bluuebunny/crossref_metadata_2025 huggingface dataset:
Birefringence of native cellulosic fibers. I. Untreated cotton and ramie
Authors: Iyer K. R. Krishna , Neelakantan P. , Radhakrishnan T.
Published: April 2003

The Rayleigh‐Gans theory of light scattering by a homogeneous cylinder has been applied to the case of scattering by a pad of fibers immersed in a liquid. The theory enables one to locate precisely the matching wavelength at which the mean refractive index of a sample of optically heterogeneous fibers coincides with that of an immersion medium. Thereby it offers a method of determining the mean refractive index. Besides, it facilitates a quantitative estimation of the variability of refractive index. The new technique has been used to study the birefringence of untreated cotton and ramie. The results are presented and discussed.
Intrinsic viscosity of polymers of low molecular weight
Authors: Bianchi Umberto , Peterlin Anton
Published: April 2003

Experimental evidence concerning the dependence of the intrinsic viscosity [η] on molecular weight M in the low molecular weight range (from oligomers to M = 5 × 104) has been collected in a variety of solvents for about ten polymers, i.e., polyethylene, poly(ethylene oxide), poly(propylene oxide), polydimethylsiloxane, polyisobutylene, poly(vinylacetate), poly(methyl methacrylate), polystyrene, poly‐α‐methylstyrene, and some cellulose derivatives. In theta solvents, the constancy of the ratio [η]Θ/M0.5 extends down to values of M much lower than those predicted by current hydrodynamic theories. In good solvents, and on decreasing M, the polymers examined, with the exception of polyethylene and some cellulose derivatives, show a decrease in the exponent a of the Mark‐Houwink equation [η] = KMa. This upward curvature gives rise to the existence of a more or less extended linear region where the equation [η] = K0M0.5 is obeyed. Below the linear range, i.e., for even shorter chains, the exponent a can increase, i.e., polydimethylsiloxane, or decrease below 0.5, i.e., poly(ethylene oxide), depending on the particular chain properties. These different dependences have been discussed in terms of: (a) variations of thermodynamic interactions with molecular weight; (b) variations of conformational characteristics (as for instance the ratio) 〈r02/nl2〉, where 〈r02〉 is the unperturbed mean square end‐to‐end distance and n is the number of bonds each of length l; (c) hydrodynamic properties of short chains.
Multiple melting in nylon 66
Authors: Bell J. P. , Slade P. E. , Dumbleton J. H.
Published: April 2003

Either of the two endothermic melting peaks found by differential thermal analysis of nylon 66 may be converted to the other by appropriate choice of annealing conditions. The two peaks are considered due to the melting of two morphological species, forms I and II. Form I is relatively fixed in melting temperature, while the form II melting temperature varies with annealing conditions and can be either above or below form I. The two forms can be distinguished by whether or not the conversion I → II takes place; if the sample is in form II no change in the thermogram is observed under suitable conversion conditions. The conversion of form I to form II also takes place during cold drawing. It has been previously shown that form I results from rapid cooling from the melt, and form II results from slow cooling. Form I appears to be kinetically favored, while form II is thermodynamically preferred. The variability in the form II melting point is attributed to variable crystal size and/or perfection.
β Relaxations in polyethylenes and their anisotropy
Authors: Stachurski Z. H. , Ward I. M.
Published: April 2003

Measurements have been made of the anisotropy of viscoelastic behavior in specially oriented sheets of low‐density polyethylene. The results for the cold‐drawn sheets show a β relaxation process of very characteristic anisotropy. The annealed sheets show two relaxations in this region of temperature. The lower relaxation (about −10°C) is identified as an interlamellar shear process. The higher relaxation (about 70°C) has a very similar anisotropy to the β relaxation in cold‐drawn samples. Isotropic sheets of low‐density polyethylene have been also investigated. Two β relaxations are found in these materials.
Diffusion in polymer–solvent systems. A study of numerical methods of simulation
Authors: Riek Raymond F. , McAvoy Thomas J. , Chappelear David C.
Published: April 2003

Fickian and non‐Fickian diffusion into polymer‐solvent systems were simulated on both analog and digital computers. Methods were evaluated to solve the descriptive nonlinear ordinary and partial differential equations. Analog methods published previously have been expanded. It was shown that discrete time solutions are superior to discrete distance solutions for partial differential equations, as hardware requirements are small. Also, accuracy problems on some of the smaller installations can be reduced by reverse time integration. For highly nonlinear equations, analog methods are superior to digital in stability and effort required. Digital solutions can be require extensive preliminary work to define computation parameters. However, the errors introduced by the finite difference equations are small in moderately nonlinear equations and much more accurate solutions are possible. Generalized solutions for polymer‐solvent diffusion with exponential concentration dependence are presented for the Fickian cases. Also, typical solutions are demonstrated for all known types of non‐Fickian diffusion.
Equation for the interfacial tension between demixed polymer solutions
Authors: Vrij A.
Published: April 2003

The theory of Cahn and Hilliard is used to derive an equation for the interfacial tension (free energy) between some demixed polymer solutions, applying a simple solution model treated by Debye in his theory of light scattering near the critical solution temperature. For a (symmetrical) system containing two polymers in a common solvent it is found that the interfacial tension is given by σ = (l/12½)Ωφp 2σr, where l is the Debye l parameter for the range of molecular interaction—here equal to (2S2)½, where (S2)½ is the radius of gyration of both polymers, Ω is a heat of mixing parameter for polymer‐polymer interaction, φp is the total volume fraction of polymer and σr is a function of the ratio of temperature and critical solution temperature. The equation is in qualitative agreement with experiments of Langhammer and Nestler.
Annealing of polybutene‐1 single crystals
Authors: Woodward A. E. , Morrow D. R.
Published: April 2003

