bluuebunny/crossref_metadata_2025 huggingface dataset:
Branching in isoprene polymers of regular structure
Authors: Poddubnyi I. Ya. , Ehrenburg E. G.
Published: April 2003

Branching in isoprene polymers with cis‐1,4 content of ∼85% obtained by polymerization in the presence of a complex catalyst and under the action of lithium was determined by studying intrinsic viscosity of polymer fractions in an ideal solvent. It was established that macromolecules of polyisoprenes obtained with a complex catalyst under polymerization conditions commonly used are essentially linear. At the same time, in the polymers studied, there is a fraction (∼10% of the polymer weight) consisting of colloidal size particles formed by highly crosslinked polymer molecules. A rubber sample of the above type prepared with uncontrolled dosage of catalyst components and at elevated temperature proved to be a highly branched polymer. The discovered features in hydrodynamic behavior of macromolecules in benzene solutions suggest that trans units in the macromolecules of polyisoprenes obtained in the presence of the complex catalyst are not randomly distributed along the chain but form comparatively long blocks. The intrinsic viscosity—molecular weight relation in benzene solutions was determined for both types of polymers studied.
Permanganate—oxalic acid as a redox initiator in aqueous media. Part I. The initiating radical and general features
Authors: Palit Santi R. , Konar Ranjit S.
Published: April 2003

Polymerization of aqueous methyl methacrylate solution by oxalic acid (4.0 × 10−2 to 0.0625 × 10−2 mole/l.) and permanganate (0.633 × 10−5 to 63.3 × 10−5 mole/l.) system as redox initiator has been studied. Oxalic acid by itself can not initiate polymerization in the dark but does so strongly even in diffuse light or weak illumination. Permanganate can initiate polymerization provided the solution is sufficiently acidic to dissolve the separated colloidal MnO2 which tends to inhibit polymerization. The MnO4−‐oxalic acid system is a powerful redox initiator provided the acid strength (either of added H2SO4 or of oxalic acid itself) is sufficient to dissolve MnO2. The polymer always separates as a coarse coagulum (suspension). The polymers have been examined for endgroups by the dye test as developed in this laboratory. Oxalic acid‐initiated (in sunlight) as also oxalic acid—ferrous ion‐initiated and KMnO4—H2C2O4‐initiated polymers contain carboxyl endgroups. MnO2—H2SO4 acid‐initiated polymers, have been found to contain sulfate endgroups. On increasing the ratio of oxalic acid to permanganate, the carboxyl endgroups tend to decrease, and ultimately very faint test for carboxyl is obtained. This is in agreement with the suggestion made by previous workers that under such conditions carboxyl radical‐producing reactions are suppressed.
Methods of predicting radiation‐induced changes in the mechanical properties of high polymers
Authors: Fritz E. G.
Published: April 2003

A discussion is presented of the various problems associated with the formulation of predictive techniques relating to the mechanical response of high polymers to radiation. In particular, dosimetric difficulties and errors arising from disregard of sample variations are analyzed. Criteria for the engineering evaluation of radiation sensitivity are examined. The usefulness of rank correlation in preliminary analysis of radiation effects data is outlined. Typical examples are given of explicit correlations between properties, the application of statistical kinetic theory, and semiempirical and empirical response relationships. The limitations of the various approaches are discussed.
Polymerization in the crystalline state. II. Alkali acrylates and methacrylates
Authors: Morawetz H. , Rubin I. D.
Published: April 2003

Alkali acrylates and methacrylates were irradiated with gamma rays from a Co60 source at −78°C. and their subsequent polymerization was studied in vacuo in the temperature range 0 to 155°C. Potassium acrylate proved to be the most rapidly polymerizing solid monomer studied to date; it reacted at 0°C. faster than the lithium salt at 101°C. or the sodium salt at 120°C. The reaction rate of the acrylates decayed rapidly at low polymer yields which were, for long polymerization times, linear in the logarithm of time. The activation energy for the polymerization of potassium acrylate was 16.7 kcal./mole. The chain length of the polymer was independent of the polymer yields in all kinetic runs except one and was an order of magnitude higher for potassium acrylate than for the sodium or the lithium salt. Sodium methacrylate was more reactive than potassium methacrylate; the lithium salt of methacrylic acid was entirely inert. The sodium methacrylate polymerization had an initial accelerating phase. Studies of x‐ray diffraction of the polymerizing potassium acrylate showed only minor changes in the diffraction pattern of the monomer, the size of the unit cell remaining almost unchanged. Poly(potassium acrylate) produced in the solid state showed four diffuse diffraction rings which were not observed in samples prepared from poly(acrylic acid) obtained by polymerizing a benzene solution of the monomer. While the x‐ray data indicated the existence of a separate polymer phase in the polymerizing salts, the pronounced difference in the characteristics of the polymerization process of different salts of the same monomeric anion pointed to a control of the reaction by the geometry of the crystal lattice. The evidence suggests that the polymer lies in an amorphous phase but that the reactive ends of growing chains are anchored in the monomer lattice. Electron spin resonance spectra are similar for irradiated potassium acrylate and sodium methacrylate, but the potassium acrylate spectrum changes gradually from a three‐peak to a single‐peak structure when the sample is heated to 100°C., while the other two salts have spectra which are not affected by a similar heating cycle. The absence of the characteristic ESR spectrum of polymethacrylate radicals in irradiated sodium methacrylate suggests that under the experimental conditions used few of the primary radicals were able to initiate chains. A five‐peak ESR spectrum was observed in irradiated sodium acrylate.
Polymerization in the crystalline state. III. Methacrylic acid and butadiene‐1‐carboxylic acid
Authors: Morawetz H. , Rubin I. D.
Published: April 2003

