bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acid hydrolysis and molecular weights of various corn amylopectin and glycogen
Authors: Erlander Stig R. , French Dexter 
Published: April 2003

AbstractAmylopectin samples were obtained from mature and immature sweet, dent, and waxy varieties of corn starch samples by dispersing the starch samples with either 6 M LiBr or bufered amyl alcohol solutions. The degree of branching, molecular weights, and radii of gyration were obtained on these amylopectins. The results were explained assuming that Erlander's proposed mechanism for the synthesis of starch from glycogen is valid. The corn amylopectins and an immature sweet corn glycogen sample obtained from Schoch were hydrolyzed at a pH of 4.2 at the refluxing temperature. Samples were taken at various time intervals. The values of Mw obtained from these samples showed that glycogen and amylopectin behave as randomly formed polymers. The rates of hydrolysis obtained in these studies indicate that the large molecules in all corn endosperm amylopectins and glycogens exist in chemical aggregates of four. These chemical aggregates do not appreciably influence the statistical size distribution of the amylopectin and glycogen molecules. A comparison of the properties of a sweet corn glycogen sample and an immature sweet corn amylopectin sample indicates strongly that glycogen is a precursor to starch.
Crystalline modifications of cellulose. Part III. The derivation and preliminary study of possible crystal structures
Authors: Jones D. W. 
Published: April 2003

AbstractScale models are described for a stereochemical study of the cellulose chain assuming standard armchair β‐glucose residues crystallizing in space‐group P21. Infrared evidence about the hydrogen bonding and intensity data for the strongest equatorial and meridional x‐ray reflections are utilized in assessing the validity of many models. The structures published by Meyer and Misch and by other workers do not comply with the criteria thus set up. Some fully hydrogen bonded structures, which are likely to form the basis of the most highly ordered regions in cellulose I and II, are discussed.
A thermistor method of determining the rate constant for the copolymerization of vinyl acetate and methyl methacrylate
Authors: Suzuki M. , Miyama H. , Fujimoto S. 
Published: April 2003

AbstractThe authors have tried to measure the overall rate for the copolymerization of vinyl acetate and methyl methacrylate at various monomer ratios and by use of a thermistor method to obtain the absolute rate of “crossed” chain termination. Although an assumed value was used for the heat of copolymerization to convert the rate of temperature rise into the rate of copolymerization, the agreement between the assumed and analytical values of this conversion factor was satisfactory. By substituting our results into Walling's equation, ϕ = 170 was obtained. Moreover, the use of the values of termination constants for vinyl acetate obtained previously and those for methyl methacrylate measured by Melville et al. led to a value of 1 × 1010 for the absolute rate of “crossed” chain termination at 24°C.
The problem of osmometer membranes partially permeable to the solute
Authors: Tung L. H. 
Published: April 2003

AbstractThe problem of measuring osmotic pressure with membranes partially permeable to the solute has been treated from a kinetic point of view. The results show that, under favorable conditions, the method of extrapolation to zero‐time pressure gives values reasonably close to the true osmotic pressure of the starting solution. When the diffusion of the solute through the membrane becomes excessive, such an extrapolation will not be valid. The importance of choosing a fast osmometer has been demonstrated.
Preparation and properties of polybenzylidene
Authors: Bawn C. E. H. , Ledwith A. , Matthies P. 
Published: April 2003

AbstractPolybenzylidene was prepared by the decomposition of phenyldiazomethane in the presence of boron trifluoride etherate as catalyst. The polymerization was carried out in toluene at −80°C., and polymer having a degree of polymerization of 30–35 was obtained in 80–85% yield. Examination of the infrared spectrum confirmed the “pendent” polybenzylidene structure, which is to be expected by analogy with the formation of other polyalkylidenes from the corresponding diazoalkanes. The infrared spectrum and melting point of polybenzylidene were found to be very different from those of polybenzyl‐type polymers in accordance with the dissimilarity in their structures. A mechanism is proposed involving the step‐wise growth of a boron‐alkyl chain, and it is shown that alcohols retard the polymerization.
Polymers and copolymers of hydronopyl acrylate
Authors: Marvel C. S. , Schwen Roland , Hobson R. W. , Coleman R. J. 
Published: April 2003