The effects of thermal treatment in the 70–90°C. region on polybutene‐1 crystals, prepared by precipitation from dilute pentyl acetate solutions and with lath, hexagonal, and square morphologies, have been studied by using electron microscopy. The stability of polybutene‐1 crystals to thermal treatment increases in the order: lath < hexagonal < square. Elucidation of the crystallographic directions in unheated lath crystals with respect to the overall morphology was carried out; evidence for restricted folding in these crystals is discussed.
Solution properties of polystyrene–polybutadiene block copolymers
Authors: Utracki Lechoslaw A. , Simha Robert , Fetters Lewis J.
Published: April 2003

Dilute solution viscosity and osmotic pressure measurements were performed on polystyrene (PS), polybutadiene (PB), polystyrene–polybutadiene (SB) diblock and polystyrene–polybutadiene (SBS) triblock copolymers. Anionic polymerization was used in such a way that the molecular weight of the PS block was kept constant (ca. 10 000), while the molecular weight of the PB block varied from 18000 to 450000. The measurements were carried out at a fixed temperature of 34.20°C in three solvents, namely toluene, a good solvent for PS as well as for PB, dioxane, which is a good solvent for PS and almost a theta solvent for PB, and cyclohexane, which is nearly a theta solvent for PS and a good solvent for PB. The compositions of SB and SBS, as derived from kinetic data agree with ultraviolet measurements in CHCl3 solutions. The viscosity and osmotic pressure results indicate that the properties of SB and SBS are similar. Their intrinsic viscosities and second virial coefficients can be calculated from their chemical compositions, molecular weight, properties of parent polymers, and values of the interaction parameter \documentclass{article}\pagestyle{empty}\begin{document}$\bar \beta _{{\rm SB}}$\end{document} between styrene and butadiene units, for molecular weights not exceeding approximately 105. The magnitude of \documentclass{article}\pagestyle{empty}\begin{document}$\bar \beta _{{\rm SB}} $\end{document} varies with the solvent. The results suggest that the domains of the PS and PB blocks overlap to a great extent.
La luminescence différée du styrène en solution vitreuse dans le méthylcyclohexane
Authors: Hayashi K. , Déroulède A. , Kieffer F.
Published: April 2003

The trapping of electrons and styrene cations and anions has been studied in a methylcyclohexane glass by the techniques of deferred luminescence. Radiothermoluminescence curves consist of two peaks, at 90 and 95°K, in this matrix. The second peak increases linearly with styrene concentration up to 2 × 10−2M when it reaches a constant value, whereas the first peak increases from 10−4 to 10−3M and then decreases at higher concentrations and is not discernible at concentrations above 10−2M. We propose two mechanisms which are qualitatively consistent with this behavior and are based essentially on the recombination of styrene cations with thermally detrapped electrons in the first peak and with anions in the second peak. Photothermoluminescence (i.e., thermoluminescence after photoionization with ultraviolet light) similarly consists of the 90 and 95°K peaks for a 10−3M solution and of the 95° peak alone for a 10−d M solution.

Radiophotoluminescence excitation spectra at 77°K, corresponding to absorption spectra of trapped electrons and styrene anions, show that anions are the predominant negative species in 10−2 molar solution, and trapped electrons in 10−3 molar solution. Spectral analysis of radiothermoluminescenece shows the presence of two emission bands, one of which is identical with styrene fluorescence excited by the 254 Nm mercury line (λmax = 292, 302, 307, and 317 Nm). The other band has three fairly poorly resolved maxima at 474, 486 and 496 nm and seems to correspond to the fluorescence of C6H5ĊH‐CH3 radicals formed during radiolysis.
Polymerization of aromatic nuclei. XIV. Polymerization of toluene with aluminum chloride–cupric chloride
Authors: Kovacic Peter , Ramsey J. S.
Published: April 2003

The polymerization of toluene with aluminum chloride and cupric chloride was performed in carbon disulfide and in a neat system. The solvent reaction produced an insoluble, light‐brown product which did not melt below 350°C. In the neat system, polymerization was much more vigorous, yielding a dark, purple‐brown solid with mp ∼250°C and molecular weight of 634. Infrared, NMR, and ultraviolet spectroscopy, along with elemental analysis and oxidative degradation, indicated that the backbone chain contains o‐polyphenylene units with the methyl group situated in the 4‐position. Some p‐polyphenylene structures may also be present. Evidence for small amounts of benzyl and polynuclear moieties was obtained. The mechanistic aspects are discussed. Our principal conclusions concerning oligomer structure are in disagreement with those of Kuwata.
Effect of a trifluoromethyl group on the polymerizability of α‐olefins by transition metal catalysts
Authors: Overberger C. G. , Khattab G.
Published: April 2003