Methacrylic acid polymerized in the solid state leads to a much less syndiotactic polymer than when polymerized in the liquid state. This is taken as additional evidence for the importance of the geometry of the monomer crystal lattice in solid state polymerization. Butadiene‐1‐carboxylic acid polymerizes spontaneously in the solid state to a cross‐linked product, while the sodium, potassium, and barium salts of this acid are stable and polymerize very little, even on gamma‐ray irradiation.
Polymer size distribution and average molecular weights for reactions involving variable propagation rates
Authors: Maget Henri J. R.
Published: April 2003

General equations are derived to predict product distribution and number‐average molecular weight of consecutive competitive second‐order reactions, where rates of propagation are different for the m first reaction steps and become identical for all subsequent reactions. The equations have been applied to experimental results obtained for the propylene oxide—water reaction.
Kinetics of thermal decomposition of dimethyl‐N‐(2‐cyano‐2‐propyl)ketenimine by nuclear magnetic resonance spectroscopy
Authors: Smith P. , Muller N. , Tosch W. C.
Published: April 2003

The kinetics of the thermal decomposition of dimethyl‐N‐(2‐cyano‐2‐propyl)ketenimine, DKI, in benzene solution over the 61–92°C. range have been investigated by means of proton magnetic resonance spectroscopy for quantitative analysis of reaction mixtures. The NMR equipment used comprised a Varian Model 3311 spectrometer, operating at a fixed radio frequency of 56.445 Mcycles/sec. and equipped with the Model V‐K 3506 super‐high‐resolution field‐stabilizing unit and the Model V‐K 3507 slow‐sweep unit. The kinetic data obtained tally closely with those reported earlier for a nitrometric and ultraviolet spectrophotometric study of the thermal breakdown of 2,2'‐azobisisobutyronitrile, AZO, in the same solvent within the 60–80°C. range. Consequently the general mechanism assumed in interpreting the previous results for the AZO decomposition is confirmed. They also agree with all other comparable data available as well as expected. As a natural part of this study, it has been shown that NMR provides reliable and convenient methods of quantitative analysis of reaction mixtures when DKI or AZO is thermally decomposed. One variation of the analytical technique practiced involved comparison of the C13‐sidebands in the NMR spectrum of a major constituent of a mixture with the main spectrum from a minor constituent. This was especially valuable for settling the initial purity of the DKI decomposed and the extent to which side products such as isobutyronitrile, methacrylonitrile, and 2,3,5‐trimethyl‐2,3,5‐tricyanohexane were formed.
A critical investigation of polyethylene gas permeability
Authors: Alter Harvey
Published: April 2003

The effect of polymer density on the gas permeability of polyethylene film has been studied. The experimental data for permeability P are described by the equation P = K(1 — d)n, where K is a constant characteristic of each gas and d is the sample density. This equation is similar to previous analytical descriptions of the permeability—density relation. Values of K and n (n ≈ 2) and confidence limits for P are given for N2, O2, and CO2. Permeability—density values are reported for approximately 100 film samples for each of the three gases over a density range from 0.899 to 0.975 g./cc. The density was measured for each sample inserted in the permeability apparatus. The above mathematical model chosen to describe the experimental data is interpreted to mean that the effect of the crystalline phase is to decrease both the gas solubility and diffusion. Gas solubility and diffusion are linear functions of the volume fraction of amorphous material. Permeability, the product of diffusion and solubility, is consequently proportional to the square of the volume fraction of amorphous material. Permeability is related to density rather than volume fraction of amorphous material to avoid choosing a single value for the density of the amorphous fraction. The experimental results suggest additional lowering of the permeability due to restraints on the segmental motion of the amorphous chains.
Permanganate–oxalic acid as a redox initiator in aqueous media. Part II. Kinetics and degree of polymerization
Authors: Palit Santi R. , Konar Ranjit S.
Published: April 2003

The rate of polymerization of aqueous methyl methacrylate under nitrogen at 32°C. is proportional to the first power of catalyst (MnO4−) concentration (0.633 to 15.83 × 10−5 mole/l.) at fixed concentrations of the activator (0.8 × 10−2 mole/l.) and monomer (6.204 × 10−2 mole/l.), independent of activator concentration over a wide range (0.50 to 0.0625 × 10−2 mole/l.), and proportional to the first power of monomer concentration within the range (0.94 to 7.52 × 10−2 mole/l.) at fixed concentrations of the catalyst (3.16 × 10−6 mole/l.) and the activator (0.8 × 10−2 mole/l.). The initial rate of polymerization attains a maximum value at 45°C., but falls with further rise in temperature. The rate of polymerisation is depressed by agitation after initiation, salts and organic solvents, and is accelerated by MnSO4 and complexing agent like NaF (only at low monomer concentration), and in presence of peptizers like sodium cetyl sulfate or cetyltrimethylammonium bromide. The separating phase in the absence of peptizers is a course coagulum, and possibly a steady state with respect to radicals is not attained at high catalyst concentration. Injection of catalyst late in a run increases both the rate of polymerization and yield in unpeptized systems and does the reverse in peptized systems. The molecular weight of the polymers increases in the course of a run and is also affected by change of catalyst concentration but not by activator concentration in the range where the rate of polymerization is independent of activator concentration.
Orientation studies on drawn polyolefins
Authors: Hoshino S. , Powers J. , Legrand D. G. , Kawai H. , Stein R. S.
Published: April 2003

