bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical properties of some solutions with charge‐transfer interaction
Authors: Wisdom N. E. , Forster E. O.
Published: June 2010

Liquid binary mixtures of pyridine‐benzonitrile, pyridine‐trinitrotoluene, and mesitylene‐benzonitrile are expected to exhibit charge‐transfer interaction between the two components. These pairs of compounds have also been found to exhibit maxima in electrical conductance in mixtures as compared with either pure component. Conductance enhancement of as much as 100‐fold has been observed. A very great conductance enhancement was observed in the mixture pyridine‐iodine which has its maximum at the saturation limit of iodine in the solution. The conductance of these solutions has previously been ascribed to ionization. Conductance properties now measured under direct current make this description appear inadequate. Iodine solutions in pyridine have been found to conduct current at low d.c. voltages with no apparent polarization and to sustain the passage of high d.c. currents for long times without change after an initial decline. These results, coupled with those of other earlier workers, indicate that both electronic and ionic conductivity at comparable levels can occur in these solutions. Application of polarizing direct current was found to produce peculiar changes in the capacitative properties of the electrode interface in pyridine‐iodine solutions. The capacity in a parallel‐plate conductance cell was increased by application of a sufficiently great d.c. voltage. The amount of increase depends upon the duration of the voltage application and could be reversed by a reverse voltage.
Low resistivity polyacenequinones
Authors: Mason J. W. , Pohl H. A. , Hartman R. D.
Published: June 2010

A group of polyacenequinone radical polymers prepared from a homologous series of heterocyclic acenes and two aromatic anhydrides including mellitic trianhydride were studied in an attempt to produce materials with enhanced conduction. The specific resistivities, thermal activation energies, and energy intervals of these materials are reported. It has been shown that the conductivity of these polymers can be enhanced by about three orders of magnitude by the substitution of heterocyclic acenes.
The meaning of crystallinity when judged by x‐rays
Authors: Statton W. O.
Published: June 2010

This discussion of the variability of polymer x‐ray diffraction patterns tries to show that there is no simple definition of crystallinity when judged by x‐ray diffraction, and that x‐ray crystallinity may differ sharply from judgments of order by other techniques. It is recommended that a clear distinction be made between a measurement obtained from a diffraction pattern and the model which is used to interpret that measurement. Many precise and valuable measurements can be made of the varying aspects of the pattern. These measurements are perfectly valid and, if done in a consistent and verifiable manner, allow one to compare and relate samples having different treatment histories or different physical properties. These relationships are useful and meaningful as such. Difficulties arise from the interpretation of these measurements. The interpretation involves an unfortunate combination of semantics, morphology, and mental models. It is shown that there is no unequivocable interpretation that completely satisfies everyone in this fast‐changing area of study. The cause of this dissatisfaction stems from the simple fact that we do not really know the exact arrangement of the polymer chain from one of its ends to the other. Thus, all models and all interpretations have no meaning beyond being useful concepts. Difficulty comes when we make the mistake of assuming that our models are true pictures of the solid state of polymers. It is hoped that, in time, enough detailed measurements will be obtained so that generalities can be drawn and so that some of the dilemmas of interpretation can be resolved.
Aromatic Poly‐1,3,4‐Oxadiazole Fibers
Authors: Frazer A. H. , Reed T. A.
Published: June 2010

This work has demonstrated the preparation of aromatic poly‐1,3,4‐oxadiazole fibers with a high level of physical properties by the cyclodehydration of undrawn high molecular weight copolyhydrazide fibers and subsequent drawing of the converted fiber to high orientation. The fibers have a high level of thermal stability, good property retention at high temperature testing, and excellent resistance to hydrolytic degradation.
Anisotropic inorganic glass fibers
Authors: Kroenke William J.
Published: June 2010

The synthesis of inorganic glass fibers with oriented structures analogous to those obtained in orientable organic fibers is discussed. Emphasis is placed on the orientation of molecular structure in vitreous silicate fibers. A comprehensive review of the pertinent literature is given. A new research study to prepare anisotropic glass fibers is described. Anisotropic glass fibers of spodumene, LiAlSi2O6, were prepared. However, the anisotropy did not result from the orientation of molecular structure. It is concluded that orientation of molecular structure in vitreous inorganic fibers has not been demonstrated. Anisotropic inorganic glass fibers apparently result from the orientation of crystalline material or some other phase in an amorphous matrix. Several possibilities are given to explain the failure of many investigators to orient molecular structure. Property‐composition relationships of glasses and glass fibers from a simple binary join of a quaternary silicate system are reported. The results of this physicochemical study further supports the importance of phase equilibrium relationships in understanding the structure and properties of glasses and glass fibers. For example, the molar volume‐composition curves exhibited breaks at compositions corresponding to the phase boundary. This suggests a possible dependence of the glass structure on the structure of the primary crystalline phase.
Uniaxial stretching and anisotropy
Authors: Müller F. H.
Published: June 2010

