methanol, ethanol, n‐propanol, and 1,2‐ethanediol
Authors: Priel Z. , Silberberg A. 
Published: April 2003

AbstractThe intrinsic viscosity of poly(methacrylic acid) has been studied in mixtures of 0.002N HCI and a series of aliphatic alcohols. The behavior found previously with ethanol is shown to apply in the case of admixture with methanol, n‐propanol, and 1,2‐ethanediol. The intrinsic viscosity first drops to a minimum and then increases sharply to a maximum. With ethanol and n‐propanol the maximum is followed by another minimum and maximum. With methanol and 1,2‐ethanediol this effect is absent or much smaller. Methanol and 1,2‐ethanediol are equivalent, molecule for molecule, in their influence on the intrinsic viscosity. With ethanol and n‐propanol there are in addition one and two shoulders, respectively, in the passage from the first minimum to the first maximum. Good correlation of the data is obtained if alcohol concentration is plotted as the mole fraction of carbon atoms per OH group (in the alcohol). The first maximum in particular was shown to correspond to the point where the number of water molecules per alcohol in the solvent mixture equals the number of C atoms per hydroxyl in the alcohol. The shoulders and first minima were found to correspond to other simple ratios. This behavior reflects changes in alcohol–water structure. The maximum in the case of ethanol was found to be the most pronounced and ethanol seems to possess optimal properties from this point of view.
Conformation of poly(methacrylic acid) in alcohol–water mixtures. III. Dependence on molecular weight
Authors: Priel Z. , Silberberg A. 
Published: April 2003

AbstractPoly(methacrylic acid) has been studied in 0.002N HCl–ethanol mixtures as a function of molecular weight. A different dependence on molecular weight is noted at different alcohol concentrations. Since the intrinsic viscosity passes through a series of extrema with changes in alcohol concentration, the dependence on molecular weight has been considered in two regions of alcohol concentration in particular. The region of the first minimum and the region of the second minimum (or overall maximum). In the region of the first minimum, intrinsic viscosity is proportional to M½, just as in 0.002N HCl. The Huggins coefficient k′ is large (ca. 60) but drops to about 10 when the molecular weight exceeds 320,000. In the region of the second minimum the dependence on molecular weight is complex. Intrinsic viscosity is proportional to molecular weight both at low and at high molecular weight and thus indicates freely draining structures. There is a conformational contraction, however, at molecular weight about 320,000 leading from one type of structure to the other. The structure at higher molecular weight may involve a specially strong bond between specifically grouped segments in the chain. The positions of the extrema along the alcohol concentration axis are not molecular weight dependent, particularly above 320,000. Results available for molecular weight dependence in methanol agree well with this picture. The present results confirm prediction inherent in the model of Silberberg and Priel and Silberberg.