bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature‐dependent x‐ray small‐angle scattering from melt‐crystallized polyethylene
Authors: Schultz J. M. , Robinson W. H. , Pound G. M. 
Published: April 2003

AbstractThe temperature dependence of x‐ray small‐angle scattering from fractionated linear polyethylene crystallized from the melt was determined experimentally over a range of temperatures from room temperature to the melting point. It was found in general that only the most intense of the several small‐angle peaks exhibited a thermally dependent behavior. Below the crystallization temperature this peak increased in intensity with temperature, at constant peak position. Recrystallization was manifest in a discontinuous shift of the peak. During isothermal crystallization, the peak intensity first increased, then decreased, with time. It is concluded from supplementary electron microscopy and from the behavior of the peak that its position reflects the period of stacking of lamellae and that its intensity is controlled primarily by the thickness of the layer separating lamellae. The reversible peak intensity effect is attributed to an entropydriven growth of the interlamellar layer at the expense of the crystalline lamellae. The intensity effects observed during crystallization are associated with the primary and secondary phases of crystallization. Lamellar surface free energies were computed from melting point observations and were found to increase with molecular weight.
Gel permeation chromatography of polyethylene: Effect of long‐chain branching
Authors: Wild L. , Guliana R. 
Published: April 2003

AbstractThe effect of long‐chain branching on the size of low‐density polyethylene molecules in solution is demonstrated through solution viscosity and molecular weight measurements on fractionated samples. These well‐characterized fractions are analyzed by gel permeation chromatography (GPC), and it is shown that the separation of the polymer molecules by this technique is sensitive to the presence of long‐chain branching. By using fractions of branched polyethylene possessing differing degrees of branching, one observes that a single curve is adequate in relating elution volume to molecular weight. This calibration curve is applied in the GPC analysis of a variety of commercial low‐density polyethylene resins and it is shown, by comparison with independent osmometric and gradient elution chromatographic data, that realistic values for molecular weight and molecular weight distribution are obtained. The replacement of molecular weight M by the parameter [η]M as a function of elution volume, leads to a single relationship for both linear and branched polyethylenes. This indicates that GPC separation takes place according to the hydrodynamic volumes of the polymer molecules. The comparison of data for polyethylene and polystyrene fractions suggests that this volume dependence of the separation will be observed for other polymer–solvent systems.
Melting temperature of trans‐polyoctenamer
Authors: Calderon Nissim , Morris Marion C. 
Published: April 2003

AbstractThe effect of microstructure on crystallizability of polyoctenamers prepared by R3Al‐WCl6 catalyst was studied. The results indicate that polyoctenamers with a broad range of trans‐vinylene content do crystallize. The measured melting points are dependent on the trans‐vinylene content. From the dependence of melting temperature on copolymer composition, a value of 73 ± 2°C. for the melting point and a molar heat of fusion ΔHu of 3520 cal./mole are calculated for 100% trans‐polyoctenamer. From the melting point depression in the presence of diluent, a value for ΔHu of 4800 cal./mole is obtained.
Light‐scattering study of polyacrylonitrile solution
Authors: Shibukawa Takashi , Sone Masao , Uchida Akiyoshi , Iwahori Kimihiko 
Published: April 2003

AbstractLight‐scattering measurements of polyacrylonitrile (PAN) prepared by aqueous suspension polymerization and solution polymerization were made in both dimethylformamide (DMF) and γ‐butyrolactone (γ‐BL). The following relations between the intrinsic viscosity [η] (in deciliters per gram) and the weight‐average molecular weight were obtained: [η] = 3.35 × 10−4 M̄w0.72 (in DMF at 30°C.) and [η] = 4.00 × 10−4 M̄w0.69 (in γ‐BL at 30°C.). The relation in DMF is in agreement with the results of many other researchers, but differs from the results of Bisschops et al. and Peebles. Analysis of the results by the recent viscosity theory reported by Inagaki et al. indicates that the steric factor σ is 2.17 on PAN in both DMF and γ‐BL. It is found that the root‐mean‐square radius of gyration of the chain measured by light scattering 〈S2〉w1/2 (LS) is in good agreement with the root‐mean‐square radius of gyration of the chain calculated by using the viscosity theory of Inagaki et al. 〈S2〉w1/2 (vis) in both DMF and γ‐BL.Relations between the root‐mean‐square radius of gyration of the chain (in Angstroms) in DMF and γ‐BL and the molecular weight were obtained: 〈S2〉w1/2 = 7.94 × 10−2 M̄w0.66 (in DMF) and 〈S2〉w1/2 = 2.19 × 10−1 M̄w0.57 (in γ‐BL). From the estimation of the second virial coefficient A2 and the value of B obtained from viscosity theory, it is found that DMF is a better solvent than γ‐BL.
Morphological changes of twisted nylon 66 and poly(ethylene terephthalate) monofilaments
Authors: Cooper S. L. , McKinnon A. J. , Prevorsek D. C. 
Published: April 2003

