bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain birefringence of sodium hyaluronate films
Authors: Dersarkissian Vahak M. , Bettelheim Frederick A. 
Published: April 2003

AbstractStrain birefringence of swollen sodium hyaluronate films was measured. Typical Wiener curves were obtained in solvents with different refractive indices. The orientation birefringence of sodium hyaluronate was evaluated from the minima of the Wiener curves and was found to increase with increasing elongation. Up to 30% elongation, the swollen hyaluronate films show quasi‐rubberlike behavior. Above this elongation, the interchain hydrogen bonding further hinders the chain mobility and the orientation increases only slightly.
Effect of side‐chain structure on poly‐α‐olefin properties
Authors: Dunham K. R. , Vandenberghe J. , Faber J. W. H. , Contois L. E. 
Published: April 2003

AbstractSeries of α‐olefins were prepared and polymerized with Al(C2H5)3–VCl3 catalyst. Melting points, softening points, and degrees of crystallinity of the polymers were measured and the physical nature of the systems was discussed. Olefins studied were those having the general formula CH2CH(CH2)xR, where x = 0−3, and R is methyl, isopropyl, tert‐butyl, phenyl, or cyclohexyl.
Kinetic study of the crosslinking of gelatin by formaldehyde and glyoxal
Authors: Davis P. , Tabor B. E. 
Published: April 2003

AbstractA study has been made of the effect of concentration of the crosslinking agent, gelatin concentration, and pH on the rate of increase of viscosity with time, for gelatin solutions containing either formaldehyde or glyoxal. The results are consistent with the kinetic relationship:

For formaldehyde, n is 2. For glyoxal, n is 1, as was expected for this bifunctional hardener. Initial formation of gelatin–methylol compounds is proposed in both cases. With formaldehyde, it is suggested that this leads to a methylene‐ether crosslink between a gelatin amino‐methylol compound and an unspecified gelatin–methylol compound, while in the case of glyoxal, there is evidence to suggest that the crosslinkage involves two side‐chain amino groups and results in a charged crosslink.
Polymer NMR spectroscopy. VII. The stereochemical configuration of polytrifluorochloroethylene
Authors: Tiers G. V. D. , Bovey F. A. 
Published: April 2003

AbstractThe NMR spectrum of polytrifluorochloroethylene in 3,3′‐bistrifluoromethylbiphenyl solution at 150°C. consists of two doublets having unequal components. Those at lower field correspond to CF2 chain units, while those at higher field correspond to CFCL units. In the CF2 doublet, the weaker component (at lower field) is found to have half the area of the stronger (at higher field), for polymers prepared over a 120°C. range of polymerization temperatures. By comparison to the spectra of the model compounds meso‐ and dl‐CF2ClCFClCF2CFClCF2Cl, the peaks of which closely coincide with those of the polymer when both are compared at 150°C., it is concluded that of the two CF2 peaks in the polymer spectrum, the weaker one represents CF2 groups which are between monomer units in isotactic dyads whereas the stronger one represents CF2 groups which are between monomer units in syndiotactic dyads. It follows that in trifluorochloroethylene propagation, syndiotactic dyad formation is twice as probable as isotactic dyad formation. This preference for syndiotactic placement corresponds to an activation entropy for isotactic propagation 1.38 e.u. more negative than that for syndiotactic propagation; there is no difference in the activation enthalpies. This behavior is in contrast to that previously found for methyl methacrylate propagation; here, preference for syndiotactic placement is entirely dictated by a greater activation enthalpy for isotactic placement.
Polyamides containing phosphorus. I. Preparation and properties
Authors: Pellon Joseph , Carpenter W. G. 
Published: April 2003

AbstractThis study has for the first time provided a series of high molecular weight polymers having trivalent phosphorus in the backbone structure (as phosphine‐containing polyamides) and has extended the series of phosphine oxide polyamides beyond the previously disclosed bis(carboxyphenyl)phosphine oxide types. It was found that bulk polymerization rather than solution or interfacial procedures was the preferred method of preparing these materials. The phosphorus polyamides generally were found to be amorphous, relatively low softening materials having an extended solubility range. Most polyamides containing trivalent phosphorus slowly degrade in formic acid solution. A comparison of the thermal stability, adhesive bond strengths, and mechanical behavior of typical polyamides containing phosphine or phosphine oxide groups in their backbone structure to those of analogous regular nylons disclosed no major differences.
Experimental data on dilute polymer solutions. I. Hydrodynamic properties and statistical coil dimensions of poly (n‐butyl methacrylate)
Authors: Van Leemput R. , Stein R. 
Published: April 2003

