bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic strain‐birefringence apparatus for polymer films
Authors: Hopkins Robert C. 
Published: April 2003

AbstractA new apparatus for investigating dynamic strain birefringence in polymer films at frequencies up to 10 Hz and at various degrees of internal sample orientation is described. Samples are elongated at constant low rates while simultaneously being strained sinusoidally. Fast changes in sample retardance are recorded while slow changes are automatically compensated with a servo‐controlled Soleil‐Babinet compensator. The signal‐to‐noise ratio of the system is greatly enhanced by incorporating a highly monochromatic laser light source, a synchronous amplifier, and a light beam modulator based on a rotating polarizer. Data obtained from this apparatus can be used to elucidate polymer relaxation mechanisms at various frequencies over a wide range of static strains.
Molecular weight distribution in branched polymers
Authors: Saito O. , Nagasubramanian K. , Graessley W. W. 
Published: April 2003

AbstractThe distribution of molecular weights in realistic free‐radical polymerizations with branching was analyzed theoretically. Series solutions were obtained for the fraction of molecules with r repeating units and the number of branch points contained in molecules with r repeating units. Branching by transfer processes was found to increase the proportion of both high and low molecular weight components in the system. The apportioning of branch points among r‐mer molecules was shown to be somewhat narrower than a Poisson distribution. The major difference between the calculated distributions and previous model distributions for branched systems was the absence of discontinuities in the moments at all levels of branching.
Intrinsic viscosity in branched free‐radical polymers
Authors: Nagasubramanian K. , Saito O. , Graessley W. W. 
Published: April 2003

AbstractThe intrinsic viscosity ratio [η]B/[η]L was calculated as a function of average branching density for trifunctionally branched, free‐radical polymers. Calculations were made for the g1/2, g3/2, and h3 rules, using realistic distributions of molecular weights and branches. Experimental data on branched poly(vinyl acetate) lay between the curves obtained from the g1/2 and h3 relations.
Laser‐excited Raman scattering in polybutene‐1
Authors: Cornell S. W. , Koenig J. L. 
Published: April 2003

AbstractRaman spectra are described for the three crystalline modifications of polybutene‐1. The Raman frequencies are compared with infrared results and give good agreement. A normal‐coordinate analysis for A‐mode vibrations is presented for five possible helical conformations. The behavior of several calculated helix‐sensitive bands is characterized. These results are applied to the experimental Raman frequencies and lead to the prediction of a 103 helix for the orthorhombic form III modification.
Extended‐chain crystals. I. General crystallization conditions and review of pressure crystallization of polyethylene
Authors: Wunderlich Bernhard , Davidson Theodore 
Published: April 2003

AbstractThis is the first paper of a series of reports concerning extended‐chain crystals of flexible, linear high polymers. The general conditions for crystal growth are discussed. Polymer crystallization is described as a two‐step process: nucleation of each crystallizing molecule to a folded‐chain conformation, followed by an increase in fold length in a solid‐state reorganization step. This reorganization step is enhanced in the case of polyethylene by crystallization at high temperature under elevated pressure. Mechanical deformation during crystallization is also able to produce extended‐chain crystals. The most promising method, however, is crystallization during polymerization. Previous work on crystallization of polyethylene under elevated pressure is critically reviewed.
Extended‐chain crystals. II. Crystallization of polyethylene under elevated pressure
Authors: Davidson Theodore , Wunderlich Bernhard 
Published: April 2003

AbstractA report on crystallization of polyethylene at elevated pressures to an extended‐chain morphology is presented. The crystals have been characterized by electron microscopy and density determination. Pressure, supercooling (temperature), and crystallization time have been varied to find the best conditions for production of perfect crystals. At 10–30°C supercooling completely crystallized polyethylene was obtained between 4.5 and 7 kb crystallization pressure in 1–8 hr. Analysis of fracture surfaces of samples crystallized for different lengths of time shows an increase in size and number of crystal lamellae and an improvement of extended chain crystals in the early stages of crystallization. A further improvement of the less well crystallized material between the lamellae occurs after 15 min of crystallization time.
Extended‐chain crystals. III. Size distribution of polyethylene crystals grown under elevated pressure
Authors: Prime R. Bruce , Wunderlich Bernhard 
Published: April 2003

