bluuebunny/crossref_metadata_2025 huggingface dataset:
Cationic copolymerization of tetrahydrofuran with propylene oxide. V. Effect of diol cocatalyst structure and concentration with antimony pentachloride as catalyst
Authors: Alvarez E. J. , Hornof V. , Blanchard L. P.
Published: April 2003

The effects of the chemical nature and the concentration of diol cocatalysts in the copolymerization of propylene oxide (PO) and tetrahydrofuran (THF) catalyzed by antimony pentachloride were studied. The least bulky diol, 1,2‐ethanediol, was found to be the most active species, judging from the highest rate of copolymerization. The variation of rate was much smaller with the other diols used. Furthermore, the position of the hydroxyl groups did not have much effect on the rate. The concentration of cocatalyst strongly influenced the rate of consumption of both monomers. This is explained by the effect of diol concentration on the equilibrium that exists between the catalyst and the cocatalyst on one side, and the active oxonium complex on the other. The mechanism of cocatalytic effects is discussed in terms of newer concepts of ionic polymerization. Specific solvation of ion‐pairs is visualized as partly responsible for the overall effect of the cocatalysts. Water in quantities commeasurable with those of the cocatalyst was found to retard the reaction. It also gave rise to oligomeric products, as evidenced by gel‐permeation chromatography.
Asymmetric polymers. XXVI. Optically active polyamides: (–)poly‐(S)‐4‐tert‐butoxymethyl‐ and 4‐hydroxymethyl‐6‐hexanamide
Authors: Overberger C. G. , Kozlowski John H.
Published: April 2003

Racemic and optically active hexahydro‐5‐tert‐butoxymethyl‐2H‐azepin‐2‐one were polymerized, and the resulting poly‐4‐tert‐butoxymethyl‐6‐hexanamides were treated to remove the tert‐butyl protective group. ORD and CD spectra of (–)‐poly‐(S)‐4‐tert‐butoxymethyl‐6‐hexanamide and (–)poly‐(S)‐4‐hydroxymethyl‐6‐hexanamide were compared with spectra of their low molecular weight models, (S)(–)‐6‐acetamido‐4‐tert‐butoxymethyl‐N‐methylhexanamide and (S)( – )‐6‐acetamido‐4‐hydroxymethyl‐N‐methylhexanamide, in 2,2,2‐trifluoroethanol, p‐dioxane–water mixtures, and methanol–water mixtures.
Icosahedral carboranes. XIX. Preparation of linear trifluoropropyl‐substituted polycarboranylenesiloxanes
Authors: Scott Robert N. , Knollmueller Karl O. , Hooks Haywood , Sieckhaus John F.
Published: April 2003

A series of linear trifluoropropyl‐substituted polycarboranylenesiloxanes with molecular weights between 3,500 and 13,000 has been prepared by the tetramethylguanidine–sulfuric acid‐catalyzed condensation of various silanol‐terminated monomers as well as by simple hydrolytic condensation of m‐B10H10C2(SiMePfOSiMePfCl)2 and B5H5C2‐(SiMePfCl)2 (where Pf = CH2CH2CF3). The polymers containing the C2B5H7 and C2B10H12 carboranes range from hard glasses to viscous gums and rubbers, are more thermally stable than fluorinated silicones with comparable resistance to solvents, and are potentially useful as high‐temperature fuel tank sealants.
Organoaluminum catalyst for polymerization reaction. Synthesis of isotactic polyacetaldehyde by AIR3–alkali metal hydroxide catalysts in situ
Authors: Aoyagi Takanobu , Araki Takeo , Tani Hisaya
Published: April 2003

The catalytic behavior of binary systems derived from AIR3 and alkali metal hydroxide in a molar ratio of 1 to 0.5 in situ for stereospecific polymerization of acetaldehyde was studied for the purpose of preparation of isotactic polyacetal. The polymer obtained can be readily stretched to a film. The polymerization proceeds slowly (in ∼20 hr). The polymer yield and stereospecificity of the polymerization by AlEt3–LiOH (1:0.5) catalyst were not significantly changed by the nature of solvent or dilution as far as studied. AlEt3–NaOH, AlEt3–KOH, AlEt3–CsOH, AliBu3–LiOH and AlMe3–LiOH in molar ratios of 1 to 0.5 behaved similarly. AlMe3–NaOH, AlMe3–KOH and AliBu3–NaOH also gave isotactic polymer of high stereoregularity but in lower yields.
Copolymerization with depropagation. VIII. A general solution for reversible multicomponent polymerization
Authors: Kang B. K. , O'Driscoll K. F. , Howell J. A.
Published: April 2003

A method is described for calculating instantaneous polymer composition for an n‐component system polymerizing under conditions where reversibility of the propagation reaction must be considered. The resulting equations are compared with Monte‐Carlo simulations and were also tested experimentally by using the terpolymerizing system acrylonitrile–methyl methacrylate–α‐methylstyrene over both a wide temperature and concentration range.
Interaction of urea with poly(2‐hydroxyethyl methacrylate) hydrogels
Authors: Ratner Buddy D. , Miller Irving F.
Published: April 2003