The effect of different thermal treatments on the degree and type of orientation produced by cold drawing three polyolefin films: polyethylene, polypropylene, and polybutene‐1, was studied by two complementary techniques: x‐ray diffraction for the measurement of crystal orientation and birefringence for the measurement of the total film orientation. Variations in the texture of these polymer films were characterized by these techniques as well as by density, tensile stress measurements and photomicrographs. The birefringence–strain data showed a decrease in birefringence values at a given strain as the polymer side group size increased. This decrease appears to be associated with a more symmetrical polarizability ellipsoid and hence a decrease in crystal birefringence. The birefringence–strain curves for the same polymer system showed a decrease in birefringence value at a constant strain with increased annealing. X‐ray diffraction data indicate that the a and b axes in both polyethylene and polybutene‐1 film orient by different amounts at a given strain. Polypropylene, on the other hand, shows equal amounts orientation of the a and b axes. The different orientation behavior for these polymer systems is discussed in terms of variation in the ease with which polymer crystals may be deformed.
Low temperature polymerization of methyl methacrylate initiated by ethylsilver
Authors: Bawn C. E. H. , Janes W. H. , North A. M.
Published: April 2003

The free‐radical polymerization of methyl methacrylate at low temperatures has been studied in a series of solvents of differing solvent power and ability to form weak complexes with monomer. In every case the polymer was predominantly syndiotactic, which suggests that monomer association or complex formation are not important stereoregulating factors, and that the treatment of the propagation reaction as two concurrent addition reactions between monomer and a free propagating species is justified. The polymerization has been studied over the temperature range −20 to −60°C. with ethylsilver as initiator. Over these temperatures the overall rate law is Rp = K[M]3/2 [Ag]1/2 where K, a composite constant, can be expressed as 1.7 exp{ −5100/RT} 1. mole−1 sec.−1. The polymerization proceeds by a free radical mechanism, the initiation step appearing to be the decomposition of a ethylsilver–monomer complex to form metallic silver, and a free radical capable of initiating polymerization. The first‐order rate constant for this decomposition in ethyl acetate as solvent has the value 1.5 × 102 exp{−6600/RT} sec.−1. The molecular weights of the polymers formed are higher than would be predicted by extrapolation of data from higher temperatures, and also indicate that transfer reactions to catalyst components are negligible in the range of initiator concentrations studied.
Polymerization induced by ionizing radiation at low temperatures. I. Evidence for the simultaneous existence of ionic and free‐radical mechanisms in the polymerization of styrene and 2,4‐dimethylstyrene
Authors: Chen Catherine S. Hsia , Stamm Robert F.
Published: April 2003

By means of initiation with ionizing radiation, styrene and 2,4‐dimethylstyrene have been polymerized in the crystalline solid state, in the pure liquid state, and in solution at different temperatures (−80°C. to 25°C.). In solution polymerization, it has been found that for the same type of initiation, other conditions being constant, the mechanism by which these monomers polymerize is temperature‐dependent. At lower temperatures a cationic mechanism predominates; at higher temperatures a free‐radical mechanism is in the ascendency. At intermediate temperatures, both cationic and freeradical polymerizations take place. Furthermore, these intermediate temperatures are different for different monomers, being higher in a monomer whose electronic structure is more favorable for cationic polymerization. The difference in mechanism at different temperatures has been proved by: (1) the dose rate dependencies, both of the polymerization rates and of the molecular weights of the resulting polymers; (2) the activation energies for the polymerization; and (3) the relative reactivities in the polymerizations of styrene and substituted styrenes.
Kinetics of ethylene polymerization initiated by free radicals
Authors: Friedlander H. N.
Published: April 2003

Ethylene polymerization can be carried out under milder conditions than heretofore because of the development of peroxydicarbonate catalysts. This simplifies study of polymerization kinetics. Diethyl peroxydicarbonate undergoes first‐order decomposition in tert‐butyl alcohol with an energy of activation of 33 kcal./mole, and a half‐life of 1.5 hr. at 60°C. The rate of decomposition, 1.3 × 10−4 sec.−1, does not change in the presence of polymerizing ethylene. The rate of polymerization can be followed by pressure change. But, because the concentration of ethylene in tert‐butyl alcohol as a function of pressure is not known accurately, it is better to measure polymerization rate by isolating the polymer. A mathematical relationship was developed between initiator decomposition and polymer formation. It is based on a conventional free‐radical polymerization mechanism and is supported by the experimental data. Polymer molecular weight is independent of initiator concentration and increases only slightly with duration of polymerization. The effects of reaction variables of molecular weight are explained by normal free‐radical transfer reactions. The polymer contains ethyl carbonate groups from homolytic scission of diethyl peroxydicarbonate, and it exhibits the same absorption bands in the infrared as does ethyl n‐octyl carbonate. These bands disappear on saponification and are not present in polyethylene made with other peroxide catalysts.
γ‐radiation of p‐substituted polystyrenes
Authors: Burlant W. , Neerman J. , Serment V.
Published: April 2003