AbstractA comparison of the x‐ray diffraction from twisted nylon 66 and poly(ethyleneterephthalate) monofilaments is made with the scatter predicated by a model assuming an affine deformation of the fiber. The x‐ray diffraction of the model is characterized by an approximately constant intensity over the entire range of the azimuthal dispersion. With twisted nylon 66 fibers the (010) reflection is split into a bimodal intensity distribution about the equator, while the (100) reflection maintains a distinct maximum on the equator. It is proposed that this difference is due primarily to the fact that a plastic deformation involving rotation of crystal planes occurs more readily when the shear stress acts in [010] direction than in the case when it acts in the [100] direction. A similar behavior is found with poly(ethylene terephthalate) fiber.
Aminimides. IV. Homo‐ and copolymerization studies on trimethylamine methacrylimide
Authors: Culbertson B. M. , Slagel R. C. 
Published: April 2003

AbstractTrimethylamine methacrylimide (TAMI) has been homo‐ and copolymerized with methyl methacrylate, vinyl acetate, vinyl chloride, hydroxypropyl methacrylate, and acrylonitrile by free‐radical initiators to soluble, low molecular weight polymers containing pendant aminimide groups along the backbone of the polymer chains. The reactivity ratios in the copolymerization of TAMI (M1) with acrylonitrile (M2) were determined: r1 = 0.10 ± 0.01, r2 = 0.37 ± 0.04. The Alfrey‐Price Q and e values for TAMI were also calculated: Q = 0.18, e = −0.60. This preliminary work indicates that TAMI has potential for the preparation of reactive polymers.
Solution properties of cellulose triacetate. II. Solubility and viscosity studies
Authors: Howard P. , Parikh R. S. 
Published: April 2003

AbstractThe solubility of cellulose triacetate in a range of solvents was measured, and the results for tetrachloroethane, chloroform, and acetic acid were compared with those from initial phase separation in solvent–nonsolvent mixtures and viscosity–concentration studies. The correlation found between solubilities, precipitation values, and values of the Huggins viscosity constant is discussed with reference to the type of polymer–solvent interaction proposed previously to explain fractionation behavior. A qualitative comparison of solubility–swelling behaviour was also made for a very low molecular weight cellulose triacetate sample in a wide range of solvents. Results are compared with those for higher molecular weight samples and discussed with regard to the cohesiveenergy densities of solvent and polymer. Some attempt has been made to predict suitable solvents for cellulose triacetate, based on consideration of their molecular structures.
Emulsion polymerization. IV. Experimental verification of the theory based on slow termination rate within latex particles
Authors: Gardon J. L. 
Published: April 2003

AbstractA large body of data shows that the time dependence of conversion fits the equation P = At2 + Bt in the interval where, according to the Smith‐Ewart model, the relationship should be linear. For latexes of very small particle size the Smith‐Ewart linear relationship (P = Bt) is often observed, and for latexes of very large particle size the conversion was found to be proportional to t2. The experimental value of parameter B was in good agreement with independent theoretical predictions. From A and B the ratio between termination and propagation constants was calculated and was in the 5–200 range. Independent estimates of this ratio give the same order of magnitude. These independent estimates are from the literature and are obtained from the increase in conversion rate at catalyst post‐addition during emulsion polymerization or from emulsion polymerization initiated by intermittent irradiation or from homogeneous polymerization in the presence of inert polymers of high viscosity. The conversion–time curves describing the whole conversion process generally have sigmoid shape. The molecular weight is often found to pass through a maximum as the conversion increases. In one experiment this maximum coincided with the calculated maximum in the average number of radicals per particle Q. The variation of experimental molecular weights with conversion accurately followed the theoretical predictions. The deviation from the Smith‐Ewart model was often significant. The value of Q was not 0.5, as the Smith‐Ewart model requires it to be, but often reached values much larger, as large as 10. The particle size distribution broadened with increasing conversion and became increasingly skew. Numerous data taken from the literature are in good quantitative or qualitative agreement with the theory proposed in Part III and for these data the observed deviations from the Smith‐Ewart theory are readily explainable. The new data obtained with styrene, n‐butyl methacrylate, and methyl methacrylate are also in quantitative agreement with the new theory. One experiment involving methyl methacrylate is analyzed in great detail. The variation of time, of Q, of molecular weight, of average particle size, and of particle size distribution with conversion are reported. The molecular weight distribution is also calculated from the conversion dependence of molecular weight.
Polymerization of isocyanates. IV. Polymerization by aqueous initiator systems
Authors: Iwakura Yoshio , Uno Keikichi , Kobayashi Norio 
Published: April 2003

