bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethylene polymerization with supported bis(triphenylsilyl) chromate catalysts
Authors: Carrick Wayne L. , Turbett Robert J. , Karol Frederick J. , Karapinka George L. , Fox Adrian S. , Johnson Robert N.
Published: April 2003

Bis(triphenylsilyl) chromate is an active catalyst for ethylene polymerization without further treatment or additives. Catalytic activity is markedly increased when the compound is deposited on silica–alumina and is further increased if it is deposited on silica and then treated with an aluminum alkyl. Polymer molecular weight can be controlled by reaction temperature, hydrogen addition, support type, and reducing agent structure to give polymers ranging in melt index from essentially zero to > 100. In the supported catalysts the bis(triphenylsilyl) chromate appears to be bound to the support and to undergo a reduction step either by reaction with ethylene or with aluminum alkyl prior to polymerization. The active site is envisioned as chromium alkyl, bound to the support, with propagation occurring by insertion of the monomer into a CrC bond. Chain termination is by chain transfer to monomer.
Long branching in poly(vinyl acetate) and poly(vinyl alcohol). II. Polymerization of vinyl acetate in the presence of crosslinked poly(vinyl alcohol)
Authors: Nozakura Shun‐Ichi , Morishima Yotaro , Murahashi Shunsuke
Published: April 2003

It is a common view that poly(vinyl acetate) has many branches at the acetyl side group, but that the corresponding poly(vinyl alcohol) has little branching. In order to study the branching in poly(vinyl acetate) and poly(vinyl alcohol) which is formed by chain transfer to polymer, the polymerization of 14C‐labeled vinyl acetate in the presence of crosslinked poly(vinyl acetate), which was able to be decrosslinked to give soluble polymers, was investigated at 60°C and 0°C. This system made it possible to separate as well as to distinguish the graft polymer from the newly polymerized homopolymer. Furthermore, the degree of grafting onto the acetoxymethyl group and onto the main chain were estimated. It became clear that, in the polymerization of vinyl acetate, chain transfer to the polymer main chain takes place about 2.4 times as frequently at 60°C as that to the acetoxy group and about 4.8 times as frequently at 0°C.
Investigation into the mechanism of tack of rubbers
Authors: Bauer R. F.
Published: April 2003

The tack of cis‐polybutadiene was measured by means of a Skewis tackmeter, and the results, which showed considerable variability, could be represented by a double exponential cumulative distribution function of Gumbel. It was concluded that there exists a linear relationship between the applied forces (contact and break) and the time that these forces are applied in the tack test. The mechanism of tack is considered in terms of two distinct processes: (a) the development of a bond and (b) the strength of the bond thus formed. The latter is rationalized by applying Eyring's absolute rate theory. A simple equation is derived which predicts an inverse linear relation between the breaking time and breaking force, which is in agreement with the experiment. The theory also suggests that the area of actual interpenetration of polymer interfaces depends largely on the contact pressure, whereas the depth of penetration appears to depend to a similar degree on both contact pressure and contact time.
Structure of ethylene–chlorotrifluoroethylene copolymers
Authors: Sibilia John P. , Roldan Luis G. , Chandrasekaran Swayambu
Published: April 2003

The structures of copolymers of ethylene and chlorotrifluoroethylene have been studied by infrared, nuclear magnetic resonance, and x‐ray diffraction techniques. Copolymers varying in ethylene composition from 80 to 50 mole‐% were prepared at a number of different temperatures with a peroxide catalyst system. Compositions of 50/50 mole ratio were found to be semicrystalline and to have melting points as high as 241°C. These materials were found to be copolymers with a high degree of one‐to‐one alternation. They were similar in structure to 1:1 copolymers which had been reported previously by other workers who used a triethylboron catalyst system. The x‐ray evidence indicated that the copolymers prepared with the peroxide catalysts were not stereoregular. A hexagonal unit cell with a theoretical density of 1.70 g/cc was determined for the alternating one‐to‐one copolymer by x‐ray techniques. A value of 262°C was determined for the melting point of the theoretical 100% alternating one‐to‐one copolymer. Values of ΔHƒ = 4500 cal/mole and ΔSƒ = 8.4 cal/deg‐mole were also calculated for the alternating 1:1 copolymer. The preferred conformation of the material appears to be a “kinked” structure with the crystalline phase having ethylene units in one chain lining up opposite chlorotrifluoroethylene units in the adjacent chain. Polar association which can occur between fluorine and hydrogen atoms in this arrangement may account in part for the relatively high melting point of the alternating one‐to‐one copolymers.
EPR studies of mechanically induced bond rupture in elastomers
Authors: Devries K. L. , Roylance D. K. , Williams M. L.
Published: April 2003

Electron paramagnetic resonance (EPR) spectroscopy was used to compute the surface bond rupture density in polyurethane and to determine the phase experiencing fracture in styrene‐butadiene block copolymers when these elastomers are subjected to mechanical degradation by grinding. The polyurethane grinding was done at temperatures above and below the glass transition Tg; 0.155 × 1013 radicals/cm2 of fracture surface area were formed above the Tg and 4.42 × 1013 radicals/cm2 for grinding below the Tg. These values are essentially equal to those found earlier for spherulitic polymers. In all cases the fracture appears able to progress along preferential paths so as to rupture significantly fewer molecular chains than one would expect on the basis of calculations of the number of chains passing through each square centimeter of cross section. Comparison of EPR spectra formed by grinding styrene‐butadiene copolymer with those of styrene and butadiene above indicated that at cryogenic temperature, the fracture in the copolymer takes place in the butadiene phase.
Particle size analysis of polymer latexes by light scattering. V. The significance of an assumed distribution in the analysis of angular scattering data
Authors: Wallace T. P. , Kratohvil J. P.
Published: April 2003