The electronic environment about the main chain atoms in polystyrenes has been varied systematically by introducing electronegative or electropositive substituents (H3C, CH3O, Br, Cl, NC, and O2N groups) in the p‐position of the ring. Energy yields for γ‐initiated H2 formation and crosslinking, both a measure of the radiation sensitivity of the backbone, were determined above and below Tg from (1) mass spectrometric examination of the decomposition gases and (2) molecular weight changes. For most of the polymers, it is concluded that the backbones of p‐substituted polystyrenes are more radiation stable than that of polystyrene, and that main chain macroradicals formed early in the reaction are responsible for the major changes observed, i.e., hydrogen evolution and crosslinking. The role of the p‐substituent on the latter effects is interpreted qualitatively in terms of the contribution by the substituent to the resonance stability of these intermediate polymer radicals. In the case of poly‐p‐bromo‐ and poly‐p‐chlorostyrene, the inordinately high sensitivity to crosslinking and the absence of halogen atoms in the decomposition gases suggest the importance of a chain reaction in the radiation chemistry of these molecules.
Polyperfluoroalkyl oxetanes: A new class of thermally stable polymers
Authors: Case L. C. , Todd C. C.
Published: April 2003

Two perfluoroalkyl oxetanes, 2‐heptafluoropropyloxetane and 3‐ethyl‐3‐nonafluorobutyloxetane, were synthesized and polymerized. The 2‐heptafluoropropyloxetane was prepared by the ring closure of heptafluoro‐1,3‐hexanediol with sulfuric acid and sodium hydroxide. The 3‐ethyl‐3‐nonafluorobutyloxetane was prepared from diethyl ethylmalonate and perfluorobutyryl chloride. The sodium salt of the ester was acylated with the acid chloride. The resulting ketodiester was reacted with sulfur tetrafluoride to give diethyl α‐ethyl‐α‐perfluorobutylmalonate. This ester was then reduced with lithium aluminum hydride to give 2‐ethyl‐2‐perfluorobutyl‐1,3‐propanediol. This diol was then converted to the oxetane with sulfuric acid and sodium hydroxide. These oxetanes were polymerized in methylene chloride solution with boron trifluoride as the catalyst. Both polymers were viscous oils. The oxetane polymers were exposed as thin molten films to air at 300°F. Also tested under these conditions were polyethylene oxide, polypropylene oxide, polytrimethylene oxide, poly(3,3‐dimethyl)oxetane, and Teracol 30. The polymer from 2‐perfluoropropyloxetane was more stable than all the nonfluorinated polyethers tested. After an initial high weight loss, attributed to impurities, the polymer from 3‐ethyl‐3‐perfluorobutyloxetane was the most stable polyether tested.
Thermal decomposition of natural cellulose in vacuo
Authors: Murphy E. J.
Published: April 2003

An investigation of the thermal decomposition of natural cellulose is described, in which the rate of the reaction was determined by the rate of evolution of gas in vacuo in the temperature range 100–250°C. Two states of the material could be distinguished with respect to thermal decomposition behavior, the “initial” state and a state produced by protracted heating which is described as the “stable” state. In the initial state the rate of evolution of CO is given by k = 2.8 × 109 exp {−34.0 × 103 RT}, in the stable state by k = 1.0 × 1011 exp {−39.4 × 103/RT}, where k is expressed in moles of CO per mole of cellobiose per second, R is the gas constant, and T the absolute temperature in degrees Kelvin. The composition of the gas evolved in the initial state is given by xH2O:yCO2:1CO, where x is observed as a range of values fairly close to 3, and y to 1, depending upon the stage of the reaction. In the stable state the composition of the gas evolved is about 10H2O:2.5CO2:1CO; these ratios remain within rather close limits (about 10%) in observations made over a considerable range of conditions. The ratio 2.8 × 109/1.0 × 1011 may be interpreted, on the basis of simplifying assumptions, to represent the fraction of the structure which decomposes with the lower activation energy (i.e., 34.0 kcal./mole). This fraction may be regarded as a measure of the concentration of some secondary aspect of the structure of the material which may be described as internal surfaces, a micellar structure, or the endgroups of long‐chain molecules. Because of the stability of the value 39.4 kcal./mole with respect to protracted heating and to variations in secondary composition, this value is regarded as the activation energy for the thermal decomposition of the α‐cellulose present in natural cellulose. At all temperatures natural cellulose decomposes at rates given by the first of the above equations for the initial stage and by the second equation for later stages of the reaction. (There are, of course, intermediate states between the extremes represented by these equations.) The effect of partial thermal decomposition of natural cellulose on its physical properties, such as water adsorption, can be studied as a function of the degree of thermal decomposition as measured by the rates given by these equations. The “endpoint” in the drying of cellulosic materials can also be determined from the thermal decomposition data. Water removed after this point has been reached does not result in increased dryness of the material, but is a measure of the progress of the thermal decomposition reaction.
Macromolecular stable free nitrogen radicals
Authors: Braun D. , Löflund I. , Fischer H.
Published: April 2003