Several α‐olefins containing the trifluoromethyl group were prepared and characterized. 4,4,4‐Trifluoro‐1‐butene, 3‐trifluoromethyl‐1‐butene, 5,5,5‐trifluoro‐1‐pentene, and 4‐trifluoromethyl‐1‐pentene were homopolymerized with VCl3–Al(i‐Bu)3 catalyst. The trifluorobutenes gave low‐melting polymers with low fluorine contents. Polymers obtained from the trifluoropentenes were soluble having moderately high intrinsic viscosities. Copolymerizations of these monomers with their nonfluorinated homologs by the same catalyst system indicated low reactivities of the fluoromonomers. Nuclear magnetic resonance spectra of the fluorinated and nonfluorinated monomers and their respective spectroscopic studies with the catalyst (C5H5)2TiCl2–Al(CH3)3 indicated an electron deficiency of the vinyl group of the fluorobutenes. This was related to the inductive effect of the trifluoromethyl group. The inductive effect of this group was absent in the fluoropentenes and the nonfluorinated monomers. The electron‐deficient vinyl group of the fluorobutenes apparently did not allow these monomers to coordinate with the active sites of the catalyst. Polymerization studies of the nonfluorinated monomers, 1‐butene, 3‐methyl‐1‐butene, 1‐pentane, and 4‐methyl‐1‐pentene, with the catalyst VCl3–Al(Bu)3, were performed in the presence of compounds containing the trifluoromethyl group. Results indicated that this group did not retard the rate of polymerization of these monomers. Evidence is presented to show that a catalytic amount of benzotrifluoride enhanced the rate of polymerization of α‐olefins, particularly that of sterically hindered monomers such as 3‐methyl‐1‐butene.
Tri‐o‐tolylphosphine: A rapid photopolymerization initiator
Authors: Eldred Roger J.
Published: April 2003

The rate of tri‐o‐tolyphosphine‐initiated photopolymerization of methyl methacrylate was found to be significantly higher than that for the triphenylphosphine initiated polymerization. The mechanism was shown to be dependent upon the concentration of the initiator. At low concentrations (10−4 mole/l.), an activated complex is the initiating species, while at higher concentrations (above 10−2 mole/l.) homolytic cleavage of the phosphorus–carbon bond is the radical source. Steric inhibition of resonance is advanced as an explanation for the enhanced activity of tri‐o‐tolylphosphine over triphenylphosphine.
γ‐Ray‐induced terpolymerization of carbon monoxide, aziridines, and cyclic ethers
Authors: Kagiya Tsutomu , Kondo Masatsune , Maruta Isao , Fukui Kenichi
Published: April 2003

The terpolymerization of carbon monoxide, aziridines, and cyclic ethers was carried out by γ‐irradiation. A partially crystalline solid copolymer was obtained. The infrared spectrum of the copolymer obtained indicated characteristic peaks due to the secondary amide and ester groups. The results of elementry analysis, infrared spectra, and x‐ray diffraction of the copolymer showed that terpolymerization of carbon monoxide, aziridine, and cyclic ether took place by γ‐irradiation. 2‐Vinyl‐1,3‐dioxolane was polymerized in the system of carbon monoxide and ethylenimine to give a solid polymer. The infrared spectrum showed characteristics of the secondary amide and dioxolane ring, while no absorption due to carbonyl group of ester was observed. The infrared spectra and results of elementary analysis confirmed that the terpolymerization of carbon monoxide–ethylenimine–2‐vinyl‐1,3‐dioxolane occurred.
The high‐temperature degradation of poly(2,6‐dimethyl‐1,4‐phenylene ether)
Authors: Factor A.
Published: April 2003

The thermal degradation of poly(2,6‐dimethyl‐1,4‐phenylene ether) has been investigated to 1000°C in an inert atmosphere. X‐ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were employed to study the physical changes in the polymer, and vapor‐phase chromatography, infrared spectroscopy, and mass spectrometric thermal analysis were used to elucidate the chemical aspects of the degradation process. It was found that degradation occurs in two steps: (1) a rapid exothermic process occurs between 430 and 500°C, leading to the evolution of phenolic products, water, and a black, highly crosslinked residue, and (2) a slower, char‐forming process occurs above 500°C, characterized by the evolution of methane, carbon monoxide, and hydrogen. The chars formed in process 2 were found by x‐ray analysis to be amorphous. The infrared spectrum of a sample heated to 510°C is nearly identical with that of the starting polymer, indicating that oxidative reactions are not important in the first process. The data for the low‐temperature process are consistent with a thermal degradation scheme based on the radical‐redistribution reaction of polyphenylene ethers and/or the degradation of o‐benzylphenols formed by the thermal rearrangement of o‐methyl diphenyl ethers. The char‐forming process is best explained by simultaneous operation of the Szwarc mechanism of toluene pyrolysis, producing hydrogen and methane and reactions that cleave the aromatic rings and produce carbon monoxide.
Isolation and identification of the linear and cyclic oligomers of poly(ethylene terephthalate) and the mechanism of cyclic oligomer formation
Authors: Peebles L. H. , Huffman M. W. , Ablett C. T.
Published: April 2003

Chromatographic techniques are described which can be used to isolate and identify the linear and the cyclic oligomers of poly(ethylene terephthalate). Extraction of the oligomers from high molecular weight polymer produces at least eight different cyclic species, some of which are isolated and identified.