In the analysis of light scattering data from polymer latex systems or other systems of spherical particles, it is necessary to assume a particle size distribution function. Theoretical angular scattering functions based on the assumed distribution and representing a wide range of size distribution parameters are compared to experimental data in order to obtain a best fit. In previous work, it has been shown that as the polydispersity increases beyond certain limits the uncertainty in the assignment of the size distribution parameters (i.e., the best fit) increases. This report is concerned with the analysis of angular scattering from unimodal systems and simulated cases where theoretical scattering functions for wide, negatively skewed distributions are used as “experimental data,” are analyzed by utilizing four different distribution functions. These functions represent different degrees of skewness and include negatively, positively, and normally skewed distributions. The results from the use of the various distribution functions are discussed with respect to the uncertainly in the assignment of distribution parameters resulting from the loss of structure in the angular scattering pattern due to increased polydispersity. Scattering data from the bimodal distribution are analyzed by assuming a unimodel distribution, and the consequences of this assumption are assessed.
Hydration‐dependent enthalpy changes in the helix–coil transition in tendon
Authors: Delisi Charles , Shamos Morris H.
Published: April 2003

The shrinkage phenomenon in bovine achilles heel tendon was studied calorimetrically as a function of water content of the tendon. The transition temperature was found to increase from 67°C to 98°C as the water content decreased from 53% by weight to 26% by weight. The enthalpy change was found to increase with increasing percentages of water. The data is interpreted by considering the possibility of water binding to the polar sites on the solute molecule which become free after the transition. A calculation is carried out in which the melting shifts are taken to be related to the free energy of binding. The increase in enthalpy with an increase in water content is shown to have a semiquantitative interpretation in terms of the structural aspects of water.
X‐ray diffraction relaxation of polyethylene
Authors: Oda T. , Stein R. S.
Published: April 2003

The change in x‐ray diffraction intensity with time following rapid stretching by various amounts is measured for a low‐density polyethylene sample at several temperatures. An appreciable decrease in intensity with time at the meridian of the diffraction from the 110 and 200 planes is observed to occur within the first 5 sec following stretching. The change takes considerably longer times at lower temperatures. By use of a calibration curve, the change in crystal orientation functions for the a, b, and c crystal axes were calculated, and an increase in c‐axis orientation was shown. From the results of birerringence measurements on the same sample, the crystalline and amorphous contributions to birefringence were calculated. It was shown that stretching is initially accompanied by a greater amount of amorphous than crystalline orientation, and that relaxation involves an increase in crystalline orientation accompanied by a decrease in amorphous orientation.
Conformation of random polypeptide chains
Authors: Srinivasan A. R. , Rao V. S. R.
Published: April 2003

The characteristic ratios Cof and C∞ are calculated for infinitely long poly(L‐amino acid) chains having aCH2R′ substitution at the Cα atom, as functions of the valence angle τ at the Cα atom. The value of Cof is found to increase from 1.6 to 2.3 as τ varies from 105 to 115°. On the other hand, C∞ decreases with increasing τ in the range 105–111°, passes through a minimum at 111°, and then increases slowly. Since, C∞ is much less dependent on τ in the most commonly observed range (110–115°), any variation in τ in this range due to solvent would not appreciably affect C∞. The calculated temperature coefficient of C∞ is negative and increases significantly in absolute magnitude even for small deviations in τ from 110°.
Differential scanning calorimetry of chlorinated polyethylenes
Authors: Erä Väinö A. , Lindberg J. Johan
Published: April 2003

The heats of fusion of low‐density polyethylene and chlorinated polyethylenes of varying chlorine content have been investigated by differential scanning colorimetry (DSC). Linear correlations are found between the chlorine content and the apparent heat of fusion, crystallinity, and the maximum specific heat measured in the temperature range 90–120°C. The effect of heat treatment on crystallinity is shown to be strongly dependent on the chlorine content of the polymers.
Influence of entanglements on viscoelastic properties of polyisoprenes
Authors: Barešová V. , Szilágyi L. , Danusso F.
Published: April 2003

The contribution of entanglements to the relaxation modulus of four samples of cis‐polyisoprene has been studied in detail. The average number of chain atoms between neighboring entanglements has been calculated according to the theory of Chompff et al. Relaxation spectra and modulus produced by the entanglements were also calculated from the theoretical model. Good agreement was achieved between the modulus measured experimentally and the values predicted theoretically.
Adsorption of polymers at the solution‐solid interface. VII. Poly(acrylic acids), model compounds, and vapors on nylon fibers
Authors: Cole D. , Howard G. J.
Published: April 2003