AbstractHydronopyl acrylate has been synthesized by direct esterification of the alcohol with acrylic acid. Its homopolymer and a variety of copolymers, terpolymers, and a tetrapolymer have been prepared and their properties determined. The terpolymer containing equal weights of the acrylate, butadiene, and acrylonitrile is a good oil‐resistant rubber with a gum tensile strength double that of a 31% acrylonitrile‐69% butadiene copolymer. These properties were obtained at the expense of good low temperature properties. Some evidence has been obtained that hydronopyl acrylate polymerized in the presence of vinyl chloride gives a compatible mixture of polymer which can be milled satisfactorily.
Microgel: An idealized polymer molecule
Authors: Shashoua Victor E. , Beaman Ralph G. 
Published: April 2003

AbstractPure microgels (i.e., those free from any linear or branched admixed polymers) were prepared by an emulsion polymerization process. The products were characterized by ultracentrifuge measurements. The best crosslinking agent for acrylonitrile microgels was found to be N,N′‐methylene bisacrylamide, while divinylbenzene gave the best styrene and methyl acrylate microgels. A study of the viscosity of microgel solutions vs. concentration showed that there was a sudden transition from a low viscosity to a high viscosity at a characteristic gel point, G, dependent upon the degree of crosslinking. For monodisperse systems, this coincides with the point where hexagonal close packing of the swollen spherical microgel particles occurs. The following equations relating the gel point and intrinsic viscosity of a microgel were found to apply: [η] = (0.025/ρ)S and (G/ρ)S = π/3√2, where S is a swelling factor which is equal to the ratio of swollen to dry volume and ρ is the density of the dry microgels. The above relationships were developed by considering microgels as swollen Einstein spheres. Evidence is presented to support the equations by some light scattering and viscosity measurements. The Flory equation relating swelling factor, polymer‐solvent interaction parameter, and degree of crosslinking was successfully applied to microgel solutions. A simple empirical equation, found to correlate the intrinsic viscosity [η] with the mole ratio of crosslinking agent, x for the microgels, was [η] = K(1/x) + 0.025/ρ where K is a constant.
Studies on the low pressure polymerization of ethylene using catalysts containing sodium alkyls
Authors: Zilkha Albert , Calderon Nissim , Frankel Max 
Published: April 2003

AbstractThe low pressure polymerization of ethylene with the use of catalysts prepared from various sodium alkyls and titanium tetrachloride was studied. Catalysts prepared from amylsodium were very active over a wide range of molar ratios of amylsodium to titanium tetrachloride (2–50); the activity decreased sharply with lower molar ratios. Rate of polymerization was found to decrease sharply, probably as a result of fusing of polyethylene particles to the catalyst surface during polymerization. Up to a pressure of about three atmospheres, the polymerization gave better yields with increase in pressure, but no increase in rate was observed on using higher pressures. Yields increased also with lowering of temperature; 0°C. gave the best yields. Molecular weight determinations showed that the polyethylenes produced had high molecular weights which did not vary over a wide range. With butylsodium, catalysts similar to those with amylsodium were formed; they showed a smaller optimum range (5–9) of molar ratios of alkyl sodium to titanium tetrachloride. Catalysts prepared from phenylsodium were much weaker, and the optimum molar ratio of phenylsodium to titanium tetrachloride, contrary to the other sodium alkyls, was found to lie at much lower molar ratios of alkyl sodium to titanium tetrachloride. Polymerizations were, in the case of phenylsodium, accompanied by an induction effect. Preliminary studies on the preparation of catalysts for the low pressure polymerization of ethylene in the presence of cyclopentadienylsodium and titanium tetrachloride were as yet not successful.
Interaction between particles suspended in solutions of macromolecules
Authors: Asakura Sho , Oosawa Fumio 
Published: April 2003