The cyclic dimer, the cyclic trimer, and the cyclic tetramer of poly(ethylene terephthalate) have also been prepared by acid chloride esterification and transesterification. Similar materials can be isolated from the ethylene glycol distillate obtained from the polymer melt. The mechanism of cyclic oligomer formation has been studied by determining the rate of formation of the cyclic oligomers during polymerization and during melt extrusion of polyesters which did not initially contain cyclic oligomers. The rate of formation depends upon the concentration of hydroxyl groups; hence, the cyclic oligomers are formed by transesterification from the chain ends or cyclodepolymerization. Therefore oligomers are inevitably produced during polymerization.
Copolymerization of some epoxides by coordination‐type catalysts
Authors: Price Charles C. , Brecker Lawrence R.
Published: April 2003

Copolymerizations of tritiated phenyl glycidyl ether with p‐ and m‐methoxy, p‐methyl, and p‐chloro analogs, as well as with propylene oxide and epichlorohydrin are reported. The relative reactivities indicate greater Lewis acid character for triethylaluminum–water than for diethyl‐zinc–water or ferric chloride–propylene oxide catalyst systems. The copolymerization of the PGE analogs is promoted by electron‐donor groups and retarded by electron‐withdrawing groups.
Preparation and properties of isomeric polyphenylacetylenes
Authors: Kern R. J.
Published: April 2003

Polyphenylacetylenes were prepared using ferric acetylacetonate and (i‐Bu)2AlH, RhCl[(C6H5)3P]3 and thermal initiation. Color, infrared spectra, softening temperatures, ultraviolet fluorescence, solubility, and crystallinity are described. A method is presented for assigning to these three macromolecular species predominantly cis, trans, and cis–trans copolymer structures, respectively. The dominantly cis polymer is believed to form in a transoid conformation which can easily be transformed to a more helical arrangement which exhibits a degree of crystallinity. Pyridine promotes the isomerization of cis to trans structure. The rhodium phosphine is thought to effect chain growth by repeated additions of the acetylenic CH of monomer across a terminal triple bond. Phenylacetylene thus behaves as a bifunctional molecule in this system. Color, polymer conformation, and crystallinity appear to be strongly interrelated.
Generation of free radicals at subzero temperatures. III. Polyamine–hydroperoxide–iron system
Authors: Minato Hiroshi , Hisada Ryuki
Published: April 2003

The mechanism of the reaction of tetraethylenepentamine (TEPA) with cumene hydroperoxide (CHP) and iron ions was investigated. It was found that (1) TEPA did not reduce Fe(III); (2) TEPA was consumed by this reaction; (3) both Fe(II) and Fe(III) were effective for this reaction. It was shown that though the OO bond of a hydroperoxide could be cleaved only at elevated temperatures, it could be easily cleaved by the reaction with the iron–TEPA complex. The function of this iron–TEPA complex is discussed.
Polyaddition reaction of biscarbodiimides. II. Synthesis of polyguanidines by polyaddition reaction of biscarbodiimides with diamines
Authors: Iwakura Yoshio , Noguchi Kohji
Published: April 2003

A series of polyguanidines was prepared by the polyaddition reaction of biscarbodiimides with diamines. The polyaddition reaction was carried out in solution. The polymers thus obtained had intrinsic viscosities up to 0.84 and molecular weights up to 15000. The structure of the polymers was identified by comparison of their infrared spectra with those of model compounds, elementary analysis, and a study of the reaction conditions. Thermogravimetric study indicated that the polyguanidines decomposed over 170°C under nitrogen. The polyguanidines were highly resistant to hydrolytic degradation by strong acid or alkali. The polyguanidines had basic groups and formed stable hydrochloric salts when they were treated with hydrochloric acid.
Room‐temperature polycondensation of β‐amino acid derivatives. V. Synthesis of hydrophilic polyamide by the polycondensation of β‐amino acid derivatives
Authors: Sanui K. , Ogata N.
Published: April 2003

N‐(Hydroxyalkyl) β‐alanine ester which was obtained from amino alcohol and acrylate yielded polyamide at room temperature in the presence of a basic catalyst. Alkali and alkali earth metal alkoxides had a strong catalytic effect on the room‐temperature polycondensation of N‐(hydroxyethyl)‐β‐alanine esters. The catalytic activity of metal alkoxides decreased in the order: Li > Na > K > Cs and Ca > Zn > Mg. Aluminum and titanium alkoxide had a weak catalytic effect, while boron (III), tin (IV), antimony (V), and tellurium (VI) alkoxides did not show any catalytic activity for the polycondensation. It was also found that solvent had an effect on the course of the polycondensation of N‐(hydroxyethyl)‐β‐alanine esters, and the highest molecular weight polymer was formed only in methanol solution. The solid‐phase polycondensation of the low molecular weight prepolymer resulted in a high molecular weight polymer with an inherent viscosity of 1.0 in the presence of a catalytic amount of phosphoric acid. The polymer obtained is hydrophilic and its moisture absorption is more than twice that of nylon 6.
New method for preparing saturated and unsaturated aliphatic polyurethanes
Authors: Miyake Yasuhiko , Ozaki Shoichiro , Hirata Yoshio
Published: April 2003

Saturated and unsaturated aliphatic polyurethane were obtained from three different routes. In route 1, 1,4‐dichloro‐2‐butene, sodium cyanate, and methanol were reacted to give dimethyl 2‐butene‐1,4‐dicarbamate. This is hydrogenated easily to give dimethyl butane‐1,4‐dicarbamate. Ester exchange reaction of this compound with glycol gave saturated aliphatic polyurethane. In another procedure, route 2, 1,4‐dichloro‐2‐butene, sodium cyanate and excess glycol were reacted to give bis(ω‐hydroxyalkyl)‐2‐butene‐1,4‐dicarbamate. This was hydrogenated to give bis(ω‐hydroxyalkyl)‐butane‐1,4‐dicarbamate. A glycol elimination reaction gave poly(polymethylene tetramethyl‐enedicarbamate). By route 3, 1,4‐dichloro‐2‐butene, sodium cyanate, and glycol were reacted to give poly(polymethylene 2‐butene‐1,4‐dicarbamate), a new unsaturated aliphatic polyurethane.
Polymerization of 3,4‐dihydro‐2H‐carboxyaldehyde (acrolein dimer). Part II. Copolymerization with isocyanates
Authors: Kitahama Yoshiharu , Ohama Hiroshi , Kobayashi Hidehiko
Published: April 2003

