bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymers and group interactions. VI. Intramolecular acylations on copolymers of styrene and acrylic acid derivatives, a route to poly‐2,4‐methylenetetralone
Authors: Teyssié Ph. , Smets G.
Published: April 2003

The intramolecular cyclization of 50/50 styrene‐acrylic acid (or derivatives) copolymers has been investigated; the purpose of this work was the synthesis of a high molecular weight poly‐2,4‐methylenetetralone. The cyclization of styrene‐(meth)acroyl chloride copolymers in the presence of aluminum chloride gives under rather mild experimental conditions high yields of tetralone units, together with some tricyclic units of the hexahydrophenalenedione type. This cyclization reaction was, however, always concomitant with a strong degradation of the polymeric chains: it results from the formation of a carbonium ion on the main chain through a secondary decarbonylation reaction, as shown by chemical determination. The cyclodehydration of a styrene(meth)acrylic acid copolymer was carried out with good yields in an acetylating mixture, in the presence of various catalysts such as zinc chloride, polyphosphoric acid, or phosphorus oxychloride. The cyclization to tetralone units is concomitant with the formation of anhydride groups, and in the case of acrylic acid, of enol‐ester groups: the alkaline hydrolysis of the products yields terpolymers of styrene, acrylic acid, and methylenetetralone. Moreover, using polyphosphoric acid or phosphorus oxychloride, the intrinsic viscosity of the cyclized copolymers remains important, even at rather high degree of conversion. The cyclization of styrene‐methyl(meth) acrylate copolymers in heterogeneous medium, in polyphosphoric acid, was also carried out; the degradation process is very small. The methacrylic ester copolymers undergo, however, an important gelification, while the acrylic copolymers yield, besides the usual tetralone units, some tetracyclic units of the tetrahydro‐3,4‐benzophenanthrene type.
Radiation crosslinking of rubber—effect of additives
Authors: Turner D. T.
Published: April 2003

The effect of a range of additives on the crosslinking of rubber by pile radiation has been investigated. Retardation of crosslinking has been correlated with the reactivity of the additive towards free radicals. At least two‐thirds of the crosslinks can be stopped by large amounts of radical acceptor. Preliminary results with a butadiene‐styrene copolymer and with Co‐60 γ‐radiation also indicate the importance of free radicals. Some halogenated compounds increased the degree of crosslinking.
The surface tension of viscous polymers
Authors: Tarkow Harold
Published: April 2003

A procedure is described for measuring the surface tension of polymeric liquids whose bulk viscosity is at least 1500 times that of glycerol. The procedure is based on the determination of the force necessary to separate two spheres held in contact by the test liquid. A series of silicones was examined. Following a relatively sharp rise in surface tension for the lower members, the rate of increase in surface tension with bulk viscosity is extremely small and seems to be approaching a constant value.
Polymerization of acrylonitrile by boron trifluoride in amide solvents
Authors: Campbell Tod W.
Published: April 2003

The observed activity of boron fluoride‐dimethyl formamide as a catalyst for the polymerization of acrylonitrile has been studied. It has been found that oxygen is a necessary third component, and that the polymerization is a free radical process. Evidence is presented that oxygen reacts with acidic complexes of dimethylformamide to give peroxides of the type HCON(CH3)CH2OOH, which acts as typical peroxide initiators.
Vinyl acetate emulsion polymerization
Authors: O'Donnell J. T. , Mesrobian R. B. , Woodward A. E.
Published: April 2003

Vinyl acetate emulsion polymerization at 70°C. using potassium peroxydisulfate as initiator and a partially hydrolyzed polyvinyl acetate as emulsifying agent has been studied. In agreement with the Smith and Ewart scheme for emulsion polymerizations, the polymerization rate was found to be independent of the total monomer amount present and approximately dependent on the 3/5 power of the emulsifier concentration. Instead of a 2/5 power dependence on initiator concentration for the rate of polymerization, a 0.7 power dependence was found. From surface tension measurements an “apparent critical micelle concentration” was determined for aqueous solutions of the emulsifier. However, light scattering studies gave no indication that aggregates of the emulsifier exist in aqueous solutions.
Viscoelastic properties of concentrated polymer solutions
Authors: Takemura Tetuo
Published: April 2003

It is shown that the relaxation time spectra of concentrated polymer solutions are obtained on the basis of molecular theory using the network structure model. These spectra are considered to be reflecting two kinds of relaxation mechanisms; (a), the vibrational modes between network structures, (b) the vibrational modes of intra‐chain submolecules in the network. In this paper the vibrational modes of each mechanism are calculated independently. The results show that the wedge‐type distribution of the relaxation spectrum can be obtained from the mechanism (b) and the box‐type distribution can be obtained from the mechanism (a), respectively, and that the deviations from Ferry's master curves originate from interactions between these networks. Good agreement is shown between this theory and experiments.
Crystallization in natural rubber. V. Chemically modified rubber
Authors: Gent A. N.
Published: April 2003

Measurements are described of the rate and final extent of crystallization at a temperature of −25°C. in natural rubber which has been modified by the chemical combination of sidegroups to the rubber molecule. The substances added were six thiol acids. Their efficiencies in retarding crystallization are compared with that previously reported for peroxide crosslinking and with the value predicted by a simple banned volume treatment for crystal nucleus formation. They are found to be generally greater than the large value predicted theoretically. Possible reasons for this are discussed.
Dynamic mechanical properties of nylon 66 and the plasticizing effect of water vapor on nylon
Authors: Quistwater J. M. R. , Dunell B. A.
Published: April 2003