The interaction of poly(2‐hydroxyethyl methacrylate) [poly(HEMA)] and other similar hydrogels with dilute urea solution has been studied by a variety of techniques, including swelling experiments, fluorescence quenching, near infrared spectroscopy and fundamental band infrared spectroscopy. The results obtained indicate that the anomalous swelling behavior of poly(HEMA) gels in the presence of such dilute urea solutions is probably not due to the disruption of a secondary hydrophobic bond structure as has been generally believed. Although poly(HEMA) gels do contain sites that can participate in hydrophobic bonding, the evidence gathered indicates that dilute urea solutions have no effect on such bonds. A plausible model that does fit all the data involves the interaction of urea with a secondary structure composed of hydrogen‐bonded hydroxyl groups, stabilized by the exclusion of water molecules from the regions containing the bonds.
Investigation of the mechanism of polymerization of butadiene by π‐allylic nickel complexes
Authors: Bourdauducq P. , Dawans F.
Published: April 2003

Various π‐allylic nickel complexes were synthesized by reacting bis(1,5‐cyclooctadiene)‐nickel with an allylic ester of trifluoroacetic acid. A study of the stereospecific polymerization of 1,3‐butadiene initiated by these catalysts showed the strong influence of the initial substitution in the π‐allylic ligand as well as of the solvent used for synthesis of the catalysts on the course of the reaction, i.e., on both the polymerization rate and the stereospecificity. Moreover, new catalytic species were isolated by adding electron‐accepting or electron‐donating ligands to some of the π‐allylic complexes. In that way, we were able to modify the behavior of the catalysts and, in some cases, to enhance catalytic activity considerably.
Influence of the average content of sulfur in polysulfide polymers on the depolymerization of polysulfide polymers by dithionite ions
Authors: Radosavljević Slobodan D. , Tenc‐Popović Mirjana E. , Rekalić Vladimir J.
Published: April 2003

The results of our studies show that it is possible to depolymerize polysulfide polymers with a nominal sulfur content in excess of 2 per segment of polymer, without previous desulfurization, in order to obtain disulfide polymers. For this purpose it is necessary to take larger amounts of sodium dithionite per segment of polymer, than with a disulfide polymer, to obtain approximately the same of the average molecular weight of the depolymerized product. It is also possible to complete depolymerization with an amount below 2 moles of sodium hydroxide per mole of sodium dithionite, though the upper limit of the ratio of Na2S2O4 to NaOH, at which depolymerization occurs, remains unchanged, i.e., 1:4. During the depolymerization reaction the occurrence of larger or smaller amounts of hydrosulfide, depending on the labile sulfur content, as well as the change of the color of the reaction dispersion, first white, then bright yellow or gray, thereafter white again and, finally, dingy pink, was observed. The reaction, representing in the best way the optimum conditions of depolymerization and the actual relations in the reaction system, is proposed.
Sulfur‐containing polymers. IV. Preparation and properties of poly(sulfenyl thiocarbonates)
Authors: Kobayashi Norio , Fujisawa Tamotsu
Published: April 2003

Poly(sulfenyl thiocarbonates) have been prepared for the first time by the stepwise condensation of chlorocarbonylsulfenyl chloride with diols and dithiols. The polymers were obtained in high yield. Generally they were crystalline solids and were soluble in chlorinated hydrocarbons. On treatment with benzyl mercaptan in the presence of triethylamine, the polymers afforded a diol, carbonyl sulfide, and a disulfide compound. This reaction was extended to the preparation of alternating copolydisulfides.
Polymerization of methyl methacrylate by the binary system of the copper–amine complex type resin and carbon tetrachloride
Authors: Koyama Kiyoshi , Nishimura Masato
Published: April 2003

The polymerization of vinyl monomers initiated by binary initiator systems composed of a copper–amine complex type resin and organic halides has been studied. These binary systems initiated the polymerization of various vinyl monomers. A kinetic study of the polymerization of methyl methacrylate initiated by the copper–amine complex resin–CCl4 system was carried out, and it was found that the polymerization proceeds by way of a radical mechanism. This fact was also supported by the copolymerization of methyl methacrylate with styrene. The overall activation energy of the polymerization of methyl methacrylate was estimated as 8.4 kcal/mole. The activity of the initiator systems was greatly dependent upon the dissociation energy of carbon–halogen bonds in the organic halides. A possible initiation mechanism with the binary systems is proposed and discussed.
γ‐radiolysis of acetylated cotton cellulose: An ESR study
Authors: Chidambareswaran P. K. , Sundaram V. , Singh B. B.
Published: April 2003

The nature and behavior of free radicals induced in acetylated cotton celluloses irradiated with γ‐rays have been studied by electron spin resonance (ESR) spectroscopy. Dehydrogenation and deacetylation appear to be responsible for the free radicals observed from samples irradiated at 77°K. The degree of substitution enhanced the yield of acetyl radicals when the samples were irradiated at 77°K and adversely affected the overall radical concentration when irradiation was done at 300°K. In addition, the ESR spectra of samples irradiated under vacuum at 300°K were more intense than those obtained from samples irradiated in air. The nature, yield, and post‐irradiation behavior of the primary radicals are discussed in the light of the ultimate chemical effects observed.
Radiation‐induced polymerization of glass‐forming systems. III. Effect of melting point and glass transition temperature on the formation of the glassy phase
Authors: Kaetsu Isao , Okubo Hiroshi , Ito Akihiko , Hayashi Koichiro
Published: April 2003