Copolymers of 3,4‐dihydro‐2H‐pyran‐2‐carboxyaldehyde (acrolein dimer) with phenyl isocyanate were obtained under several conditions. Infrared and NMR analyses showed that the isocyanate always reacted with acrolein dimer forming urethane linkages, not block units of isocyanate. An alternating copolymer was obtained from the copolymerization in the presence of anionic catalysts such as butyllithium at room temperature, irrespective of the monomer ratios employed. The isocyanate content in the copolymer prepared with an Al(C2H5)2Cl catalyst was increased by elevating polymerization temperature. The copolymerizability of aldehydes with the isocyanate depends upon the polarity of aldehyde group.
Energy transfer and radiolytic product formation in the system polystyrene–pyrene
Authors: Wilske J. , Heusinger H.
Published: April 2003

In γ‐radiolysis of polystyrene at room temperature, the formation of radicals detected by ESR spectroscopy is greatly reduced in the presence of pyrene, while crosslinking and hydrogen production are almost unchanged. The formation of these radicals was shown to start from the first excited singlet state of polystyrene competing with radiationless energy transfer to pyrene. Crosslinking and hydrogen production, on the other hand, are independent of the formation of these radicals and attributable to hot hydrogen or ion‐molecule reactions. Besides energy transfer from polystyrene to pyrene by dipole–dipole interaction the results indicate that intramolecular energy transfer within polystyrene is present.
Electron spin resonance study of radiation degradation of polytetrafluoroethylene
Authors: Hedvig Péter
Published: April 2003

Electron spin resonance measurements were performed at different stages of radiation degradation of polytetrafluoroethylene. It was found that under radiation, peroxy radicals were transformed into chain‐end fluorocarbon radicals, which in turn became into chain‐side radicals. On the basis of these data, a scheme for the degradation mechanism is given.
Reaction of nitrogen dioxide with polystyrene films
Authors: Jellinek H. H. G. , Flajsman F.
Published: April 2003

The reaction of nitrogen dioxide with thin polystyrene films has been investigated at 35°C with different partial pressures of NO2 (0.1, 2, 15, 30, and 60 cm Hg) and at several temperatures (25, 35, 45 and 55°C). The films were thin enough (ca. 20 μ) so that the reaction was independent of the diffusion of gas into the polymer. The experimental results can be represented by a chain mechanism. The whole degradation process is controlled by the diffusion of polymer radicals out of cages. This diffusion in turn, is affected by the decrease in viscosity or decrease in weight‐average molecular weight as degradation proceeds. This leads to an acceleration of the degradation process. A straight‐line relationship between the logarithm of the reciprocal weight‐average molecular weight and the logarithm of a reaction–time function was found. The dependence on the rate was substantiated by degrading polymer fractions. The energy of activation for the process is small, in agreement with a diffusion process for chain scission. Nitro and nitrite groups are incorporated along the backbone of polystyrene during exposure. The number of these polar side groups appears to pass through a maximum with time, as is evidenced by aggregation of polymer molecules in benzene solution only during the middle stage of the degradation. The final stage of the process is slowed down by retarder being produced. This retarder can be removed by reprecipitation of exposed polymer films. Degradation in solution is similar to that of films. Isotactic polystyrene shows less irregularities in its degradation curve than the atactic polymer. This is, presumably, due to its more homogeneous morphology, large molecular weight, and broader molecular size distribution. The plot of the degree of degradation versus time for the isotactic polymer can be satisfactorily approximated by a straight line.
Kinetics of the reverse Diels‐Alder reaction of dicyclopentadienecarboxylate groups on cotton cellulose
Authors: Franklin W. E. , Mack C. H. , Rowland S. P.
Published: April 2003

Cotton cellulose in the form of fabric has been esterified with dicyclopentadienecarboxylic acid to a degree of substitution of 0.44. The kinetics of the reverse Diels‐Alder reactions of the dicyclopentadienyl groups of the resulting cellulose ester in the presence of trapping agents and of swelling and nonswelling liquids have been measured with the differential scanning calorimeter. Fiber width measurements indicate that the esterified cotton fibers are swollen in the presence of the trapping agents dibutyl maleate, N‐phenylamaleimide, and N‐phenylmaleimide in tetraglyme solution, and in the presence of the nonreactive swelling agents tetraglyme and glycerol. The activation parameters for the dissociations in the swollen fibers are: Ea = 28–33 kcal/mole and ΔS* = −5 to +5 e.u. These kinetic parameters are similar to those previously found for the dissociation of methyl dicyclopentadienecarboxylate in solution. Fiber width measurements indicate that the esterified cotton fibers are collapsed in the dry state and in the presence of paraffin oil, deposited Carbowax 6000, or deposited glyceryl tristearate. The activation parameters for the dissociations in the collapsed fibers are Ea = 18–24 kcal/mole and ΔS* = −20 to −30 e.u. The kinetics are discussed in terms of the state of the cellulose matrix in the swollen and in the collapsed fibers.
Spin‐probe studies. I. Applications to latexes and micelle characterization
Authors: Rabold Gary Paul
Published: April 2003