AbstractExtended‐chain crystals of high molecular weight polymethylene, a polyethylene with a broad molecular weight distribution, and three fractions of polyethylene were grown from the melt under elevated pressure. Comparison of the crystal size distribution in the molecular chain direction (measured on fracture surfaces by electron microscopy) with the molecular weight distribution (measured by gel‐permeation chromatography) gave the following results. Up to molecular weight 10,000 all samples showed eutectic separation into fully extended chain crystals of narrow molecular weight distribution. Above molecular weight 10,000 mixed crystals were formed. Under the chosen crystallization conditions larger chain extension was achieved with higher molecular weights. However, an increase in molecular weight by a factor of 1000 led only to a tenfold increase in chain extension. These facts are discussed in the light of a proposed mechanism of crystal growth.
Extended‐chain crystals. VI. Annealing of polyethylene under elevated pressure
Authors: Gruner Charles L. , Wunderlich Bernhard , Bopp Richard C. 
Published: April 2003

AbstractPolyethylene crystals of different degrees of perfection were annealed at 5.1 kb pressure for 20 hr at various temperatures and analyzed by electron microscopy, thermal analysis, and density determination. No annealing took place until the temperature was close to the melting point of the starting material. Up to 235°C increasing solidstate annealing was observed. Mixed crystals of up to 0.989 g/cm3 density and 1500 Å thickness in the chain direction could be produced. At slightly higher temperature recrystallization to extended‐chain crystals rather than annealing occurred. The annealing process at atmospheric pressure seems to be similar in nature, but takes much longer for comparable perfection. From a comparison of annealing and crystallization it is concluded that polymer crystallization goes through a stage of internally imperfect order during which most of the observed chain extension occurs. Estimates of this outer imperfect layer of a growing crystal place its depth at 30,000 Å.
Birefringence and dichroism of rubbery copolymers
Authors: Shindo Y. , Stein R. S. 
Published: April 2003

AbstractThe Kuhn‐Grün theory for the birefringence and dichroism of rubbery polymers is extended to the case of copolymers consisting of two or more statistical segments of differing lengths. It is shown that the previous equations are applicable provided that the anisotropy of polarizabilities and absorptions are replaced with suitable averages in which the segment anisotropies are weighted by the squares of their segment lengths. This indicates that the stress‐optical coefficient will not generally vary linearly with composition. The orientation measured from the dichroism of bands arising from different segments will be different.
Ketone‐zinc chloride combination as an initiator of polymerization
Authors: Dutt Prabir K. , Palit Santi R. 
Published: April 2003

AbstractDihydrocivetone, a macrocyclic ketone, has been found to be a weak initiator of vinyl polymerization. Anhydrous zinc chloride strongly promotes this to form a novel initiating system. Monomers tried successfully are methyl methacrylate, acrylonitrile and α‐methylstyrene. The characteristic feature of polymerization of α‐methylstyrene differs greatly from those of other monomers and those have been discussed and compared.
ESR studies of vinyl polymerization. II. Initial reactions of vinyl esters with redox systems in aqueous media
Authors: Takakura Koichi , Rånby Bengt 
Published: April 2003

AbstractESR measurements of transient radicals during redox polymerization of various vinyl esters in aqueous solutions have been made by using the rapid‐mixing flow method. The initiation was by means of hydroxyl and amino radicals from the systems titanous chloride‐hydrogen peroxide and titanous chloride‐hydroxylamine, respectively. The well resolved hyperfine structures obtained at monomer concentrations of about 0.05 mole/1. are unambiguously assigned to the monomer radicals formed by addition of initiator radicals to monomers. At higher monomer concentrations, additional weak signals attributed to the growing polymer radicals were observed. The effect of reaction conditions on the signal intensity has been studied in particular for vinyl acetate. The coupling constants of monomer radicals from various vinyl esters (acetate, propionate, butyrate, crotonate, and isopropenyl acetate) were obtained and the spin densities calculated. From the ESR spectra, the monomer radicals have a conformation with the substituent R (R = HO or NH2) of RCH2CH(OCOR′) locked in a position above or below the radical plane. This is tentatively interpreted as due to formation of intramolecular hydrogen bonds to ring structures or complexes with titanium ions. In addition, hydrogen abstraction reactions of some model compounds for poly(vinyl acetate) have been briefly studied in relation to chain transfer and grafting reactions.
Thermal stability of structurally related polymers containing carborane and phthalocyanine groups
Authors: Delman A. D. , Kelly J. J. , Simms B. B. 
Published: April 2003

