bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton magnetic resonance relaxation in a series of dimethylsiloxane polymers
Authors: Powles J. G. , Hartland A. , Kail J. A. E.
Published: April 2003

Measurements of the longitudinal and transverse proton magnetic resonance (p.m.r.) relaxation times are reported for a series of unadulterated dimethylsiloxanc polymers over the temperature range ‐180 to +250°C. At lower temperatures the measurements were made with steady‐state broad‐line apparatus, and at higher temperatures, with spin echo equipment. The polymers ranged in molecular weight from a fluid of 3 cs. (centistoke) viscosity at 25°C. to a gum of 107 cs. The changeover from liquidlike to polymerlike properties with increasing chain length is discussed. All the samples showed high apparent crystallinity a t low temperatures as determined by p.m.r., annealed samples appearing in some cases to be over 90% crystalline. The crystal melting transition occurs within two or three degrees but is subject to supercooling. Signals from the crystalline and amcrphous regions differ considerably. In the liquids the transverse decay is complex and is thought to be owing to a slowly modulated nuclear magnetic interaction between the methyl groups and may be described as a narrowbroad line. The estimated correlation frequencies for proton motion correlate quite well at both high and low temperatures with the few dielectric measurements available showing how the methyl protons move with the SiO bond. Some evidence is found for a slower motion which is associated with chain drifting and for which the magnetic interaction may be within or between chains. A study of the same materials when crosslinked shows, among other things, the importance in p.m.r. of residual unlinked material. Removal of unlinked material leaves samples which show that crosslinking changes the p.m.r. behavior in important respects and aids in distinguishing the effects of local and large‐scale molecular motions. A study of the effects of extent of crosslinking and the various methods of crosslinking by p.m.r. will be valuable. Interpretation of the results is greatly handicapped by a serious lack of scientific data about the polydimethylsiloxanes, especially those at low temperatures.
Viscosity measurements on oligoesters from terephthalic acid and glycol
Authors: Seidel B.
Published: April 2003

Viscosity measurements on a series of linear oligoesters of terephthalic acid and ethylene glycol BzO‐T‐(G‐T‐)nOBz, n = 0–5 with molecular weights from 350 to 1300 at 50.0°C. in tetrachloroethane give a relationship [η] = 1.38 × 10−2 × M0.87 for the higher members of the series. The Kuhn equation [η]v = 2.5 + p2/8, connecting viscosity with the axial ratio of the solute molecules, is found to hold reasonably well at its lower limit, also, for the determination of the axial ratio of small molecules. An attempt is made to calculate the overall dimensions of the solute molecules.
Thermodynamic properties of polystyrene and styrene
Authors: Warfield R. W. , Petree M. C.
Published: April 2003

A Tarassov function has been used to estimate the specific heat of polystyrene between 0° and 60°K. These data, together with published Cp data, have been used to calculate the entropy, enthalpy, and free energy of styrene and polystyrene from 0° to 298.16°K. The entropy of polymerization of styrene at 298.16°K. was found to be 26.69 cal./mole°.The thermodynamic function Cp/T versus T as calculated for polystyrene, increases to a maximum at 65°K. and then increases again at the glass transition temperature. The Tarassov function, which is shown to be useful in estimating the specific heat of amorphous polymers, should be combined with a T3 Debye function to yield more accurate cv data at low temperatures. The number of classically vibrating units per repeating unit of polystyrene was found to be 6.57. The difference Cp – Cv was calculated at 273°K. and found to be 2.0 cal./mole°.
Synthesis and polymerization of an alkene‐substituted norbornylene
Authors: Dekking Henri G. G.
Published: April 2003

Bicyclo[2.2.1]‐hept‐2‐ene‐5‐butylene was synthesized in 20% yield by reacting equimolar amounts of cyclopentadiene and 1,5‐hexadiene at 190°C. for 16 hr. The same product was obtained by forming the Diels‐Alder adduct of cyclopentadiene and allylchloride (60% yield), making this adduct react with magnesium to form the Grignard reagent (99% yield), and then coupling the Grignard reagent with allylbromide (46% yield). The monomer was polymerized at 25°C. by means of a LiAl(decyl)4‐TiCl catalyst. Infrared analysis of the polymer indicates that the monomer polymerizes as a substituted norbornylene and as a cycloalkane‐substituted alpha‐olefin. The polymer is soluble in benzene and softens at 150°C.
Collective interactions in polymerization processes at low temperatures and in polymers with conjugated bonds
Authors: Semenov N. N.
Published: April 2003