The general empirical rules about glass formation of organic compounds including monomers were studied. It was found that the difference of Tm (melting point) and Tg (glass transition temperature) was the most important factor in glass formation, that is, the glass‐forming property of organic systems, mono‐ or multicomponent, could be expressed as a function of Tm and Tm – Tg at the cooling temperature −196°C. The glassforming property was further divided into four classes according to the relation between Tm and Tm – Tg, and each class was related to several patterns in DTA curves. From these results it was clarified that the phases are completely or partially glassified depending on the different values of Tm – Tg in eutectic and noneutectic compositions. The overall phase diagrams covering the whole composition with the variation of Tm and Tg were determined, and they also supported the relationship between Tm – Tg and the glass‐forming property. The distinct glass‐forming property of binary systems with large molecular interaction was attributed to the great lowering of Tm and elevation of Tg in those systems. The effect of the number of components on glass formation was also studied; it was shown that if Tm, Tg, and ΔH (sum of heat of melting and of mixing) are given, the number of components necessary to glassification can be estimated.
Radical reactions initiated by chelate complexes of transition metals. X. Catalytic decomposition of α,α′‐azobisisobutyronitrile
Authors: Horanská V. , Bartoň J. , Maňásek Z.
Published: April 2003

The decomposition of αα′‐azobisisobutyronitrile (AIBN) in the presence of bis(‐)‐ephedrine copper (II) chelate was studied in 1,3,5‐trimethylbenzene. It was found that the chelate accelerated the decomposition of AIBN and at the same time interacted with the free radicals arising in the course of this process. The decomposition of AIBN as well as the decay of paramagnetic Cu+2 particles is a reaction of order 0.3 with respect to the chelate and of order 1.3 and 1.1 with respect to AIBN, respectively. The activation energy of the AIBN decomposition in the presence of chelate is 13–22 kcal/mole for the molar ratio [AIBN]0/[Chelate]0 ranging from 1 to 100. On the basis of the kinetic results and analysis of reaction products the mechanism of the interaction of chelate with AIBN is discussed.
Polymerization of pyromellitic dianhydride with 3,3′‐diaminobenzidine in aprotic solvents I. Reaction variables
Authors: Johnston Norman J.
Published: April 2003

The solution polymerization of pyromellitic dianhydride with 3,3′‐diaminobenzidine to form poly(amide acid amine) was investigated under a variety of reaction conditions. Polymer viscosity and gel formation were highly affected by changes in the order of monomer addition, the type of process (powder or solution), monomer concentration, monomer stoichiometry, and type of solvent. Minor effects were noted with changes in polymerization temperature and the presence of small amounts of water. A limiting intrinsic viscosity of 1.2–1.5 dl/g was observed, regardless of polymerization conditions. The polymerization had a strong tendency to gel at high concentrations and when monomer molar ratios approached 1:1. The conditions which retarded or promoted the formation of macrogel were well‐defined, and macrogel but not microgel could be prevented. The polymerization was conducted successfully only in aprotic solvents. No imidazopyrrol‐one units were detected in polymer made in polyphosphoric acid at elevated temperatures.
Polymérisation anionique de l'isoprène: Nature de la paire d'ions et stéréospécificité
Authors: Essel Alain , Pham Quang Tho
Published: April 2003

With accumulated HR‐NMR spectra of anionic polyisoprenes, it has been possible to study the influence of the nature of the propagating species on the microstructure of the obtained polymers If free ions are responsible for the propagation, the microstructure (1,4‐: 25%, 1,2‐: 33%, 3,4‐: 42%) does not depend on the nature of the cations. But with contact ion pairs, the different addition modes are governed by the size of the alkali metal counterions. Mechanisms of anionic propagations via diene–cation coordination are proposed.
Effect of low molecular weight compounds on the relaxation behavior of poly(2‐hydroxyethyl methacrylate) in the glassy state and in the transition region from the glassy to the rubberlike state
Authors: Kolařík Jan , Janáček Josef
Published: April 2003

The method of free torsional vibrations was used to determine the temperature dependence of the storage and loss shear modulus of poly(2‐hydroxyethyl methacrylate) samples swollen with ethylene glycol, formamide, n‐propanol, and water. The measurements included the glassy region (starting with temperatures from −130 to −190°C) and the main (α) transition from the glassy to the rubberlike state. At a volume fraction of the low molecular weight compound vd > 0.2, the above systems exhibit, besides the α dispersion, only the secondary (βSW) dispersion, which is generally attributed to the relaxation motions of the hydroxyethyl groups of the side chains interacting with molecules of the diluent. If no separation of the diluent in a second phase occurs at the measurement temperatures, the temperatures of both dispersions decrease with increasing vd and approach the glass transition temperature of the low molecular weight compound. The concentration dependences of the dispersion temperatures were described by an equation derived elsewhere for the concentration dependence of the glass transition temperature. The results indicate that molecules of the diluent contribute significantly to the intensity of the βSW transition and simultaneously affect its limiting temperatures (for vd = 1 and vd = 0). Specific differences among the systems described above appear only at those temperatures where same of the low molecular weight compound separates into a crystalline or glassy phase.
Creep and other tensile properties of rubber cross‐linked by dicumyl peroxide
Authors: Wood Lawrence A. , Bullman George W.
Published: April 2003