AbstractThese studies were undertaken to determine the thermal behavior of structurally related polymers having a carborane nucleus in the recurring unit. Three of these products also contained phthalocyanine rings in their molecules. Results of thermal analysis studies show generally that the relative heat stability of the polymers conforms closely with indications given by similar investigations of structurally related intermediate and model compounds. A polymer with dimethylsiloxane units exhibited more resistance to thermal decomposition than similar products having urethane groups in their molecules. The urethane polymers derived from tolylene diisocyanate were found to be somewhat less heat‐stable than analogous materials synthesized from methylenebis‐(p‐phenyl isocyanate). The relative order of thermal resistance of these materials follows that of more conventional polyurethane elastomers.
Equilibrium concentration of trioxane in cationic polymerization
Authors: Miki T. , Higashimura T. , Okamura S. 
Published: April 2003

AbstractIn the cationic polymerization of trioxane and tetraoxane near room temperature, the equilibrium trioxane concentration is not negligible during polymerization. In this work, tetraoxane was polymerized with BF3 • O(C2H5)2 in various solvents and the equilibrium concentration of trioxane produced during the polymerization of tetraoxane and equilibrated with the growing polyoxymethylene chain was determined. The equilibrium trioxane concentrations were 0.05, 0.13, and 0.19 mole/l. in benzene, ethylene dichloride, and nitrobenzene at 30°C, respectively, and 0.20 mole/l. in thhylene dichloride at 50°C. The values in ethylene dichloride showed that the approximate values of ΔHp and ΔS were −4.2 kcal/mole and −9.7 cal/mole‐deg., respectively.
Benzimidazole polymers from aldehydes and tetraamines
Authors: Higgins Jerry , Marvel C. S. 
Published: April 2003

AbstractA new method for the preparation of benzimidazole polymers is described. The solution polymerization of aromatic tetraamines with isophthalaldehyde bis bisulfite adduct in N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (MP), and dimethyl sulfoxide (DMSO) produced polybenzimidazoles with viscosities (ηinh) in the range of 0.3–0.5 measured in formic acid solution. Also a model compound study with benzaldehyde, benzaldehyde diethyl acetal, and benzaldehyde bisulfite adduct with o‐phenylenediamine was carried out. The results showed that the reaction of benzaldehyde bisulfite adduct with o‐phenylenediamine in DMAc as the solvent gave quantitative yields of 2‐phenylbenzimidazole. Excellent yields of 2‐phenylbenzthiazole, 2‐phenylbenzoxazole, and 2‐pyridylbenzimidazole were also obtained with the benzaldehyde bisulfite adduct and picoline‐2‐carboxaldehyde bisulfite adduct with o‐aminothiophenol, o‐aminophenol, and o‐phenylenediamine. The reaction conditions for the preparation of the polymers and the model compounds are very mild and the reaction times range from 15 min to 1 hr for the model compounds and 3–5 hr for the polymers. Longer reaction times did not increase the viscosities of the polymers to any extent.
Reactions of polyolefins with strong lewis acids
Authors: Carrick Wayne L. 
Published: April 2003

AbstractTreatment of a cyclohexane solution of low density polyethylene and polystyrene with anhydrous aluminum chloride causes chemical reaction between the two polymers which results in the formation of a graft copolymer. The initial copolymer‐forming reaction is very rapid, and prolonged contact of the polymers with aluminum chloride causes subsequent degradation in molecular weight. Treatment of separate solutions of polyethylene, isotactic polypropylene, and ethylene–propylene copolymers with aluminum chloride was studied as a function of time. The intrinsic viscosities of the polymers dropped from initial values of 2.4–6.5 to 0.55–0.85 in 5 min, followed by a slower decline over the next 2 hr. In the case of polypropylene, the low molecular weight fragments largely retained the isotactic structure, which demonstrates that stereochemical isomerization is not a major reaction.
Uses of electron paramagnetic resonance in studying fracture
Authors: Devries K. L. , Roylance D. K. , Williams M. L. 
Published: April 2003