The dynamic tensile modulus and energy loss have been measured for nylon 6‐6 at 35°C. over a wide range of humidity in forced longitudinal vibration experiments. The frequency range covered was about 3 to 30 cps. (radian frequency 20 to 200 sec.−1). Dispersion of mechanical properties was observed with changing humidity, the maximum in the loss factor, tan δ, occurring at about 70% RH. Small variation of energy dissipation with change in frequency is such as to suggest that the dispersion region extends over a wide frequency range and that at low humidity an energy loss maximum should be expected at a frequency below one cycle per second. Increase in the amount of water adsorbed by the nylon with increasing relative humidity leads to plasticization of the fiber and consequent increase in freedom of motion of chain segments in the amorphous region of the fiber. Examination of individual runs shows that the dynamic modulus tends to increase with increasing frequency and that the increase is of a reasonable order of magnitude for the relaxation phenomena involved.
Glass transition temperatures of copolymers
Authors: Wood Lawrence A.
Published: April 2003

The Gordon‐Taylor equation relating the glass transition temperature θ of a copolymer to the glass transition temperatures θ1 and θ2 of the homopolymers is equivalent to

where c1 and c2 are the weight fractions of the constituents and A1 and A2 are constants. It can be recast into the following forms suitable for linear plots

and

where k = A2/A1. Data from the literature on 10 copolymer systems, including butaciene‐styrene copolymers, give linear plots, verifying the equation within experimental error. However, the observed value of k is in most cases significantly smaller than the ratio of the differences of the volume‐temperature coefficients for each homopolymer in the rubbery and glassy states, as required by the derivation of Gordon and Taylor. The glass transition temperature (in °C.) for a butadiene‐styrene copolymer prepared by emulsion polymerization at 50°C. may be calculated from the weight fraction c2 of bound styrene as

and for a similar 5° copolymer as
The fractionation of polyethylene
Authors: Hawkins S. W. , Smith H.
Published: April 2003

Four of the new high‐density polyethylenes and one conventional high‐pressure, low‐density polyethylene have been fractionated by a fractional solution technique. The number‐average molecular weights, infrared absorption spectra, and densities of the fractions were measured by standard techniques, modified where necessary to accommodate the low solubility of the new high‐density polyethylenes. The results show: (1) The solubility of polyethylene is determined primarily by a shape parameter—number of methyl groups per hundred carbon atoms—rather than molecular weight. (2) Crystallinity is not a reliable index of the solubility of polythene unless considered in relation to molecular weight. (3) The unusual physical properties of the new high‐density polyethylenes arise from their having an essentially unbranched molecular structure rather than high molecular weights.
The fine structure of polytetrafluoroethylene
Authors: Bunn C. W. , Cobbold A. J. , Palmer R. P.
Published: April 2003

Electron micrographs of highly crystalline PTFE crystallized by slow cooling from temperatures not far above the melting point show well‐marked bands, often with striations perpendicular to the bands; optical evidence shows that the chain molecules are parallel to the striations. The structure is in marked contrast to the spherulitic structure of most polymers; it appears that in PTFE the molecules are straight and parallel for much greater distances than in other polymers, and it is suggested that the width of the bands is a measure of molecular length. The unusual structure is attributed to the unusual stiffness of the fluorocarbon chain; the molecules in the liquid are straighter and less tangled than in other polymer melts. Heating to 500°C., followed by slow cooling, gives a modified structure approaching the spherulitic type found in other polymers; it is suggested that this is due to increased molecular tangling in the melt at higher temperatures. One type of polymer shows bands of remarkably uniform thickness, suggesting unexpected uniformity of molecular length. PTFE wax made by thermal or radiation degradation of the high polymer shows well‐defined spiral growth steps due to dislocations; the step heights suggest an unexpected uniformity of molecular length.
Solvation of polyvinyl alcohol in solvent–nonsolvent mixtures
Authors: Levi D. W. , Scherer P. C. , Hunter W. L. , Washimi K.
Published: April 2003

The sorption of solvent and nonsolvent by polyvinyl alcohol from water–acetone and water–n‐propanol mixtures was measured by using the dipping refractometer to follow changes in concentration of the liquid phase. Beyond about 15% acetone no selective sorption was observed. The values calculated for n‐propanol and water sorbed are a function of the n‐propanol concentration of the equilibrium solvent.
Degradation of addition polymers by ultrasonic waves. III. Experimental
Authors: Mostafa M. A. K.
Published: April 2003

The degradation of an addition polymer sample (polystyrene) has been studied. In conformity with theory, the process of degradation does not proceed below a limiting chain length. A rate constant has been derived. The experimental size distributions of the polystyrene at different stages of the degradation have been determined and compared with their corresponding theoretical distributions. The experimental values of the number of broken links at the early stages of degradation have been determined photometrically and compared with their corresponding theoretical values as derived from the theory of ultrasonic degradation. Satisfactory agreement has been found between experiment and theory for the main features of the degradation.
Structure and mechanism of dehydrochlorination of polyvinyl chloride
Authors: Baum B. , Wartman L. H.
Published: April 2003