Natural rubber crosslinked by dicumyl peroxide in amounts up to 25 parts per hundred of rubber (phr) showed a maximum in tensile strength near 1 phr, followed by a steep decrease to a minimum near 5 phr. The ultimate elongation decreased from 870% at 0.5 phr. to about 10% above 10 phr. The modulus increased linearly with increase of crosslinking. The creep rate decreased from 5.6% per decade at 0.5 phr to zero at 5 phr and higher values. Crystallization, with a resultant abrupt increase in creep, was noted in specimens held in the stretched condition for more than one day. Between 5 and 25 phr this system (when crystallization is avoided) appears to function as an ideal elastic network and can be recommended for studies of rubber elasticity since no variation of modulus with time is observed.
Photoelastic studies of polymers and copolymers in the rubbery state
Authors: Morgan R. J. , Treloar L. R. G.
Published: April 2003

Photoelastic investigations have been carried out on a number of polymers in the crosslinked rubbery state. These include cis‐polyisoprene, two polybutadienes of different structural configurations, an ethylene‐propylene terpolymer, and a range of styrene—butadiene copolymers. From the measured values of stress‐optical coefficients, together with calculated values of the optical anisotropies of the monomer units in the chain (based on Denbigh's values of bond polarizabilities), estimates are made of the number of monomer units in the equivalent random link (of the Kuhn‐Grün theory) for the polymeric chains considered. Further, from a study of the temperature dependence of the stress‐optical coefficient, the temperature dependence of the lenght of the equivalent random link, and hence of the statistical length of the chain, is derived. The interpretation of the temperature dependence data is discussed in a semiquantitative manner in terms of internal energy differences between different rotational states.
Crystallization of branched polymers. I. Ethylene–vinyl acetate and ethylene–acrylic acid copolymers
Authors: Kortleve G. , Tuijnman C. A. F. , Vonk C. G.
Published: April 2003

The following quantities were measured on a number of ethylene–vinyl acetate (EVA) and ethylene–acrylic acid (EAA) copolymers: (1) the small‐angle x‐ray scattering invariant, (2) the overall density, and (3) the crystallinity. Assuming a two‐phase structure, the separate values of the densities of the crystalline and amorphous regions can be calculated from these data. Of these, the crystalline density is compared with the value obtained from the lattice constants. A systematic difference is observed which is ascribed to the presence of comonomeric side groups in the crystalline regions. For the EVA and EAA samples, their concentration is at least 0.3 and 0.5 times the overall concentration, respectively. The amorphous densities are found to be higher than the values calculated from completely amorphous copolymers by extrapolation procedures.
Calorimetric investigation of poly(methacrylic acid) and poly(acrylic acid) in aqueous solution
Authors: Crescenzi V. , Quadrifoglio F. , Delben F.
Published: April 2003

The enthalpy of dissociation of poly(acrylic acid) and of poly(methacrylic acid) in water and in 0.5N NaCl at 25°C has been measured over a wide range of degrees of neutralization of the polyelectrolytes. In the case of poly(methacrylic acid) the calorimetric data permit the direct evaluation of the enthalpy of conformational transition of the polymer. For this transition, with the aid of standard free energy data derived from potentiometric titrations, the change in entropy was also estimated. The relative accuracy of the thermodynamic data, and the possibility of deriving therefrom information on the mechanism of transitions of the type, globular coils → expanded coils for partially hydrophobic synthetic polyelectrolytes in aqueous solution are discussed.
Characterization of the structure and organization of β‐form crystals in type III and type IV isotactic polypropylene spherulites
Authors: Samuels Robert J. , Yee Rena Yang
Published: April 2003

Anisotropic growth of β‐form crystals of isotactic polypropylene in type III and type IV spherulites has made possible microanalysis of the unit cell structure, optical properties, and crystal arrangement within the spherulites. Micro x‐ray studies of the type III and type IV spherulites show that interspherulitic β‐form crystals have a hexagonal unit cell with dimensions; a = 19.08 Å and c = 6.49 Å. The intrinsic refractive indices of these β‐form crystals are 1.506 along the a axis and 1.536 along the c axis. The organization of the crystals within the spherulites and the optical properties of the spherulites are also quantitatively evaluated. Both the type III and type IV spherulites have the a axis of the crystal radial while the crystals rotate randomly around the type III spherulite radii and periodically around the type IV spherulite radii. The radial refractive index for both the type III and type IV spherulites has the same value of 1.496. The tangential refractive index of the type III spherulite has a constant value of 1.509; it varies periodically between a minimum of 1.496 and a maximum of 1.519 in the type IV spherulite. Microtechniques such as micro x‐ray diffraction, interference microscopy, birefringence, and optical microscopy were required for acquisition of the data.
Polytetrafluoroethylene: Effects of γ‐radiation on fine structure
Authors: Pinkerton D. M. , Thompson K. R. L.
Published: April 2003

The structure of granular polytetrafluoroethylene has been studied by electron microscopy. On the basis of the texture of surfaces resulting from fracture a model of the structure is proposed which suggests that PTFE consists of extended chain crystals with both inter‐ and intra‐lamellar noncrystalline regions. The effects of γ‐radiation on the structure have been investigated by examining the texture of irradiated fracture surfaces and also the texture produced by post‐irradiation fracture. The irradiations have been performed in vacuo and in oxygen. In both atmospheres PTFE undergoes degradation with a concurrent increase in crystallinity. However, the texture of the surfaces of high crystallinity PTFE, prepared by radiation, differs markedly to the texture of fracture surfaces of high crystallinity PTFE prepared by thermal annealing. It is proposed that radiation causes rupture of bonds in the interlamellar (chain fold) and intralamellar regions, resulting in the production of chain ends and interlamellar links. Due to scavenging of the free radicals, interlamellar linking is pobably a minor process with irradiation in oxygen. These chemical changes cause modifications to the extended chain lamellar crystals and consequently alterations to the physical properties of the polymer.
Confined‐growth crystallization of polyethylene
Authors: Mencik Z. , Plummer H. K. , Van Oene H.
Published: April 2003

