bluuebunny/crossref_metadata_2025 huggingface dataset:
High frequency effects in polyelectrolyte solutions
Authors: Johnson G. A. , Neale S. M.
Published: April 2003

Conductivity measurements of solutions of sodium polymethacylate (PMA), sodium carboxymethyl cellulose (CMC), and sodium alginate (AA) are presented. Measurements were made in the frequency range of 1 to 30 Mcycles/sec. The increment of electrical conductivity is taken as a measure of the dielectric loss occurring in the solution. The theories of Debye,1 Debye–Falkenhagen,2 Maxwell–Wagner,3 and the recent ionic model proposed by O'Konski4 are discussed and it is shown that the results can be satisfactorily explained only with an ionic model of the form of O'Konski's. Previous work is shown to fit in satisfactorily with this theory. In a few cases measurements of loss factors and dielectric constants are presented, and are shown to give additionnal support to the model of O'Konski.
The kinetics of the thermal degradation of polystyrene and polyethylene
Authors: Anderson David A. , Freeman Eli S.
Published: April 2003

The nonisothermal method of Freeman and Carroll is used to investigate the kinetics of the thermal degradation of polyethylene and polystyrene. The reactions were studied thermogravimetrically under a vacuum of 1 mm Hg. Decomposition appears to occur in stages. The rate parameters were determined for each region of reaction. Mechanisms of degradation are suggested. The results of this investigation are compared with the kinetic parameters reported by other investigators for the decompostion of these polymers.
Proton magnetic resonance studies of the microstructure of polymethacrylic anhydride
Authors: Miller W. Lamar , Brey Jr. Wallace S. , Butler George B.
Published: April 2003

Methacrylic 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

Since 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

A 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

Mechanical 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

Practically 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

The 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

The 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

The 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

The 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

In 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

Proton 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

Dimethyl 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

The 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

The 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

The 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

This 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

The 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

It 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

A 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

It 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

A 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.
Ultraviolet irradiation of plastics. II. Crosslinking and scission
Authors: Stephenson C. V. , Moses B. C. , Burks R. E. , Coburn W. C. , Wilcox W. S.
Published: April 2003

Ultraviolet irradiation of polyethylen, nylon, Mylar, and Acrilan produces higher scission‐to‐crosslinking ratios when irradiation is performed in a nitrogen atmosphere than it does when irradiation is in a vacuum. Irradiation of polyethylene in nitrogen causes a sharp decrease in molecular weight while irradiation of Acrilan in vacuum causes an equally notable increase in molecular weight.
Polyurethanes. II. Effect of cis‐trans isomerism on properties of polyurethanes
Authors: Lyman D. J.
Published: April 2003

The cis and trans isomers of 1,4‐cyclohexanediol and 1,4‐cyclohexanedimethanol were reacted with methylene bis(4‐phenyl isocyanate), using solution polymerization techniques, to form the corresponding cis and trans polyurethanes. The properties shown by these polyurethanes indicate that enhanced flexibility due to inclined rotating bonds is responsible for differences in polymer melting points. The polymer chain shape, or configuration, has also been shown to influence the polymer properties. This approach has been extended to include differences in polymer solubilities, molecular weight/inherent viscosity ratios, initial modulus, and water absorption.
N‐Carboxyglycine anhydride polymerization with p‐bromoaniline
Authors: Moos Gilbert E. , Merritt Paul E. , Chen Francis P.
Published: April 2003

The presence of a p‐bromoaniline initiator fragment in polyglycine formed from N‐carboxyglycine anhydride has been confirmed by bromine and infrared analyses. Carius halogen analyses, sodium fusions, and Beilstein halogen tests prove the presence of bromine in the polymer. Both the per cent bromine and the per cent amino nitrogen data specify essentially the same molecular weight, 1500–1700, for the polymer. Per cent yield of polymer data provide a second‐order catalytic constant for p‐bromoaniline‐initiated polyglycine in dioxane at 37°C. of 1.8 × 10‐3 l. mole‐1 sec.‐1 for the first 51% of the reaction, and the calculated constant beyond that falls off rather rapidly.
Laterally ordered polymers: Polyacrylonitrile and poly(vinyl trifluoroacetate)
Authors: Bohn C. R. , Schaefgen J. R. , Statton W. O.
Published: April 2003