Polyvinyl chloride when heated loses HCl, presumably by a “zipper” mechanism. The loss of each molecule of HCl from the polymer results in the formation of a double bond, which activates adjacent chlorine and causes the decomposition reaction to propagate along the resin chain. Virgin and degraded resins were subjected to ozonization in order to ascertain the type and location of the labile structures responsible for initiating the “zipper” HCl loss. The molecular weight decrease and formation of carbonyl structures (detected by infrared) produced by ozone indicate that unsaturated chain ends are primarily responsible for HCl loss. Tertiary chloride chain branches contribute to a lesser degree in the initial stages but become more important as dehydrochlorination proceeds. Stability measurements on simple prototypes of structures presumed to be present in polyvinyl chloride provide additional information which is in essential agreement with this mechanism.
Diffusion‐controlled stress relaxation in polymers. II. Stress relaxation in swollen polymers
Authors: Fujita Hiroshi , Kishimoto Akira
Published: April 2003

Stress relaxation in the systems PVAc (polyvinyl acetate)‐water, PVAc‐methanol, PMA (polymethyl acrylate)‐water, and PMA‐methanol was measured at several temperatures above the glass‐transition points of the pure polymers in ranges of sufficiently low concentrations of diluents. It was found that the time‐concentration superposition principle as proposed by Ferry is applied successfully to these data to obtain master relaxation curves of the pure polymers at fixed temperatures. The master relaxation curves so obtained at different temperatures were further superposed with each other by horizontal shift along the log time axis, in agreement with the time‐temperature superposition principle. The concentration shift factor ac as a function of diluent concentration C at fixed temperature was well interpreted in terms of the modified Doolittle's free volume equation for the viscosity of supercooled systems on the assumption that the fractional free volume of the system increases linearly with C. The proportionality coefficient, β, of this linear relation provides a measure of the plasticizing effect of a given diluent on a given polymer. It was found that β is practically independent of temperature at sufficiently small C and is larger for water than for methanol in both polymers studied. On the basis of Doolittle's viscosity equation modified to account for the concentration effect, it is shown that the glass‐transition temperature Tg of a given polymer‐diluent pair decreases with C in a linear fashion in the range of small C. The value of β can also be calculated from the slope of this linear relation. Values of β determined in terms of this procedure from literature data on a variety of polymer‐diluent pairs are given in a tabular form. For a given polymer the β values generally become smaller as the size of diluent molecule is increased, but no unique relation can be obtained between the two quantities. Equilibrium sorption and integral sorption processes were studied on the four pairs of polymer and diluent mentioned above, not only to obtain data needed for analyzing the present stress‐relaxation data but also to find information which will serve a study described in Part III of this series which is concerned with diffusion‐controlled stress‐relaxation in amorphous linear polymers. Some correlation (though not definite) appears to exist between the diffusion coefficient D (at zero concentration) and the plasticizing parameter β for a given polymer. This may be expected because both D and β are quantities depending on the frequency at which polymer segments jump cooperatively in the presence of a low molecular weight diluent.
An evaluation of molecular weight distribution in high pressure polyethylene
Authors: Mussa I.V. C.
Published: April 2003

A particular kind of plot has been used, yielding graphs tending toward straight lines, to compare the fractionation and viscometry data of eight high pressure polyethylene samples with the distribution formula deduced by Beasley. These graphs are equivalent, except for an additive constant in the abscissas, to the log‐log plots of intrinsic viscosity versus molecular weights. In this way an evaluation of the distribution parameters defined by Beasley can be obtained for all the investigated samples. By means of these parameters and the absolute determination of the (number‐)average molecular weight of a single sample, an evaluation of all the molecular weights and of their distribution in the given samples has been proposed. Within the limits of experimental uncertainty of the measurements of high pressure polyethylene in diluted solutions, these results are in some agreement with the experimental findings of other authors.
Polymerization of p‐isopropenylstyrene
Authors: Dreyfuss P. , Notley N. T.
Published: April 2003

p‐Isopropenylstyrene was synthesized and its polymerization characteristics are essentially the same as those of divinylbenzene. A soluble prepolymer can be separated from polymerization in a solvent having chain transfer properties but polymerization in bulk or in an inert solvent gives crosslinked infusible polymer.
Thermodynamic properties of dilute solutions of cellulose derivatives
Authors: Moore W. R. , Tidswell B. M.
Published: April 2003

Heats and entropies of dilution of dilute solutions (concentration range 0.2–1.0 g./100 ml.) of cellulose acetate, ethyl cellulose, and cellulose nitrate, of similar degrees of substitution and polymerization, in a number of representative solvents, have been obtained from temperature coefficients of osmotic pressure. In some cases, degradation of polymer at the higher temperature used seems possible and an attempt is made to allow for this in the estimation of values of ΔH̄1 and ΔS̄1. Heats of dilution for the cellulose acetate and ethyl cellulose systems are generally endothermal, those for the cellulose nitrate systems being exothermal. Entropies of dilution are less than those obtained for comparable systems containing less polar and more flexible polymers. Those for the cellulose nitrate systems do not differ much from “ideal” values. The value of ΔH̄1/ϕ22, where ϕ2 is the volume fraction of polymer calculated from the density of the bare polymer, for each cellulose acetate system and most of the ethyl cellulose systems seems to be effectively independent of concentration. Values for the cellulose nitrate systems seems to be effectively independent of concentration. Values for the cellulose nitrate systems become less negative as the concentration increases. Values of ΔH̄1 for the cellulose acetate and ethyl cellulose systems are generally in the order to be expected from the solubility parameters of the solvents and polymers. ΔS̄1/ϕ22 may vary with concentration in a manner rather similar to that suggested by simpler lattice theories. These results are tentatively interpreted in terms of solvation of polymer and possible endothermal mixing of solvated polymer and solvent. Although values of the entropy contribution to the interaction parameter χ1 for the cellulose acetate and ethyl cellulose systems are not always inagreement with the predictions of simpler lattice theories it is possible, if solvation, segment size, and chain stiffness are allowed for, that the thermodynamic properties of dilute solutions of cellulose derivatives may be at least qualitatively interpreted in terms of such theories.
Behavior of human serum albumin in acid solution: Light scattering study
Authors: Sedláe K B. , Štokrová Š.
Published: April 2003