AbstractAn attractive force appears between particles suspended in solutions of macromolecules when there is neither direct interaction between two particles nor energetic interaction between particles and solute macromolecules. The magnitude of this force is of the order of the osmotic pressure of the solution of macromolecules and the range is of the order of the diameter of macromolecules. This force is calculated as a function of concentration, shape, and charge of macromolecules, and it is shown that it becomes stronger in solutions of chain macromolecules or of macromolecules of dissymmetrical shape than in solutions of rigid spherical macromolecules at the same net concentration. If macromolecules have charge, the force can be greatly intensified. In every case numerical estimation is made, and it is found that actually this kind of force can have a remarkable influence on the state of suspended particles. Numerical examples of the critical concentration of particles at their macroscopic aggregation are given. Finally a short description is added on the effect of energetic interaction between particles and macromolecules.
A study of graft copolymers. II. Viscosity and light‐scattering measurements
Authors: Manson J. A. , Cragg L. H. 
Published: April 2003

AbstractMeasurements of intrinsic viscosity and light scattering were made on fractions of polymers prepared by the redox polymerization of styrene in the presence of oxidized polystyrene or copolymers of skyrene and 4‐vinylcyclohexene‐1. For comparison, similar measurements were made on fractions of linear polystyrene. The conclusion that branching had taken place by graft polymerization was confirmed. Values found for the intrinsic viscosity, the molecular size, and the second virial coefficient were generally lower for fractions of the graft polymers than for fractions of linear polystyrene of the same molecular weight. It was also observed that fractionation of the graft polymers took place with respect to molecular size, not molecular weight, and that the most highly branched fractions were the most soluble. A comparison of experimental values of the branching ratio g with values calculated for a model having linear branches equally spaced along a backbone chain indicates that the graft polymers contain up to at least 6 branches per molecule. Values of Huggins' k′ for these branched molecules did not differ significantly from those for linear polystyrene (0.30 < k′ < 0.40). It is concluded that though k′ is sensitive to bushy branching, it is not measurably affected by the presence in the polymers of a few linear branches per molecule.
The degradation of polymer molecules in solution under the influence of ultrasonic waves. Part II. The rate equation and the limiting degree of polymerization
Authors: Allen P. E. M. , Burnett G. M. , Hastings G. W. , Melville H. W. , Ovenall D. W. 
Published: April 2003

AbstractThe breaking of polymer bonds in solutions of polystyrene, polyvinyl acetate, and polymethyl methacrylate in benzene and toluene while under the influence of ultrasonic irradiation has been studied by following the consumption of a radical scavenger, α,α′‐diphenyl‐β‐picryl hydrazyl added to the solution. The results are consistent with the rate equation proposed in an earlier paper, dBi/dt = k(Pi – Pe)ni and its relevant solutions, where dBi/dt, Pi and ni are, respectively, the rate of breakage of bonds, the degree of polymerization, and the number of molecules of the ith species, and where Pe is the limiting degree of polymerization, k is a constant, characteristic of the system and dependent on the weight concentration of the solution. Earlier literature is discussed and, in one case, the results are found to be more consistent with the above equation than with the forms: dB/dt = k(P ‐ Pe) and dB/dt = k log P/Pe. Values of Pe found by extrapolation are 1700, 2000 and 2800, respectively, for polystyrene, polyvinyl acetate, and polymethyl methacrylate. The various values of Pe for these systems to be found in the literature are discussed.
A study of the high field conductance of three polyelectrolytes
Authors: Wissbrun Kurt F. , Patterson Andrew 
Published: April 2003