AbstractIsocyanates were polymerized by aqueous solutions of numerous alkali salts at a low temperature. Polymer could be obtained even in the presence of a large excess of water to monomer in the polymerization system. The initiating species was proposed to be hydroxide ion.
Polymerization of D‐α‐methylbenzyl methacrylate by n‐butyllithium and the tacticity and optical rotation of the polymer
Authors: Yuki Heimei , Ohta Koji , Uno Katsuhiro , Murahashi Shunsuke 
Published: April 2003

AbstractD‐α‐Methylbenzyl methacrylate, [α] = +51.3° (neat), was polymerized by n‐butyllithium in toluene–tetrahydrofuran mixtures of various solvent ratios at −78°C. The polymers obtained were converted into poly(methyl methacrylate)s, which were analyzed for tacticity by high resolution NMR spectroscopy. A linear relationship was obtained between the optical rotation and the isotacticity of poly(D‐α‐methylbenzyl methacrylate). The extrapolation of the data gave +120° and +99° for [α] of the fully isotactic and syndiotactic polymers, respectively. The copolymerization of the D‐ and L‐isomers in toluene gave copolymers which were less isotactic than the homopolymer of the D‐isomer. The optical rotation of the copolymer was proportional to the excess of one isomer in the polymer.
Studies on the tacticity of polyacrylonitrile. III. NMR spectra of stereoisomers of 2,4,6‐tricyanoheptane as model compounds of polyacrylonitrile
Authors: Murano Masao , Yamadera Reizo 
Published: April 2003

AbstractThe three stereoisomers of 2,4,6‐tricyanoheptane were separated and their NMR spectra were studied as the three‐unit model compounds of polyacrylonitrile. The chemical shifts and coupling constants obtained from the NMR spectra were compared to those of the two‐units model compounds. The geminal protons for the isotactic methylene are not equivalent, but the difference of the chemical shifts is smaller than that in the meso two‐unit model. The racemic methylene signals appear at higher field than the meso methylene in the heterotactic three‐unit model as in the case of the racemic and the meso two‐unit models. The signals of the methinic protons in triads appear in the order: isotactic CH, heterotactic CH, and syndiotactic CH from the high field. From the observed values of the vicinal coupling constants, the chain conformations of the model compounds are also discussed.
Structure and reactivity of α,β‐unsaturated ethers. III. Cationic copolymerizations of alkenyl alkyl ethers
Authors: Okuyama T. , Fueno T. , Furukawa J. , Uyeo K. 
Published: April 2003

AbstractThe relative cationic polymerizabilities of the geometrical isomers of various alkenyl alkyl ethers were studied both in copolymerizations with each other and in their respective copolymerizations with vinyl isobutyl ether as standard. Copolymerizations were carried out in methylene dichloride at −78°C. with boron trifluoride etherate as catalyst. The cis isomers have been found to be more reactive than the corresponding trans isomers. A primary alkyl substituent on the β‐cis position of vinyl ethyl ether enhances the reactivity. Yet the steric effect is noticeable when the substituents are bulky. Compounds substituted with cis‐β‐isobutyl and with β‐dimethyl showed little tendency to homopolymerization. It was proved that the polymer ends derived from cis and from trans monomers are respectively different in character because of the restricted rotation of the end unit around the terminal carbon–carbon bond. The alternation tendency, remarkable in the copolymerization of cis monomers with vinyl ether, was explained in terms of the cis‐opening mechanism.
Homopolymers and copolymers of vinyl ethers of rosin‐derived alcohols
Authors: Fukuda Wakichi , Saga Motoo , Marvel C. S. 
Published: April 2003