Low molecular stable free nitrogen radicals have been investigated frequently. There are, however, only a few records on corresponding high polymers. Preparation of macromolecular radicals of the diphenylpicrylhydrazyl type is described. Poly‐4‐fluorostyrene is nitrated to poly‐3,5‐dinitro‐4‐fluorostyrene, a compound in which the fluorine by analogy with similar low molecular compounds, is very reactive. By reaction with diphenylhydrazine, poly(α‐vinyldinitrophenyl‐β,β‐diphenyl hydrazine) is obtained; this can be oxidized without difficulty to the corresponding hydrazyl. The polymer is a stable free nitrogen radical. Its structure follows from the comparison of the absorption spectra and the electron spin resonance spectrum with suitable compounds. The polymer corresponds in its chemical behavior to the low molecular free nitrogen radicals, e.g., it easily oxidizes hydroquinone, ascorbic acid, or hydrazobenzene. It is a typical high polymer inhibitor for the polymerization of styrene, whereas the polymer hydrazine has no inhibiting effect.
Use of dimaleimides as accelerators for the radiation‐induced vulcanization of hydrocarbon polymers
Authors: Miller S. M. , Roberts R. , Vale R. L.
Published: April 2003

The effect of alkyl and aryl dimaleimides on the rate of crosslinking of natural rubber is described by means of experiments with ionizing radiation. The dose for vulcanization can be reduced from 5 × 107 to 2.0 × 106 rad by use of purified rubber and 5% of additive, and the reaction is dose‐rate dependent with an intensity exponent of 0.57. The reaction is further accelerated by the addition of small quantities of solvents. By use of C14‐labeled dimaleimides it is shown that there is approximately one dimaleimide unit to each crosslink. Possible chain mechanisms for the reaction are discussed.
Formation and characteristics of the crystalline cellulose x modification of cellulose
Authors: Ellefsen Ø. , Norman N.
Published: April 2003

Previously reported experiments dealing with the formation of the new cellulose × modification in precipitates after treatment of cotton and wood pulp with strong hydrochloric acid are summarized and discussed in connection with results from a recent investigation where other swelling systems have been applied. It has been demonstrated that very pure precipitates of cellulose x may be obtained by means of treatment with phosphoric acid (84.5%) at 50°C. The hypothesis for the formation of the new modification has been discussed, and it is suggested that the necessary condition for the formation of cellulose x is swelling to such a degree that the complexes (C6H10O5·4H2O·HCl)n and (C6H10O5·2H2O·H3PO4)n are obtained. The most probable unit cell for cellulose x, as judged from the x‐ray experiments, is one having the same dimensions as cellulose IV, but with different reciprocal positions of the corner and central cellulose chains in the lattice. The infrared spectrum of cellulose x lies between those of cellulose II and IV, and bears a somewhat closer resemblance to that of cellulose II.
Differential thermal studies on plant gums
Authors: Kulshrestha V. K.
Published: April 2003

Differential thermal analysis studies have been done on nine different gums belonging to different families and genera and differing in their chemical constituents and structure, along with their respective gum acid and hydrolysis products. The gums studied include gum sterculia urens, gum azadirechta indica, gum acacia catechu, gum limmonia accidissma, gum lannea grandis, gum anogesius latifolia, gum acacia leucopholea, gum prosopis galandulosa, and gum swietenia mahagony. Certain reactions take place when these substances are heated uniformly to an elevated temperature, which are manifested in the form of endothermic or exothermic peaks depending on the nature of the reaction. These are due to the removal of the adsorbed moisture, the removal of the structural (OH) groups with the elimination of water and CO2, partial decomposition of the gum followed by a rearrangement of the molecule, etc. The thermograms so obtained are quite distinct from each other and afford a “finger print” device in the identification and characterization of these substances. The DTA studies have been further correlated with infrared studies and these support the views already expressed.
Studies on biocolloids and polyelectrolytes: The plant gums. Electrochemistry of azrechtic acid
Authors: Kulshrestha V. K.
Published: April 2003

The conductivity and pH of azrechtic acid (ARA), a polyelectrolyte obtained from the electrodialysis of gum azadirechta indica have been investigated under different experimental conditions. The plot of equivalent conductivity A versus √C (phoreogram) is much steeper than for a comparable simple electrolyte. The phoreogram is strongly concave upward. It is shown that the conductivity is largely due to the hydrogen counterions. The equivalent conductivity has been expressed by the equation Λ = KCb where K and b are constants, K = 18.2 and b = −0.1452. The conductivity further follows the equation Λ −° Λ = −√C/(A + B√C), Λ° is the equivalent conductivity of ARA at infinite dilution and equals 73.5, A = 8.4 × 10−4 and B = 1.831 × 10−2. The degree of dissociation has been determined from measurement of electrical conductivity and pH. A discrepancy in the results has been tentatively explained. The degree of dissociation decreases with the concentration of ARA. It is noted that the conductance of an ARA—electrolyte mixture is 5–12% higher than the calculated value. The pH of ARA with dilution follows the equation pH = D + E log C, where D = 2.96 and E = −0.85. It has been further shown that the pH with dilution also follows the expression pH = A1Ca, where A1 = 2.96 and a = −0.1009.
Some mechanical aspects of the swelling and shrinking of polymeric solids. Part I. External and internal restraints
Authors: Rosen Bernard
Published: April 2003