A new typical orientation pattern of polyethylene has been observed in extruded, melt‐drawn composites containing 10% polyethylene and 90% polystyrene. In these composites, the polyethylene phase is dispersed in the polystyrene matrix as thin, long ribbons (width 1000 Å, thickness 500 Å). The b axis of the crystallites is found oriented preferentially along the long dimension of the ribbons, i.e., in the extrusion direction. The a and c axes of the crystallites show no preferred orientation. This texture pattern is attributed to the fact that, in view of the small cross section of the polyethylene phase, crystallization can proceed only along the long axis of the ribbons. Since the b axis is the direction of fastest growth in polyethylene (and the radial direction in a spherulite), most polyethylene unit cells are oriented with their b axes in the long dimension of the ribbons.
Size distribution analysis of polymer latex systems by use of the extrema in the angular light scattering pattern. III. Unpolarized and horizontally polarized scattered light
Authors: Wallace Thomas P. , Scott Wayne B.
Published: April 2003

The extrema in the unpolarized and the horizontally polarized angular scattering patterns are used as a basis for size‐distribution analysis of polymer latex systems composed of single, spherical, optically isotropic particles. The method of analysis is similar to that recently proposed for vertically polarized scattered light and the polarization ratio, where the modal diameter and a distribution width parameter are determined from the experimental angular scattering pattern and prepared theoretical diagrams obtained by Mie theory calculations. The method of analysis, based on all four scattering functions, is illustrated by use of a Dow polystyrene latex sample.
Fracture of tendon collagen
Authors: Yannas I. V. , Huang C.
Published: April 2003

A study of rat‐tail tendon fibers, about 200 μ in diameter, by scanning electron microscopy of fractured specimens reveals that these crimped fibers are largely made up of cylindrical units, about 10 μ in diameter. These, in turn, are made up of the well‐known collagen fibrils, ca. 0.1 μ in diameter, which have been observed previously by transmission electron microscopy and small‐angle x‐ray diffraction. Both the 10‐μ and 0.1‐μ cylindrical units were found to be arranged parallel to the macroscopic fiber axis rather than helically about it, as has been often proposed in the past. Significant improvement in resolution of the fracture surfaces was obtained by dehydration of the tendon. Microscopy of undehydrated tendon fibers undergoing solubilization by dilute aqueous acetic acid confirmed the results obtained by fractography.
Theoretical study of a conjugated reaction‐center model of anionic acetylene polymerization
Authors: Kříaž J.
Published: April 2003

The energy of the ground state, charge distribution, and bond orders were calculated by a MO method in the SCF‐CNDO/2 approximation for various configurations of the monomer, dimer, and trimer model of both the associated and dissociated reaction center of an anionic acetylene polymerization. According to the results of these calculations, cooperation of π and σ bonds leads to a charge delocalization which increases with growing chain length and is the reason for kinetic deactivation of the center. Propagation is stopped, probably by a cooperative effect of the kinetic and thermodynamic factors.
Kinetics of thermal decomposition of polymers. II
Authors: Atkinson J. , Maccallum J. R.
Published: April 2003

The rate equations for the thermal decomposition of a polymer by a random scission reaction followed by rapid depolymerization of a constant number of monomer units from both fragments together with rapid evaporation of low molecular weight species are solved by using a different approach from that used by previous workers. The results obtained are more specific and differ slightly from previous treatments.
Novel diffraction effects in the combined wide‐angle and low‐angle X‐ray diffraction patterns of solution‐grown nylon crystals
Authors: Dreyfuss P. , Keller A. , Willmouth F. M.
Published: April 2003

It was shown previously that in sedimented mats of solution‐grown nylon crystals the 001 wide‐angle reflection due to the unit‐cell period along the chain and the low‐angle reflection due to the lamellar periodicity are both along the same azimuth (meridian) in the x‐ray diffraction pattern.1 Presently in photographs which contain both the wide‐angle and low‐angle regions a series of new meridional reflections have been observed between the low‐angle and 001 reflections and between 001 and 002 reflections. This finding implies that, with the large chemical repeat distances in question, diffraction effects at low and wide angles cannot be considered in isolation as is usual in most polymer crystal studies. In particular, the new reflections promise to provide a direct diffraction approach to the structure of the chain‐folded lamellae.
Structure analysis of chain‐folded lamellar polyamide crystals from X‐ray diffraction
Authors: Atkins E. D. T. , Keller A. , Sadler D. M.
Published: April 2003

