bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton magnetic resonance studies of the microstructure of polymethacrylic anhydride
Authors: Miller W. Lamar , Brey Jr. Wallace S. , Butler George B. 
Published: April 2003

AbstractMethacrylic anhydride was polymerized, in high yields, at temperatures ranging from 1 to 80°, in benzene solution, to linear, soluble polymers. The polymethacrylic anhydride so prepared was hydrolyzed to the corresponding polymethacrylic acid and this poly(acid) esterified by reaction with diazomethane to yield polymethyl methacrylate. The result is given of an x‐ray diffraction study of an unstretched film of polymethyl methacrylate prepared in a similar manner. The determination of the fraction of the polymer present in each of the three possible stereoconfigurations, isotactic, syndiotactic, and heterotactic, was made from a nuclear magnetic resonance investigation of the derived polymethyl methacrylate. The results indicate that the stereoconfiguration is influenced by the cyclic polymerization mechanism. The results also indicate that there is a bias toward increasing isotactic character in the polymers with an increase in polymerization temperature. Two possible explanations are offered: one in terms of a kinetic control of the steric placements and the other in terms of a balance between equilibrium and kinetic considerations.
Linear polyesters
Authors: Wilfong R. E. 
Published: April 2003

AbstractSince the classical syntheses by Carothers and co‐workers of linear polyesters, many types have been prepared and examined. The methods of preparation, kinetics of ester exchange and condensation, and the types of catalysts employed are reviewed. The classes of linear polyesters reported in the literature are tabulated, and selected examples are used to review the relationships between structure and polymer melting points.
Crystallite orientation and spiral structure of cotton. Part II. Decrystallized and mercerized cottons
Authors: DeLuca Lloyd B. , Orr Rollin S. 
Published: April 2003

AbstractA method is demonstrated by which both crystallite orientation and spiral angle can be directly determined from the x‐ray tracings of the 002 diffraction are of combed bundles of cotton fibers. Balls has shown that cotton has a spiral structure, and Sisson has shown qualitatively that these 002 arcs can be explained by applying two equal crystallite distributions separated by twice the spiral angle. If this distribution of crystallites is assumed to be a Gaussian distribution, the experimental are can be generated theoretically. This method of analysis is applied to x‐ray data for decrystallized and mercerized cottons. X‐ray diffraction shows the effects on fine structure of after‐treatments, such as tension and boiling in water, applied to samples of slack amine‐decrystallized and mercerized cotton yarns. The comparison of the calculated parameters with those of the gross arcs are given, as well as the relationships of these quantities to the tensioning force which produced them.
Internal friction in polyoxymethylene
Authors: McCrum N. G. 
Published: April 2003

AbstractMechanical relaxation was studied in bulk polyoxymethylene by means of a torsion pendulum. The magnitude of the large γ peak at 203°K. (for f = 1.1 cycles/sec.) decreases with increasing density. The magnitudes of the β peak at 260°K, and the α peak at 400°K. do not depend on density. The β peak is small unless the specimen contains water or has just been cooled from a temperature above ca. 370°K. The activation enthalpies of the α and γ relaxations are 24 and 27 keal./mole, respectively. The relaxation time distribution and activation enthalpy of the γ relaxation do not depend on density.
Stereospecificity and optical properties of polymers
Authors: Tsvetkov V. N. , Magarik S. Ya. , Boĭtsova N. N. , Okuneva M. G. 
Published: April 2003