According to a classic process of Sénarmont, the values of heat conductivity in the parallel and the horizontal stretch directions may be determined if the absolute value for the isotropic condition is known. Changes of stretch speed and stretch temperature in the range above the freezing temperature determine essentially the anisotropy attained. By careful deductions a deformation mechanism of the network is deduced. The relationships which were found here and in connection with other anisotropic properties permit a statement concerning the anisotropy of segments.
Gel permeation chromatography: A study of several factors affecting chromatogram interpretation
Authors: Hazell J. E. , Prince L. A. , Stapelfeldt H. E.
Published: June 2010

Various gel permeation chromatography (GPC) factors affecting chromatogram interpretation have been studied. These include the variation of refractive index with polymer concentration and molecule size, the concentration effect, calibration curve selection, and column deterioration. Several assumptions inherent in GPC interpretation were found to be valid with reasonable limitations. The area under the GPC trace was found to be directly proportional to the weight of dissolved polymer, and the advantages of a method of calculating molecular weight averages by means of area rather than the conventional count height technique have been demonstrated. A synthetic broad distribution standard, composed of a wide molecular‐size range of narrow‐distribution standards, has been proposed for the diagnosis of the condition of GPC column systems.
Gel permeation chromatographic studies of polynuclear aromatic hydrocarbon materials
Authors: Edstrom T. , Petro B. A.
Published: June 2010

Information on the molecular size or weight distribution of pyrogenous raw materials that are complex mixtures of aromatic hydrocarbons has been difficult to obtain. The relatively new technique of gel permeation chromatography (GPC), augmented by the excellent apparatus made available by Waters Associates, offers the opportunity to measure routinely such distribution curves. For years we studied the composition, properties, and thermal reaction mechanisms of complex polynuclear aromatic mixtures such as coal tars, pitches, and heavy petroleum residues. A great deal of work has also been done on pure compounds, with the result that we have accumulated a large number of high‐purity reference aromatic and heterocyclic compounds. We recently determined the elution behavior of more than a hundred polycyclic compounds and also fractionated a variety of thermally produced aromatic residues, using a Model 200 Waters Gel Permeation Chromatograph. Our results with model compounds in tetrahydrofuran solutions indicate that GPC separations occur, not as a function of a single parameter, but as a complex function of molecular size, shape, and polarity. The simplicity of operation and reproducibility of the GPC method will make it extremely useful both as a means of studying the composition of thermal residual products and as a routine screening technique.
Characterization of the chain length distribution of wood celluloses by gel permeation chromatography
Authors: Muller Thomas E. , Alexander W. J.
Published: June 2010

Cellulosics are similar to synthetic polymers in that they are composed of molecules with a given size distribution. Analysis of the chain length distribution of wood celluloses by gel permeation chromatography (GPC) is a new approach to the characterization of cellulose purity and uniformity. Cellulosics are either nitrated or acetylated prior to analysis in a tetrahydrofuran solution under ambient conditions; a column combination consisting of one each of 107, 106, 105, and 104 A. columns was found to be applicable for a wide range of degree of polymerization (DP). Narrow‐distribution cellulose standards were prepared for calibration studies. Cellulosics analyzed included a 650 and 2000 DP sulfite and a 1075 DP sulfate pulp, cotton linters representing several DP levels, cellulose sponge and fibrous casing, regular and high wet modulus rayon, and microcrystalline cellulose. The extraction of a 650 and 2000 DP pulp with 10 and 18% NaOH at 20°C. was monitored by GPC. Alpha, beta, and gamma portions of cellulose were clearly distinguished; the low‐DP carbohydrate fractions reflect a predictable pattern of chain length distribution. GPC offers advantages in speed, ease of operation, and potential versatility over precipitation or solution fractionation. The method is reproducible.
Polymerization of Styrene with ZrCl4 and ZrCl3 in combination with Al(I‐C4H9)3
Authors: Malhotra S. L. , Deshpande A. B. , Kapur S. L.
Published: June 2010

The polymerization of styrene with two catalyst systems, consisting of Al(i‐C4H9)3 in combination with ZrCl4 and ZrCl3 respectively, has been examined in toluene at 40°C. The catalyst complexes formed in both the systems exhibited the dual effect of accelerating and retarding the polymerization reaction. The rate of polymerization with respect to monomer and the total catalyst concentration was found to be first‐order for ZrCl4‐Al(IC4H9)3 and second‐order for ZrCl3‐Al(i‐C4H9)3. The second‐order dependence on total catalyst concentration in the latter system has been explained on the assumption that the solid catalyst species interact bimolecularly to produce an active center, which takes part in the polymerization reaction. Thus the order with respect to active‐center catalyst concentration remains 1. The overall activation energy of polymerization was 14.74 kcal./mole for ZrCl4‐Al(i‐C4H9)3 and 10.3 kcal./mole for ZrCl3‐Al(i‐C4H9)3. These catalysts exhibited very high rates of polymerization and gave low molecular weight, amorphous polymers.
Participation of imidazole in vinyl polymerization in the absence of radical initiator
Authors: Imoto Minoru , Takemoto Kiichi , Sutoh Hiroyuki , Azuma Heiichi
Published: June 2010