AbstractThe uses of electron paramagnetic resonance (EPR) in studying aspects of polymer fracture are discussed. The sensitivity of EPR is such that all phases of fracture are not amenable to investigation by these means. This paper attempts to define those areas where the authors' experience would indicate that success might or might not be expected. A discussion of the difference between the tensile fracture of drawn polymer fibers, in which strong signals are obtained, and cast and molded materials is given.
Stereoregular poly(methacrylic acids)
Authors: Aylward N. N. 
Published: April 2003

AbstractA convenient method is described for the preparation of isotactic and syndiotactic poly(trimethylsilyl methacrylates) by using the monomer trimethyl silyl methacrylate and butyllithium initiation in toluene and tetrahydrofuran, respectively. The structure of these polymers enables complete hydrolysis to the corresponding poly(methacrylic acids), which were characterized with respect to tacticity and molecular weight. The asymmetric induction in toluene produced 89% isotactic polymer, while that in tetrahydrofuran gave polymer <90% syndiotactic and heterotactic in terms of triads. A method of fractionation of the polyelectrolytes by gel‐permeation chromatography on a preparative scale was shown to be applicable.
Synthesis and reactions of polyvinylcyclopropane
Authors: Overberger C. G. , Halek G. W. 
Published: April 2003

AbstractVinylcyclopropane was polymerized with a catalyst of diethylaluminum chloride and titanium trichloride and fractionated to yield isotactic, atactic, and stereoblock fractions, as shown by a combination of physical and chemical evidence. The atactic fraction contained a significant portion of product from 1,5‐polymerization as well as the usual 1,2‐polymerization, and this occurrence is explained by modifications in a mechanism for normal 1,2‐coordination polymerization such that abnormal alkylations occur during the propagation step in the coordination sphere of the catalyst surface. Addition of hydrogen bromide to the isotactic fraction yielded predominantly poly‐3‐bromo penten‐1 and in‐chain cyclohexane and vinylidene structures. A mechanism is proposed for these occurrences involving a hydride shift and various reactions of the initially generated carbonium ion with neighboring cyclopropyl rings. Addition of acetic acid yielded 25% addition and 25% cyclization and crosslinking. Hydrogen sulfide did not add to the cyclopropyl ring. Hydrogenation of the atactic fraction yielded poly‐3‐methylbutene‐1 quantitatively, demonstrating that the polymeric environment did not affect the direction of ring opening but that the state of crystallinity as compared to the isotactic polymer did affect the extent of reaction. In general, the cyclopropyl ring in a polymeric environment underwent its usual reactions but was subject to reactions with neighboring groups resulting from its fixation in a polymer chain.
Polymerization initiated by an electron donor–acceptor complex. Part IV. Kinetic study of polymerization of methyl methacrylate initiated by the charge‐transfer complex consisting of poly‐2‐vinylpyridine and liquid sulfur dioxide
Authors: Matsuda Minoru , Ishioroshi Yasuhiro 
Published: April 2003

AbstractA kinetic study has been made of the polymerization of methyl methacrylate (MMA) initiated by a charge‐transfer complex of poly‐2‐vinylpyridine (electron donor) and liquid sulfur dioxide (acceptor) in the presence of carbon tetrachloride. It is concluded that the polymerization proceeds through free‐radical intermediates, as with the pyridine‐liquid sulfur dioxide complex system. The association constants K of acceptor and polymer electron donors which range widely in their molecular weight were determined spectrophotometrically, and it has been found that both K and overall rate of polymerization Rp of MMA decrease with increasing molecular weight of polymer donor; contrary to this, molecular weight of PMMA formed increases with increasing molecular weight of the polymer donor. Other kinetic behaviors was essentially the same as in the pyridine–liquid sulfur dioxide system, i.e., Rp is proportional to the square root of the concentration of the complex and to the 3/2‐order of the monomer concentration; Rp is clearly sensitive to the carbon tetrachloride concentration at low concentration of carbon tetrachloride, but for a higher concentration it is practically independent of the carbon tetrachloride concentration. It has been deduced from a kinetic mechanism for the initiation that a primary radical may be produced from the reduction of carbon tetrachloride by an associated complex consisting of liquid sulfur dioxide–polymer donor and the monomer.
Polymerization of vinyl acetate in aqueous media. Part III. Distribution of free monomer and its effect upon the particle size of poly(vinyl acetate) latices
Authors: Netschey A. , Alexander A. E. 
Published: April 2003