The first part of the paper is concerned with low‐temperature polymerization, and a hypothesis explaining its mechanism is proposed. Physical properties of new classes of polymers are discussed in the second part. The importance of electron collectivization and energy levels both in polymerization processes and in physical properties is emphasized.
Trifluoronitrosomethane/tetrafluoroethlylene elastomers dilute solution properties and molecular weight
Authors: Morneau G. A. , Roth P. I. , Shultz A. R.
Published: April 2003

The copolymer prepared from tetrafluoroethylene and trifluoronitrosomethane was studied by light scattering in 1,1,2‐trichloro‐2,2,1‐trifluoroethane (Freon 113) and by solution viscosity in Freon 113 and perfluorotributylamine (FTBA). Molecular weights ranging from 2 × 105 to 2.4 × 106 were measured. Viscosity–molecular weight relationships were obtained for both solvents. They are:

The extreme resistance of the polymer to nonfluorinated solvents is explained on the basis of its low solubility parameter, δ, which was established to be 5.2. From a consideration of the root‐mean‐square end‐to‐end chain length, the freely jointed segment is 24 chain atoms. Fractionation of the polymers shows a wide range of molecular weights with an abnormally large, low molecular weight portion.
Synthesis and properties of some aromatic polymers
Authors: Berlin A. A. , Liogon'Kiǐ V. I. , Parini V. P.
Published: April 2003

Multinuclear aromatic compounds are distinguished by considerable thermostability. In a number of cases they have been shown to be endowed with semiconductor properties. In view of this the development of a method of synthesis and investigation of aromatic polymers with a common system of conjugated bonds has both theoretical and practical interest. Such substances have been synthesized by the authors on decomposing bisdiazo compounds by an ammoniacal solution of univalent copper, and also on decomposition of bisnitroso acetates. In particular, 4,4′‐bisdiazobiphenyl, 4,4′‐bisdiazobitoyl, 4,4′‐bisdiazobiphenyl‐3,3‐dicarboxylic acid, and benzidine N,N′‐bis‐nitroso acetate were employed. On decomposition of the bisdiazo compounds a powder of orange to brown color was formed, soluble in concentrated sulfuric acid and isoluble in most organic solvents. Analysis showed it probably to possess the composition:

where R may be H, COOH, or CH3. On the average one azo group is present for each 4–10 benzene rings and two chlorine atoms for each 10–20 rings. The mean molecular weight determined for one of the carboxylated polymer specimens was found to be 3000. On heating to 400° the polymer decarboxylates. At 450° decomposition sets in. Viscosity curves of the solutions (plots of ηsp/C vs. C) exhibit an anomalous rise within the limits C = 0.1–1%. The concentration of unpaired electrons in the polymers was shown by the electron resonance method to be ∼1019/g. Heating the substances leads to an increase in concentration of unpaired electrons by 1–2 magnitudes. The spectra and x‐ray diagrams of the substance were obtained. Evidently the formation of polymers from bisdiazo compounds is of a radical nature, leading to the formation of stable radicals of low activity. Low molecular fractions isolated from the polymers are fusible and soluble in benzene. They are capable of reacting with diethynylbenzene with the formation of nonmelting and insoluble thermostable products. Carboxylated polymers form salts with transition elements that evidently are of the nature of intracomplex compounds with intermolecular crosslinkage. Products of the decomposition of benzidine bisnitroso acetate are in general similar to those resulting from bisdiazodiphenyl, but contain less unpaired electrons.
The radiation‐induced graft copolymerization of 4‐vinyl pyridine and acrylamide to nylon 6.6
Authors: Sykes J. A. W. , Thomas J. K.
Published: April 2003

Appreciable quantities of 4‐vinyl pyridine and acrylamide have been grafted to nylon 6.6 by decomposing in their presence the peroxides and hydroperoxides formed on irradiating the polymer in air with γ‐rays. The kinetics of the grafting process is interpreted in terms of a diffusion of the monomer into the nylon. The enhanced dyeing of the amine grafts and the lowering of the surface resistance of the graft by quaternization with dimethylsulfate are also reported.
The reaction of ozone with surfaces of natural rubber, and its dependence upon strain
Authors: Andrews E. H. , Braden M.
Published: April 2003