The structure and properties of two laterally ordered (directionally crystallized) polymers are discussed, namely, polyacrylonitrile and poly(vinyl trifluoroacetate). Evidence from x‐ray diagrams, infrared measurements, thermal expansion data, and fiber properties are interpreted in terms of molecular structure. It is concluded that the existence of only chain‐to‐chain order (lateral order) in polyacrylonitrile and poly(vinyl trifluoroacetate) is principally due to steric and dipolar intramolecular repulsions. These lead to a chain stiffening effect, regardless of tacticity, which is so great in the former case that the backbone chain is forced to assume a twisted, kinked configuration. The stiff molecular chains may be thought of as rigid rods which pack in a lattice array. The side groups, nitrile or trifluoroacetate, assume varying angles with the respect to the rod axis in order to minimize the steric and dipolar repulsion forces. This variation gives rise to diffuse off‐equatorial scattering in the x‐ray diagram of the oriented polymers and low values of the dichroic ratios of selected bands in the infrared. The chain stiffening effect is greater in polyacrylonitrile and this polymer exhibits a higher “melting point”, higher fiber tenacity at equivalent orientation, less solubility, more general diffuse scattering in the x‐ray diagram, and lower dichroic ratios in the polarized infrared spectrum than does poly(vinyl trifluoroacetate). In fact, polyacrylonitrile, in contrast to poly(vinyl trifluoroacetate), acts as if it were all ordered and contained no amorphous regions in the usual sense, as judged from thermal expansion data and the lack of a definite amorphous halo in the x‐ray diagram. Poly(vinyl trifluoroacetate) is concluded to be no more syndiotactic than conventional poly(vinyl acetate), since laterally ordered poly (vinyl trifluoroacetate) can be derived from commercial poly (vinyl alcohol) by esterification. Therefore, the observed lateral order in poly (vinyl trifluoroacetate) is not due to a predominantly syndiotactic structure. These laterally ordered polymers have a properties intermediate between those of normally crystalline polymers and those of amorphous polymers.
Phase equilibrium of polydispersed polymer solution and fractionation
Authors: Okamoto H. , Sekikawa K.
Published: April 2003

Phase equilirium of a polydispersed polymer solution was investigated. Experiments on the system of linear polyethylene, xylene, and ethylene glycol were found to be approximately described by Flory's theory. To obtain a more precise description, the authors give a modification of Flory's relation. Methods by which the molecular size distribution of the fractionated polymer can be calculated from that of the unfractionated are proposed. Conditions favorable to effective fractionation are also briefly discussed.
Radiation‐induced graft polymerization: The trommsdorff effect of methanol
Authors: Odian George , Sobel Marjorie , Rossi Albert , Klein Robert
Published: April 2003

The radiation‐induced graft polymerization of styrene to low density polyethylene was investigated. It was found that dilution of the styrene monomer with methanol accelerates the rate of graft polymerization with a maximum effect occurring at approximately 70 vol.‐% methanol. Both the accelerated and unaccelerated graft polymerizations yield volumetric or homogeneous graft copolymers. Experiments in which n‐octane was substituted for methanol as the diluent showed that the accelerative effects of methanol are best explained by the incursion of a Trommsdorff‐type effect. The kp2/kt values for the grafting reaction in the various styrene‐methanol solutions were calculated. It was found that the kp2/kt term is larger in grafting than in homopolymerization by a factor of 103, and that it increases as the methanol concentration of the monomer solution increases.
Diffusion of gases and vapors through polyvinyl chloride‐polyvinyl acetate copolymer films I. Glass transition effect
Authors: Kumins C. A. , Roteman J.
Published: April 2003