Nylon fibers of various draw ratios have been used as the adsorbents in the adsorption of low molecular weight acids and of polyacrylic acids from solution. Polymer adsorption is lower than on a precipitated nylon and decreases with fiber orientation; however, propionic acid and glutaric acids do not show this dependence on nylon structure. The structural alterations consequent on fiber drawing also reduce swelling in hydroxylated liquids. The greater accessibility of the precipitated nylon is shown by vapor sorption and extends to nonhydroxylated vapors; however, the differences in behavior between polyamide powder and fiber cannot be fully attributed to the former possessing a porous structure, in the sense normally employed in surface chemistry.
Adsorption of polymers at the solution‐solid interface. VIII. Competitive effects in the adsorption of polystyrenes on silica
Authors: Howard G. J. , Woods S. J.
Published: April 2003

The adsorption behavior on silica of some polystrenes of moderate molecular weight distribution, both singly and in mixtures, has been examined. The adsorption isotherms indicate that, in both a good solvent (trichloroethylene) and under theta conditions, the species of higher molecular weight is preferentially adsorbed at or near full surface coverage, but that the smaller adsorbate has an improved opportunity for adsorption at low surface coverage. The use of tritiated adsorbates substantiate the isotherm data in cyclohexane solution.
Permeation phenomena near the penetrant condensation point
Authors: Leitão Dorodame Moura
Published: April 2003

The permeation and solubility of propylene in polyethylene films were measured at temperatures and pressures near the condensation point of the vapor. Diffusion coefficients were calculated from these data. On the basis of the behavior of activation energies with relative vapor pressure, it is shown how diffusion and sorption influence permeation phenomena in this region.
Thermal behavior of annealed organic glasses
Authors: Petrie S. E. B.
Published: April 2003

The influence of annealing processes on the thermal behavior of organic glasses in the glass‐transition interval has been investigated and analyzed quantitatively. In detailed annealing studies of atactic polystyrene and Aroclor 5460, the absorption of thermal energy superposed on the increase in the specific heat at the glass transition, observed with suitably chosen heating rates, was followed by the differential thermal method. It is concluded that the absorption of thermal energy observed under these conditions parallels the extent of molecular relaxation that has taken place during the annealing period. It is not necessary to postulate a first‐order process to account for the energy absorption. Moreover, such a postulate leads to severe conceptual difficulties regarding the development of crystallinity in crystallizable materials. The areas and the shapes of the endotherms are considered in terms of the original physical properties of the quenched glasses and the anticipated equilibrium properties. Relationships between the extent of energy absorption and time‐dependent processes such as volume relaxation are discussed.
Multiple endotherm melting behavior in relation to polymer morphology
Authors: Sweet G. E. , Bell J. P.
Published: April 2003

The two endotherms found during DSC analysis of annealed or drawn poly(ethylene terephthalate), PET, are discussed in greater. detail. Earlier workers proposed that the endotherms were the result of separate morphologies, i.e., extended‐chain and folded‐chain crystals, but more recently Roberts and others have presented data on the effect of DSC heating rate on annealed PET endotherm areas which indicate that the higher temperature endotherm is the result of recrystallization in the DSC. The present work explains the reasons for recrystallization, and presents data showing that samples cooled at various rates from the melt also exhibit recrystallization in the DSC, in much the same manner as samples annealed for different lengths of time. Further, by prolonged annealing before analysis, part of the recrystallization exotherm can be observed in the DSC scan. Drawn nylon 66 also exhibits recrystallization in the DSC, in a manner similar to annealed or slowly crystallized PET. The amount of material that recrystallizes is determined by the time and supercooling available between first melting and the ultimate recrystallization temperature, i.e., a temperature at which there is too little time and temperature driving force for further recrystallization to occur. Infrared absorption data show an increase in “regular” fold content during prolonged annealing of PET, while dynamic mechanical data show a marked decrease in a dispersion that is likely associated with the looser fold crystal morphologies. Annealed PET does superheat in the DSC, leaving unanswered the question as to whether any partially extended material is present along with the regular‐fold material. For cold‐drawn PET, the infrared data indicate disappearance of regular folds and the dynamic mechanical data indicate disappearance of the looser folds. Cold‐drawn PET also superheats. These data indicate a likelihood of at least partially extended morphologies in cold‐drawn PET; these observations do not apply to PET drawn at high temperatures or to polyethylene.
Pulsed photoconductivity and current oscillations in poly(vinyl chloride)
Authors: Ranicar J. H. , Fleming R. J.
Published: April 2003

Transient photocurrents in poly(vinyl chloride) films are shown to be due to photo‐injection of electrons from metallic cathodes. Most of the injected electrons are promptly trapped, but some drift across the sample to the anode under the influence of an external electric field. The mobility of these electrons, determined by transient photoconductivity techniques, is 4.7 ± 0.5 × 10−4 cm2/V‐sec at 27°C, and rises to 3.4 ± 0.5 × 10−3 cm2/V‐sec at 43°C, the measuring cell having been evacuated to a pressure of 10−6 torr at both temperatures. Diffusion of helium into the samples appears to decrease the electron, mobility. It is suggested that electron transport is correctly described by using an energy‐band model for intramolecular motion and an activated hopping model for intermolecular transfer. Oscillations observed in the transient photocurrents in the frequency range 103–105 Hz are attributed to electron avalanche formation at the anode, with photosuccessors.
Configurational statistics of polysaccharides. VI. Linear (1→4)‐linked galactan
Authors: Yathindra N. , Rao V. S. R.
Published: April 2003