The progressive reaction of ozone with surfaces of natural rubber (cis‐polyisoprene) has been studied by means of replica electron microscopy. Unstrained rubber suffered surface degradation at a rate consistent with the predictions of a theory of diffusion with simultaneous chemical reaction. In strained surfaces the rate of ozone penetration was appreciably greater, but this is attributed to physical rather than chemical causes. Sites of preferred reaction (etch pits) were observed in both strained and unstrained specimens, the former also displaying oriented fissure systems. The origin of these features is explained in terms of Griffith's criterion and it is necessary to postulate, in the unstrained specimens, pre‐existing surface strains. The relation of the microscopic etch and fissure patterns to macroscopic ozone cracks is briefly discussed.
Sulfur‐induced cis‐trans isomerization of polybutadiene
Authors: Bishop William A.
Published: April 2003

Both high cis‐1,4‐polybutadiene and high trans‐1,4‐polybutadiene were found to isomerize when heated in the presence of elemental sulfur. The kinetics of the sulfur induced isomerization of high cis‐1,4‐polybutadiene were studied over a wide range of temperature and sulfur concentration and found to obey a first‐order kinetic expression having an effective rate constant directly proportional to the initial sulfur concentration. The apparent activation energy was found to be 30.1 ± 0.4 kcal./mole. Isomerization was also found to be induced by dicumyl peroxide. A comparison of the mechanisms involved in the sulfur and peroxide induced isomerization indicate a basic difference in the nature of the initial interaction of the double bond with the sensitizing species. The initial interaction of the sulfur and the double bond is pictured as a π‐complex that decomposes to a freely rotating radical, whereas the peroxide induced isomerization is presumed to involve direct radical addition to the double bond.
γ‐Radiation‐initiated polyethenesulfonamide
Authors: Wiley Richard H. , Alvey F. B.
Published: April 2003

The rate of the radiation‐initiated polymerization of ethenesulfonamide, which is relatively high (1.25%/min.), is dependent on the 0.96 power of the intensity of the radiation. At increasing radiation dose levels the viscosity decreases and then remains constant indicating a balance between radiation‐induced degradation and branching. The polyelectrolyte character of the polymer is shown in both viscosity and light‐scattering data.
Interference microscopy of crystalline high polymers. Determinations of the thickness of single crystals
Authors: Wunderlich Bernhard , Sullivan Peter
Published: April 2003

The quantitative analysis of single crystals of polyethylene with the two‐beam interference microscope has been described. The thickness of single crystals formed at 87°C. is 134 A. The variation thickness is equal or less than 6 A. A general pattern of growth is discussed.
Elektronenspinresonanz‐untersuchungen an bestrahltem polypropylen
Authors: Fischer H. , Hellwege K.‐H.
Published: April 2003

Die Untersuchung der Richtungsabhängigkeit der Elektronenresonanzlinien von bestrahltem orientertem Polypropylen erlaubt eine relativ sichere Bestimmung der gebildeten Makroradikale. Es wurde festgestellt, dass bei 77°K bei der Bestrahlung vorwiegend ein Radikal der Form
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entsteht, während bei Zimmertemperatur vermutlich ein Radikal vom Allyltyp der Struktur
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sich durch hohe Lebensdauer auszeichnet.
The concentration‐dependent diffusion of styrene in ethyl cellulose
Authors: Vanderkooi William N. , Long Merton W. , Mock Richard A.
Published: April 2003

The diffusion of styrene vapor in ethyl cellulose film has been studied as a function of styrene solubility in the film at 50°C. Methods and data are presented for determining the equilibrium solubility of styrene in ethyl cellulose as a function of vapor pressure at 50°C. The permeation rates of styrene vapor through 3‐mil film were determined under steady state conditions for various pressures of pure styrene vapor on one side of the film and vacuum on the other side. From a plot of permeation rates versus styrene solubility the diffusion coefficient was calculated as a function of concentration. Measurements made over a concentration range of 0 to 0.7 g. styrene/cm.3 of unswollen film show that the diffusion coefficient first increases rapidly with concentration, then goes through a maximum, and finally levels off at 10−7 cm.2/sec. In the limited range of 0.06 to 0.10 g./cm.3 the diffusion coefficient varies exponentially with concentration as has been reported for other systems in a similar range. However, such a functionality does not represent the present system over a broad concentration range. These results, if generally applicable to other systems, indicate that the nature of the diffusion process for organic vapors in polymers may be considerably more complicated than formerly supposed.
Kinetics of mutual radiation grafting of styrene in ethyl cellulose film
Authors: Mock Richard A. , Vanderkooi William N.
Published: April 2003