The osmotic or swelling pressures of polymeric gels are necessarily complicated by structural stresses generated by the swelling or expansion against the longer‐ranged cohesive contributions of the bulk. For externally unrestrained, true swelling equilibria, one need only consider the hydrostatic tensile stresses created by the fixed resistance against the polymer expansions afforded by the primary bonded crosslinks of truly long‐ranged three‐dimensional networks. However, in trivial expansions of extremely slowly relaxing polymeric gels, one need also consider the effective permanency of internal, near‐range structural restraints afforded by these virtually elastic gels. When the structural relaxation times are shorter, this latter hydrostatic stress takes on a time dependency which affects one's experimental perspective of the swelling equilibria to a degree which is a function of the time employed for the measurements. Therefore, one encounters a “drift” in the apparent swelling equilibria. This ambiguous situation, frequently met in the swelling equilibria of slowly relaxing polymeric gels, is also encountered in their thermal expansions and appears to be a general consideration involving relaxations of flux‐generated, structural tensions. Although admittedly very approximate, this is a preliminary attempt to extend the major conceptual perspective of the swelling of rubbers towards the relative volume expansion processes in glassy polymeric solids. It appears that this unorthodox approach is still demanded for any proper explanation of the basis for the abnormal solute absorption and drying kinetics of these glasses. This approach also has some conceptual advantages in the general interpretation of the abnormal heat absorption kinetics in these same, and other types of glassy systems. The major effect tentatively appears to be related to the isotropic, anelastic deformational responses to flux‐induced volume changes in these solids. This possibly is an intrinsic peculiarity of all anelastic solids, but is most strongly felt in considerations of the very highly anelastic, polymeric solids.
Examination of kinetics of thermal decomposition of peroxides of polymethyl methacrylate
Authors: Turska E. , Połowiński S.
Published: April 2003

The kinetics of thermal decomposition of the peroxides obtained by γ‐irradiation of polymethyl methacrylate in air was investigated. The method of examination of the velocity of this reaction based on the reaction of DPPH with free radicals. The measurements resulted in finding the reaction to be of the first order. The rate constants for the thermal decomposition of the peroxides at temperatures of 70, 80, 90, and 100°C. were determined. The constants for the Arrhenius formula were determined and the relationship k = 3.61 × 105e−8e−15,000/RT was found.
New elastomers derived from copolymers of tetrahydrofuran and propylene oxide
Authors: Dickinson L. A.
Published: April 2003

The homopolymers of tetrahydrofuran, polytetramethylene glycols, may be chain‐extended to form polyurethane elastomers. These materials, while possessing a low glass point temperature, suffer from cold hardening, and it was decided to investigate copolymers of tetrahydrofuran and propylene oxide as elastomer ingredients. The preparation of these copolymers has been achieved by use of a boron trifluoride etherate polymerization catalyst. Details are given of the properties of both the copolymer and derived elastomers at nominal compositions in the range 50–85 wt.‐% of tetrahydrofuran. The copolymers described were synthesized as ingredients for castable elastomers, and in consequence viscosity effects are important. It has been found that no significant increase in viscosity occurs until the tetrahydrofuran content exceeds 75 wt.‐%. This indicates that each side methyl group exerts a screening effect over an average of 13 atoms of the polymer backbones. The mechanical testing of the derived elastomers indicates that the copolymerization of tetrahydrofuran and propylene oxide leads to material possessing a low glass point temperature and much better physical properties than the homopolymer of propylene oxide. The elastic properties of a chain‐extended diol are dependent on the degree of crosslinking and on the incidence of network deficiencies. Network deficiencies are caused by the presence of monofunctional species in the copolymeric diols, and a novel technique for determining diol monofunctionality based on analysis of physical test data was evolved for these studies.
Polymerization of ethylene with a preactivated aluminum‐titanium(IV) chloride catalyst and a statistical study of the polymerization variables
Authors: Joyner F. B. , Shearer N. H. , Coover H. W.
Published: April 2003

Conversion of ethylene to a high‐density polymer was readily effected at low pressures and temperatures with the use of a catalyst consisting initially of a mixture of aluminum and titanium(IV) chloride. The principal factors influencing the polymerization and properties of the resulting polyethylene were investigated. These reactions at preferred catalyst concentrations were always preceded by a prolonged induction period; consequently, a means of reducing this period was developed. Factors influencing the polymerization included the nature of the aluminum in the catalyst, type of solvent, and molecular weight regulators. The effects of pressure, temperature, aluminum concentration, and Al/TiCl4 mole ratio on induction period, reaction rate, and polymer properties were determined from a factorial experiment in which each factor was investigated at two levels. The polymerization could be initiated at low catalyst concentrations and temperatures by preactivating the Al‐TiCl4 mixture, that is, partially converting it to aluminum chloride and titanium(III) chloride. Optimum catalyst efficiency was obtained at an Al/TiCl4 mole ratio of 0.5 to 1.0; the aluminum concentration was 0.0028 to 0.04% based on weight of solvent. Polyethylene yields as great as 1873 parts/part total catalyst were obtained at aluminum concentrations of 0.0028 to 0.008% and ethylene pressures of 150 to 280 psi. Liquid aliphatic hydrocarbons were more effective than aromatic hydrocarbons as media for the polymerization. Low molecular weight polymers and high‐density waxes were produced when hydrogen was used in the polymerization. The statistical study showed that the induction period was reduced by increasing the ethylene pressure and by decreasing the Al/TiCl4 mole ratio. The average reaction rate was increased by increasing the pressure, temperature, and aluminum concentration. A kinetic analysis of the data showed that the length of the induction period was inversely proportional to the first power of the pressure and titanium(IV) chloride concentration. The rate equation for the polymerization was found to be

where P is the ethylene pressure. Formation of high molecular weight polymers was favored by high monomer concentrations and low titanium(IV) chloride concentrations. High‐density polyethylene (0.950–0.960 g./cc.) can be produced conveniently, safely, and economically at low pressures (40 to 280 psi) and low temperatures (50 to 85°C.) with the use of preactivated Al‐TiCl4 catalyst.
Radiation‐induced solid‐state polymerization of ring compounds
Authors: Okamura Seizo , Hayashi Koichiro , Kitanishi Yasuhisa
Published: April 2003