AbstractPractically the only physical method of determining stereoregularity is x‐ray analysis, permitting one to judge the presence of a crystalline structure in a given polymer. However, crystallinity is a phase property, only indirectly reflecting the molecular structure of a substance. It is well known that a stereospecific polymer may be both in the crystalline and in the amorphous states. It is therefore highly important to find a property of the polymer which would directly (and unilaterally) indicate stereoregularity in its structures. Attempts to use the geometrical properties of molecular chains for this purpose have up to the present been unsuccessful, the sizes of macromolecules in solution (as determined by viscometry or light scattering) being found to be independent of stereoregularity. In the present work another approach has been sought, the attempt being made to ascertain whether the optical anisotropy of a molecule would be a more sensitive index of the stereospecificity of the molecular chain. With this in mind the flow birefringence was investigated, of solutions of polystyrene (from Dzerzhinsk) and of polymethylmethacrylate (from the laboratory of A. A. Korotkov) with varying degrees of stereoregularity. Experimental investigation of both polymers showed a marked increase in the segmental anisotropy α1 – α2 of the macromolecules when passing from the atactic to the isotactic specimens. Thus for atactic polystyrene α1 – α2 = 140 × 1025 cm3. whereas for isotactic polymer, α1 – α2 = 200 × 10−25 cm3. In the case of polymethyl methacrylate the difference was still greater. The increase in α1 – α2 in the case of polystyrene may be explained by the increased hindrance to rotation of the phenyl side chains on transition from the atactic to the isotactic polymer. The interpretation in the case of polymethyl methacrylate is not so evident and requires further elucidation. At the same time the fact itself of the influence of the stereoregularity of a polymer chain on its optical properties lays open the possibility of utilizing the latter to characterize the former.
Influence of donor‐type impurities on the polymerization of propylene catalyzed by a titanium trichloride‐triethylaluminum system
Authors: Veselý K. , Ambroẑ J. , Vilím R. , Hamr̂ík O. 
Published: April 2003

AbstractThe influence of some typical oxygen‐, sulfur‐, and nitrogen‐containing impurties on the polymerization of propylene in a hydrocarbon medium under the catalytic action of titanium trichloride and triethylaluminum was studied. Both these catalyst components used in polar‐coordinated polymerizations of α‐olefins are very reactive toward substances having atoms with a free electron pair. Triethyl aluminum forms complex compounds with these substances. Some of the complexes are so stable as to allow distillation; attempts to isolate the original components often lead to the destruction of the whole molecule. Donor‐type compounds do not attack triethylaluminum only; they also attack titanium trichloride which displays the properties of a strong sorbent. The transitional metal (Ti) with incompletely occupied d‐orbits and a lone electron gives ample opportunities for chemisorbing molecules of olefins as well as molecules containing atoms of the fifth and sixth groups of the periodic table. Donor‐type substances were studied on the one hand from the viewpoint of the interaction with the separate catalyst components (the influence of the so modified catalyst on the polymerization being studied) and on the other hand from the viewpoint of the influence of the donor‐type substance during the course of polymerization, i.e., the effect on both unmodified catalyst components (including the active complex) simultaneously. Changes of the principal characteristics of the polymerization process (viz., the overall rate of reaction, the molecular weight, and the percentage of amorphous matter) have been followed. It became evident that the interaction between the donors and the solid phase of the catalyst is governed by rules of adsorption (excluding cases involving deeper changes of the solid phase during the reaction, e.g., its dissolution). Compounds which are sorbed influence the polymerization process in a significant manner. They come into play more intensely than the products of the interaction of donor‐type substances with triethylaluminum which generally result in the formation of complex compounds not influencing the course of polymerization so strongly. It has been found that from among the characteristics studied the overall rate of polymerization is the one which is most affected by the presence of substances with free electron pairs. With minor exceptions the molecular weight was found to increase through the agency of the admixtures. A similar relationship has been found to hold for the percentage of amorphous matter as well.
The decomposition of benzoyl peroxide in polymers. III
Authors: Haas Howard C. 
Published: April 2003

AbstractThe decomposition of benzoyl peroxide in polystyrene in the presence of air has been studied spectrophotometrically over an expanded (55 to 98°C.) temperature range. Rates of decomposition of benzoyl peroxide in polyvinyl chloride films are also presented. Peroxide decomposition in both polymers obeys first‐order kinetics and the Ea for decomposition appears to change at or near the second‐order transition temperature of the polymers. Rates of peroxide decomposition are lower and energies of activation are higher in polyvinyl chloride than in polystyrene.
The effect of radiation on copolymers of styrene and α‐methylstyrene
Authors: Kotliar A. M. 
Published: April 2003