A study of radical polymerization in the absence of radical initiator, in which imidazole or imidazyl groups may participate, was made. Polymerization of 1‐vinyl‐2‐methylimidazole was found to proceed easily at low temperatures in the presence of macromolecule, carbon tetrachloride, and water. Kinetic results showed that the polymerization concerned was of radical character, the overall activation energy being estimated to 13.7 kcal./mole. Vinyl polymerization could be also initiated in the presence of imidazole and carbon tetrachloride, and it was found that the polymerization was accelerated by the addition of some macromolecules in the system. The initiation mechanism is discussed.
The synthesis of organic polymers containing hypervalent Iodine
Authors: Livingston H. K. , Sullivan J. W. , Musher Jeremy I.
Published: June 2010

Polyesters of the formula have been made from iodosobenzenes + acid anhydrides and from iodobenzene diacetates + dicarboxylic acids. The products do not resemble in solubility behavior the iodosobenzene esters of monocarboxylic acids, the polyesters of convential diols, or the ionic salts of dicarboxylic acids. Under the best conditions they are more stable thermally than iodobenzene diacetate or dipropionate, but none is stable above 200°C. There are indications that polymers containing hypervalent atoms represent a new class of polymers by virtue of their unusual solubility behavior and physical properties.
The addition of carbalkoxycarbenes to stereoregular unsaturated polymers
Authors: Lishanski I. S. , Tsitokhtsev V. A.
Published: June 2010

The reactions of electrophylic addition of carbalkoxycarbenes to cis‐1,4‐polybutadiene and cis‐1,4‐polyisoprene, resulting in the formation of ester‐substituted cyclopropane groups in the polymer chains, were investigated. The conversion of double bonds into the cyclopropane groups is accompanied by a gradual increase in the glass‐transition temperature, tensile strength, and relative elongation at break. Infrared spectroscopic study with the aid of model substances demonstrated that the addition of even unsymmetric carbene does not destroy the stereo‐regularity of the macromolecule. Only a certain transformation of stereoregularity takes place: the cis configuration of the substituents at the carbon‐carbon double bond is replaced with a new type of stereoregularity, characterized by the steric positions of the substituents (including a new one due to the carbene) with respect to the cyclopropane ring. The ozonolysis of modified polybutadiene (30% conversion of double bonds) indicates that the addition of the carbene does not lead to a block distribution of cyclopropane units. The study of competitive reactions of carbene addition showed that the relative rate constant of carbene addition to polymer does not depend on the degree of conversion, and at low degree of conversion is independent of temperature and of the nature of the solvent and is slightly affected by the nature of the catalyst.
Reactions of low molecular weight polypropylene induced by titanium compounds
Authors: Kresta J. , Majer J. , Veselý K.
Published: June 2010

The thermal and thermooxidative reactions of polypropylene oligomer in the presence of α‐TiCl3, TiOCl2, Ti(O‐i‐Pr)4, and HCl were studied. HCl is formed during the reaction of α‐TiCl3with hydrocarbon; the rate of formation is a function of the C–H bond strength. In the oxidation reactions of the polypropylene oligomer Ti3+acts as a terminator of the oxidation chain and, if its concentration is higher than that of the hydroperoxides, it inhibits the process. Ti4+(TiOCl2, Ti(O‐i‐Pr)4) retards oxidation, and HCl acts as catalyst.
Photodestruction and photooxidative destruction of polyurethanes
Authors: Tarakanov O. G. , Nevskji L. V. , Beljakov V. K.
Published: June 2010

The ultraviolet‐irradiation stability of polyurethanes synthesized on different diisocyanate bases was estimated in this work. The composition of the gaseous products formed during the photolysis of different polyurethanes was analyzed. The quantum yield of CO2 into the gaseous phase was evaluated. It is shown that the formation of gaseous products in photolysis proceeds through the breaking of NC and CO bonds in the urethane group of the polymer. From the electron spin resonance spectra of irradiated polyurethanes it was concluded that the strong delocalization of unpaired electrons takes place along the conjugation system formed in polyurethanes based on aromatic diisocynates. Kinetic oxygen absorption curves in ultraviolet irradiation of polyurethanes based on different diisocyanates were obtained. It is shown that the amount of absorbed oxygen depends primarily on the degree of crystallinity of the polyurethanes. The accumulation of peroxidates in polyurethane photooxidation was studied.
Molecular structure and nmr spectra of stereoregular poly(methyl acrylate) models
Authors: Doskočilová D. , Sýkora S. , Pivcová H. , Obereigner B. , Lím D.
Published: June 2010

NMR spectra of the meso and d,l isomers of methyl‐2,4‐pentanedicarboxylate and of isotactic, heterotactic, and syndiotactic methyl‐2,4,6‐heptanetricarboxylate have been measured and analyzed. From the values of vicinal coupling constants the energy differences between various conformational structures of these isomers were estimated. The limitations of the procedure are discussed.
Dielectric properties of polytetrafluoroethylene and tetrafluoroethylene‐hexafluoropropylene copolymer
Authors: Koizumi Naokazu , Yano Shinichi , Tsuji Fukuju
Published: June 2010