The interaction of sodium dodecyl sulfate (NaDS) with styrene—butadiene latexes was investigated by application of the recently developed spin‐probe technique. It is possible by this method to detect the presence of micelles in a latex reasonably quantitatively. The effective surface area occupied per molecule of soap was calculated to be 53 Å2. Differences in purity can readily be detected for several NaDS samples. The less pure samples show a lower critical micelle concentration (CMC) and a significantly more ordered micelle structure. The addition of hexane to NaDS solutions above the CMC leads to a greater immobilization of the spin probe. This is interpreted as reflecting a tighter packing of the soap molecules. The addition of ethanol, acetic acid, and acrylic acid leads to a looser association of the probe with the micelles. The micelles catalyze the decomposition of the nitroxide probe in the presence of organic acids. The aggregation of sodium deoxycholate was also conveniently followed by the spin‐probe method.
Polysiloxanes having aromatic heterocyclic units. I. Polydimethylsiloxane benzimidazole polymer
Authors: Nakajima Toshinari , Marvel C. S.
Published: April 2003

A polymer containing dimethylsiloxane units (35) and benzimidazole units (1) has been prepared by the condensation of 3,3′‐diaminobenzidine and an α,ω‐bis‐(γ‐carboxy‐n‐propyl) polydimethylsiloxane. The new polymer has some rubbery properties, but it decomposes catastrophically at 400°C.
Vinyl polymerization photosensitized by anthraquinone sulfonates in aqueous solutions
Authors: Anwaruddin Q. , Santappa M.
Published: April 2003

The kinetics of the photopolymerization of the vinyl monomers MMA and MA sensitized by anthraquinone sulfonate‐NaCl‐HClO4 systems have been studied systematically. The wavelength 365 mμ was used for irradiation. Sodium anthraquinone‐2‐sulfonate and disodium anthraquinone‐2,6‐disulfonate were used as sensitizers, and all experiments were conducted in deaerated conditions. The polymerization was followed by the measurement of monomer disappearance (gravimetrically), rate of sensitizer disappearance (spectrophotometrically) and the chainlength of the polymer formed (viscometrically). Monomer concentration, kε, [NaCl], and I were varied. In the light of the experimental results a prima facie kinetic scheme was proposed. The specific rate constants for the various steps have been evaluated.
Polymers of 2‐vinyl‐1,3‐dioxolanes
Authors: Nordstrom J. David
Published: April 2003

Lewis acid‐initiated polymerizations of 2‐vinyl‐1,3‐dioxolanes have been studied. Evidence is presented showing at least three types of structural units in the polymer. Polymerization is propagated by 1,2 addition, by acetal ring opening, and by rearrangement, ring opening mechanisms. Polymerization is accompanied by the formation of a dimer consisting of a 1,4‐dioxepane and 1,3‐dioxolane ring. Film formers from methacrylate esters of vinyl dioxolane compounds are also described.
Role of polymer oxidation in the adhesion of polyethylene to metals
Authors: Sykes J. M. , Hoar T. P.
Published: April 2003

Untreated polyethylene will adhere well to aluminum only if it is applied in an oxidizing atmosphere. Peel strengths for coatings applied to various bright copper surfaces are far lower, probably because of decrease in polymer oxidation when copper is present. Preoxidized polyethylene sheet adheres well when melted on to copper in nitrogen. In view of earlier evidence for the formation of a weak interfacial layer containing shortchain material, it is proposed that the weak bond strengths so caused are substantially improved by the preferential adsorption of longer‐chain surface‐active oxidized species in the polymers.
Structure and properties of cellulose graft copolymers. III. Cellulose–methyl methacrylate graft copolymers synthesized by the ceric ion method
Authors: Huang Robert Y. M. , Chandramouli P.
Published: April 2003

The ceric ion‐initiated graft copolymerization of methyl methacrylate onto wood cellulose was found to depend on the concentrations of initiator, monomer, and cellulose. The structure of cellulose—methyl methacrylate graft copolymers was studied by hydrolyzing away the cellulose backbone to isolate the grafted poly(methyl methacrylate) branches. The molecular weights and molecular weight distributions of the grafted poly(methyl methacrylate) were determined by using gel‐permeation chromatography. The number‐average (M̄n) molecular weights ranged from 36 000 to 160 000 and the polydispersity ratios (M̄w/M̄n) varied from 4.0 to 7.0. The grafting frequency or the number of poly(methyl methacrylate) branches per cellulose chain calculated from the per cent grafting and molecular weight data varied from 0.38 to 3.2. The structure of cellulose—methyl methacrylate graft copolymers and the effect of stepwise addition of initiator on the structure are discussed.
Vinyl polymerization with Fe(III)‐thiourea as initiator system. Part I. General features and kinetics of Fe(ClO4)3‐thiourea reaction
Authors: Mandal B. M. , Nandi U. S. , Palit S. R.
Published: April 2003

Initiation of polymerization of methyl methacrylate, styrene, and acrylonitrile with the redox system Fe(III)—thiourea has been examined. For the heterophase polymerization any of the ferric salts, such as FeCl3, Fe2(SO4)3, and Fe(ClO4)3 can be used as oxidant, but there is no polymerization in the homogeneous phase when FeCl3 is used as oxidant. It was also observed that Fe(ClO4)3 retards the radical polymerization of styrene, though this salt has hardly any effect on the radical polymerization of methyl methacrylate. Further, the reaction between Fe(ClO4)3 and thiourea was found to be kinetically of second order. The rate is largely influenced by the nature of the solvent. It is concluded that apart from the dielectric constant of the solvents, specific effects like complex formation of Fe(III) with solvents should have a marked influence on the rate of this reaction.
Thermal stabilities of homopolymers of amino acids
Authors: Obata Hiroko , Ogawa Shigeo
Published: April 2003