The conformational energies for (1→4)‐linked α‐D‐ and β‐D‐galactans have been computed by considering nonbonded, torsional, and electrostatic interactions. The electrostatic interactions are estimated by assigning the charges to various atoms in the molecule by the method of Del Re. The characteristic ratios CN = 〈r2〉0/Nlv2 are computed for α‐D‐ and β‐D‐galactans as a function of the degree of polymerization N and the angle τ at the bridge oxygen atom. These values of characteristic ratios obtained for α‐D‐galactan are very much higher than for β‐D‐galactan, indicating that the former assumes a highly extended conformation compared to the latter. The values of characteristic ratios of both these polysaccharides show a decrease with increase in τ similar to that observed for other (1→4)‐linked polysaccharides. The calculated values of C∞ of (1→4)‐linked polysaccharides show no correlation with the number of allowed conformations but are affected both by the orientation of the interunit glycosidic bonds and the hindered potential associated with chain units. It has also been shown that the magnitude of the steric factor σ may not be used as an index of flexibility for polysaccharides which differ in type of linkage.
Mechanism of submicrocrack generation in stressed polymers
Authors: Zhurkov S. N. , Zakrevskyi V. A. , Korsukov V. E. , Kuksenko V. S.
Published: April 2003

Submicrocracks, free radicals, and endgroups of scissioned molecules formed in polyethylene, polypropylene, and polycaprolactam under uniaxial tension have been investigated. Measurements were carried out by small‐angle x‐ray scattering, electron paramagnetic resonance, and infrared spectroscopy. The concentration of submicrocracks is almost the same as that of free radicals but is smaller than the concentration of scissioned macromolecules by approximately three orders of magnitude. The number of scissions per crack proved to be close to the number of macromolecules passing through the cross section of a submicrocrack calculated on the assumption of close packing. It is concluded that submicrocracks in stressed polymers are formed as a result of chain reactions of macromolecular decomposition initiated by the active end primary free radicals.
Crystallization of poly(ethylene oxide) fractions: Crystallization isotherms
Authors: Beech D. R. , Booth C. , Dodgson D. V. , Hillier I. H.
Published: April 2003

The crystallization kinetics of a range of fractions of poly(ethylene oxide) are presented and analyzed. It is concluded that deviations from the Avrami equation with exponent of 3 are mainly due to rejection of low molecular weight molecules for the low molecular weight fractions (M̄n < 6,000) and to a process of crystal perfecting for the high molecular weight fractions (M̄n > 6,000).
Effect of solvents on the cryogenic dynamic mechanical properties of polystyrene
Authors: Morgan R. J. , Nielsen L. E.
Published: April 2003

Young's modulus and mechanical damping of 15 organic liquids in polystyrene have been measured from 4°K to 250°K. The concentration was generally in the range from 10 to 15%, but the polystyrene–toluene system was investigated over the range from 0 to 16%. Some liquids cause the 40°K damping peak of polystyrene to disappear, other liquids do not. Seven of the liquids which cause the disappearance of the 40°K peak give rise to new large damping peaks at the temperature expected for the secondary glass transition temperatures of the liquids, that is, at 0.77 Tg of the liquids. Some of the liquids produced large unexplained damping peaks at temperatures above the expected glass transition temperatures Tg of the liquids. It is suggested that the γ peak in polystyrene is caused by styrene monomer.
Rheological properties of poly(2,6‐dimethylphenylene oxide)—polystyrene blends
Authors: Prest W. M. , Porter Roger S.
Published: April 2003

The viscoelastic (VE) response of freeze‐dried blends of polystyrene (PS) and poly‐(2,6‐dimethyl phenylene oxide) (PPO) has been studied as a function of composition, frequency, and temperature to examine the degree of rheological compatibility. When blended together, the relaxation processes of both molecular species exhibit the same temperature dependence. However, the temperature dependence of the VE response is a function of composition. It is shown that this behavior can be predicted from the measured glass transition temperatures by assuming the additivity of the free volumes of the components. The properties of the blends are compared at equal free volumes. The effective segmental friction factor is found to be independent of composition while the modulus of the rubbery plateau increases with PPO concentration. This result is interpreted as a change in the entanglement molecular weight Me of the blends. When the changes in Me are considered, the relationship between the zero‐shear viscosity η0 and the 3.4 power of the weight‐average molecular weight, commonly found for high molecular weight homopolymers, predicts the compositional dependence of η0 for the PPO–PS blends. It is concluded that the PPO–PS system forms a rheologically compatible blend.
Change in infrared dichroism during and following high‐speed elongation of polyethylene
Authors: Uemura Y. , Stein R. S.
Published: April 2003

Use of a new apparatus is described which enables infrared dichroism to be followed as a function of time following the rapid stretching of a sample. The apparatus is double beam in dichroism, in that the infrared beam is alternately polarized parallel and perpendicular to the stretching direction and the transmitted intensity is observed on an oscilloscope. Results are presented for the stretching of a low‐density polyethylene sample by approximately 28% in a time of approximately 0.1 sec. The infrared dichroism is observed to change in times of the order of 50 to 100 msec after stretching, confirming the observation made by other techniques that crystal orientation changes during this time.
Crazing of glassy polymers in alcohols and hydrocarbons
Authors: Narisawa I.
Published: April 2003