Precision measurements of dielectric properties of polytetrafluoroethylene and copolymers of tetrafluoroethylene and hexafluoropropylene were made over a temperature range of –40 to +180°C. at frequencies of 10 Hz to 300 kHz. Polytetrafluoroethylene exhibited the typical dielectric behavior of a nonpolar substance: no dielectric loss peak was found over the experimental range of temperature and frequency. The dissipation factor remained constant, being about 2 × 10−5. Copolymers of tetrafluoroethylene and hexafluoropropylene showed two dielectric loss peaks: one occurred at about 100°C. and the other at about −20°C. There was a break point, or an abrupt bend, near 60°C. in the curve of dielectric constant versus temperature, indicating the existence of a transition point. The high‐ and low‐temperature loss peaks correspond to the α and γ relaxations, respectively, which have been found for the mechanical behavior of this copolymer. The dielectric relaxation in the copolymer was attributed to the slightly polar nature of the perfluoromethyl side groups. The activation enthalpy and entropy are 80 kcal./mole and 180 eu for the α relaxation and 12 kcal./mole and 15 eu for the γ relaxation, respectively. The σ and γ relaxations are discussed in connection with the molecular motion of the copolymer chain.
Diffusion behavior of polymer molecules in solution
Authors: Kotera Akira , Matsuda Hideomi , Konishi Katsutoshi , Takemura Kenji
Published: June 2010

Diffusion experiments were carried out with a decalin solution of polystyrene at temperatures from room temperature to 110°C., to establish an experimental technique at higher temperatures. Values of diffusion constants obtained were checked by substituting them in the theoretical equations of diffusion behavior of polymer solutions. Results were satisfactory. For example, effective bond length of polymer chain calculated from Miyake's theory compares with those obtained by light‐scattering measurement. The apparent activation energy of diffusion is about 3 kcal./mole.
Polymerization of 3,4‐dihydro‐2H‐pyran‐2‐carboxyaldehyde (acrolein dimer). Part I. The homopolymerization
Authors: Kitahama Yoshiharu , Ohama Hiroshi , Kobayashi Hidehiko
Published: June 2010

Polymerizations of 3,4‐dihydro‐2H‐pyran‐2‐carboxyaldehyde (acrolein dimer) were investigated under several conditions. Polyacrolein dimer obtained at room temperature was found to have structural units (III) of 6,8‐dioxabicyclo[3,2,1] octane produced by an intraintermolecular reaction, in addition to the ordinary structures (I) produced by the unsaturated ether‐group polymerization and those (II) produced by the aldehyde‐group polymerization. The lower the polymerization temperature, the higher the selectivity of (II). The stronger the acidic character of initiators, the higher the selectivity of (I) and (III). With anionic catalysts, such as Al(C2H5)3 and dibenzene chromium, acrolein dimer gave a polymer containing only recurring structural units (II) at −78°C., while it did not give any polymer above –20°C. There consequently seems to be a ceiling temperature in the polymerization with anionic catalysts. The solubility of the polymers increased with increasing amounts of the bicyclic structure (III).
A study of cellulose trinitrate structure
Authors: Watanabe Sadayoshi , Hayashi Jisuke , Imai Kiyoshi
Published: June 2010

The structure of cellulose trinitrate was studied by x‐ray analysis and polarized infrared spectroscopy. Its meridional reflections and fiber period suggest that the molecule is approximately in the 5‐fold screw structure. If a glucose residue of the molecule is of the chair form, no molecular conformation satisfying these requirements can exist. The hydroxyl groups on adjacent carbons C2 and C3 of the glucose residue will be transformed from the gauche conformation to the trans conformation during nitration because of bulkiness of nitrate groups. As a consequence, the glucose residue is transformed from the chair form to the half‐boat form, and the molecule is changed from the 2‐fold screw structure to the 5‐fold screw double‐helix structure. Then it can satisfy the requirements. Screw sense is left‐handed in the direction from C1 to C4. The change of absorption bands related to the skeletal structure of glucose residue during nitration suggests the transformation of the configuration of glucose residue. Orientations of CH2 and NO2 groups were studied by polarized infrared spectroscopy.
Chlorination of ethylene–propylene copolymer
Authors: Ramp Floyd L.
Published: June 2010

Cleavage of ethylene propylene rubber by oxygen may occur during chlorination at 25°C. Peroxy groups are first introduced without chain cleavage. Chain cleavage occurs only after all chlorine has been consumed. Vanadium, required to give cleavage under these conditions, is probably reduced and in turn cleaves the peroxy linkages. The distribution of tertiary chlorine along the chain was determined by dehydrohalogenation and oxidative cleavage.
Computer calculations of dimensions of linear alkanes and their use in the theory of diffusion in liquid solution
Authors: Burkhart R. D. , Merrill J. C.
Published: June 2010

The method of Flory was used to calculate unperturbed mean‐square dimensions of linear alkanes at 25°C by utilizing the assumption of three‐fold rotational isomerism and allowing, but giving small statistical weight to, configurations involving successive gauche rotations of opposite sign. The necessary 15 × 15 matrix multiplications were made with an IBM 1620 computer. The reciprocal square root of these calculated dimensions were assumed equal to <1/R>Av, and diffusion coefficients of pentane through dotriacontane were then computed by means of the Kirkwood‐Stokes equation. These coefficients were then compared with experimental values from four different solvents and with self‐diffusion measurements. In general, it may be said that theory and experiment agree well for solvents of low viscosity. For more viscous solvents (tetralin and decalin) experimental diffusion coefficients are about 80% larger than those calculated for pentane. As chain length increases, however, better agreement is observed.
Electronic computations of light scattering functions for heterodisperse systems of isotropic spheres
Authors: Yajnik M. , Witeczek J. , Heller W.
Published: June 2010