In order to study the thermal stabilities of the α‐helical polyamino acids in the solid state, measurements of the infrared spectra at high temperature, weight loss by thermogravimetry, and the expansion of the α‐helix by x‐ray diffractometry were carried out on poly(γ‐methyl D‐glutamate), poly(γ‐benzyl L‐glutamate), poly‐L‐alanine, poly(β‐benzyl L‐aspartate), poly‐δ‐carbobenzoxy‐L‐ornithine and poly‐ε‐carbobenzoxy‐L‐lysine. The thermal degradation temperatures of these polymers lie between 140°C and 230°C. The α‐helical conformation is stable at high temperature in these polyamino acids, except for poly(β‐benzyl L‐asparatate), unless thermal degradation takes place. As temperature rises, the amide A and the amide I bands of the infrared spectra shift slightly to higher frequencies and the amide II band to lower frequencies. At the same time, the intensities of these amide bands decrease. These changes differ among the different molecules. From the x‐ray measurement, it was found that the α‐helix expands along the helical axis with temperature. It is expected that the intramolecular hydrogen bonds of the α‐helix become weak with increasing temperature and that the state of the hydrogen bonds of the α‐helices depends upon the molecules.
Studies of Japanese lacquer: Urushiol dimerization by the coupling reaction between urushiol quinone and a triolefinic component of urushiol
Authors: Kato Takashi , Kumanotani Ju
Published: April 2003

Previously, the formation of urushiol quinone from urushiol was demonstrated in the laccase‐catalyzed oxidation process of the sap of the Japanese lacquer tree (Rhus vernicifera D.C.) or of lacquer formed from it. This paper presents the results of the investigation on the participation of urushiol quinone in the oxidative polymerization and crosslinking of the sap or the lacquer. The polymeric urushiol was obtained by the fractionation of the mildly oxidized sap (Japanese lacquer), and a specific dimeric urushiol was isolated from it by thin‐layer chromatography (TLC). Structural analysis of the dimer illustrated that it has a conjugated triene structure and may be formed by a coupling reaction between urushiol quinone and a triolefinic component of urushiol. Further support for this was given by the spectroscopic study of the reaction between 4‐tert‐butyl‐o‐quinone and the triolefinic component of dimethylurushiol, and by the isolation and identification of the coupling product between them.
Polymerization of tetrahydrofuran: A radiochemical study of the initiation mechanism
Authors: Pasika Wallace M. , Wynn John W.
Published: April 2003

14C‐tagged triphenylmethyl hexachloroantimonate was used to initiate the polymerization of THF. An activity count on the polymers indicated no incorporation of initiator fragments into the macromolecule. On ascertaining the fate of the tagged trityl fragment it was found that the activity resided in the triphenylmethane isolated from the methanol supernatant. This indicates that at least one sequence of the initiation reaction in this polymerization involves hydride ion abstraction.
Synthesis of polymerizable tetrafluorohydrazine–diene addition compounds
Authors: Reed Samuel F.
Published: April 2003

The reaction of tetrafluorohydrazine with alkenyl acrylates and methacrylates under appropriate conditions resulted in the isolation of olefinic bis(difluoramines) capable in some instances of undergoing free‐radical‐initiated polymerization and copolymerization. Monomer and polymer synthesis and characterization are discussed.
Thermal decomposition products of polypropylene
Authors: Tsuchiya Yoshio , Sumi Kikuo
Published: April 2003

Isotactic polypropylene was decomposed under vacuum at 360, 380, and 400°C, and the volatile products from C1 to C12 hydrocarbons were analyzed by gas chromatography. The formation of the main products is discussed on the basis of a free‐radical mechanism in which intramolecular radical transfer is assumed to play an important role. The mechanism of the formation of a number of products suggested by previous workers is criticized on the basis of the results of a more comprehensive analysis of this investigation.
Gel‐permeation chromatography of cellulose esters. Effect of average DP, DS, substituent size, and primary hydroxyl content
Authors: Brewer R. J. , Tanghe L. J. , Bailey S.
Published: April 2003

Hydrolyzed cellulose acetates and cellulose tripropionates prepared over wide ranges of intrinsic viscosity (DP) were fractionated by gel‐permeation chromatography (GPC). An increase was observed in the polystyrene equivalent length (PSEL) at 50% cumulative height with increasing DP of the ester. Cellulose acetates and propionates over wide range of acyl content (DS), and a homologous series of triesters (propionate through heptanoate) of the same DP were fractionated by GPC. Increased amount and size of acyl gave relatively small increases in PSEL. The molecular size of cellulose acetates was not affected by the amount of primary hydroxyl present in the esters. The breadth of molecular weight distribution of the cellulose esters, as measured by the weight‐average to number‐average molecular size ratio, M̄w/M̄n, was not affected by any variation in the composition of the esters. A blend of cellulose tripropionates of widely differing DP gave a broadened GPC curve in agreement with that calculated from the components of the blend.
Radiation‐induced solid‐state polymerization of derivatives of methacrylic acid. III. An electron spin resonance study of radical reactions in irradiated octadecyl methacrylate
Authors: Bowden M. J. , O'Donnell J. H.
Published: April 2003