AbstractTwo vinyl ethers of rosin‐derived alcohols were homopolymerized with free‐radical and cationic initiators. A polymer was obtained from the vinyl ether of the alcohol from Foral in good conversion by free‐radical initiators but it was not a high molecular weight product. Cationic initiators were more effective; boron trifluoride etherate proved to be best. All of the homopolymers were obtained as white powders with high crystallinity. Copolymerizations of the vinyl ethers and vinyl chloride have been studied with the use of free‐radical initiators. Cationic‐initiated copolymers of the vinyl ethers and isobutyl vinyl ether were studied. Those containing less than 20% of the rosin vinyl ethers were rubbery, of high molecular weight, and could be crosslinked with peroxide.
Radiation grafting of vinyl monomers to wool. III. Location of the grafted polymer
Authors: Ingram P. , Williams J. L. , Stannett V. , Andrews M. W. 
Published: April 2003

AbstractStudies of properties such as water sorption of grafted wool have shown the importance of the location of the polymer in the fiber. Electron microscopy and low‐angle x‐ray diffraction studies have been used to determine the location of grafted polystyrene in wool. Samples grafted from 15 to 800% (dry weight increase) all exhibit a large increase in contrast in the cell membranes (IR) and nuclear‐remnant regions (NR) in the electron micrographs. This is considered to be due in part to an unevenness in mechanical response to sectioning and in part to the deposition of ungrafted homopolymer in IR and NR, particularly at grafts of greater than about 100%. Analysis of the change in the 83 A. equatorial x‐ray reflection suggests that most of the grafted polymer resides in the keratinous matrix regions between the microfibrils within the cortical cells. At larger grafts the wool still retains its basic histological character, but the increase in this spacing is no longer proportional to the amount of graft, and the desposition of polymer becomes very inhomogeneous.
A tracer study of the hydrolysis of methyl methacrylate and methyl acrylate units in homopolymers and copolymers
Authors: Baines F. C. , Bevington J. C. 
Published: April 2003

AbstractHomopolymers and copolymers were prepared from methyl methacrylate, methyl acrylate, and styrene by radical reactions at 60°C. Monomers suitably labeled with carbon‐14 were used so that it was possible to monitor the hydrolysis of ester groups in the polymers during treatment under alkaline conditions. It was found that methyl acrylate units were hydrolyzed completely whatever their environment in a polymer chain. Under the same conditions only about 9% of the ester groups in a homopolymer of methyl methacrylate reacted; the proportion was increased by the introduction of comonomer units into the polymer chain. For copolymers of methyl methacrylate with methyl acrylate the extent of reaction may be correlated with the lengths of the sequences of methyl methacrylate units.
Studies on the charge transfer complex and polymerization. XVI. Spontaneous copolymerization of cyclopentene and sulfur dioxide
Authors: Iwatsuki Shouji , Okada Tsuneyoshi , Yamashita Yuya 
Published: April 2003

AbstractThe alternating copolymerization of cyclopentene and sulfur dioxide was studied. It takes place spontaneously at −15°C. The rate of copolymerization in toluene was found to be proportional to [CPT]3 and [SO2]2 with the overall activation energy of 16.5 kcal/mole. Terpolymerizations with eight different third monomers were carried out to examine the character and behavior of the copolymerization system of CPT and SO2. However, the polymerizations with styrene and methyl methacrylate as the third monomers were found to be extraordinary, in that all the three components are not incorporated into the polymer chain.
Emulsion polymerization. V. Lowest theoretical limits of the ratio kt/kp
Authors: Gardon J. L. 
Published: April 2003

AbstractIt is assumed that the propagating polymeric radicals have no diffusive mobility in the very highly viscous medium within latex particles. Chain growth takes place on a lattice when the polymeric radical reacts with a monomer present on a lattice site adjacent to that occupied by the reactive chain end. For termination, two radical chain ends must be positioned on adjacent lattice sites at the same instant. The kt/kp ratios calculated with this model are either similar to or somewhat lower than the values determined in emulsion polymerization experiments. A minimum value of kt/kp can be calculated with the aid of the rate equation of Part III by assuming that only “living” polymer is produced during emulsion polymerization. This value of kt/kp is significantly lower than that calculated by the lattice model. Since the value corresponding to the lattice model gives the slowest practically achievable termination rate, it is concluded from these calculations that emulsion polymerization cannot be carried out under conditions in which chain termination is completely suppressed.
Polymerization of acrylamide and methacrylamide photoinitiated by azidopentamminecobalt(III) chloride
Authors: Natarajan L. V. , Santappa M. 
Published: April 2003