AbstractViscometric, light‐scattering, and osmotic pressure measurements were carried out on poly(n‐butyl methacrylate) fractions in methyl ethyl ketone and acetone. Relationships between the limiting viscosity number, the average molecular weight, and the mean dimensions were obtained. Heterogeneity corrections were applied to all relationships, assuming a Schulz‐type distribution. Values of Φ, calculated according to the Flory‐Fox equation, were found to be 2.3 × 1023 and 2.1 × 1023 in MEK and acetone, respectively. No significant trend with molecular weight was noticed in the range investigated, though the dependence of [η] on the mean radii of gyration is less than that predicted by the Flory theory.
Crosslinking of natural rubber by dicumyl peroxide in the presence of oxidation inhibitors
Authors: Scanlan J. , Thomas D. K. 
Published: April 2003

AbstractA number of phenols, simple and N‐substituted aromatic amines, thioamides, and thioanilides which are known to inhibit free radical reactions have been introduced into dicumyl peroxide–natural rubber cures, and their influence upon the degree of crosslinking has been determined. A simple kinetic scheme allows a calculation of the relative reactivities of these additives and the values obtained are compared with those of other workers for the same additives but in different systems. It is concluded that the additives interfere with the crosslinking reaction by exchanging a hydrogen atom with the free radicals involved, and the sequence of reactivities is readily explained in terms of current theories for the effect of substituents upon the reactivity of organic compounds. Types of materials likely to be useful as antioxidants in dicumyl cures are discussed.
Radiation‐induced cationic polymerization of ethylene
Authors: Tabata Yoneho , Shibano Hiroshi , Sobue Hiroshi , Hara Kiyoshi 
Published: April 2003

AbstractRadiation‐induced polymerization of liquid ethylene was investigated at −78°C. No induction period was observed. The rate of polymerization was proportional to the first power of the dose rate. Radical scavengers did not inhibit the polymerization. On the other hand, methylene chloride accelerated the polymerization appreciably. It was concluded that the polymerization of liquid ethylene at low temperature proceeds by a cationic mechanism.
Calculation of the displacement distance for a three‐choice cubic lattice chain
Authors: Tokita Noboru , Krigbaum W. R. 
Published: April 2003

AbstractThe matrix procedure of Hoeve for the chain displacement length calculation is applied to a three‐choice cubic lattice model. Although rotation about each link is correlated, the model is simple enough for the final result to be obtained as a closed algebraic expression. Certain special cases, resulting from particular assignments of the probability parameters, are examined.
Corresponding state relations for the viscosity of moderately concentrated polymer solutions
Authors: Utracki L. , Simha Robert 
Published: April 2003

AbstractCorresponding state relationships are considered for good (toluene) and θ‐solvents. The polymers investigated are polystyrene, polymethyl methacrylate, and a copolymer of approximately 49 mole‐% of methyl methacrylate with styrene. The choice of the reduced variables ηsp(c[η]) and c/γ permits the construction of master curves, characteristic of a given polymer‐solvent system over a wide range of molecular weights. The concentration parameter γ varies with the degree of polymerization less rapidly than c0, the concentration for overlap of average coils, particularly in the good solvent. Here γ is independent of temperature. In cyclohexane, γ is proportional to the critical concentration for phase separation. The existence of such universal relations results in an explicit form for the coefficients of the power series expansions of the viscosity as a function of c. In particular the parameter k1 is predicted to be a slowly decreasing function of molecular weight in the good solvent, but to be almost independent in cyclohexane. This is in accordance with recent observations for polystyrene fractions below 50,000. However, the scatter in the experimental data does not permit a quantitative comparison. Moreover, the results must be sensitive to polydispersity and depend on higher moments of the distribution, as is indicated by the relation between γ and the critical concentration.
On the helical structure of polytetrafluoroethylene
Authors: Iwasaki Machio 
Published: April 2003