Fortran programs were developed to compute light scattering functions for heterodisperse systems that can be described by a biparametric, uni‐modal, exponential distribution function. The programs had to include the evaluation of the Mie functions for angular scattering for any arbitrary values of the size parameter α. This involves the calculation of the Riccati‐Bessel functions and Legendre polynomials. Several methods of numerical integration of the expressions containing the products of the Mie functions and the distribution function were investigated. Gaussian quadrature could yield the results of integration with better precision, but its use required a considerable amount of machine time, and thus it was adopted only for part of the results obtained. The simpler Simpson's rule allowed one to store the Mie functions needed in the integration and, as some of our studies have shown, its results come close (within the limits of experimental error of light scattering methods) to those obtained by the Gaussian method. The computer has also been used for fitting the experimentally obtained light scattering data with the theoretical ones.
Polymer science & technology (POST): A computer‐based information service
Authors: Siegel H. , Veal D. C. , McMullen D. A.
Published: June 2010

The integration of computer support into information processing provides many services for workers in science and technology. These services result from the simultaneous generation of printed text and machine records in the processing of data for publication, in effect, producing a complete information system rather than simply a publications system. Polymer Science & Technology (POST), a new service of the American Chemical Society's Chemical Abstracts Service (CAS), exemplifies such a multifaceted, computer‐based information system. POST consists of two units: POST‐J covers the journal and report literature, and POST‐P covers patents. Each unit is available in both computer language and printed journal form. This new system serves the needs of the practicing scientist for current, deeply indexed, subject‐oriented, printed information which has been specially formatted to simplify scanning and searching. The computer tape version of POST is supplied along with well‐documented search programs for use in the subscriber's computer installations or, if the subscriber wishes, computer searching can be done at CAS. This paper describes the POST information system in relation to the total CAS operation.
Structure‐property relationships for styrene‐diene thermoplastic elastomers
Authors: Morton Maurice , McGrath James E. , Juliano Peter C.
Published: June 2010

A study has been carried out on block polymers of the A‐B‐A type, the thermoplastic elastomers, where A represents polystyrene and B polybutadiene or polyisoprene. The objective was to relate the mechanical properties of these elastomers to their molecular architecture. For this purpose a series of styrene‐butadiene and styrene‐isoprene block polymers were synthesized by means of organolithium initiators, in which the block lengths of the polystyrene and polydiene were varied. It was found that the stress‐strain properties of styrene‐butadiene polymers are mainly dependent on the polystyrene content, regardless of the block sizes, and that the center, elastic block does not appear to behave as the “molecular weight between crosslinks” of these networks. However, the monodispersity of the chain length of these elastic blocks does appear to contribute substantially to higher tensile strengths. The polystyrene appears to be aggregated in small domains, of the order of several hundred angstrom units, and these undergo an irreversible deformation under stress, which is, however, completely recoverable above the Tg of the polystyrene. At high polystyrene contents (∼40%) these elastomers exhibit an irreversible yield point at very low elongations, and this is ascribed to the presence of a continuous phase of connected polystyrene domains, which can be re‐formed by raising the temperature above the Tg of the polystyrene. Although the stress‐strain curves are not affected by the thermal history of the sample, the tensile strength, especially at high styrene contents, is strongly dependent on “annealing” of any frozen stresses in the polystyrene phase. The useful range of block molecular weights is about 10,000–20,000 for polystyrene and 40,000–80,000, respectively, for polybutadiene. The lower limit is probably governed by the minimum polystyrene chain length required to insure the formation of a heterogeneous phase; while the upper limit is set by the high viscosity of both blocks, which might seriously hamper domain formation.
Developments in self‐reinforced elastomers
Authors: Brunwin D. M. , Fischer E. , Henderson J. F.
Published: June 2010

Until recently it has been believed that either stress‐crystallization or the presence of reinforcing filler is necessary for the development of high strength in elastomers. Now it has been observed that gum vulcanizates of isoprene/acrylonitrile copolymers have tensile strengths in the order of 3000–4000 psi in the absence of fillers. In this case crystallization does not occur and the strength is associated with the ability of the polymer molecules to become highly oriented on stretching. Similar observations have been made with ABA block copolymers polystyrene‐polybutadiene‐polystyrene which are highly elastomeric in the absence of chemical crosslinks. The elastomeric properties and high strength of the block copolymers are attributed to the mutual incompatibility of the A and B blocks which leads to phase separation on a microscopic scale. The effective network structure can be temporarily destroyed by heating the polymer above the softening temperature of the resinous blocks which makes the material readily processable. The initial decrease in retractive force with increasing temperature up to 60–70°C is attributed to an increase of mobility of the resinous domains in the rubbery matrix. At higher temperatures the crosslinking effectiveness decreases markedly due to softening of the resinous regions. The process of yielding, hysteresis effects, and delayed elastic creep arise because of viscous forces which oppose the motions of the colloidal polystyrene domains. The strength and effectiveness of physical crosslinks in block copolymers shows a similar temperature dependence as has been observed for other filled and unfilled vulcanizates. The process of self‐reinforcement in isoprene‐acrylonitrile copolymers and polystyrene‐polybutadiene‐polystyrene block copolymers is attributed to viscous effects which make possible the alignment of a large number of polymer chains in the stretching direction.
Anionic emulsion polymerization of siloxanes
Authors: Weyenberg D. R. , Findlay D. E. , Cekada J. , Bey A. E.
Published: June 2010