AbstractThe kinetics of polymerization of acrylamide and methacrylamide, photoinitiated by azidopentamminecobalt(III) chloride in homogeneous aqueous acid medium was studied systematically. Monochromatic wavelengths 365, 405, and 435 mμ were employed for irradiation. Polymerization proceeded without any induction period, and the reaction was followed by measurements of rate of monomer disappearance (bromometrically), rate of complex disappearance (spectrophotometrically), and the chain lengths of the polymer formed (viscometrically). The dependences of the rate of polymerization on variables like light intensity, light absorption fraction by the complex, wavelength, monomer concentration, hydrogen ion concentration, nature of the acid used (HClO4, HNO3, and H2SO4), etc., were studied. The rate of polymerization of acrylamide depended on the unit power of monomer concentration and on the square root of light absorption fraction kε and light intensity I. The rate of methacrylamide polymerization was proportional to the unit power of monomer concentration and fractional powers of 0.25 and 0.30 of kε and I, respectively. A kinetic reaction scheme is proposed and discussed in the light of the experimental results, and it has been concluded that (1) the primary photochemical act is an electron transfer reaction from the azide ion to Co(III) in the complex, (2) initiation of polymerization is by azide radical, (3) termination is by mutual destruction of polymer radicals.
Anionic graft copolymerization of diene polymers with vinyl monomers
Authors: Minoura Yuji , Harada Hiroshi 
Published: April 2003

AbstractA mixture of homopolymer and graft copolymer was obtained by adding the monomer at 0°C to the polylithiodiene solution. Styrene, methyl methacrylate, and acrylonitrile were used as the monomers. Polylithiodienes were prepared by the metalation of diene polymers, i.e., polybutadiene or polyisoprene, with the use of n‐butyllithium in the presence of a tertiary amine (N,N,N′,N′‐tetramethylethylenediamine) in n‐heptane. The graft copolymers were separated by solvent extraction and were confirmed by turbidimetric titration and elementary analysis. Oxidation of the polybutadiene–styrene grafts revealed that the molecular weight of the side chains was the same as the molecular weight of the free polystyrene formed. The grafting efficiency and grafting percentage were studied for polybutadiene–styrene graft copolymers prepared under various conditions.
Four‐center type photopolymerization in the solid state. II. Polymerization mechanism of 2,5‐distyrylpyrazine
Authors: Nakanishi Hachiro , Suzuki Yasuzo , Suzuki Fusae , Hasegawa Masaki 
Published: April 2003

AbstractThe polymerization mechanism of trans,trans‐2,5‐distyrylpyrazine (DSP) has been investigated and some crystal changes along with the polymerization process have been observed through polarizing microscope and x‐ray diffraction pattern. Information has been obtained on the active species, polymerization reaction type, and other factors such as light intensity, reaction temperature, or crystalline state. The polymerization of DSP occurs only in the solid state by photoirradiation. Reduced viscosity increases gradually with the increase of conversion and increases sharply above 80% conversion. Polymerization rate increases with the increase of light intensity and temperature. On the other hand, reduced viscosity decreases with the increase of temperature but does not depend on light intensity within the range investigated. The polymer obtained at low conversion as well as at high conversion has high crystallinity, and the direction of polymer axes is simply related to that of monomer crystal. It was concluded that the four‐center type polymerization of DSP proceeds topochemically by a photochemically induced stepwise mechanism.
Radiation chemical studies of protein reactions: Effect of irradiation liquid containing aromatic hydrocarbons and pH on viscosity
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractWhen protein is irradiated by γ‐rays from a 60Co source in various liquids containing aromatic hydrocarbons, such as benzene, naphthalene, and phenanthrene, the effect of the radiation varies with the irradiation liquids containing aromatic hydrocarbons. An empirical equation for the viscosity change was obtained. Protein irradiated by γ‐rays from a 60Co source in air showed the effect of pH on protein reactions. An empirical equation for the viscosity change was obtained.