Folded‐chain crystals of certain polyamides present some novel diffraction effects due to the small number of repeat units within the lamellar thickness. X‐ray diffraction evidence is available in the complete range from low to wide angles. This information is interpreted in terms of the structure factor of an individual lamella together with the lattice factor appropriate for the stacking of lamellae. When due account is taken of the lattice factor, whose effect can be detected even at large angles, three features of the lamellar structure can be deduced. First, the evidence is in favor of the straight‐chain stems traversing almost the total thickness of each lamella, implying sharp folds at the lamellar surfaces. Some consequences of this result on the interpretation of data obtained from annealed mats are mentioned. Second, the detailed determination of the stem structure demands that the majority of the folds in nylon 66 lie in the acid group. Third, there are regions of depleted electron density at the lamellar surfaces, though features of the crystal structure are still retained. This indicates the presence of some folds deeper in the crystal than the majority.
Adsorption of polymers at the solution‐solid interface. VI. Polyacids on nylon powder
Authors: Cole D. , Howard G. J.
Published: April 2003

The adsorption of some polyacids, principally poly(acrylic acid), on nylon powder has been studied. In aqueous solutions at low pH the adsorption behavior of poly(acrylic acid) is controlled by adsorbate coil dimensions rather than by electrostatic effects. Less adsorption takes place from methanol solutions but the process is much more rapid than from water. Above a critical value, increase of adsorbate molecular weight leads to a reduced adsorption, the effect being particularly evidenced by aqueous solutions. Model compounds (propionic and glutaric acids) are rapidly adsorbed from both methanol and water, but give low specific absorptions. Adsorption of poly(acrylic acids) and model compounds, is reduced, but not eliminated, by modification of the nylon adsorbent through acetylation or methoxymethylation. The adsorption of poly(acrylic acid) on nylon is not readily reversible; however, partial neutralization will release preadsorbed poly(acrylic acid) from nylon powder. The adsorption behavior of copolymers of acrylic acid with N‐vinylpyrrolidone is reported, as are brief studies on some other homopolyacids. The results are generally interpreted on the basis of sorption of the macromolecules into a swollen, flexible adsorbent.
Anisotropy of mechanical and dielectric relaxation in oriented poly(ethylene terephthalate)
Authors: Davies G. R. , Ward I. M.
Published: April 2003

The anisotropy of the α and β relaxations in oriented poly(ethylene terephthalate) has been studied by dynamic mechanical and dielectric relaxation measurements. The α relaxation shows considerable mechanical anisotropy but gives rise to an isotropic dielectric process. The β relaxation, on the other hand, shows pronounced dielectric anisotropy but very little mechanical anisotropy. The implication of these results with regard to possible interpretations of the relaxations are discussed.
Crystallization kinetics of isotactic polystyrene from isotactic‐atactic polystyrene blends
Authors: Yeh G. S. Y. , Lambert S. L.
Published: April 2003

In an attempt to facilitate a better understanding of the role of noncrystallizable components on the crystallization kinetics, spherulitic growth rates as well as the morphology and melting behavior of isotactic polystyrene in blends with various molecular weight atactic polystyrenes (900 to 1,800,000) over a wide range of concentrations have been studied. The growth rates are uniformly depressed with increasing amounts of atactic diluent. In addition, they are dependent on the molecular weight of the added polystyrene, generally decreasing in the molecular weight ranges between 4800 and 19,800 and between 51,000 and 1,800,000. However, between these two ranges, anomalous growth rates showing a sudden increase are observed, which may be explained by an increase in the entrapment of the noncrystallizable diluent. An explanation based on morphological observations, which showed an increase in coarseness of the spherulites with increasing molecular weight of the added atactic polystyrene, is offered.
Plastic deformation of polypropylene. IV. Wide‐angle x‐ray scattering in the neck region
Authors: Morosoff N. , Peterlin A.
Published: April 2003

Wide‐angle x‐ray scattering (WAXS) patterns of two polypropylene samples, a quenched sample drawn at 21°C and an annealed sample drawn at 100°C, were investigated in a range of values of draw ratio λ very closely spaced through the neck region. In both cases, a range of small λ where deformation occurred by spherulite deformation was followed by one of higher λ where microfibrils were formed. The contribution to the WAXS pattern of microfibrils could be clearly distinguished from that of deformed spherulites because of the better orientation parallel to the draw direction of the former as compared to the latter. Additionally, for a drawing temperature of 21°C, microfibrils crystallize in the “smectic” phase as compared to the monoclinic phase for the initial sample and deformed spherulites. At this temperature, plastic deformation proceeds through the spherulite deformation mechanism up to λ = 1.4 accompanied by an increase in chain orientation with increasing λ. For λ > 1.4 plastic deformation appears to occur exclusively through microfibril formation. For drawing at 100°C, spherulite deformation is accompanied by very little change in chain orientation up to λ = 2, where microfibril formation begins. For λ > 2 (Td = 100°C) plastic deformation is accompanied by both microfibril formation and some spherulite deformation as reflected by changes in both orientation and crystallite size. At this temperature the lateral crystallite size in the microfibrils is related to the long period according to the “equilibrium crystallite shape” previously found for annealed polypropylene.
Effect of orientation, anisotropy, and water on the relaxation behavior of nylon 6 from 4.2 to 300°K
Authors: Papir Yoram S. , Kapur Sudhir , Rogers Charles E. , Baer Eric
Published: April 2003