AbstractResults of high field conductance measurements on solutions of polyacrylic acid, polystyrenesulfonic acid, and poly‐4‐vinyl‐N‐n‐butylpyridinium bromide have been presented. All the samples studied required appreciable time to reach a steady conductance value after the application of field, this effect diminished with increasing field, was the largest for PSA samples, intermediate for PVPBuBr samples, and smallest for the PAA samples. The extrapolated relaxation times ranged from 2 to 20 microseconds. In the one case where the results for solutions with appreciably different molecular weight polymers could be extrapolated, it appeared that the time lag increased with increase in molecular weight. The high field conductance quotients increased linearly with increasing field in a manner characteristic of weak electrolytes such as acetic acid, but the observed conductance increases were from 6 to 55‐fold larger than for acetic acid at the same field strength. The slopes of the conductance‐versus‐field curves varied as the degree of neutralization or quaternization was varied, indicative of differing degrees of association. In the one case, PAA, where there was appreciable change in the concentration of the samples studied, the high field conductance quotient decreased with increasing concentration, corresponding to an increase of association with increased concentration. Also with PAA, the Wien effect increased with increased molecular weight.
Tensile strength of filled GR‐S vulcanizates
Authors: Bueche F. 
Published: April 2003

AbstractThe tensile strengths of high and low temperature GR‐S rubber vulcanizates containing various fillers have been measured. The fillers used were HAF black, calcium carbonate, and a high styrene‐butadiene copolymer (Pliolite S‐6). Measurements were made as a function of filler concentration, temperature, and degree of crosslinking. These measurements are compared with the predictions of a molecular theory for tensile strength previously published. The following major conclusions are drawn. (1) The theory previously presented for the tensile strength of rubbers is correct in general concept. (2) The increase in strength of GR‐S with added filler is a result of the fact that the filler particles distribute more widely the additional load imposed when a chain breaks. (3) In order for the filler to be effective, the polymer chains must adhere well to its surface. (4) The decrease in effectiveness of fillers at high temperatures is a direct result of the poorer adhesion at higher temperatures.
The strain dependence of stress relaxation in cellulose monofilaments
Authors: Passaglia Elio , Koppehele H. P. 
Published: April 2003

AbstractThe stress relaxation behavior of isotropic and oriented cellulose filaments has been studied at 25° and 50°C. and 50% relative humidity at strains between 0.5 and 5%. Log modulus–log time plots were found to be different at different strains, but superposable one upon the other by simple translation along the log time axis. In this manner a master curve for the relaxation modulus may be obtained. This behavior is hypothesized to result from a strain dependence of the relaxation times in which all the relaxation times have the same dependence on strain. The master curves are used to obtain generalized relaxation distribution functions, which are considerably broader for the isotropic filaments than for the oriented filaments.
Huggins' constant in mixed solvents
Authors: Strauss Ulrich P. 
Published: April 2003

AbstractWhen the reduced viscosity of a polymer is determined in a mixed solvent, selective absorption may depress the observed value of Huggins' constant so that comparison with results obtained in single solvents or different mixed solvents becomes meaningless. This undesirable effect would be eliminated if the polymer solutions were first brought to equilibrium with the desired solvent mixture through a semi‐permeable membrane. A method is derived whereby Huggins' constant determined in the conventional manner may be corrected, provided appropriate thermodynamic data are available. The method is demonstrated for a polyelectrolyte‐in simple electrolyte solutions.
Degradation of addition polymers by ultrasonic waves. V. Effect of initial average chain length
Authors: Mostafa M. A. K. 
Published: April 2003

AbstractThe effect of initial weight average chain length of addition polymers (polystyrene in benzene) on the degradation parameters is studied in the light of previously developed theories. Results obtained are compared with those of Jellinek and White. An alternative mechanism of ultrasonic degradation of high polymers is suggested. Its mathematical analysis shows that resonant vibration of polymer molecules is possible. Factors affecting mechanism are discussed to account for the discrepancy between theoretical and experimental results.
Initiation of polymerization by cyclic peroxides
Authors: Baysal B. 
Published: April 2003