In 1959, Hyde and Wehrly described an emulsion polymerization of permethylcyclosiloxanes. This unique example of an emulsion polymerization proceeding via an ionic mechanism involved base catalysis with a cationic surfactant. An analogous acid‐catalyzed anionic emulsion polymerization has now been developed which employs dodecylbenzene‐sulfonic acid as the catalyst and surfactant. Polydimethylsiloxane emulsions with particle diameters of 500–5000 Å are obtained on heating aqueous dispersions of permethylcyclosiloxanes with dodecylben‐zenesulfonic acid at 50–100°C. Polymerization is completely arrested by neutralization of the catalytic surfactant. As in the earlier cationic emulsion polymerization, the molecular weight of the polymer is easily controlled by the temperature of polymerization via the equilibrium between siloxane, water, and silanol. Polymers with molecular weights of 49,000 and 172,000 are obtained at 90°C and 25°C, respectively. The use of alkyltrimethoxysilanes in this anionic emulsion polymerization makes available a new system of colloidal silsesquioxanes with extremely small and uniform particle size. Colloidal methylsilsesquioxanes with particle diameters of 70–1000 Å are obtained by the addition of methyltrimethoxysilane to an aqueous dodecylbenzenesulfonic acid solution. Methylsilanetriol and methylsiloxanols were shown to be intermediates in this latter reaction.
Emulsion polymerization: A stochastic approach to the polymer size distribution
Authors: Saidel Gerald M. , Katz Stanley
Published: June 2010

The dynamic behavior of emulsion polymerization is described both stochastically and deterministically. A partially stochastic approach is taken when the rate of radical arrival at the emulsion particles is much less than the rate of termination. In this case, the radical arrival which alternately starts and stops a growing polymer is considered to be random, but the growth of polymers and particles are treated deterministically. When the rate of radical arrival is much greater than the rate of termination, many growing polymers may coexist in a given particle. Under these conditions a (completely) deterministic model is found applicable. Both these models show how the reactant concentrations, the number of emulsion particles, and the reaction and transport rate coefficients effect the moments of the polymer size distribution and the rate of polymerization.
Relationship between electric conductivity, thermally stimulated currents, thermoluminescence and polymer structure
Authors: Kryszewski M. , Kasica H. , Patora J. , Piotrowski J.
Published: June 2010

In order to study the relation between polymer structure and their d.c. conductivity the measurements of current‐ voltage characteristics, thermally stimulated currents /TSC/ and thermoluminescence /TL/ measurements of poly (ethylene terephthalate) films were carried out. The PET samples were subject to different thermal treatment and deformations (unixial stretching). The degree of crystallinity of the thermally treated films was determined on the basis of density measurements and their supermolecular structure by means of light scattering technique. It was found that PET samples exhibit non ohmic behaviur and different TSC curves depending on crystallinity degree and orientation. The TSC curves analysis allowed establishing of the trap levels energy depth and trap densities. The shallow trap levels energy was also calculated from TL glow curves. The trap depth was correlated with the structure of the investigated specimen. The observed behaviour of PET films in d.c. field and the related phenomena were interpreted in terms of the injected current carrier theory.
Influnce of the chemical structure on the morphology and physical properties of crosslinked macromolecules synthesized by polyaddition reaction
Authors: Schmid R. , Lohse F. , Fisch W. , Batzer H.
Published: June 2010

The investigations in epoxy resins and other polymers have shown that by selecting the structure of the segments between the crosslinks it is possible to vary to a great extend the morphology and the physical properties. In a survey, a classification of 7 systems is given, cach of them characterized by specific morphological and physical properties. It is demonstrated that conventional epoxide resins show a distinct maximum of the mechanical damping and elongation at rupture nearly at the same temperature. The toughness‐temperature characteristic however shows a maximum 20°–30°C below the glass transition temperature. One system, the slightly crosslinked epoxy resins e.g. obtained by reacting long chain acid polyesters and diepoxides show a very high toughness in the transition range, compared to the conventional high crosslinked polymers.
The adsorption behavior of polymer mixtures
Authors: Botham Ruth , Thies Curt
Published: June 2010