The relaxation behavior of nylon 6 from 4.2 to 300°K was investigated as a function of orientation, anisotropy and moisture content by using an inverted free‐oscillating torsion pendulum. Three new relaxations, δ at 53°K, ϵ below 4.2°K, and ζ at 20°K, were discovered. The characteristics of these new relaxations strongly depend on the orientation anisotropy, and concentration of adsorbed water in the specimens. The results suggest that the mechanism of the γ process is associated with the motions of both the polar and methylene units. The mechanism of the β relaxation is postulated to originate with motions of both non‐hydrogen‐bonded polar groups and polymer—water complex units. The behavior of the α peak is consistent with the hypothesis that it originates with the rupture of interchain hydrogen bonding due to the motions of long‐chain segments in the amorphous regions. Finally, the data strongly support the proposition that two types of water, tightly bound and loosely bound, exist in nylon 6.
Time‐dependent elongational viscosity of a solution of elastic dumbbells
Authors: Nicodemo L. , Marrucci G. , Hermans J. J.
Published: April 2003

The elongational viscosity of dilute polymer solutions must always be measured under nonsteady‐state conditions. To predict the time dependence of this viscosity for a polymer solution in which a constant stretching rate is maintained, a simple model is considered in which the polymer molecules are represented by elastic dumbbells. The non‐Hookean elastic force in the dumbbell is determined by the conformational entropy of the chain. Use is made of Peterlin's approximation which replaces the elastic force by a function of the root‐mean‐square end‐to‐end distance. Application to the transient state is straightforward; it can be extended to include the effect of “internal” chain viscosity by means of approximations that are similar to Peterlin's.
Determination of crystallinity in polyester fibers by x‐ray methods
Authors: Włochowicz Andrzej , Jeziorny Andrzej
Published: April 2003

The methods of Hermans and Weidinger and of Wakelin et al. (the correlation and integral methods) were used to determine the degree of crystallinity in poly(ethylene terephthalate) (PET) fibers. A standarization of cutting of the amorphous background scattering in PET fibers, indispensable for the method of Hermans and Weidinger, is put forward. On using a partial standardization of the intensity diffracted and scattered in the fiber, namely, on taking into account the x‐ray density of the specimen, variability in the intensity due to differences in absorption in the specimen at different angles 2θ and variability in the specimen mass reflecting x‐rays in the function of the diffraction angle, good agreement of the PET fiber crystallinity values is observed.
Rheo‐optical studies of polyurethane block polymers
Authors: Seymour R. W. , Estes G. M. , Huh D. S. , Cooper S. L.
Published: April 2003

Stress and birefringence relaxation have been measured for two polyurethane block polymers at several temperatures to 140°C. Superposition of the stress curves is possible, but the existence of multiple relaxation mechanisms makes such a process of questionable validity. Simple superposition of the birefringence relaxation was not possible. The time and temperature dependence of the stress‐optical coefficient implies different mechanisms for mechanical and optical relaxation process. Analysis of the birefringence data requires consideration of nonorientational sources of birefringence.
Anisotropy of the dielectric relaxation of a crystalline polymer
Authors: Phillips P. J. , Kleinheins G. , Stein R. S.
Published: April 2003

A theory which relates the change in the strength of absorption to the change in crystal orientation function is presented for the anisotropy of dielectric relaxation for the dipolar orientation change in an oriented crystalline polymer. Experimental measurements are presented for the α dielectric absorption of a stretched ethylene–carbon monoxide copolymer and compared with the orientation of crystals of this copolymer as determined by x‐ray diffraction.
Thermomechanical behavior of rubberlike materials
Authors: Peng T. J. , Landel R. F.
Published: April 2003

A simple form of nonisothermal free energy function A(λ1, λ2, λ3, T) for rubberlike materials results from postulating that the entropy is a separable symmetric function of the extension ratios λi along the principal strain directions and considering the fundamental properties of rubberlike materials, i.e., that rubber elasticity is associated primarily with changes in entropy and the variation of elastic tension with changes in temperature is linear. The explicit representation of A is reduced to the Valanis‐Landel strain energy function for isothermal cases.
Nitric acid oxidation of irradiated polyethylene
Authors: Bodily David M.
Published: April 2003

Samples of high‐density polyethylene were irradiated with x‐rays and oxidized with concentrated nitric acid to determine the location of unsaturated groups. Vinyl groups initially present in the polymer were rapidly oxidized to the extent of 85% and are assumed to be excluded from the crystals. Vinylene groups show a rapid oxidation followed by slow oxidation. The initial oxidation is about 35%, which is slightly greater than the 25% amorphous content of the polymer prior to irradiation. Diene groups are rapidly oxidized by nitric acid but are formed at about the same rate in crystalline and amorphous samples. This is interpreted to indicate that diene groups are formed throughout the polymer but form large defects in crystalline regions and are accessible to oxidation. Defects formed in crystalline regions during irradiation lower the melting point to a greater extent than predicted by the mole fraction of noncrystallizable units.
X‐ray study on the effect of moisture on the crystalline state of cellulose
Authors: Seitsonen Sulo , Mikkonen Ilkka
Published: April 2003

A method is presented for measuring the change of the intensity of x‐ray diffraction peaks of cellulose specimens as a consequence of humidity changes of the specimens. Measurements performed showed a decrease of this intensity after drying pulp specimens initially kept in humid air. Thus the order in cellulose decreased during drying.
Domain structure of amorphous block copolymers cast from solution
Authors: Soen Toshiichi , Inoue Takashi , Miyoshi Katsunori , Kawai Hiromichi
Published: April 2003