AbstractThe distribution of the monomer vinyl acetate between an aqueous phase and its polymer (the latter in the form of a latex) has been measured at 20 and 40°C. The diameter of particles in a fine poly(vinyl acetate) latex has been measured in the presence of various concentrations of monomer in the aqueous phase, by means of the analytical ultracentrifuge. Comparison of the diameters so measured with those calculated from the distribution data show quite reasonable agreement (<3.7%).
Polymerization of vinyl acetate in aqueous media. Part IV. Influence of preformed (“seed”) latex upon polymerization kinetics and particle size
Authors: Netschey A. , Alexander A. E. 
Published: April 2003

AbstractThe polymerization of aqueous solutions of vinyl acetate initiated by K2S2O8, has been studied in the presence of different concentrations of a fine “seed” latex, both in the absence and in the presence of a surfactant (sodium hexadecyl sulfate). Both kinetics and final latex size were measured, the latter showing whether fresh nucleation had occurred or not. The results suggest that surfactant adsorbed on the latex surface greatly influences the capture, by the latex surface, of oligomers formed in the aqueous phase and this, in turn, markedly affects both nucleation and kinetics. The number of free radicals per particle does not appear to be constant even with the finest particles used (ca. 50 mμ).
Effect of hydrogen on the γ‐radiation‐induced polymerization of ethylene
Authors: Mitsui Hiroshi , Hosoi Fumio , Kagiya Tsutomu 
Published: April 2003

AbstractThe effects of hydrogen on the γ‐radiation‐induced polymerization of ethylene were studied from the viewpoint of polymer structure and kineties. All experiments were carried out at 30°C. In the polymerization of ethylene containing 21.6% hydrogen, the solid polymer was obtained as a main product, while no liquid product was found. There was no difference in hydrogen contents before and after the irradiation; and acetylene, ethane, butane, and butene‐1 were found as gaseous products. The polymer yield increased almost proportionally with dose rate in the presence of 8.0% hydrogen; on the other hand the molecular weight was independent of dose rate. At hydrogen contents of 0–8%, the polymerization rate increased with reaction time and decreased with hydrogen content. The molecular weight also increased with the time, and the extent of the increment decreased with the time and hydrogen content. The number of moles of polymer chain increased proportionally with the reaction time and increased linearly with hydrgen concentration. These results were analyzed by using a graphical evaluation method for kinetics, and the effects of hydrogen on the each elementary step in the polymerization were discussed.
Polymerization of coordinated monomers. IV. Copolymerization of methyl methacrylate– and methacrylonitrile–Lewis acid complexes with styrene
Authors: Ikegami Tadashi , Hirai Hidefumi 
Published: April 2003

AbstractComplexes of methyl methacrylate and methacrylonitrile with Lewis acids (SnCl4, AlCl3, and BF3) were copolymerized with styrene at −75°C under irradiation with a high‐pressure mercury lamp in toluene solution. The resulting copolymers consisted of equimolar amount of methyl methacrylate or methacrylonitrile and styrene, regardless of the molar ratio of monomers in the feed. NMR spectroscopy showed the copolymers to have an alternate sequence. The tacticities of the copolymers varied with the complex to have an alternate sequence. The tacticities of the copolymers varied with the complex species: the copolymer from the SnCl4 complex system had a higher cosyndiotactieity, while those from the AlCl3 and the BF3 complex systems showed coisotacticity to predominate over cosyndiotacticity. NMR spectroscopic investigation of the copolymerization system indicated the presence of a charge‐transfer complex between the styrene and the methyl methacrylate coordinated to SnCl4. The concentration of the charge‐transfer complex was estimated to be about 30% of monomer pairs at −78°C at a 1:1 molar ratio of feed. The growing end radicals were identified as a methyl methacrylate radical for the AlCl3 complex–styrene system and a styrene radical for the SnCl4 complex–styrene system by the measurement of the ESR spectra of the copolymerization systems under or after irradation with a high‐pressure mercury lamp. The tacticity of the resulting polymer appears to be controlled by the structure of the charge transfer complex. In the case of the SnCl4 complex a certain interaction of SnCl4 with the growing end radical seems to be a factor controlling the polymer structure. These copolymerizations can be explained by an alternating charge‐transfer complex copolymerization scheme.