AbstractBulk and photo initiated polymerization of styrene at 60° have been investigated in the presence of diradical‐producing initiators. Cyclic peroxides such as cyclohexanone peroxide, ascaridole, ergosterol peroxide, dimeric benzaldehyde peroxide, and cyclohexene were used as polymerization initiators. It is concluded that the propagation reactions proceed via monoradicals for these photoinitiated reactions.
The formation of negatively birefringent spherulites in polyhexamethylene adipamide (nylon 66)
Authors: Khoury F. 
Published: April 2003

AbstractCrystallization of nylon 66 at and above the optical melting point of the polymer has been studied. When heated at constant temperature in the ∼250–265°C. range, the polymer, originally crystallized in the form of positively birefringent spherulites, melts and subsequently crystallizes in the form of negatively birefringent spherulites. The number of spherulites formed and their birefringence decrease as the temperature at which the polymer is heated in the ∼250–265°C. range is increased. In the limit at 265–266°C., non‐birefringent spherulites are formed in the polymer. No crystallization has been detected in polymer heated at constant temperature above 266°C. Negative spherulites are found to grow from predetermined nuclei which persist in the melt above the optical melting point of the polymer. The decrease in the number of spherulites, and hence of effective nucleation centers, with increasing temperature is taken to indicate that nucleation is from polymer aggregates or crystallites and not from foreign particles. Additional evidence is provided to support this view. The optical melting point of the negative spherulites is 268–270°C. Spherulites formed at 260°C. have a degree of crystallite perfection comparable to that of undrawn annealed nylon yarn. Etching experiments indicate that the crystallinity of the spherulites varies inversely with the temperature at which they are formed.
α,β‐unsaturated ketones. III. Copolymers of perfluoroalkyl propenyl ketones with dienes
Authors: Jones F. B. , Coleman L. E. , Stickney P. B. 
Published: April 2003

AbstractThe preparation and properties of copolymers of three perfluoroalkyl propenyl ketones with different 1,3‐dienes are described. Emulsion copolymerization at 50°C. and at 5°C. of perfluoromethyl, perfluoropropyl, and perfluoroheptyl propenyl ketones with 1,3‐dienes, such as butadiene, 1, 1,2‐trifluoro‐3‐chlorobutadiene, 1,1,2‐trifluorobutadiene, and isoprene, has been accomplished and many of the products have exhibited elastomeric properties. Attempted copolymerization of perfluoropropyl propenyl ketone with 1,1,2‐trifluoro‐3,4,4‐trichlorobutadiene or 1,1,2‐trifluoro‐3,4‐dichlorobutadiene did not yield any polymeric products at either 50°C. or at 5°C. Qualitative determinations of thermal stability and solvent resistance have been made for some of the ketone/diene copolymers for comparison with commercial cold GR‐S rubber.
The nitrosation of nylon
Authors: Porter M. R. 
Published: April 2003

AbstractThe nitrosation of nylon 66, with the use of four different nitrosating agents, has been investigated. By the more vigorous nitrosating reactions, heterogeneous nitrosation of nylon yarn occurs rapidly and proceeds to completion in a few hours. In this reaction the amide hydrogen is substituted by a nitroso group to give the structure

By heating the nitrosated polyamides, nitrogen is evolved, and polyesters are formed. The kinetics of this change have been fully investigated. Caustic alkali reacts rapidly with nitrosated nylon. Free radicals are produced on exposure of the nitrosated nylon to visible radiation. Partial nitrosation of nylon yarns has been carried out with the use of a running threadline system; the physical properties of the resulting yarns have been examined.
Purification and viscosity experiments on gum arabic
Authors: van Beek L. K. H. 
Published: April 2003

AbstractA purification procedure for gum arabic is reported. The impurities can be entirely removed by treating the aqueous solutions with cation exchange resin. The samples are precipitated by acetone. The ionic impurities are found to consist of Mg, and traces of Fe have been confirmed. The effect of these ions on the viscosity contribution is investigated. The presence of these impurities causes a decrease in the limiting viscosity number which can be explained by electrovalent crosslinking. A similar effect is ob served for a sample that has been dried over concentrated sulfuric acid and can in this case be explained by covalent crosslinking.