The behavior of human serum albumin in acid solutions containing chloride ions and in citrate and acetate buffers of pH 1 to 5 has been investigated by the method of light scattering. The reduced intensity of the scattered light was found to increase with decreasing pH: this change is most marked in acetate buffers, somewhat less marked in citrate, less again in the presence of higher concentrations of sodium chloride, and least in solutions of low ionic strength and in water. The phenomenon cannot be ascribed to the presence of lipoid substances alone: the possibility of complex formation must also be taken into account.
The charge and deformation of protein molecules
Authors: Pasynskii A. G.
Published: April 2003

The density of like‐charged groups distributed along the molecules of proteins is much lower than in molecules of polyelectrolytes. From this it follows that the degree of deformation of the protein molecules resulting from the charge is much less. In buffered solutions—if the correction for hydration (measured by the compressibility method) is taken into account—the shape of gelatin particles (as measured by viscosity) practically does not depend on the pH, while in unbuffered solutions it varies roughly in proportion to the fourth to fifth root of the number of charges. For molecules of serum albumin and egg albumin the deformation is proportional to the 25th to 30th root of the number of charges, i.e., completely negligible. This comparison also shows that the deformation of the threadlike molecules of gelatin occurs much more easily than with the firmly molecules of the globular proteins. For globular proteins the following expression has been derived

where E is the modulus of elasticity, n the number of charges inthe molecule, m the relative elongation of the molecule, a0, b0, and S the semi‐axes and surface of the ellipsoidal molecule and κ the reciprocal thickness of the ionic atmosphere. A value of E = 10–40 kg./mm.2 was calculated according to this relation for the molecules of these globular proteins (for soft rubber E = 0.14 kg./mm.2, for polyamides 70–80 kg./mm.2, for ebonite 50–80 kg./mm.2, etc.). These results for the first time quantitatively characterize the high rigidity of the molecules of globular proteins.
Propriétés diélectriques du bromure de polyvinyle en solution
Authors: Kryszewski Marian , Marchal Jean
Published: April 2003

Le bromure de polyvinyle a été préparé par photopolymérisation et la masse moléculaire des fractions a été mesurée par diffusion de la lumière. Nous avons étudié l'absorption diélectrique pour comparer les variations des composantes du pouvoir inducteur spécifique de ce polyère en solution dans deux solvants en fonction de la fréquence du champ électrique comprise entre 1 et 32 MHz et de la température. Une étude analogue a été faite sur le chlorure de polyvinyle. Nous avons interprété les temps de relaxation et les énergies d'activation de ces deux polymères.
Zum verhalten von makromolekülen in lösung
Authors: Elias H.‐G. , Patat F.
Published: April 2003

Die an 15 Polyvinylacetat‐Fraktionen in Butanon bei 25°C. durch Lichtstreuungs‐, Sedimentations‐, Diffusions‐, Osmose und Viskositäts‐Messungen gefundenen Beziehungen

(h = Fadenendenabstand) werden anhand der hydrodynamischen Theorien von Kirkwood‐Riseman, Kuhn‐Kuhn, Debye‐Bueche, Peterlin und Fox‐Flory diskutiert. Die experimentell bestimmten Fadenenden‐Abstände stimmen mit den aus Viskosität und Molekulargewicht nach den Theorien von Kuhn‐Kuhn, Peterlin und Fox‐Flory ausgezeichnet, nach Kirkwood‐Riseman noch innerhalb 10% überein, bei den nach Debye‐Bueche berechneten traten grössere Abweichungen auf. Die aus Sedimentation und Diffusion nach Kuhn‐Kuhn berechneten Fadenenden‐Abstände decken sich mit den experimentell aus Streulicht‐Messungen gefundenen, bei allen anderen Theorien treten mehr oder minder starke Abweichungen auf. Die gleichzeitige Gültigkeit von (1) und (2) wird durch einen mit dem Molekulargewicht abnehmenden hydrodynamischen Radius gedeutet. Die Unstimmigkeiten bei den einzelnen Theorien werden im Lichte dieser Anschauung diskutiert.
Polymer fractionation into summative fractions
Authors: Broda Andrzej , Gawronska Barbara , Niwinska Teresa , Połowinski Stefan
Published: April 2003

The problem of the systematic error of fractionation methods and its dependence on the selectivity of polymer separation are discussed. Comparisons of the results of a theoretical analysis and of an experimental fractionation by means of summative and of successive methods of fractionation are presented. For the purpose of comparing the polydispersity of polymers, the application of the method of fractionation into summative fractions alone is sufficient, since the results of this method depend only on the selectivity.
A thermistor ebulliometer for high molecular weight measurements
Authors: Lehrle R. S. , Majury T. G.
Published: April 2003