In the crazing of glassy amorphous polymers, wetting ability and penetration of the fluid are the important practical parameters governing the activity of the fluid. Higher molecular weight and the presence of polar groups in the fluids result in an increase in the critical stress for craze initiation in polystyrene and polycarbonate. The Eyring treatment of the craze process can describe fairly well the temperature and strain rate dependence of the critical stress. The parameters involved in the Eyring theory suggest that the crazing takes place by a molecular motion of lower energy than does macroscopic yielding.
Alternating copolymerization of isoprene and butadiene with acrylonitrile
Authors: Koma Yasuo , Iimura Kazuyoshi , Takeda Masatami
Published: April 2003

Copolymerizations of acrylonitrile and isoprene or butadiene were carried out in the presence of a new catalytic system containing Cr(O‐tert‐Bu)4 and AlEtCl2. It was found that the copolymer compositions have a highly alternating structure, even with varying feed ratios of monomer. The nuclear magnetic resonance spectra of the copolymers obtained with this catalytic system were observed and are discussed in terms of the alternation.
Aminolysis of n‐butyl methacrylate–styrene copolymer with Di‐ and trifunctional amines
Authors: Gibson Harry W. , Bailey F. C.
Published: April 2003

Aminolysis of a random copolymer of styrene and n‐butyl methacrylate (2.54:1.00 mole ratio) with 6‐aminohexanol has been studied. Kinetics were determined by covalently dyeing the functional polymer and spectrally measuring dye content. In the presence of 1,4‐diaza[2,2,2]bicyclooctane (DABCO), an activation energy of 22.2 ± 1.0 kcal/mole was calculated from the temperature dependence of the overall rate of reaction. The rate is independent of solvent polarity. The rate at 189°C is 2.1‐fold slower than that of poly(n‐butyl methacrylate). The phenyl group of the styryl moiety inhibits the reaction, apparently via a steric effect. This aminolysis technique affords noncrosslinked (similar M̄n and M̄w) functional polymers. By a similar process an aminediol and an alcohol which contained a secondary and a primary amino group also yielded noncrosslinked functionalized polymers.
Polymerization of propadiene. III. Catalyst systems based on various rhodium (I) complexes
Authors: Scholten J. P. , van der Ploeg H. J.
Published: April 2003

The polymerization of propadiene to 1,2‐polyallene by various Rh(I) based catalysts is described and discussed. Also the interrelations between these Rh(I) complexes are discussed and an overall reaction scheme is given. A mechanism is put forward in which the formation of a common intermediate from propadiene and different Rh(I) complexes is the rate determining step. It is found that the activity decreases in the order: cis‐Rh(CO)2P(C6H5)3Cl > [Rh(CO)2Cl]2 > Rh(CO)3Cl. The complexes Rh[P(C6H5)3]2(CO)Cl and Rh[P(C6H5)3]3Cl proved to be inactive in the polymerization of propadiene.
Anionic polymerization of propylene oxide
Authors: Blanchard L. P. , Hornof V. , Moinard J. , Tahiani F.
Published: April 2003

The anionic polymerization of propylene oxide with the use of potassium tert‐butoxide and naphthalene sodium as initiator and dimethylsulfoxide, tetrahydrofuran and mixtures of both as solvent was investigated. The reactions were carried out in vacuum‐sealed dilatometers over the temperature range 20−60°C. The products were analyzed by gelpermeation chromatography and infrared spectroscopy. The object of the investigation was to obtain information on the mechanism of the reaction and elucidate some of its kinetic aspects. It is shown that the polymerization occurs by two different processes depending on the experimental conditions: one involving free ions and ion‐pairs, the other, ion‐pairs alone. In the first case, where DMSO was used as solvent, the order of the reaction with respect to the initiator is greater than unity (∼1.7), while in the second case, involving the mixture of DMSO and THF and ion‐pairs alone, the reaction order is only one. Transfer to monomer is believed to take place only in the strongly dissociating DMSO medium, where free ions are present.
Polyesters containing the norbornane structure
Authors: Wilson John C. , Hamb F. Lynn
Published: April 2003

Several norbornane and norbornane condensed diesters and dimethanols have been synthesized. Varying the points of substitution in the norbornane moiety has been found to have little effect on the glass transition temperatures of polyesters prepared from these compounds. Increasing the number of norbornane residues as polymer side chains results in a linear increase in the Tg. The increase is an apparent function of the size of the norbornane moiety relative to the polymer repeating unit.
Application of mass spectrometry to the study of fluoropolymers. III. Polyperfluorobut‐2‐yne
Authors: Flowers W. T. , Haszeldine R. N. , Janik A. , Lee A. K. , Marshall P. G. , Sedgwick R. D.
Published: April 2003

Mass spectra of the volatile fractions from polyperfluorobut‐2‐yne have been obtained. The polymer appears to be thermally stable up to 300°C and molecules containing up to 12 monomer units have been identified. A regular structure is indicated by the mass spectrum which is characterized by unusually intense doubly charged ions. The endgroups are readily identified, and a conjugated polyolefin structure is indicated.
Polyorthocarbonates
Authors: Takekoshi Tohru
Published: April 2003

Hitherto unreported aromatic polyorthocarbonates have been synthesized by the reaction of dichlorodiphenoxymethane and various aromatic dihydroxy compounds.
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The polymers possess the structure of a methanetetra‐ol ether (carbonic acid orthoester) in the main chain. The direct structural evidence was obtained by 13C NMR. High molecular weight, linear polyorthocarbonates were derived from sterically unhindered bisphenols. The polymers were noncrystalline, and clear, flexible films were obtained by casting from solution. Aromatic polyorthocarbonates decomposed above 360°C under nitrogen. The polymers were extremely stable under basic conditions but were unstable in strongly acidic media, particularly at elevated temperatures.
Closed‐form solution of the finite torsion problem by use of the λ form of the strain‐energy function
Authors: Valanis K. C.
Published: April 2003