The electron spin resonance spectrum of gamma‐irradiated octadecyl methacrylate (m.p. ≈ 12°C.) was due to a mixture of three radicals formed by (1) loss of a hydrogen atom from the paraffin chain, (2) addition of a hydrogen atom to the double bond, and (3) addition of a monomer molecule to radicals formed by (1) or (2). On warming monomer added to radicals (1) and (2) between −170 and −50°C., and above −50°C. the spectrum was solely due to propagating methacrylate radicals. The total radical concentration decreased slightly at −150°C. and was then constant up to −30°C. A marked decrease in radical concentration occurred from −30 to +12°C., it took place rapidly and reached an equilibrium value after each successive increase in temperature. Differential thermal analysis indicated a solid—solid phase change at −30°C. When the sample was kept at 0°C. there was no further decrease in radical concentration even with 50% conversion to polymer. With 2% added chloranil the (chloranil)− was observed to be of about the same concentration as methacrylate radicals. The initial total radical concentration was lower and decreased to zero by 0°C. on warming. No polymer was obtained.
Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. II. Properties of acrylonitrile–styrene copolymer
Authors: Yabumoto Shigeru , Ishii Kiyoshi , Kawamori Masakiyo , Arita Koichiro , Yano Hiroshi
Published: April 2003

The properties of the acrylonitrile–styrene copolymer prepared in the presence of zinc chloride were investigated in comparison with those of a copolymer having the same overall composition and prepared by the ordinary radical procedure. The characteristics of the polymer prepared with ZnCl2were as follows: (1) less coloration by alkali treatment, (2) less coloration by thermal treatment and (3) higher glass transition temperature. These features may be attributed principally to the structure of the copolymer, which has more unlike bonds and less long sequences as described in the first article of this series. The effects of residual salt in the copolymer on the properties were also investigated.
Molecular weight distribution in radiation‐induced polymerization. I. γ‐radiation‐induced free‐radical polymerization of liquid styrene
Authors: Huang R. Y. M. , Westlake J. F. , Sharma S. C.
Published: April 2003

The kinetics of γ‐radiation‐induced free‐radical polymerization of styrene were studied over the temperature range 0–50°C at radiation intensities of 9.5 × 104, 3.1 × 105, 4.0 × 105, and 1.0 × 106 rad/hr. The overall rate of polymerization was found to be proportional to the 0.44–0.49 power of radiation intensity, and the overall activation energy for the radiation‐induced free‐radical polymerization of styrene was 6.0–6.3 kcal/mole. Values of the kinetic constants, kp2/kt and ktrm/kp, were calculated from the overall polymerization rates and the number‐average molecular weights. Gelpermeation chromatography was used to determine the number‐average molecular weight M̄n, the weight‐average molecular weight M̄w, and the polydispersity ratio M̄w/M̄n, of the product polystyrene. The polydispersity ratios of the radiation‐polymerized polystyrene were found to lie between 1.80 and 2.00. Significant differences were observed in the polydispersity ratios of chemically initiated and radiation‐induced polystyrenes. The radiation chemical yield, G(styrene), was calculated to be 0.5–0.8.
Change with temperature of the ESR spectra of methacrylic acid radicals
Authors: Sakai Yoshiro , Iwasaki Machio
Published: April 2003

In order to elucidate the structure of methacrylic acid radicals, the change with observation temperature of the ESR spectrum of free radicals trapped in solid methacrylic acid γ‐irradiated at −196°C was studied. Below −80°C, we found a 9‐line spectrum, which is similar to the ordinary 9‐line spectrum observed in irradiated poly(methacrylic acid) or poly(methyl methacrylate), but which differs in the stronger intensity of the so‐called 4‐line component. Our 9‐line spectrum changes reversibly into a 13‐line spectrum above −80°C. With broad‐line NMR measurements of methacrylic acid, it was found that there is such an unusual crystalline transition around −30°C that the line width is narrower in the lower‐temperature region (phase II) than that in the higher‐temperature region (phase I). The change of the ESR spectrum can be interpreted in terms of the exchange of the two β‐protons due to the hindered oscillation around the CαCβ bond of the single radical ···CβH2Cα(CH3)COOH if one assumes the gradual change of the hindering potential barrier caused by the crystalline transition and the lower barrier in phase II. The modified Bloch treatment gave the hindering potential barrier to be 7.2 kcal/mole in phase I and 1.5 kcal/mole in phase II. The difference between our 9‐line spectrum and the ordinary one with the very weak 4‐line component comes from the difference of the surrounding matrix.
ESR study of radical sites in crystalline texture of irradiated polypropylene by means of nitric acid etching
Authors: Kusumoto Naoshi , Matsumoto Kazuki , Takayanagi Motowo
Published: April 2003

Bulk‐crystallized isotactic polypropylene samples with different crystalline textures were etched by fuming nitric acid to remove the disordered region. The radicals produced by irradiation of γ‐rays or ultraviolet light on these etched samples in vacuum at liquid nitrogen temperature were investigated by the ESR method. A triplet spectrum in addition to the original spectrum of polypropylene radicals was separated for the etched samples. It was concluded that this triplet was caused by radical species associated with nitro groups introduced on the surface of the crystalline residues by etching. The difference in the intensity of this triplet among the samples was ascribed to differences in crystalline textures and interpreted in a quantitative way. The concentration of polypropylene radicals corrected for the triplet differed among the quenched, annealed, and cold‐drawn samples and the sample annealed one after drawing. This fact was interpreted on the basis of the hypothesis that radical sites were almost concentrated in the defects of crystal domain. The well known nonet spectrum, which can be observed at liquid nitrogen temperature after annealing the irradiated samples at room temperature, was also confirmed to be attributable to the defects of crystals. The behavior of free methyl radicals induced by ultraviolet irradiation was also found to be strongly dependent on the state of aggregation of the polymer molecules.