Molecular weight studies on polyamides have necessitated the construction of an ebulliometer of greater sensitivity than any so far described. This has been achieved by the use of thermistors as the temperature‐sensitive elements; they are incorporated in a bridge circuit whose output is amplified and fed to a pen‐recorder. This apparatus affords a differential temperature sensitivity of better than 0.02 mdeg. Difficulties caused by some lack of reproducibility in readings taken at this sensitivity have been overcome by a design which enables repeated readings of the elevation of the boiling point of a given solution to be taken consecutively. This is achieved by mounting the thermistors in a tube which can be raised or lowered through a gland at the top of the ebulliometer. In the lowered position, one thermistor is at the temperature of the solution and the other at the temperature of the vapor as in normal practice; in the raised position both thermistors are at the temperature of the vapor. This arrangement enables the thermistors to be “zeroed” in the vapor phase after each determination of elevation so that difficulties such as those caused by overall drift can be eliminated. The design also enables the effects of superheating and the temperature gradient in the ebulliometer column to be examined. The instrument has been calibrated with substances of known molecular weight; assessment of the results indicates that values of molecular weights can be obtained having a probable error of less than 3%. Examples of preliminary work on the application of the apparatus to a study of N‐substituted polyamides are given.
Polymer association. IV. Hydrogen bonding and melt viscosities in copolymers of styrene with methacrylic acid
Authors: Longworth Ruskin , Morawetz Herbert
Published: April 2003

Melt viscosities of styrene homopolymers and copolymers with 1.5 to 23 mole‐% methacrylic acid were measured with a parallel plate plastometer. Apparent viscosities were found to drop off sharply with increasing rate of shear in the range 10−4 to 10−1 sec.−1. An increasing concentration of carboxyl groups led to a pronounced increase in the melt viscosity and the activation energy for viscous flow. Infrared spectra of the copolymers were recorded while the samples were subjected to various thermal cycles. Equilibrium in the dimerization of carboxyl groups was established very rapidly above about 100°C., but the equilibrium was effectively frozen at lower temperatures. Samples as originally prepared by precipitation from dilute solution were further removed from equilibrium than samples quenched from high temperatures. The results are discussed in terms of the rate process theory of viscosity.
Kinetic effects of salts on vinyl polymerization in non‐aqueous systems
Authors: Bamford C. H. , Jenkins A. D. , Johnston R.
Published: April 2003

The polymerization of vinyl monomers in non‐aqueous solvents, such as N,N‐dimethylformamide, is influenced by a variety of inorganic salts, and both the cationic and anionic components of the salt may be active in this respect. Cations derived from metals possessing several valency states may terminate the kinetic chains by a one‐electron transfer process, e.g., with styrene

equation image

The kinetics of the polymerization of several monomers in the presence of ferric chloride have been worked out, and the absolute rate constants for the termination reactions calculated. Their magnitude is briefly discussed in terms of the structure of the radicals. It is pointed out that these reactions provide a very useful method of determining rates of initiation. Even cations such as lithium, which have only a single valency state, may have an effect on the kinetics of polymerization, for example in the case of acrylonitrile. This arises from association between the metal ions and the radicals which modifies the reactivity of the latter. The associated anions may also interact with radicals in a similar manner. This effect is particularly marked with chloride ions and acrylonitrile, and leads to an increase in the rate of propagation and chain transfer with electron accepting reagents such as carbon tetrabromide.
Polycondensations in the formation of catechin tannins and of lignin
Authors: Freudenberg K.
Published: April 2003

Catechin tannins are formed by the action of protons on catechins, by condensation of the carbon atom from the ether bridge in the 2‐position with one of the phenyl rings of the next molecule. As the molecule is bi‐ or polyfunctional, the reaction can proceed further until it ceases, on account of the low solubility of the reaction product. Lignin is formed by dehydrogenation of p‐hydroxy‐cinnamic alcohols. The radicals produced stabilize themselves by combining, giving various types of dimeric products. These, too, are phenols and by virtue of further dehydrogenation, are subjected to a mixed condensation and, in part, to polymerization. In both cases, a highly irregular polymer molecule is formed from a single basic substance.
On the viscometry of poly‐6‐caproamide
Authors: Rybnikář F.
Published: April 2003

In the viscometric evaluation of poly‐6‐caproamide (6‐PA), the following effects were studied in detail: influence of water in tricresol, influence of molecular weight, and influence of temperature. The water present in the tricresol lowers the measured value of [η] proportionately to the water content. The value of K in the Huggins equation ηsp/c = [η] + K[η]2C remains constant within the limits of experimental errors. The value of K in the Huggins equation was found to be influenced significantly by molecular weight. For low values of [η], the constant K increases manyfold. The constant K was, therefore, replaced by a function which takes account of the increase of K due to the molecular weight:

where K1 = 0.26, K2 = 285.5, and x = 1.48. At higher temperatures, the measured value of [η] decreases, and the constant K in the Huggins equation remains constant within the limits of experimental error. The following equation was used to give the dependence of the viscosity of 6‐PA on temperature:

where the constant a is independent of [η], while b is a function of [η].
Effect of structure on polymerizability: Olefin polysulfone formation
Authors: Cook R. E. , Dainton F. S. , Ivin K. J.
Published: April 2003