A closed‐form solution for the stress distribution in a cylindrical elastic rod under finite torsion is given involving use of the logarithmic λ form of the strain‐energy function proposed by Valanis and Landel. Experimental torque data on natural rubber which give support to the present solution over a large range of angles of twist are shown. It is also shown how torsion data may be used to determine the λ form for deformations that lie outside the range of applicability of the logarithmic function if certain conditions apply. A solution, also in closed form, is given by using another λ form proposed by Dickie and Smith on the basis of experiments on styrene—butadiene rubber.
X‐ray measurement of cellulose crystallite orientation in cotton fibers
Authors: Seitsonen Sulo , Inkinen Pentti
Published: April 2003

The orientation of crystallites in a bundle of parallel cotton fibers was studied by x‐ray diffraction. The intensity distributions of the 101 and 002 diffraction rings showed the distributions of (101) and (002) planes to be identical within the limits of accuracy. Therefore, the crystallites in the cotton fibers very likely had random orientation about their long axes. The orientation distribution of these axes was calculated by using the intensity distribution of the 002 diffraction ring. The cylindrically symmetrical density distribution J(β) thus obtained was multiplied by sin β to obtain the distribution of relative numbers of crystallites at given angles β to the long axis of the fiber. The average 〈β〉 was found to be in agreement with the value of 〈sin2β〉 measured from the 002 diffraction ring. The intensity distributions on the 101 and 002 diffraction rings showed small fluctuations. These fluctuations appeared much stronger in the J(β) and sin β J(β) distributions, indicating clear discontinuities in the pitch angle distribution.
Infrared study of out‐of‐plane deformation vibrations of linear and cyclized 1,2‐ and 3,4‐polyisoprenes
Authors: Vodehnal J. , Drahorádová E.
Published: April 2003

This study concerns the influence of 3,4 and 1,2 addition in cyclic polyisoprenes on the extinction coefficients of the absorption bands at 890 and 910 cm−1 due to out‐of‐plane vibrations of CH2 of the isopropenyl and vinyl groups (correspoding, respectively, to 3,4 or 1,2 addition). In contrast to analogous bands characteristic of 1,4 addition (especially in the case of cis‐1,4 units of polybutadiene), the shape, position, and intensity of these bands are not influenced by changes in the structure of the macromolecular chain. The extinction coefficients of both bands did not change substantially, although the overall presence of both linear and cyclic forms varied over a wide range. It can be assumed, therefore, that the influence of configurational changes upon the intensity of the absorption bands of out‐of‐plane vibrations for double bonds is not a general phenomenon.
Annealing during polymerization of crystalline poly(ethylene terephthalate)
Authors: Miyagi Arata , Wunderlich Bernhard
Published: April 2003

Melt‐crystallized poly(ethylene terephthalate) and etched oligomer lamellae from the same polymer have been annealed under vacuum at temperatures between 200 and 260°C and times between 3 and 48 hr. The annealed samples were analyzed through determination of viscosity‐average molecular weight, x‐ray low‐angle spacing, density, heat of fusion, and variation of melting point with heating rate. In all cases it could be shown that the crystal lamellar surfaces remained chemically reactive. Chain folds and chain ends in the surface were converted by chemical reaction to tie molecules between different crystals or different locations on the same lamella.
Influence of crystallization temperature, molecular weight, and additives on the crystallization kinetics of poly(ethylene terephthalate)
Authors: Van Antwerpen F. , Van Krevelen D. W.
Published: April 2003

The spherulite growth rate, the maximum spherulite radius, and the overall rate of crystallization of poly(ethylene terephthalate) (PETP) were measured by means of scattering and transmission of depolarized light. The influence of crystallization temperature, molecular weight, and additives on the above‐mentioned quantities was investigated. An expression has been derived for the spherulite growth rate of PETP as a function of crystallization temperature and the number‐average molecular weight for M̄n in the range of 19,000 to 39,000.
A model for the spherulite‐to‐fibril transformation
Authors: Robertson Richard E.
Published: April 2003

Based on an analogy with the growth of kink bands in oriented and annealed crystalline polymers, a mechanism is suggested for the deformation‐induced spherulite‐to‐fibril transformation. Oriented and annealed material was employed as a model because it has roughly the same structure as the lamellar bundle of the spherulite. Under conditions that minimize the fibrillar quality and maximize the lamellar bundle quality, oriented and annealed crystalline polymers deform with the formation and growth of kink bands. The characteristics of kink bands are the sharpness of the kinks, occurring within zones ca. 100 Å wide, and mirror symmetry of the fibrils about the kink‐zone planes. The spherulite‐fibril transformation is suggested by analogy, then, to occur in the narrow zones that indeed are often found and to result in mirror symmetry of the chain axes about the transformation‐zone planes, which may not exactly occur because of a tendency for the tie molecules to be pulled from the lamellae during drawing. The implications for the transformation are (a) that the microfibril backbones are derived from the tie molecules between lamellae and (b) though some unfolding occurs as blocks that were adjacent within the lamellae become separated, the crystals remain mostly intact during the transformation. The analog is supported by or at least is consistent with various other results, including those from morphological and small‐ and wide‐angle x‐ray studies.
Spectrum of light scattered from polydisperse polymer solutions
Authors: Benbasat Julyet Aksiyote , Bloomfield Victor A.
Published: April 2003