The interfacial behavior of several mixtures of incompatible polymers has been examined at 24°C using finely divided silica as the adsorbent and trichloroethylene as the solvent. Displacement experiments have shown that poly (ethylene‐vinyl acetate) (EVA) (20.4% by wt. vinyl acetate) completely displaces polystyrene (PS) from silica within 1 hr. while poly (vinyl acetate) (PVAc) displaces ethyl cellulose (EC) within 3 hrs. A given EVA copolymer displaces one of lower vinyl acetate content; EVA (44.2% vinyl acetate) is displaced by EC. EC tends to displace poly (methyl methacrylate) (PMMA), but the process is slow and incomplete. The fraction of adsorbed polymer segments attached directly to silica, as determined by infrared spectroscopy, can be correlated with the displacement results. Experiments with PS/PVAc, PS/PMMA, and polydimethylsiloxane/EVA (20.4% vinyl acetate) mixtures have shown that adsorbance values of the preferentially adsorbed PVAc, PMMA, and EVA are increased by the second polymer, when polymer concentrations which cause phase separation are approached. Increases in adsorbance are accompanied by lower infrared bound fraction values, implying formation of a more extended adsorbed layer.
Enzymes covalently bound to various polymers and the effects on the properties of these enzymes
Authors: Manecke G. , Günzel G. , Förster H. J.
Published: June 2010

It was investigated how polymers which carry 2,4‐dinitro‐fluorobenzene or isothiocyanate groups could be used for preparing protein and enzyme resins. Furthermore it is demonstrated that the quantities of covalently bound enzymes as well as the properties of the enzymes themselves are dependent on the structure and chemical composition of the polymer matrices.
Comparative lethal action of ethyl methanesulfonate, nitrogen mustard, myleran and diepoxybutane on T7 coliphage
Authors: Brakier L. , Verly W. G.
Published: June 2010

Interstrand crosslinks can be shown in phage T7 DNA after treatment by nitrogen mustard or DL‐diepoxybutane, but not after treatment by myleran. Lethality increases after an ethylmethanesulfonate or myleran treatment; this increase is related to the increase of depurinations. Lethality first increases after the nitrogen mustard treatment, then decreases and finally increases again. Crosslinks account for the whole lethality at the end of the treatment, and the evolution of lethality with time can be related to the evolution of crosslinks; the subsequent increase could be correlated to the appearance of fragmentations. Lethality remains constant after the DL‐diepoxybutane treatment; the number of crosslinks is smaller than the number of dead phages; the disappearance of the crosslinks would compensate the biological effect of the increase of depurinated sites so that the lethality remains constant during the first hours after the end of the treatment. The inactivation of the T7 phage by any of these agents is a one‐hit process.
Properties of quench‐rolled polyethylene film
Authors: Kwei T. K. , Wang Tsuey T. , Bair H. E.
Published: June 2010

The dynamic mechanical properties, creep, and melting characteristics of a transparent polyethylene film prepared by a novel process of simultaneous high speed quenching and shear were examined. A high degree of orientation was attained in the process, the polymer chain backbone being aligned in the direction of shear. As a result of chain orientation, the dynamic in‐phase moduli in the temperature range from −160 to +120°C are about three to seven times the values for the compression‐molded material. Changes in β and α dispersion peaks are also noticed. The quench‐rolled film contains high melting point fractions which suggest very strongly the presence of thick crystals, perhaps up to about 1000 Å in thickness. Excellent resistance to creep, comparable to that of the cold‐drawn polyethylene, was observed.
Fluorescence methods in polymer science
Authors: Nishijima Yasunori
Published: June 2010

Various aspects of the application of fluorescence characteristics in the field of polymer research are described. The polarization characteristics of fluorescence, that is, the angular distribution of the intensity of the polarized component, are indicative of the distribution patterns of fluorescent molecules in the medium. This principle can be utilized for the investigation of molecular orientation behavior in polymer solids. Examples are given for the molecular orientation behaviors during the deformation of poly(vinyl alcohol) and polypropylene films. The phenomenon of rotational depolarization of fluorescence is applied to the measurement of micro‐Brownian motions of polymer chains and the local viscosity of polymer solutions and melts. The internal structure of concentrated poly(styrene) solutions and the molecular motions in the melts of n‐paraffins and polyethylene homologs are discussed. Rotational relaxation time ranging from 10−12 to 10−5 sec can be measured by this method by using the lifetime of excitation of fluorescent groups as the reference time scale. The phenomenon of the excimer fluorescence emitted from the excited dimer provides a new method for studying molecular configuration and conformation of polymer molecules. Examples are given for the case of naphthalenecontaining polymers. The sequence of monomeric units in copolymers of vinylnaphthalene and styrene are studied from the intensity of excimer fluorescence relative to that of ordinary fluorescence from the naphthalene groups. The intramolecular excimer formations of polymer molecules are also discussed in relation to molecular motions.
On the use of electron paramagnetic resonance in fracture mechanics
Authors: Devries K. L.
Published: June 2010

Electron spin resonance (ESR) provides a sensitive tool by which microscopic bond rupture can be monitored simultaneous with measurements of macroscopic deformation and failure. The use of this tool to study fracture of semicrystalline polymers, rubber at very low temperatures, and rubber in the presence of ozone is discussed. In these cases, a large number of ruptured bonds precedes macroscopic failure. The micromacro behavior of these materials will be discussed in terms of some various stages of fracture and some recently proposed models of polymers. To reliably predict the strength of a polymer from the strength of the molecular chains, it is important to understand the distribution in effective length of these load‐carrying chains. ESR provides a means of obtaining insight into such information. Straining rubber before lowering its temperature to −100°C results in crystallization and subsequent fracture behavior very similar to that of polycrystalline polymers. Rate of molecular bond scission is successfully correlated by a Griffithtype energy balance to the strain energy release rate during ozone cracking of rubber.
Relaxations during the formation of films
Authors: Myers Raymond R.
Published: June 2010