Polymerizability in the thermodynamic sense is measured by the free energy of polymerization. The effect of structure on polymerizability can be measured in two ways: (1) we may compare standard free energies (which are directly related to equilibrium monomer concentrations) at a given temperature; or (2) we may compare the temperatures at which the actual free energy changes are zero for a chosen monomer concentration. These temperatures are termed “ceiling temperatures” Tc and have been determined for the 1:1 copolymerization of sulfur dioxide S. with a wide variety of unsaturated compounds M, under the standard conditions [M] [S] = 27 mole2.1−2(binary mixture, mole fraction of M approximately 0.09). The polymers have the general formula
magnified image
Tc was determined by extrapolating the photochemical rate‐temperature relation to zero rate. In the straight chain 1‐olefin series Tc falls from ethylene (gt;135°) to propylene 90°, to butene‐1 64°, and thereafter remains approximately constant with increasing chain length. With 2‐olefins there is a progressive decrease from butene 34°, to pentene 8°, to heptene −38°. Branching invariably lowers Tc and the effect is greatest when the branching is at the double bond: thus isobutene 4°, 3‐methylbutene‐1 36°, 4,4‐dimethylpentene‐1 14°. 2‐Ethyl substitution of a 1‐olefin, or 2, 3 or 4 substitution of a 2‐olefin results in inability to react at any temperature down to −80°. Cyclic olefins have Tc considerably higher than the corresponding 2‐olefins: cyclopentene 102°, cyclohexene 24°. A number of allyl compounds have also been investigated. Tc is related to the heat and entropy of polymerization by the relation Tc = Delta;H/ΔS and in eight cases values of ΔH and ΔS have been obtained. A change of structure mainly affects ΔH. Estimated equilibrium monomer concentrations in polysulfone formation and in vinyl polymerization at 25°C. are summarized.
A contribution to the theory of emulsion polymerization
Authors: Ryšánek A.
Published: April 2003

The polymerization curve in emulsion polymerization in presence of retarding substance was determined. The active concentration of the monomer in the vicinity of the growing radical was assumed constant, while the number of reacting particles was varied. The active concentration of the retardant in the vicinity of the reacting radical was assumed constant during the polymerization.

The following relationship was derived for the decrease in monomer concentration:

where −m, is the decrease in monomer concentration, k2 is the kinetic constant of the chain growth, (M) is the active concentration of the monomer in the vicinity of the growing radical, n is the concentration of all particles in the emulsion, V′t is the velocity of penetration of the initiator radical into the particles; the initiation velocity V′i(n – n1)/n, n1 is the concentration of reacting particles, i.e., of particles containing the growing polymer radical, V′r = nk3[R]; k3 is the constant of chain termination by a retardant molecule; V′in1/n is the velocity of termination by a primary radical, and t is polymerization time. For the polymerization with a constant number of particles we have

where −m2 is the decrease in monomer concentration during the period of constant polymerization rate. In the presence of a large amount of retardant, when V′r ≫ 2V′i the decrease in monomer concentration is given by

This equation shows that for these conditions the decrease in monomer concentration is independent of the number of polymerizing particles, but it is directly proportional to the initiation velocity, and inversely proportional to k3[R].
For the final period at the end of the polymerization, when it can no longer be assumed that the active concentration of the monomer in the vicinity of reacting radical is constant, the following formula was derived:

where −m3 is the total decrease in monomer concentration during the period of (M) ≠ const.; N is the number of particles in unit volume of the aqueous phase, NA is Avogadro's number; (M0) is the active concentration of the monomer in the period of constant polymerization rate; and t3 is the time elapsed from the beginning of this period, i.e., total polymerization time minus time of constant (M).
Reticulation du chlorure de polyvinyle sous l'action des radiations ionisantes
Authors: Wippler C.
Published: April 2003

Certains polymères se réticulent sous l'acton de radiations ionisantes. Les produits réticulés étant insolubles et infusibles leur tenue aux solvants et à la chaleur est considérablement améliorée. Cet effet est particulièrement net pour le polyéthylène, pour le chlorure de polyvinyle, par contre, les observations faites par différents chercheurs se contredisent, les unes indiquent ue dégradation, les autres une réticulation de ce polymère sous l'action des radiations. Nos propres expériences sur des poudres de chlorure de polyvinyle pur irradié à l'aide d'une source de 60 Co montrent que les deux mécanismes coexistent. Suivant que l'irradiation se fait sous vide ou à l'air l'un ou l'autre prédomine. Toutefois même après des irradiations à des doses de 150 MR les modifications restent relativement faibles. Par contre, nous montrons qu'il est possible de réticuler totalement le chlorure de polyvinyle avee des doses de l'ordre de 50 Mr en l'irradiant en présence de certains solvants sous forme de gels. Nous déterminons d'une part la quantité de C.P.V. insoluble en fonction de la dose d'irradiation, d'autre part, la masse moléculaire moyenne en poids de la fraction soluble. Ces measures sont confrontées avec les résultats théoriques publiés par Charlesby. Elles permettent d'avoir une idée sur la répartition initiale des masses moléculaires.
Donor‐acceptor interactions in cationic polymerization. III. Influence of diethyl ether on molecular weight of polyisobutene in polymerization catalyzed by aluminum trichloride
Authors: Zlámal Z. , Ambrož L.
Published: April 2003

The electric conductivity of solutions of aluminum trichloride in ethyl chloride containing varying amounts of diethyl ether and anisole was measured at −78.5°C. The dependence of the specific conductivity on composition is complicated and nonmonotonous. Two relative maxima, corresponding to complexes of the types 2ROR.AlCl3 and ROR.2AlCl3 are seen; between these two, there lies a marked minimum corresponding to the complex ROR.AlCl3.