We examine several methods for analyzing the spectrum of light scattered from polydisperse polymer solutions. General expressions are reviewed for the inelastic scattering spectra and integrated intensities due to the pure translational normal mode of motion, using both heterodyne and homodyne detection, in terms of the molecular weights, concentrations, scattering form factors, and diffusion coefficients of the individual polymeric species, These results are used to obtain general expressions for the limiting slopes and intercepts of various rearranged versions of the equation I(v) = (A/π)2/(v2 + γ2) that permit linear plotting: I(v) is the intensity of light scattered at frequency v, A is the integrated intensity, and γ is the spectral halfwidth, K2D/2π, where K is the scattering vector and D the diffusion coefficient. These results are applied to the special case of a Schulz‐Zimm distribution, neglecting form factors, to obtain explicit expressions relating the average diffusion coefficients determined by these procedures to other measurable quantities: the mean polymer radius; the diffusion coefficient of the weight‐average species; and, together with the weight‐average sedimentation coefficient, the weight‐average molecular weight. Numerical calculations for two particular cases indicate the relative merits of the various data analysis procedures. Homodyne detection gives average values that are closer to weight averages than does heterodyne detection.
Crystal orientation in a semicrystalline polymer in relation to deformation of polymer spherulites. II. Orientation distribution function of crystallites within crystal lamella as a function of lamellar orientation
Authors: Nomura Shunji , Matsuo Masaru , Kawai Hiromichi
Published: April 2003

A model relating crystal orientation in a semicrystalline polymer to the deformation of polymer spherulites is proposed. The distribution function for orientation of crystallites within crystal lamellae is assumed to be a function of lamellar orientation. In addition to the orientation of crystal lamellae in affine fashion, several parameters are introduced to characterize the untwisting of the crystal lamellae and the four different types of orientations of the crystallites within the crystal lamellae in the undeformed and deformed states of the spherulite. The model was tested by experiments in uniaxial stretching of a low‐density polyethylene. The theoretical distributions of orientation of given reciprocal lattice vectors of the crystallites, such as the reciprocal lattice vectors of the (110) and (200) crystal planes, are compared with the results of x‐ray diffraction experiments. It was found that the most important factors in fitting the model to experimental results are: (a) the fraction of crystallites having random orientation within lamella and, in turn, representing the degree of imperfection of the lamella in the undeformed state; (b) the ease of transition of crystal orientation within lamella from b‐axis orientation parallel to the lamellar axis to two types of c‐axis orientations (type Ca and type Cr) parallel to the stretching direction; and (c) the fraction of crystallites having orientation in type Cr (unfolding mechanism) rather than type Ca (rotation mechanism).
Polarographic study of the effect of solvents on the reaction of Na amalgam with some vinyl monomers
Authors: Margel Sh. , Levy M.
Published: April 2003

Acrylonitrile, methacrylonitrile, ethyl acrylate, anthracene, and Na+ were studied polarographically in four solvent media: diglyme, DMSO, 25% H2O in diglyme, and liquid NH3. Cathodic shifts were observed for Na+ and anodic shifts for the vinyl monomers in DMSO, H2O and NH3. The values of ΔE = (E1/2, monomer — E1/2, Na+) were used in interpretation of the solvent effects observed previously for the reaction of these monomers with Na amalgam. In diglyme ΔE is very large (0.49 V for MeAN and 0.37 V) for AN, and therefore very slow reaction takes place. In DMSO, MeAN still reacts very slowly (ΔE = 0.23 V), while AN (ΔE = 0.09 V) reacts considerably faster than in diglyme and 100 times faster than MeAN in DMSO. Liquid ammonia brings both MeAN and AN to very low ΔE (0.08 V and −0.05 V, respectively), and both reactions are very fast and yield only the hydrodimers. Water, on the other hand, has a large accelerating effect on the rate, but as it is a proton donor it yields only the reduced products.
Chlorinated polyethylene. II. Chlorine distribution on the polymer chains
Authors: Abu‐Isa Ismat A. , Myers Mark E.
Published: April 2003

The nature of substitution in a slurry‐phase chlorination of high‐density polyethylene was studied using NMR and IR spectroscopy. The ratios of γ (or greater) methylenes were obtained from the NMR at different chlorine levels and compared with the theoretically predicted values based on a statistical treatment for substitution polymers. The results indicted that, unlike chlorosulfonated polyethylene, chlorinated polyethylene shows a hindered‐type substitution. Molecular weight of the parent polyethylene, the degree of chlorination and the degree of residual crystallinity of the samples have no bearing on the type of substitution.
Preparation, copolymerization kinetics, and viscoelastic behavior of copolymers of 1,3‐butadiene and 1,4‐diphenyl‐1,3‐butadiene
Authors: Hsieh H. L. , Kraus Gerard
Published: April 2003