AbstractThe molecular parameters of polytetrafluoroethylene were determined from x‐ray diffraction data (Bunn and Howells) as CC = 1.54 A., CF = 1.36 A., ∠CCC = 114°36′, ∠FCF = 108°30′; each angle of internal rotation around each CC bond is 16°28′ from the trans position. Calculation of the angle of internal rotation for the most stable configuration of the polymer chain was carried out based on the steric and electrostatic interactions. The minimum position of the potential energy seems to be subject chiefly to the steric interaction. The effect of the electrostatic interaction on the minimum position was rather small as compared with the steric interaction. The calculated angle of internal rotation and the fiber period are, respectively, 19° and 16.78 A., which are in very good agreement with the experimental values 16°28′ and 16.8 A.
Copolymerization characteristics of methyl acrylate and methyl methacrylate. I. Study of copolymerization kinetics by a deuterium tracer method
Authors: Shima Mikiko , Kotera Akira 
Published: April 2003

AbstractThe kinetics of copolymerization for the methyl acrylate–methyl methacrylate system was studied by using monomers which contain deuterium as a tracer. The experiments were made on two series of copolymerizations: methyl acrylate–deuteromethyl methacrylate, (CH2C(CH3)COOCH2D), and deuteromethyl acrylate (CH2CHCOOCH2D)–methyl methacrylate copolymerization systems. Mass spectrometric analysis was employed for determining the composition of copolymers. The agreement of the experimental results of the two series was reasonable. The monomer reactivity ratios for the methyl acrylate (M1)–methyl methacrylate (M2) system were determined as r1 = 0.47 ± 0.09 and r2 = 2.3 ± 0.5 at 130°C. These values were compared with those calculated from the Price‐Alfrey Q‐e scheme.
Electron spin resonance of gamma‐irradiated cellulose
Authors: Florin Roland E. , Wall Leo A. 
Published: April 2003

AbstractIrradiation of purified cellulose with cobalt‐60 gamma rays in vacuo produces moderate yields of radicals detectable by electron spin resonance. The ESR spectrum is asymmetric, with five partially resolved peaks occupying a total region of about 50 gauss wide and a spectroscopic splitting factor near g = 2. The peaks show differing saturation behavior with increasing microwave power. Differences of crystallinity have no obvious effect on the yield or nature of the radical ESR spectrum. The presence of about 8% water during irradiation decreases the yield greatly and modifies the hyperfine structure. For dry cellulose the initial G value for radicals is near 2.8 radicals per 100 e.v. absorbed, but the concentration levels off at doses a little over 6 × 1020 e.v./g. Despite the early falling‐off in yield, the radicals in stored irradiated specimens do not decay appreciably in several days. Even upon contact with air the decay is quite slow. Thermal decay is imperfectly second‐order, fairly rapid above 120°C., and indicates several radicals of differing lifetimes.
Molecular motion in polyethylene. III
Authors: McCall David W. , Anderson Ernest W. 
Published: April 2003

AbstractProton magnetic resonance studies of polyethylene have been extended. The relationship of the rigid fraction (NMR) to the crystalline fraction is discussed, and a case is presented for the relative importance of the rigid fraction (or its complement, the mobile fraction). When the polymer has been swollen by low molecular weight solvents, the NMR spectra yield rather direct evidence that the rigid, and presumably crystalline, regions are unaffected. The nature of the molecular motion is discussed in terms of a model, and it is shown that NMR data imply a rather general type motion.
The second newtonian viscosity number
Authors: Merrill E. W. , Mickley H. S. , Ram A. , Stockmayer W. H. 
Published: April 2003

AbstractThe second Newtonian viscosities η2 of solutions of polystyrene and polyisobutylene were determined in a coaxial cylinder viscometer at shear rates near 105 sec.−1. The second Newtonian viscosity numbers (η2 — ηs)/ηsc, where ηs is solvent viscosity and c is polymer concentration, were determined as a function of concentration. For polymer species of viscosity‐average molecular weight \documentclass{article}\pagestyle{empty}\begin{document}$\overline M _v {\rm less than }1 \times 10^6 , {\rm }\mathop {\lim }\limits_{c \to 0} (\eta _2 - \eta _ {\rm s} )/\eta _ {\rm s} c$\end{document} appears almost identical to intrinsic viscosity [η]. Above M̄v ⋍ 1 × 106, a plateau of constant (η2 — η2)/ηsc is found when this function is plotted against c. For good solvents the plateau value: {(η2 — ηs)/ηsc}p lies below [η], but in poor solvents (near the θ temperature) the opposite is true. Correlation of plateau values vs. M̄v can be achieved in the manner of the Mark‐Houwink equation: [η] = K′M̄va, by writing: {(η2 — ηs)/ηsc}p = K″M̄vb. The sum of a + b of any species in two given solvents is approximately unity. Though the data are inconclusive, it appears that even above M̄v ⋍ 1 × 106, the second Newtonian viscosity number tends to approach [η] as c approaches zero.
On the ultraviolet absorption spectrum of polyvinyl alcohol
Authors: Haas Howard C. , Husek Helen , Taylor Lloyd D. 
Published: April 2003