AbstractThe G values for chain scission G(s) and crosslinking G(γ) processes were determined for unfractionated and fractionated polymers having 50–50 and 25–75 mole‐%α‐methylstyrene and styrene content and are in agreement with the reported values for the respective homopolymers, corrected for mole content. These values are G(s) = 0.12, G(γ) = 0.062, G(s) = 0.10, and G(γ) = 0.094 for the 50–50 and 25–75 copolymers, respectively. The evaluation of the resulting intrinsic viscosities from the distributions computed by the Monte Carlo sampling technique in the interval, O < P < 10 P̄n,o, and Small's asymptotic expansion in the interval Pn,o ≦ P ≦ ∞ show the best correlation when g′ values (the ratio of the mean square radii of a branched to linear molecule identical in size and composition) of 0.79 and 0.72 are used for each interval, respectively.
Hydrolytic stability of side groups in polymer having inorganic chains of molecules
Authors: Zhdanov A. A. , Andrianov K. A. 
Published: April 2003

AbstractThe hydrolytic condensation of trialkylsiloxane derivatives of the formula (R3SiO)n Me leads to the formation of an oxanometallic chain and trialkylsiloxane groups within the framework of the main chain. The formation of polymers by this mechanism is due to the hydrolytic cleavage of the metallic atom from the trialkylsiloxane group. The subsequent stability of the polymer formed to the action of water will depend also upon the hydrolytic stability of the trialkylsiloxane residues. In order quantitatively to evaluate the rate of hydrolytic cleavage of the trialkylsiloxane group from the various trialkylsiloxane derivatives a viscometric method was employed in which changes in viscosity of solutions of the compounds were followed with respect to duration of the hydrolysis and concentration of the reactants. From the changes in viscosity of the solutions the rate of hydrolysis of the compounds and the values of the hydroytic stability constants could be calculated.
Transition metal catalysts VI. Bis‐(cyclopentadienyl) transition metal polymerization catalysts
Authors: Karapinka George L. , Carrick Wayne L. 
Published: April 2003

AbstractIn the reaction of aluminum alkyls or aryls with (C5H5)2TiCl2 or (C5H5)2Ti(C6H5)2, there is rapid exchange of groups between the aluminum and titanium centers. When mixed alkyl and phenyl aluminum compounds react competitively with (C5H5)2TiCl2 to form ethylene polymerization catalysts, alkyl groups are more efficient than phenyl groups in initiating polymer chains. Since there is both selectivity in the initiation step and rapid exchange of groups, the presence or absence of phenyl endgroups in the polymer formed from different phenyl‐containing catalysts cannot be used to identify the active catalyst site, as has been proposed. Additional evidence is presented which suggests that the π‐bonding of the cyclopentadienyl compounds is disrupted either wholly or in part under the polymerization conditions, and at least part of the catalytic activity is due to the decomposition products.
Proton magnetic resonance of some α‐methyl group‐containing polymers and their monomers
Authors: Odajima A. , Woodward A. E. , Sauer J. A. 
Published: April 2003

AbstractProton magnetic resonance spectra of poly(methyl methacrylate) (PMMA), poly(methacrylic acid), poly(sodium methacrylate), poly(α‐methylstyrene), and the four corresponding monomers have been obtained from 77°K. At 77°K. all four polymers and α‐methylstyrene exhibit complex derivative line shapes. Coincidental with the loss of the broad component of the derivative shape, marked second‐moment changes in all four polymers occur in the 100–250°K region and are attributed to the onset of hindered α‐methyl group rotation. α‐Methylstyrene shows a corresponding second moment change in the 77–140°K. region which is 90–140° below that found for the polymer. At 77°K. considerable motion, presumably hindered methyl group rotation, is occurring in the methacrylate monomer crystals. At temperatures above 300°K. the NMR line narrowing is found for PMMA, poly(methacrylic acid), and poly‐(α‐methylstyrene) and is believed to be due to reorientation motions associated with the glass transition. The line narrowing process for highly isotactic PMMA and highly syndiotactic PMMA occurs rear 360 and 420°K., respectively, while for commercial samples it takes place near 410°K.—behavior in agreement with the different Tg values reported for these materials. Correlation frequencies have been calculated for the low‐temperature transition region for the four polymers and α‐methylstyrene, and are compared with theoretically derived curves.
Copolymerization of dimethyl propene‐2‐phosphonate and styrene using anionic initiation
Authors: Marvel C. S. , Paisley David M. 
Published: April 2003