1,4‐Diphenyl‐1,3‐butadiene reacts readily with sec‐butyllithium in toluene to form adducts. Although this 1,4‐substituted conjugated diene did not homopolymerize or copolymerize with styrene, with butadiene it formed copolymers having compositions varying from one end of the chain to the other. The monomer reactivity ratios found were r1 = 8.2, r2 = 0 in toluene and r1 = 2.1, r2 = 0 in toluene–tetrahydrofuran (0.2%) solution. The intramolecular composition distribution of these polymers varied from an initial butadiene‐rich composition, dependent on the ratio of monomers charged, to the equimolar composition of the alternating copolymer. In spite of this compositional heterogeneity, the crosslinked polymers exhibited a single glass transition characteristic of the mean composition. A secondary, high‐temperature dispersion observed in the dynamic viscoelastic properties of some of the products is shown to be attributable to network topological effects.
Sulfur‐containing polymers. VII. Alternating copolydisulfides
Authors: Kobayashi Norio , Fujisawa Tamotsu
Published: April 2003

A variety of copolydisulfides have been synthesized in high yields by the fragmentation polymerization of bis(sulfenyl thiocarbonates) with dithiols in the presence of triethylamine. The structures of the copolymers were investigated by x‐ray and NMR studies. Alkylene–arylene copolydisulfides were alternating. Alkylene–arylene copolymers derived from arylene dithiols were alternating, and those prepared from alkylene dithiols were generally random. It was concluded that the present procedure makes it possible to prepare various kinds of alternating copolydisulfides by using appropriate combinations of a bis(sulfenyl thiocarbonate) and a dithiol.
Dichloromaleimide chemistry. IV. Preparation of poly(maleimide–ethers) from the reaction of bisdichloromaleimides with bisphenols
Authors: Relles H. M. , Schluenz R. W.
Published: April 2003

A newly discovered reaction between phenols and dichloromaleimides has led to the synthesis of a new class of polymers of high molecular weight. These materials, represented by the general formula may be called poly(maleimide–ethers). Unlike polyimides,
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these materials are soluble in appropriate solvents and may be cast or compressionmolded into tough, flexible films.
Preparation and properties of polysulfonamideimides
Authors: Imai Yoshio , Okunoyama Hikaru
Published: April 2003

A new class of polysulfonamideimide has been synthesized by the two‐step cyclopolycondensation of 4‐chlorosulfonylphthalic anhydride with aliphatic and aromatic diamines. The polycondensation‐addition reaction proceeded through the formation of poly(sulfonamideamide acids), and a subsequent thermal or chemical cyclodehydration of the precursor polymers yielded polysulfonamideimides. The poly(sulfonamide amide acids) having inherent viscosity in the range of 0.1–0.7 in dimethylacetamide were obtained in high yield. All of the polymers were soluble in polar aprotic solvents and in basic solvents. Aromatic polysulfonamideimide derived from bis(4‐aminophenyl) ether began to decompose at around 350°C in air as determined by differential thermal analysis and thermogravimetric analysis.
Solution decomposition of poly(vinylidene chloride): Effect of solvent and evolved HCl
Authors: Agostini D. E. , Gatzke A. L.
Published: April 2003

The effect of HCl on the rate of thermal decomposition of poly(vinylidene chloride) (PVDC) in nitrobenzene solution was measured with the object of determining the catalytic activity of HCl. Unlike those reports dealing with PVC decompositions, this study shows that in the absence of a cocatalyst, molecular HCl does not catalyze the decomposition of PVDC. In the presence of metals which can react with HCl to form Lewis acids (e.g., Fe0), a strong accelerating effect was observed. The uncatalyzed reaction shows a large rate increase with increasing polarity of the solvent, suggesting that in nitrobenzene the decomposition is mainly heterolytic in nature.
Cationic polymerization of α,β‐disubstituted olefins. Part 17. Effect of polymerization conditions on the reactivity of alkenyl ethers relative to vinyl ethers
Authors: Higashimura Toshinobu , Kawamura Kazumitsu , Masuda Toshio
Published: April 2003

In order to clarify the propagation reaction, vinyl ether was copolymerized with the corresponding alkenyl ether under various conditions. cis‐Propenyl ether (cis‐PE) was several times more reactive than trans‐PE and the corresponding vinyl ether in the copolymerization catalyzed by BF3 · O(C2H5)2 in toluene. However, the reactivity of cis‐PE relative to trans‐PE and the vinyl ether was found to be greatly decreased with increasing polarity of the solvent and to be very close to unity in such polar solvents as nitroethane. On the other hand, the reactivity of trans‐IBPE relative to IBVE was scarcely changed by polymerization conditions. Also, the nature of the initiator and polymerization temperature affect the reactivity of cis‐PE relative to the vinyl ether. These phenomena were explained by the relative stability of the bridged and open car bonium ions based on the polarity of the solvent and steric hindrance due to substituents in the trans isomer.
Polymerization of N‐vinylcarbazole in presence of carbon tetrabromide. III. Oxygen‐induced photodimerization in methanol solution
Authors: Kauffmann H. F. , Breitenbach J. W. , Olaj O. F.
Published: April 2003

The rate of photochemical dimerization of N‐vinylcarbazole (NVC) in methanol solution which takes place only in the presence of oxygen is greatly increased by addition of carbon tetrabromide (CTB). Similar high rates are obtained with sensitizers like benzil and biacetyl. The mechanism of formation of the cyclic dimer, trans‐1,2‐dicarbazole‐9‐yl‐cyclobutane (I), and of the open‐chain dimeric dimethoxy derivative, 1,4‐dicarbazole‐9‐yl‐1′,4′‐dimethoxy‐n‐butane (II), is discussed in some detail.