The Stefan equation for the separation of parallel surfaces confining a viscous medium relates the tensile stress to the product of the separation velocity and the liquid viscosity. This equation is applied to roll coating; two constraints to its use are imposed as a result of incomplete relaxation of stresses during the process. These constraints are the inability of any liquid to flow rapidly enough under tension to avoid cavitation and the appearance of a sizeable elastic component in the polymer solutions which one usually applies to substrates.

During film hardening the measurement of relaxation is performed by cyclic shearing at the low and middle range of the viscoelastic spectrum. The in‐phase and out‐of‐phase components of the complex modulus of rigidity are significant in this regard. Applied as a liquid, the coating must relax to a smooth layer without sagging and then be converted into a solid without developing destructively large residual stresses. Control over the mechanical properties during the formation of films is gained only after the molecular basis of relaxation and retardation is understood.
Time‐temperature superposition in thermorheologically complex materials
Authors: Fesko D. G. , Tschoegl N. W.
Published: June 2010

Two‐phase polymeric materials such as polymer blends, block copolymers, and graft copolymers, are thermorheologically complex. Mechanical response curves obtained on such materials at different temperatures cannot, in principle, be brought into superposition by a simple shift along the logarithmic time or frequency axis. The shift factors become functions of time or frequency in addition to temperature.

A general treatment of time‐temperature superposition in thermorheologically complex materials is developed and a model is proposed from which, for a two‐phase material, the amount of shift can be calculated which is necessary to bring a point on a mechanical response curve obtained at a given temperature and time or frequency into superposition at another temperature. The mechanical responses of the constituent homopolymers and their temperature functions must be known.
Flow behavior of polyethylene melts containing dissolved gases
Authors: Blyler L. L. , Kwei T. K.
Published: June 2010

The influence of dissolved gases on the flow behavior of high and low density polyethylene melts was investigated using a capillary extrusion rheometer. Gases were introduced by decomposition of a blowing agent incorporated in the polymer. Data are presented in the form of flow curves (log shear stress vs. log apparent shear rate at the capillary wall), and the data treatment is justified by a continuum analysis which accounts for the change of specific volume of the polymer‐gas solution during transit through the capillary. The results indicate the addition of gas in the amount of 0.5% by weight to both high and low density polyethylene melts causes a viscosity reduction of approximately 20% at constant shear rate. The view is taken that the gas increases the free volume available in the system, thereby lowering viscosity. An analysis is presented which indicates that Doolittle's viscosity‐free volume equation can account for the viscosity reduction effected by the gas. The experimental observations also indicate that the flow curve discontinuity marking the onset of unstable flow of high density polyethylene is completely suppressed by the addition of gas at the 0.5%w level. This result is discussed in terms of the axial shear stress distribution in the capillary and the suppression of slip mechanisms occurring in the capillary owing to enhanced interpenetration of molecular chains across the slip interface.
Latex particle size analysis. Part III. Particle size distribution by flow ultramicroscopy
Authors: Davidson J. A. , Collins E. A. , Haller H. S.
Published: June 2010

A single particle photometer is described which enables the rapid measurement of latex particle size and size distribution in the range of 500–3500Å. The instrument is a modification of the flow ultramicroscope described previously and employs an argon ion laser light source and a photoelectric detection system to observe scattering from single particles at 90°. The data are collected on a multichannel analyzer in terms of scattered intensity versus number of particles counted. A front collecting lens half‐angle of 2° was found to be adequate for direct use of the Lorentz‐Mie theory to compute particle diameters. The instrument is calibrated by determining from a suitable latex sample, the intensity of the first maximum in the intensity versus α relationship obtained from the Lorentz‐Mie theory. Particle diameters and distributions obtained on a series of 5 Dow Polystyrene latexes agreed well with those obtained by other methods. The results were found to be repeatable to ±4% at 90% confidence.
A model for interaction of nonpolar molecules differing in size and shape
Authors: Company Jean‐Claude , Renon Henri
Published: June 2010

Thermodynamic properties of pure nonpolar liquids, including long‐chain hydrocarbons are obtained accurately by derivation from an analytical partition function and the corresponding‐states principle. The characteristic parameters are interpreted in terms of group contributions in order to relate them to the structure of the molecule and further to provide a useful basis for a predictive theory of the properties of mixtures. The model for interactions between molecules takes into account the influence of molecular shape on the number of nearest neighbors and the limited number of interacting groups in a binary intermolecular contact. One obtains energy and size characteristic group interaction parameters related to those derived from London's formula and a unique function of the number of carbon atoms to characterize the shape of the molecules. Using these results obtained from pure liquids, one can predict at the same time excess enthalpies and Gibbs free energies of mixtures.