The specific volume of a polyvinyl chloride‐polyvinyl acetate copolymer was studied as a function of temperature. It was found that two second‐order transition temperatures exist, one at 30°C. and the other at 77°C. The lower transition temperature has not been reported previously. Diffusion coefficients for several gases of varying van der Waals diameters were measured at several different temperatures and the activation energies for diffusion calculated. It was found that the activation energies were exponential functions of the gas diameters. For the smaller‐sized gases, plots of log diffusion coefficient against 1/T unexpectedly did not change slope at either of the two transition temperatures. On the other hand, the transport processes for carbon dioxide and water vapor were affected by the glass transition temperatures of the copolymer. For the former the slope changed at the lower transition temperature of 30°C. In contrast, the water vapor diffusion coefficients increased normally with temperature until the second transition temperature of 77°C. was reached. At this point the diffusion coefficients exhibited a marked increase with temperature. An explanation for the anomalously high diffusion values for water vapor is offered.
Polymerization of acrylamide with persulfate‐metabisulfite initiator
Authors: Rodriguez F. , Givey R. D.
Published: April 2003

The redox system ammonium persulfate–sodium metabisulfite (I1‐I2) was used to initiate polymerization of acrylamide (M) in water. Up to 50 to 70% conversion, the rate equation is:
where Rp is the rate of polymerization and the bracketed quantities are concentrations. [Mo] is the monomer concentration at time t = 0. In the range investigated, K (30°C.) = 1.20 1. moles‐1 sec.‐1. Activation energy is 26 kcal./mole‐1 and K depends on ferrous ion concentration, [Fe++] (mole 1.‐1):

The number‐average degree of polymerization, x̄n is independent of [Fe++], temperature, or [I1]. However:

The range of concentrations (mole 1.‐1) for which these generalizations hold at 30–50°C. and pH 7.0 are: [Mu] 0.4 bis 2.0; [Il], 0.2 to 3.2 × 10–3; [I2], 0.13 to 2.8 × 10‐3; [Fe++], 0 to 19 ×10‐6; [Il][I2], 0.16 to 3.2 ×10‐6; [Mu]/[M], 1 to 3.5.
Diffusion in a crosslinked acrylamide polymer gel
Authors: White Malcolm L. , Dorion George H.
Published: April 2003

The diffusion coefficients of sucrose, urea, potassium chloride, and heavy water (D2O) in an acrylamide–methylenebisacrylamide gel were determined as a function of total polymer concentration and degree of crosslinking, and found to decrease with increasing polymer concentration but to be relatively independent of the degree of crosslinking. Extrapolation of the values to 0% polymer gave diffusion coefficients that checked well with the known values for the solutes in pure water, indicating that there are no specific interactions of the gel with either electrolytes or nonelectrolytes. Equilibrium values for the diffusion after infinite time showed that all of the water in the gel is available for diffusion, indicating the absence of “bound” water. Calculation of average pore sizes from the diffusion data gave values that agreed with previously reported results obtained from water permeability measurements. These data confirm the hypothesis that the gel has a “brush‐heap” type of structure.
Intramolecular rearrangements of polyketones
Authors: Michel R. H. , Murphey W. A.
Published: April 2003

A number of polymeric ketones with the carbonyl groups in the polymer backbone (ethylene‐carbon monoxide copolymers) have been converted to polyamides by means of Schmidt and Beckmann rearrangements. The high degree to which these reactions are intramolecular has permitted conversion with little loss in molecular weight.
Crystallization kinetics of polycapramide
Authors: Inoue Masakazu
Published: April 2003