The positions of both maxima are changed by the concentration of the solute and the dielectric constant of the solvent. Thus it can be assumed that it is influenced by the association processes taking place in the system. Isobutene, polymerized in solutions of the same composition as that of solutions whose conductivity was measured, yielded a polymer whose molecular weight was related to the composition of the solution. This relationship was just the reciprocal of the relationship of the electric conductivity to composition. The maximum molecular weight was found for the molar ratio ROR/AlCl3 = 1, and minimum molecular weights were found in solutions with ROR:AlCl3 ratios of 2:1 and 1:2, corresponding to 2:1 and 1:2 complexes. The position of these minima was also changed with the change in concentration of the solution. Thus it can be assumed that the association influences not only the conductivity, but also the molecular weight of the polymer produced. Polar compounds, such as ethers, when added in cationic polymerizations, may cause not only a reduction in the molecular weight of the polymer, but also an increase in the latter, if their addition causes a reduction in the ionization of the system.
Copolyamides renfermant le groupement méthylène‐bis‐amide
Authors: Cannepin A.
Published: April 2003

Les polyamides l–n:

décrits il y a quelques années, donnent par extrusion à l'état fondu des filaments cassants et friables plutôt que de véritables fibres textiles. Aussi il a semblé intéressant de n'introduire le groupement méthyléne‐bis‐amide qu'en proportion limitée et définie dans une chaîne macromoléculaire linéaire. Pur réaliser de tels polymères on a fait la synthèse d'un composé bifonctionnel du type:

qui a été ensuite copolycondensé en proportions variées avec une diamine et un diacide classiques ou avec un ω‐amino‐acide. Les propriétés des copolycondensats ainsi obtenus semblent montrer que la haute cristallinité, due d'ordinaire à la présence du groupement méthylène‐bis‐amide, ne compense pas la diminution de la symétrie et de la régularité qui intervient généralement dans les copolyamides.
Hydrolyse der aluminium‐alkoxy‐chelate
Authors: Kugler Václav
Published: April 2003

Durch die Reaktion der Aluminiumalkoholate mit Azetessigäthylester werden nach der Beseitigung des freigemachten Alkohols Systeme gebildet, in denen Azetessigäthylester an Aluminium mittels der Chelat‐Valenzringe gebunden ist. Derartige Systeme weisen im Vergleich mit den Aluminiumalkoholaten eine erhöhte Beständigkeit gegenüber der Einwirkung von Wasser. In dieser Arbeit wurde die Stabilität der an Aluminium gebundener Azetessigäthylestergruppen bei der Hydrolyse mit Wasser im Molverhältnis Al:H2O = 1:1 verfolgt. Andererseits wurde die Menge des durch die Hydrolyse freigemachten Alkohols verfolgt. Durch die Reaktion von 1 Mol Aluminiumäthylat mit 1 Mol Azetessigäthylester entstehen, nach der Beseitigung des freiwerdenden Äthylalkohols, Systeme, in denen das Vorhandensein einer wesentlichen Menge Aluminium‐di‐ethoxy‐monoazetessigäthylesters angenommen werden kann. Bei der Hydrolyse der Lösung diesen Systems mit einer dem Molverhältnis Al:H2O = 1:1 entsprechenden Wassermenge wurden, unter Abgabe von Äthylalkohol, Äthoxy‐gruppen umgesetzt, während Azetessigäthylestergruppen praktisch unverändert bleiben. Die Abspaltung der Azetessigäthylestergruppen, bzw. deren Zersetzung ist erst bei den Zersetzungstemperaturen des Produkts merkbar. Durch das nach der Hydrolyse bis zu der Zersetzungstemperatur vorgenommenes Erhöhen der Temperatur kann man stufenweise eine beinahe 2 Molen auf 1 Mol des zur Hydrolyse verwendeten Wassers entsprechende Menge Äthylalkohols erhalten, d.h. dass durch diese Wassermenge in der Endphase fast alle in dem System vorliegenden, an Aluminium gebundenen Äthoxy‐gruppen hydrolytisch abgespaltet werden. Es kann primärerweise die Bildung der entsprechenden Hydroxyverbindungen angenommen werden, welche dan bei erhöhter Temperatur kondensiert werden und, wahrscheinlich, Bindungen ausbilden, in denen Aluminiumatome mittels der Sauerstoffbrücken verknüpft werden. Als Zwischenprodukt wurde eine Substanz isoliert, welche den elementaranalytischen Untersuchungen und ihren chemischen Eigenschaften nach Alkoholabgabe nach dem Schmelzen für die entsprechende Hydroxyverbindung aufzufassen ist, obgleich der Nachweis der Hydroxygruppen weder mit Lithium‐aluminiumhydrid noch mit Äthyl‐magnesiumjodid wegen der gleichzeitig verlaufenden Nebenreaktionen nicht durchgeführt werden konnte. Die Endprodukte stellen feste, spröde harzartige Substanzen dar, die auf mehrere Weise praktisch verwendbar sind, und die von uns “Aluminiumharze” benannt wurden.
The dielectric properties of solid polymers
Authors: de Brouckere L. , Offergeld G.
Published: April 2003

In this paper the influence of different molecular parameters on the dielectric characteristics of amorphous high polymers has been examined. The dielectric behaviour has been compared for several polymers which carry the same dipole in the side chain, but which differ in the flexibility of the main chain (polymethyl acrylate and polymethyl methacrylate) and in the steric hindrance of the side group (methyl, ethyl, butyl, and isobutyl polymethacrylate). Two dispersion zones have been found in the case of polymethyl methacrylate. These may be attributed to the motions of the segments of the main chain and those of the side chains. For each polymethacrylic ester and in the range of frequencies used in these experiments, only one dispersion zone has been found. The experimental results show that it must be attributed to motions of the side groups, which occur simultaneously with the deformations of the main chain. The observed dielectric dispersion do not seem to be of the same nature as those shown by the study of the mechanical properties. The observed dispersions in high polymeric systems probably have their origin in complexes and various molecular motions which need further investigation.
Molekulargewichtsverteilungen von nativen faser‐ und holzcellulosen
Authors: Marx M.
Published: April 2003