AbstractDimethyl propene‐2‐phosphonate has been copolymerized with styrene by the use of n‐butyllithium and sodium naphthalene as initiators. Only a few mole per cent of the phosphorus containing monomers was incorporated in the copolymer in any case.
High‐pressure ethylene polymerization initiated by peroxide
Authors: Kodama Shinjiro , Shimidzu Takeo , Yuasa Sachio , Kagiya Tsutomu , Fukui Kenichi 
Published: April 2003

AbstractThe polymerization of ethylene initiated by di‐tert‐butyl peroxide is studied in batch system under pressures ranging from 300 to 1700 kg./cm.2, and at temperatures of 110 to 170°C., using reaction mediums of water, ethyl alcohol, and their mixture. An experimental rate equation in water is:

The rate is proportional to the concentration of radical produced by the first‐order decomposition of initiator. A reaction scheme is proposed from which this rate equation can be derived. According to this scheme, the deactivation of radical is kinetically of the first order with respect to the radical concentration. Several relations between the reaction conditions and properties of polyethylene produced are also described.
Copolymerization of itaconic anhydride and styrene, determination of reactivity ratios
Authors: Drougas John , Guile Ralph L. 
Published: April 2003

AbstractThe copolymerization of itaconic anhydride and styrene has been studied and ther1‐r2values determined. In benzener1= 0.78,r2= 0.015; in tetrahydrofuranr10.60, =r2, 0.10. One possible explanation of the definite positive deviation from constant values in the different solvents has been advanced; it is based on the fact that the copolymer precipitates from benzene as formed. In all cases ther1,r2product is in the order of 0.01 to 0.06 and indicates that the copolymer is highly alternating in structure. Excellent agreement has been obtained between values of copolymer compositions by analysis and values predicted by copolymer theory based on the copolymer equation. Copolymers of molecular weights in the order of 50,000 to 150,000 (determined by light scattering) were prepared. The rate of copolymerization was about twenty times faster in benzene than in tetrahydrofuran.
Fundamental studies on cationic polymerizations i. the inversion temperature
Authors: Kennedy J. P. , Thomas R. M. 
Published: April 2003

AbstractThe low‐temperature AlCl3‐initiated polymerization of isobutene has been investigated. Direct evidence of the occurrence of chain‐breaking reactions is presented. The polymer molecular weight can be affected by changes in reaction temperature between ‐35 and −78°C. at the same conversion level. The discovery of inversion temperature (Ti) is described. At Ti, the molecular weight becomes independent of monomer concentration. We call Ti the temperature level at which the dependence of product molecular weight on the monomer concentration changes its sign. The inversion temperature has been observed in methyl chloride, ethyl chloride, and vinyl chloride, and vinyl choride diluents. A theory explaining the phenomenon is postulated. It is suggested that competing chain breaking process having dissimilar activation energies determine the molecular weight. Their effects cancel each other at Ti. The previously reported, unusual inverse relation existing between molecular weight and monomer concentration is explained by the concept of Ti.
A kinetic study of polymerization of ethylene with Al‐TiCl4 catalyst
Authors: Fukui Kenichi , Shimidzu Takeo , Yagi Tetsuya , Fukumoto Satoshi , Kagiya Tsutomu , Yuasa Sachio 
Published: April 2003

AbstractThis study of Al–TiCl4 catalysts for olefin polymerization continues work reported in preceding papers but with the use of aluminum wire under constant pressures. The use of aluminum having a very small surface area was convenient for the kinetic study of the reaction mechanism. The reaction time is divided into four periods. The first and second are connected with active‐center formation and are considered to be a kind of induction period. The third is a stationary period in which the rate is proportional to the square of pressure and the activation energy is ca. 16 kcal./mole. In the fourth period the rate is proportional to pressure and decreases gradually owing to a rate‐controlling diffusion step through the polymer layer produced. A kinetic consideration is proposed and a reaction scheme formulated for initiation, propagation, transfer, and termination. An ethylene‐propylene copolymerization study was also carried out, and lead to the supposition of a cationic mechanism in respect to the present type of polymerization.
The effect of stereoregularity on the polyvinyl alcohol–iodine reaction
Authors: Imai Kiyokazu , Matsumoto Masakazu 
Published: April 2003