The kinetics of the isothermal crystallization of polycapramide (nylon 6) is discussed. Temperature changes in specimens during the course of crystallization are measured. For specimens at 200–210°C., the temperature is 2–3°C. higher than that of the crystallization bath. Below 200°C., strict isothermal crystallization cannot be obtained because there are no stable supercooled states. The isothermal crystallization proceeds in two stages. In the first stage, in which the Avrami equation is appliable, n is 4 at temperatures of 210–215°C. and is 2.5 below 207°C.; it changes rapidly between 207 and 210°C. In the second stage, the relaxation of the entanglement of molecules and the perfection of crystals takes place, and the rate of density change increases with crystallization temperature, contrary to the first stage of crystallization. However, the first‐ and second‐stage processes overlap to some degree. Higher molecular weight polymer crystallizes at a lower rate than does low molecular weight polymer. The rate depends on the activation energy of melt flow, and its effect is greater at higher crystallization temperatures. If we assume n equal to 4, log k is in linear relation to Tm/(ΔT)T or T2/(ΔT)2T, where Tm is the melting point; Tm increases with crystallization temperature, especially above 210°C.
Heterogeneous hydrolysis of cellulose with high polymer acids. Part 2. Determination of acid hydrolysis effects by means of inversion of sucrose
Authors: Hartler Nils , Hyllengren Kari
Published: April 2003

The acid hydrolysis effects of polystyrenesulfonic acid and sulfuric acid have been determined for the inversion of sucrose. “Equivalent” acid concentrations which have been determined may be applied to the heterogeneous hydrolysis of cellulosic material. Observed differences in the rate of hydrolysis can be attributed to the diffusion effects of the high polymer acid over that of the low molecular weight acid.
Preparation of copoly(carbonate/urethanes) from polycarbonates
Authors: Foldi Veronika S. , Campbell Tod W.
Published: April 2003

When solutions of high molecular weight poly(diphenylolpropane carbonate) were treated with aliphatic primary and secondary diamines in a homogeneous system, degradation to hydroxyl‐terminated copoly(carbonate/urethane) macrosegments occurred. This observation led to a novel method for the preparation of high molecular weight copoly(carbonate/urethanes). This involved (1) preparation of high molecular weight polycarbonate, (2) degradation of the polycarbonate to a low molecular weight urethane‐bisphenol, (3) repolymerization with phosgene. The composition of the final copolymer could be regulated by the amount of diamine empolyed in step (2). High molecular weight copolymers were thus prepared from poly(diphenylolpropane carbonate) and piperazine, ethylene diamine, hexamethylene diamine, p‐xylylene diamine and hydrazine. These copolymers could be converted to tough drawable films which showed greatly improved hydrolytic stability over unmodified poly(diphenylolpropane carbonate).
A study of the mechanism of emulsion polymerization of styrene and chloroprene by means of reaction heat
Authors: Maňyásek Z. , Řežábek A.
Published: April 2003

Investigation of the polymerization process was carried out on emulsions placed in water‐thermostatted flasks. The temperatures of the central part of the flask and of the thermostat were measured with the aid of thermocouples. The heat balance of the reaction system under investigation is given by the differential equation:

The quantity of heat dq evolved during the time dτ in the course of the reaction raises the temperature of the system by d(ΔT), part of the heat being removed by the cooling bath. The constant K expresses the overall heat transfer, and C is the overall heat capacity of the polymerizing system. The left side of eq. (1) contains the time function of the reaction. We investigated the cases for zero‐, first‐, and second‐order reactions and derived the corresponding solution of the basic equation for ΔT = f(τ). For a zero‐order reaction:

For a first‐order reaction:

For a second‐order reaction:

K0, K1, and K2 in eqs. (2), (3), and (4) are the zero‐, first‐, and second‐order rate constants, respectively, ΔH is the heat of polymerization; Mp and ΔTp, the number of moles and the temperature difference at the start of the reaction, respectively; the difference

is the so‐called reduced exponential integral. The constants K and C may be calculated from the experimental curve ΔT = f(τ) and from two–three value for the degree of conversion in the course of polymerization. From this any number of values may be obtained for the degrees of conversion with time. For such values we derived the relation

where Δp/Δτ is the overall reaction rate expressed by the increase with time of the amount of polymer. Expression (5) has a convenient linear plot, and from the slope and the intercept on the ordinate axis the reaction order i and the rate constant Ki may be determined directly. The theory was applied to a kinetic study of the emulsion polymerisation and styrene and chloroprene. An aqueous solution of potassion laurate served as emulsifier and potassium persulfate as initiator. The reaction was carried out at 40°C. The method permits accurate determination of the overall polymerization rate and of the monomer concentration in the latex particles. In a number of experiments the reaction rates and quantity of latex particles as function of initiator concentration were determined. The results were compared with conclusions following from the Smith‐Ewart quantitative theory of emulsion polymerization. The constants of chain growth of polystyrene and polychloroprene were determined.
Electron exchange polymers. XVII. Some new methylated poly(vinylhydroquinones)
Authors: Kun Kenneth A. , Cassidy Harold G.
Published: April 2003

2,5‐Dimethoxy‐3,6‐dimethylstyrene was prepared by dehydration of 2'‐hydroxyethyl‐2,5‐dimethoxy‐3,6‐dimethylbenzene and 2,5‐dimethoxy‐3,4,6‐trimethylstyrene was prepared by dehydration of 2'‐hydroxyethyl‐2,5‐dimethoxy‐3,4,6‐trimethylbenzene and by dehydration of the 1'‐hydroxyethyl isomer. Preparation of the intermediates is described. These two relatively stable vinyl monomers were polymerized by cationic initiation to the corresponding polystyrenes, which were demethylated under acid conditions to the corresponding poly(vinylhydroquinones). Some crosslinking occurred during demethylation of the poly(2,5‐dimethoxy‐3,6‐dimethylstyrene). These methyl‐substituted polyvinylhydroquinones are new redox (electron exchange) polymers. They were prepared in order to obtain redox polymers more stable to oxidation than polyvinylhydroquinone. Oxidation of poly(3,4,6‐trimethylstyrene) yielded the flattened potentiometric titration curve characteristic of electron exchange polymers.
Polymerization of acrylonitrile with n‐butyllithium at −78°C.
Authors: Miller M. L.
Published: April 2003

The polymerization of acrylonitrile with n‐butyllithium in toluene at −78°C. was studied at three monomer concentrations, 5.7, 13, and 27%, and at butyllithium concentrations from 0.5 to 1.5 × 10−2 m./1. With high concentrations of monomer the conversion was reduced by a gel effect. At low monomer concentrations the dependence of polymerization rate on monomer and catalyst concentration was similar to the dependence observed by other workers in the polymerization of styrene with butyllithium at 20–30°C. At −78°C. in toluene there was no evidence for termination of polyacrylonitrile chains by monomer. Cyanoethylation and reactions which produce yellowing at higher temperatures were absent. The initial polymerization was rapid and the initial catalyst efficiency low. Molecular weights were from 250,000 to 1,300,000.
Glass transition and melting point of poly(vinyl chloride)
Authors: Reding F. P. , Walter E. R. , Welch F. J.
Published: April 2003

Both the glass transition temperature and the melting point of poly(vinyl chloride have been found to increase as the temperature at which the ample is polymerized is decreased). The glass transition temperature changes from about 70°C. for polymer prepared at 125°C. to about 100°C. for polymer prepared at −80°C. It is believed the increase in percentage of syndiotactic structure which results from decreasing the polymerization temperature is responsible for the change in glass transition temperature. The effect of polymerization temperature on melting point is even more striking. The melting point changes from approximately 160 to above 300°C. on lowering the polymerization temperature from 125 to −80°C. X‐ray diffraction studies show that polymers prepared at low temperature form crystals which have a substantial increase in perfection along the chain axis. It seems probable that this increase in crystalline perfection along the chain axis is responsible for the very marked increase in melting point.
Esters of polyvinyl alcohol and sulfuric acid
Authors: Fingauz I. M. , Vorob'Eva A. F. , Shirikova G. A. , Dokuchaeva M. P.
Published: April 2003