Es werden Verteilungskurven gezeigt, die nach einer neuen Fraktioniermethode ohne Abbau an den β‐Glukosidketten von nativer Baumwoll‐ und Flachscellulose erhalten worden waren. Beide Verteilungen zeigen zwei Maxima, von denen jeweils das höhere scharf und ausgeprägt ist. Die Maxima liegen bei Baumwolle zwischen 6000 und 7000, bzw. swischen 8000 und 9000, bei Flachs zwischen 7000 und 8500, bzw. zwischen 9500 und 11000. Rechnerische und experimentelle Kontrollen bestätigen die erhaltenen Verteilungskurven und damit die angewandte Fraktioniermethode. Letztere unterscheidet sich von den bisher in der Literatur bekannten dadurch, dass man rasch, in der Kälte und in Quarzgefässen arbeitet, und dass die abgetrennten Fraktionen sofort nach Auflösen gemessen und erst nachträglich Gewicht und Konzentration durch Ausfällung und Trocknen bestimmt werden. Auf Grund der angeführten Ergebnisse und Kontrollen kann angenommen werden, dass die gezeigten Verteilungskurven die tatsächliche Verteilung der β‐Glukosidketten von nativer Baumwoll‐ und Flachscellulose darstellen. Es wird weiterhin eine Verteilungskurve von weitgehend nativer Fichtenholzcellulose angegeben. Fichtenholzmehl war möglichst abbaufrei aus dem Holz isoliert und nach der oben angeführten Methode fraktioniert worden. Die erhaltene Verteilung zeigt ein etwas diffuses Maximum zwischen 5000 und 8000, das etwa 70% der Gesamtmasse enthält. Das bedeutet, dass auch die β‐glucosidischen Holzcelluloseketten in nativem Zustand Kettenlängen bis zu mindestens 8000 aufweist und dass also keine wesentlichen Unterschiede zwischen Faser‐ und Holzcellulosen bezüglich Kettenlänge und Kettenverteilung bestehen. Verteilungskurven, die durch Fraktionierungen an verschieden stark aufgeschlossenen Zellstoffen hergestellt wurden, geben abschliessend ein deutliches Bild über die Abnahme der Kettenlängen und die Änderung der Verteilung bei stärke werdendem Aufschluss.
La contraction isotherme du volume des polymères amorphes
Authors: Kovacs A. J.
Published: April 2003

Lorsqu'on trempe un polymère ainorphe à partir d'une température T0 > Tg à une température T1 < Tg, Tg, btant la température de transition vitreuse, on observe une contraction isotherme du volume à T1 qui se poursuit généralement pendant une longue periode. On decrit ce phenombne à partir des observations faites sur des échantillons de polystyrolène, d'acétate de polyvinyle, de polypiperidide et de polymorpholide acrylique. L'expression empirique des isothermes de contraction du volume, v = ƒ(log t′), contient trois paramhtres dont on discute les variations en fonction de la température. Dans la region de la transition vitreuse, les isothermes de contraction peuvent se superposer it l'aide d'une translation le long de l'axe de log t′. La variation du paramètre de super‐ position a, en fonction de la température est sensiblement la méme que celle deduite par d'autres auteurs, de la variation des paramhtres Blastovisqueux des polymeres amorphes. Ceci sugghre que les processus moléculaires responsables de la relaxation de la contrainte mécanique et ceux qui provoquent la contraction isotherme du volume, sont identiques. La valeur limite de log aT(T − Tg), lorsque T tend vers Tg, s'exprime à partir des paramhtres qui regissent la variation du volume en fonction de la température et du temps. La discussion de ces resultats conduit, enfin, à une définition cinétique précise de la température Tg qui est compatible avec sa définition usuelle à condition d'adopter un procédé expérimental adéquat.
Sur quelques polypeptides nouveaux
Authors: Parrod J. , Spach G.
Published: April 2003

Les auteurs ont préparé des polypeptides dérivant des acides α‐aminés racémiques suivants:

Les acides α‐aminés sont obtenus par action de NH3 sur les acides α‐bromés, le deuxième avec une variante: l'acide carbonique 2‐tridécanedioique, obtenu à partir de son triester éthylique, est brcmé, puis traité par NH3; l'amino‐triacide, dCcarboxylé, engendre le dl‐amino‐2‐tridbcanedioique; celui‐ci est monoestbrifib par l'alcool benzylique. A partir des acides aminbs, on passe aux dérivés de Leuchs correspondants, par l'acton directe de l'oxychlorure de carbone: hexadécyl‐4 oxazolidine dione‐2,5 et dbcamethyl‐ Bne‐4 oxazolidine dione‐2,5 carbonate de benzyle. Le dimorphisme a été observe sur ce dernier et sur l'acide bromo‐1 1‐undbcanolque. Les oxazolidines diones‐2,5‐polymérisent en solution sous l'influence d'initiateurs alcalins. AprBs fractionnement par precipita‐ tion, l'btude de la viscositb des solutions benzbniques de poly‐dl‐amino‐2‐octadbcanoique, ainsi qusla diffusion de la lumière par celles‐ci suggèrent la formation d'agrégats lorsque la concentration croit.