AbstractThe color reaction of PVA solution with iodine depends upon the conditions under which the parent polyvinyl acetate was prepared, especially on the polymerization temperature. The higher the degree of polymerization of PVA and the lower the polymerization temperature of the original polyvinyl acetate, the more intense is the blue color. When compared with samples of the same degree of polymerization, samples of PVA from polyvinyl acetate prepared at lower temperatures give the more intense blue color. The result may be explained by differences in stereoregularity.
Effect of formic acid and formates on the oxidation of hydrocarbons and hydrocarbon polymers
Authors: Yur'Ev V. M. , Pravednikov A. N. , Medvedev S. S. 
Published: April 2003

AbstractIt is known that the rate of oxygen absorption and the concentration of peroxides in the course of hydrocarbon oxidation passes through a maximum. A similar picture is observed also on oxidation of liquid hydrocarbons. However, the lowering of the oxidation rate and of the concentration of peroxides is evidently due to the accumulation of oxidation inhibitors in the system rather than to a drop in the hydrocarbon concentration. In order to ascertain the nature of the inhibiting action of the products of hydrocarbon oxidation, a kinetic study was made of the oxidation of cetane, a hydrocarbon serving as a model of the polyethylene chain, at 140–150°C. The absorption of oxygen by cetane exhibits an autocatalytic character in the initial stages of the process (to the extent of 25–30%); however, on further oxidation, there is a rapid drop in the reaction rate. When the reaction has proceeded to above 40–50% its rate becomes practically constant. The peroxide accumulation curve passes through a maximum at 25–30% reaction and then falls abruptly. At extents of reaction above 40–50% the concentration of peroxides remains practically constant. At the same time the kinetic chain length of the oxidation reaction diminishes. A study of the effect of the oxidation products on the oxidation process showed that an inhibiting action is exerted by formic acid formed in the course of reaction. Its removal from the reacting system leads to an increase in the rate of oxygen absorption, accompanied by increase in concentration of the peroxides and in the kinetic chain length. The data obtained in the study of cetane oxidation of the hydroperoxide‐induced polymerization of various monomers in the presence of formic acid, and of the decomposition of the hydroperoxides in the presence of the latter give grounds for believing that inhibition of the oxidation of hydrocarbon polymers and of liquid hydrocarbons is associated with interaction between peroxides and the free radicals formed from the formic acid.
A rapid dynamic method for osmotic pressure determinations
Authors: Bruss D. B. , Stross F. H. 
Published: April 2003

AbstractA rapid dynamic osmotic pressure technique is described, which uses a high‐speed small‐volume osmometer equipped with capillaries of small diameter to measure solvent transport rates across the membrane. Measurement of the osmotic pressure of a solution can be made in 10 to 15 min. Comparison of the dynamic results for molecular weight with those obtained by the static‐equilibrium method indicates that the dynamic method affords a much closer approximation to the true number‐average molecular weight than does the static method when membrane‐permeable components are present in the sample.
Evaluation of molecular size distributions and molecular weight averages resulting from random crosslinking and chain‐scission processes
Authors: Kotliar A. M. , Podgor S. 
Published: April 2003

AbstractIt is shown that the changes in the molecular size distribution for high polymers undergoing random crosslinking and chain‐scission processes may be evaluated by means of the Monte Carlo sampling technique and a generalized asymptotic function. The technique is applied to an initial Schulz‐Zimm type of distribution and the resultant distribution, their moments, and the intrinsic viscosity in a theta solvent are evaluated as functions of the crosslinking and chain‐scission parameters.
An approximate estimation of the number average DP of amylose and amylopectin in moderately degraded whole (unfractionated) starch by the periodate method
Authors: Schmorak J. , Mejzler D. , Lewin M. 
Published: April 2003

AbstractA method, based on periodate oxidation is proposed for the determination of approximate true number average DP of amylose and amylopectin fractions in whole starch which has been randomly degraded to a moderate extent. The method is approximate only. This is compensated for by the fact that it is not affected by associative phenomena in solution, and that no fractionation is required. A numerical example is given, showing the application of the theoretical formulas to experimental data.