Three types of domain structures, namely spherical, rodlike, and lamellar, of A‐B and A‐B‐A (or B‐A‐B) block copolymers cast from solutions are discussed on the basis of a criterion that the structures originate at a critical micelle concentration as a result of microphase separation of the block segments and the micelles formed maintain their structures into the solid state without reorganization. It is concluded that the micelles shrink mostly in the direction perpendicular to the interface between the two phases within the micelles because of the appreciable orientation of the block segments in this direction. In other words, the spherical micelle shrinks isotropically to form a spherical domain having a diameter proportional to the 2/3 power of the degree of polymerization (molecular weight) of the corresponding block segment. Rodlike and lamellar micelles, on the other hand, shrink anisotropically to form rodlike and lamellar domains such that the diameter and the thickness of the respective domains are roughly proportional to the 1/2 power of the degree of polymerization of the corresponding block segment.
Polymerization of vinyl monomer with carbon disulfide–alkali metal complex
Authors: Yamaguchi Koichi , Minoura Yuji
Published: April 2003

The reaction of carbon disulfide with one or two equivalents of alkali metal (potassium‐ or sodium) was carried out, and the deep red reaction mixture obtained only in diethylene glycol dimethyl ether. The polymerization of vinyl monomers with this reaction mixture was studied. The reaction mixtures of mono‐ and dialkali metal with carbon disulfide induced the polymerization of N‐phenylmaleimide, methyl vinyl ketone, and acrylonitrile but did not induce the polymerization of methyl methacrylate and styrene. In the polymerization of acrylonitrile with this reaction mixture of carbon disulfide with monoalkali metal, the polymerization rate was found to be proportional to the initiator concentration and to the square of the monomer concentration. The activation energy was −1.1 kcal/mole. Similar results were obtained in the case of carbon disulfide with dialkali metal. The polymer yield increased with increasing solvating power of solvents, i.e., diethylene glycol dimethyl ether, dimethyl sulfoxide, hexamethylphosphoramide, dimethylformamide, tetrahydrofuran. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of AN units.
High‐temperature aging of fluoropolymers
Authors: Brown Daniel W. , Wall Leo A.
Published: April 2003

Fluoropolymers including those of 3,3,3‐trifluoropropene, 2,3,3,3‐tetrafluoropropene, 3,3,4,4,5,5,5‐heptafluoropentene‐1, and their copolymers with tetrafluoroethylene, were aged in air and in its absence at 225 and 305°C. Intrinsic viscosities were measured before and after aging. Polymers of high tetrafluoroethylene content are most stable. In air the presence of tertiary hydrogens is associated with lowered stability but the presence of tetrafluoroethylene greatly mitigates this effect. Stress‐relaxation studies in air of a vulcanizate of 3,3,3‐trifluoropropene and tetrafluoroethylene cured by γ‐rays indicate that the vulcanizate degrades much more rapidly than the untreated polymer.
Alternating copolymers of styrene with tricyanoethylene and ethyl 2,3‐dicyanoacrylate
Authors: Noren G. K. , Hall H. K.
Published: April 2003

Ethyl 2,3‐dicyanoacrylate was prepared from ethyl 2,3‐dicyanopropionate. High molecular weight, 1:1 alternating copolymers of styrene with tricyanoethylene and ethyl 2,3‐dicyanoacrylate were prepared by bulk polymerization with the use of free‐radical initiators. Solution polymerization of styrene with ethyl 2,3‐dicyanoacrylate in acetonitrile gave the highest molecular weight copolymer (ηinh = 0.74). The copolymers showed unusual thermal properties, i.e., an initial break that was 50–75°C lower than that of polystyrene followed by the formation of an intermediate product that was fairly stable to approximately 500°C.
Photoinduced ionic polymerization. III. Cationic polymerization and copolymerization of cyclohexene oxide and α‐methylstyrene in the presence of pyromellitic dianhydride
Authors: Irie Masahiro , Tomimoto Setsuko , Hayashi Koichiro
Published: April 2003

The photoinduced ionic polymerization of cyclohexene oxide was studied in the presence of pyromellitic dianhydride. The polymerization is initiated by the excited chargetransfer complex between cyclohexene oxide and the electron‐acceptor and proceeds by a cationic mechanism. Photoinduced cationic polymerization of α‐methylstyrene was also observed in the presence of pyromellitic dianhydride. The initiation mechanism of the polymerization was elucidated by means of electron spin resonance measurements. The concentration of pyromellitic dianhydride anion‐radicals measured in this way was found to be proportional to the rate of polymerization. This result shows clearly that the photopolymerization is initiated by cation‐radicals formed from photoexcited donoracceptor complexes. The attempted photocopolymerization of cyclohexene oxide and α‐methylstyrene gave a mixture of homopolymers. The composition of the product depends on the wavelength of the light used.
Photosensitivity of polyvinylesters of substituted cinnamylideneacetic acids
Authors: Tanaka Hideaki , Sato Yoshimi
Published: April 2003

Several polyvinylesters of substituted cinnamylideneacetic acids were synthesized and their photosensitivities were investigated. It was found that polyvinylesters of planar acids reacted photochemically effectively and were spectrally sensitized by usual triplet sensitizer. On the other hand, polyvinylesters of twisted acids exhibited poor photosensitive properties. Poly(vinyl α‐cyanocinnamylideneacetate) (PV‐V) was found to be an excellent photosensitive polymer with respect to both photosensitivity and thermal stability (or storage stability).