The alcoholysis of polyvinyl acetate in ethyl alcohol solution catalyzed by sulfuric acid is accompanied by a side reaction leading to formation of a certain amount of polyvinyl sulfate. Aqueous solutions of the polyvinyl monosulfates possess a comparatively high emulsifying capacity, which increases with increase in the bound sulfur content, comprising 0.06–0.08% for 1–5% sulfuric acid in the reaction medium. Attempts to incorporate the sulfate group to a great degree with the objective of obtaining sulfated polymers of specific properties (efficient emulsifiers, stabilizers, ion exchangers etc.) did not yield satisfactory results when methods described in the literature were employed. Direct sulfation of polyvinyl acetate with subsequent conversion to polyvinyl alcohol or the sulfation of polyvinyl alcohol, to obtain a derivative with a large ester content, is impossible, owing to stereochemical hindrance. Because of this we investigated the possibility of sulfating the polymer during the process of alcoholysis of polyvinyl acetate in ethyl alcohol. It was found that under the reaction conditions for various amounts of acetate residual groups polyvinyl alcohol may be obtained with a varying content of acid or neutral esters. Under the chosen conditions a hitherto undescribed acid sulfuric acid ester of polyvinyl alcohol with 10–15% bound sulfur content was obtained. In contrast to the original polyvinyl alcohol soluble in water this sulfur‐containing product dissolved in ethyl alcohol, water or aqueous alcohol. Neutral sulfates of polyvinyl alcohol are soluble only in ethanol but not in water. The acid sulfates possess high emulsifying and stabilizing properties. If the reaction is carried out in methanol, esterification of the acid sulfuric acid ester of polyvinyl alcohol takes place as a side reaction. The resultant products are devoid of emulsifying properties.
Titanium tetrafluoride as a catalyst for some organic reactions
Authors: Latham Ross , Drago Russell S.
Published: April 2003

Titanium tetrafluoride has been successfully employed in combination with triisobutyl aluminum (TBA) as a Ziegler type of catalyst to polymerize butadiene. The resulting polymer has a higher cis to trans ratio and a higher degree of crosslinking than one prepared with the titanium tetrachloride–TBA catalyst. It is of interest that vinyl chloride, a monomer containing a donor atom, was polymerized with the TiF4–TBA catalyst. Titanium tetrafluoride is not a very effective catalyst for the Friedel‐Crafts type of reactions.
Free energies of formation of fluorocarbons and their radicals. Thermodynamics of formation and depolymerization of polytetrafluoroethylene
Authors: Bryant W. M. D.
Published: April 2003

Enthalpies and free energies of formation of a group of aliphatic fluorocarbons and their radicals for 298.15°K. and the ideal gaseous condition are calculated from the available experimental heat and entropy data, extended by means of empirical series treatments. The polymerization of tetrafluoroethylene and the thermal breakdown of the resulting polymer are recognized as thermodynamically equivalent processes, differing only in the sign of the thermal quantities involved. Free energy changes attending various intermediate steps in the free radical‐initiated polymerization are calculated. The heat and free energy of polymerization are highly exothermal at 298.15°K., compared with those for other olefinic compounds. At high temperatures reversal of the synthesis steps is to be expected. Initiation of degradation need not occur merely by reversal of the termination process, although this possibility is not excluded.
Light scattering studies on unfractionated poly(n‐docosyl methacrylate)
Authors: Levi D. W. , Valles R. J. , Schramm E. C.
Published: April 2003

Poly(n‐docosyl methacrylate) was prepared by emulsion polymerization. Since the weight‐average molecular weight of the unfractionated material appeared to be unusually large, light scattering measurements were made in three solvents and at several temperatures. No evidence of association in solution was found. Values of average molecular weight, dimensions, and second virial coefficients are reported.