AbstractA study of the ultraviolet absorption spectrum of polyvinyl alcohol (PVA) was made. Spectral examination of the solvolysis products of vinyl acetate and 1‐methoxyvinyl ester copolymers shows unequivocally that the absorption bands in PVA at 225, 280, and 330 mμ are related to carbonyl‐containing structures. The high intensities of these bands in the solvolyzed copolymers is additional evidence that the absorbing groups cannot be unconjugated carbonyl and are probably of the type \documentclass{article}\pagestyle{empty}\begin{document}$ - (\rm{C} \hbox{=\hskip-1.5pt=} \rm{C})_{n} \hbox{---} \mathop C\limits^{\mathop {||}\limits^O }\hbox{---}.$\end{document} Ultraviolet dichroism measurements tend to confirm this view. The ultraviolet absorbing bands in PVA arise predominantly from two sources: the presence of acetaldehyde, and dissolved air in the vinyl acetate monomer during polymerization. In the case of the latter, the formation of the vinyl acetate—oxygen copolymer and its subsequent decomposition to aldehydic‐type products introduce, into the polymer, chain structures similar to those introduced by acetaldehyde. By the careful exclusion of acetaldehyde and air during vinyl acetate polymerization and by a judicious choice of initiator, PVAs having minimal ultraviolet absorptions can be prepared. Treatment of PVA at room temperature with dilute aqueous alkali results in a marked diminution in the intensities of all three absorption bands. Hot dilute acid, while essentially removing the 330 mμ band, produces no consistent change in the relative intensities of the 225 and 280 mμ bands.
Reaction kinetics and tacticity of macromolecules. II. Acrylic acid copolymers
Authors: Smets G. , Van Humbeeck W. 
Published: April 2003

AbstractThe influence of steric effects and of the microtacticity of polymeric chains has been examined during the hydrolysis of acid–ester copolymers. Four different acrylic acid–ethyl ethacrylate copolymers have been prepared; their molar acid content was 50, 67, 77, and 85%. The rate of hydrolysis was examined at different degrees of neutralization in buffered aqueous solutions at 113°C. The rate was directly proportional to the content of (acid–ester–acid) triads and was highest where the degree of neutralization was equal to 0.5. The final degree of conversion is, however, limited on account of the existence of different stereochemical structures of these (acid–ester–acid) triads. Conventional and isotactic acrylic acid–methyl acrylate copolymers have also been prepared; their molar acid content was 64.5 and 80.5% for the conventional and 67 and 80% for the isotactic copolymers. From the rates of hydrolysis measured at 103°C. in buffered aqueous solutions, it becomes evident that the isotactic polymers hydrolyze 3 to 5 times more rapidly than the conventional polymers; moreover, the final degree of conversion is much higher. Finally conventional and isotactic acrylic acid–tert‐butyl acrylate copolymers have been examined; these copolymers hydrolyze only in the presence of mineral acid; any intramolecular functional interaction is absent in both cases. This stability has been explained on the basis of a different mechanism of hydrolysis of these tertiary butyl esters.
The effect of pressure on the crystallization of polyethylene from dilute solution
Authors: Wunderlich Bernhard 
Published: April 2003

AbstractLinear polyethylene has been crystallized isothermally from 0.05% toluene solution at atmospheric pressure and up to 6000 atm. hydrostatic pressure. At atmospheric pressure a high temperature form of unknown structure was found crystallizing above 90°C. Single crystal lamellae crystallized between 75 and 90°C. Dendrites were formed below 75°C. The temperature dividing the dendritic growth from single crystalline growth increases with increasing pressure. The thickness of crystals grown at approximately constant supercooling, but at elevated temperature and pressure increased only slightly. A discussion in the light of present day theories is attempted.
Grafting vinyl polymers onto cellulose by high energy radiation. I. High energy radiation‐induced graft copolymerization of styrene onto cellulose
Authors: Huang R. Y.‐M. , Immergut B. , Immergut E. H. , Rapson W. H. 
Published: April 2003