Ring compounds such as trioxane, β‐propiolactone, diketene, and 3,3‐bischloromethylcycloxabutane can be polymerized only in the solid state by γ‐radiation. These ring compounds polymerize by a ring‐opening, ionic mechanism to highly crystalline, high molecular weight, linear polymers. In general, the conversion vs. irradiation time curves reach a limiting value at relatively low yield. These saturation phenomena are due to the disruption of unreacted monomer lattice by the formed polymer. The polymers obtained from large‐monomer crystals are found to have outward appearances of large crystals which suggest the monomer crystalline lattice has influenced that of the polymer. Moreover, the polymers from large crystalline monomer have higher polymerization rate and better orientation of the crystallites, as ascertained through x‐ray diffraction and polarizing microscopic analyses. Polarizing microscopic photographs of the polymers show birefringence clearly. These facts indicate that the structure of the monomer lattice directly imposes order and orientation upon the polymer. X‐ray diffraction analyses show that the polydiketene chain has a spiral configuration and poly‐β‐propiolactone has a planar zigzag chain. Some consideration of the propagation mechanism in the crystalline state of 3,3‐bischloromethylcycloxabutene, γ‐propiolactone, diketene, and trioxane is made. Investigations of the binary systems with β‐propiolactone were carried out to determine the effects of additives upon the propagation mechanism.
On the mechanism of polymerization of caprolactam catalyzed by phosphoric acid. II
Authors: Geleji Frigyes , Szafner Alfréd
Published: April 2003

In the presence of water or catalysts giving off water, caprolactam is polymerized by several reaction mechanisms taking place simultaneously. It was investigated whether the formation of polyamide takes place according to a polycondensation or polyaddition mechanism in the presence of phosphoric acid. In order to prove the polycondensation mechanism, the formation at 250°C. of a mixed anhydride from the carboxylic acids and the orthophosphoric acid was studied. N‐phosphoryl aminocaproic acid has also been synthesized. No catalytic effect was exerted by this compound; on the basis of this fact it can be stated that in the case catalysis by orthophosphoric acid, the increase of the polyamide chain does not take place according to a polycondensation mechanism. The adduct of caprolactam and orthophosphoric acid is able to catalyze the polymerization of caprolactam. Polymerizations carried out at temperatures ranging from 170 to 200°C. proved that the acid—amide bond of the caprolactam ring is weakened by the phosphoric acid, thereby rendering possible the polymerization to take place at a lower temperature. At elevated temperatures (exceeding 160°C.), the ammonium salts of phosphoric acid undergo dissociation; thus, free orthophosphoric acid is always present in the mixture undergoing polymerization. Due to the dissociation at higher temperatures, the phosphoric acid yields a product having higher molecular weight than at lower temperatures. It has been established that the rate of polymerization is directly proportional to the square root of the molar concentration of the free orthophosphoric acid. The activation energy of the polymerization catalyzed by phosphoric acid was 46 kcal./mole.
Polymerization reactions in the presence of a metal salt
Authors: Mullier M. E.
Published: April 2003

A kinetic study of a free radical‐initiated polymerization reaction in the presence of a copper salt has been undertaken. The results show that the polymerization of styrene initiated by benzoyl peroxide or α,α,‐azobisisobutyronitrile in either dioxane or dimethylformamide is not influenced by the presence of cupric octoate in the solution. The results show also that neither the initiation nor the reaction is affected when the cupric octoate is present. In contrast, the polymerization of styrene initiated by tert‐butyl hydroperoxide in dioxane is strongly influenced by the presence of cupric octoate in the solution. The results obtained can be partially explained by assuming the formation of a complex between the hydroperoxide and cupric octoate. At low concentration of copper salt and hydroperoxide, the rate of polymerization can be represented by an equation. Moreover, the values of the intrinsic viscosities of the polymers obtained show that the total chain transfer constant is not affected by the ratio tert‐butyl hydroperoxide/cupric octoate.
The swelling of polymer solvents. III. Sorption of liquids by elastomers
Authors: Buckley D. J. , Berger M.
Published: April 2003

Sorption of liquids by elastomers is advanced as a means of studying polymer structure. Liquids represent a wider versatility in this regard over vapors since they allow choices of molecular sizes, shapes, and configurational distributions, and thermal effects not available with vapors. Configurations, coiling versus stretched‐out molecules, are examined and shown to be of considerable importance in the sorption process. The problem of determination of the concentration dependence is attacked by use of a binary solution as a sorbent or swelling agent. The binary solution is so chosen that one liquid may be considered the solvent and the other liquid a nonsolvent for the particular elastomer. The ternary solution of butyl network—hexane—acetone was used in sorption experiments at 25°C. The total uptake of the binary liquid was measured from zero time to equilibrium in an optical swelling apparatus. Simultaneously, the composition of the binary liquid sorbed at any time was measured in a recording differential refractometer. The two sets of data were combined to calculate the ratio of the two liquids sorbed. The dilution procedure succeeded in varying the apparent activity of the solvent hexane. Preferential sorption of hexane was observed, but significant amounts of the nonsolvent acetone enter the network. The known equilibrium uptake values of hexane from the binary solutions are used to determine the concentration dependence of the diffusion of liquid hexane in a butyl network at 25°C. D0 = 2 × 10−9 cm.2 sec.−1 and a concentration dependence of 10 were obtained by this method. “Activities” for the hexane in the diluted form are calculated for an elastically calibrated network. The activities for the entire concentration range studied agree well with those of a comparable swollen polymer—liquid system such as natural rubber—benzene vapor. Test of the generality of the present method is suggested. Such a test would involve examination of the dependence of the hexane activities so calculated on the nature of the nonsolvent used in the binary liquid.
Etude expérimentale des dismutations rapides que subissent la cellulose, la lignine et le bois dans l'eau sous pression au‐dessus de 280°c: le problème de la lignine
Authors: Gillet Alf. , Colson P.
Published: April 2003

A la suite de recherches précédentes sur la cellulose, la conclusion suivante avait été proposée: c'est la décomposition progressive du kérogène qui, dans les conditions de la nature, aurait produit à la fois: les pétroles d'une part et, d'autre part, les houilles anciennes. La présente communication décrit la suite des měmes recherches expérimentales. Elle porte sur la lignine et sur le bois, soumis à leur tour à des conditions similaires à celles auxquelles fut soumise la cellulose. On a trouvé que, dans ces conditions (chauffage par exemple pendant 10 h à 275°C en solution alcaline): (a) Une lignine de composition centésimale: C 63; H 6,3; O 30,7—traitée en milieu alcalin à 275°C, produit, pour 21% de son poids, une matière réduite de composition: C 62,6; H 9,7; O 27,7 ou: C 72,4; H 8,6; O 19 + 0,55 H2O. (b) La měme lignine, traitée dans l'eau pure, produit pour 9,8% de son poids, une matière réduite de composition: C 60,3; H 11,27; O 28,4 (ou C 73,87; H 9,75; O 16,4 + 0,75 H2O). Un bois de chěne de composition: C 49; H 6,2; O 44,8, produit en milieu alcalin, pour 29,5% de son poids une matière réduite de composition: Essai I: C 61; H 7,85; O 34; Essai III: C 64,2; H 7,85; O 27,9 ou D 75; H 9,15; O 17 + 10 atomes d'oxygène fixés par oxydation accidentelle au cours des manipulations. La cellulose de composition: C 44,4; H 6,19; O 49,41, avait donné pour 14,8% de son poids, un produit réduit de decomposition: C 73.5; H 10,2; O 16,3 (C12H20O2). Composition type du Kérogène: C 75; H 8,6; O 16,4.
Incorporation of halogen endgroups in polymers and their detection by the dye test
Authors: Palit Santi R. , Saha Mihir K.
Published: April 2003

The incorporation of halogen endgroups in polymers has been established in the following cases for polymerization of styrene, methyl methacrylate and methyl acrylate: (1) chain transfer with halogenated hydrocarbons (chloroform, benzyl chloride, bromoform, ethylene dibromide, octadecyl bromide, ethyl iodide, cetyl iodide); (2) copolymerization with suitable components (vinyl bromide, tetrachloroethylene, trichloroethylene); (3) use of halogen atoms as initiators, e.g. FeCl3 (+hv), FeBr3 (+hv), HCl (+hv) and KBr + H2O2 (+hv); (4) chemical transformation of a group already present in a polymer, e.g., conversion of hydroxyl endgroup to halogen endgroup by a usual method; addition of hydrogen bromide to double bond in polymers. The method of detection consists in converting a polymer with halogen endgroups to a quaternary pyridinium halide by refluxing with pyridine, a few drops of glycerol being added in the case of chlorine endgroup to facilitate the reaction. The converted quaternary halogen endgroup is detected independently by two tests developed in this laboratory: the dyeinteraction test with rhodamine 6GX conc. (Calco) dye and also the dye‐partition test for cationic group with Bromophenol Blue or Disulfine Blue VN 150 as reagents.
Formation of hydroxyl endgroups in polymers and their detection by dye tests
Authors: Palit Santi R. , Mukherjee Asish R.
Published: April 2003

The following possibilities of introducing hydroxyl endgroups in polymers have been experimentally realized: (1) redox initiation by ferrous sulfate + H2O2 (Fenton's reagent), N2H4, H2O + H2O2, FeCl3 + H2O2; photoinitiation by Fe(OH)++ + light, H2O2 + ultraviolet light or sunlight, and initiation by unstable Ag+++ complex in dark; (2) copolymerization with a trace of allyl alcohol or with traces of vinyl acetate and allyl acetate and subsequent hydrolysis; (3) chain transfer with butyl alcohols. The method of detection consists in first converting hydroxyl endgroups to carboxyl endgroups by refluxing with phthalic anhydride or 3‐nitrophthalic anhydride in benzene and pyridine medium or with maleic anhydride in benzene medium and testing the resulting polymer for carboxyl endgroup by the dye‐interaction test with rhodamine 6GX dye extract. The hydroxyl endgroup was also quickly converted to a strong acid endgroup like OSO3H by reacting the polymer with chlorosulfonic acid in chloroform medium under controlled conditions and tested by the dye‐interaction test or a dye‐partition test with methylene blue. This test is not entirely satisfactory, as the reagent attacks the thermal polymers slightly.