AbstractStyrene has been grafted onto cellulose in the form of cotton linters, cotton cloth, and rayon by ionizing radiation. Styrene was brought into intimate contact with cellulose by extension of the “inclusion” technique of Staudinger and Krässig, and graft copolymers were prepared by exposure to high energy electrons or to gamma‐rays from Co60. Substantial grafting was obtained by irradiation in air, nitrogen, or in vacuum. The products were purified by exhaustive extraction with benzene in a Soxhlet apparatus to remove the polystyrene homopolymer. The graft copolymers were characterized by removing the cellulose backbone by hydrolysis and determining the molecular weights of the residual polystyrene. Molecular weights of the grafted polystyrene were found to be considerably higher than those of the extracted homopolymer polystyrene or the polystyrene formed by irradiating styrene in bulk. Calculations based on the molecular weights of cellulose and polystyrene in the graft copolymer indicate that despite the substantial grafting, only one in 5,000–10,000 anhydroglucose units or one in 10–20 cellulose chains carried a grafted polystyrene chain.
NMR study of molecular chain structure of polyvinylidene fluoride
Authors: Wilson Chas. W. 
Published: April 2003

AbstractImproved resolution of the 40 and 56.4 Mcycle F19 NMR room temperature spectra of solutions of polyvinylidene fluoride in dimethylacetamide has resulted in a clearer understanding of the polymer chain structure. The spectra indicate that the structure of polyvinylidene fluoride consists predominantly of head‐to‐tail sequences of CH2CF2 monomer links, with 5–6% of the monomer links added “backwards” to give occasional CF2CF2CH2CH2 configurations along the chain. Identifying the four principal chemically shifted lines in the NMR spectrum with four specific local chain structures, and applying simple probability theory to compare predicted and observed spectral intensities, it was possible to compute the probabilities of head‐to‐tail monomer addition (p), head‐to‐head addition (1‐p), tail‐to‐tail addition (q), and tail‐to‐head addition (1‐q). The values of both p and q varied somewhat from sample to sample, depending on the temperature and pressure of polymerization; however, both p and q were found to be in the general vicinity of 0.94. This is believed to be the first reported instance in which the relative probabilities of head‐to‐head, tail‐to‐tail, head‐to‐tail, and tail‐to‐head monomer addition in free‐radical polymerization have been determined.
The locus of adhesive failure
Authors: Huntsberger J. R. 
Published: April 2003

AbstractThe problem of the locus of adhesive failure is discussed. It is proposed that real systems will show departures from regularity and that the interaction between phases is frequently diminished by stearic effects leading to interfacial separation. This is counter to some recently proposed views. Estimates of the magnitude of these effects required to lead to interfacial separation are given in terms of failure criteria. Interferometry was used to provide experimental evidence that interfacial separation can occur between poly‐isobutylene and a crosslinked alkyd resin. The performance of this system was also shown to be in harmony with the proposed failure criteria.
Stability of helical conformations of simple linear polymers
Authors: De Santis P. , Giglio E. , Liquori A. M. , Ripamonti A. 
Published: April 2003

AbstractThe potential energy of polyethylene, polytetrafluoroethylene, polyoxymethylene, polyisobutylene, polyvinylidene chloride, and isotactic polypropylene with a helical conformation has been calculated as a function of the angles of rotation around the bonds of the backbone chain. The use of appropriate functions to describe the interaction between nonbonded atoms in the chains, has allowed prediction with surprising accuracy of the most stable conformation for the each polymer considered, in spite of the rather drastic assumptions involved in the calculations. The most prominent feature of the potential energy diagrams are discussed with reference to the possibility of predicting the allowed helical conformations for the isolated unperturbed polymer chains considered.
Some novel effects in solution polymerization
Authors: Anderson D. B. , Burnett G. M. , Gowan A. C. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate initiated by 2,2′‐azoisobutyronitrile in the presence of halogenated benzenes and naphthalene has been investigated. In each case the order of reaction with respect to monomer is apparently of an order less than unity. Suggestions as to the possible participation of the solvent in the initiation process are discussed and shown to be in agreement with experimental measurements.