A general procedure is described by means of which the kp/kt1/2 ratio can be determined for the graft polymerization of vinyl monomers in an organic substrate. The method takes rigorous account of the influence of monomer diffusion on the reaction kinetics. As an experimental example, the mutual radiation grafting of styrene onto ethyl cellulose film by use of 2‐M.e.v. Van de Graaff electrons to initiate free radical formation is described in detail.
Calculation of the thermodynamic properties of polyelectrolytes in the presence of salt
Authors: Alexandrowicz Z.
Published: April 2003

The potential and the activities in salt‐containing polyelectrolyte solutions are calculated by extending the treatment of Lifson and Katchalsky, which deals with rodlike polyelectrolytes in solutions to which no salt is added. An approximate procedure is employed, whereby the cylindrical volume element (per macroion) is divided into two shell‐like regions, as follows: In the outer shell, in which the drop of potential is relatively small, the exponential coefficient of the local ionic concentrations is expanded linearly and the Poisson‐Boltzmann equation may be solved in terms of Bessel functions. In the inner core, the coion concentration is assumed to equal zero, so that the problem reduces to the Lifson‐Katchalsky case of saltless solutions. The resultant potential leads to activities which resemble closely the recently formulated empirical law according to which the activities may be described simply as a superposition of “effective” ionic concentrations, contributed independently by the polymer and by the salt. The significance of the results may be appreciated when the fate of the ions which come from the salt is examined. It is then found that the coions, and the additional counterions as well, are accommodated mainly in the outlying regions of the volume element and fail to penetrate and influence the immediate surrounding of the polyion.
Osmotic and donnan equilibria in polyacrylic acid–sodium bromide solutions
Authors: Alexandrowicz Z.
Published: April 2003

Osmotic and Donnan equilibria were measured in aqueous solutions of ionized polyacrylic acid and of sodium bromide. The results served to examine the validity of the previously formulated, “empirical” and “theoretical” formulas for the activities in mixed salt–polyelectrolyte systems (c.f. the preceding article). A very good agreement between the experiment and both formulas is found in case of the osmotic factor. The results obtained for the activity coefficient of the salt show a more limited agreement, and the validity of the theory seemingly does not extend—except as a very rough approximation—to the case of concentrated polymer solutions to which relatively small amounts of salt are added. Donnan and osmotic equilibria were also measured at a constant concentration of the external salt solution and the results obtained in the presence of an excess of salt interpreted in terms of the well known binding ratios (m′s – ms)/mpolymer and second virial coefficients, respectively. The former are found to increase in concentrated salt solutions, in agreement with the theory (which in this case differs largely from the empirical formula), whereas the latter are described adequately enough by the simpler empirical formulas. The limited nature with respect to both the validity and significance of constant binding ratios and second virial coefficients, is discussed.
The swelling of polymer systems in solvents. II. Mathematics of diffusion
Authors: Buckley Donald J. , Berger Martin
Published: April 2003

Data from complete swelling–time curves for crosslinked polymers in solvents are used to calculate diffusion coefficients for the penetrant at 25°C. Diffusion coefficients for constant diffusion and concentration‐dependent diffusion are obtained from Fick's law in a manner similar to that employed by Crank. For concentration‐dependent diffusion, solutions of solvent and nonsolvent in various proportions (cyclohexane and acetone for butyl vulcanizates) was employed. Although it is known that some of the nonsolvent is sorbed by the polymer from the solvent‐nonsolvent solution, the method still is applicable, in form, for determination of the diffusion coefficient of the solvent at zero solvent concentration. The sorption of liquid by the elastomer is shown to be a rather sharp advancing front, with the concentration of penetrant at the center of the sample remaining nearly zero until equilibrium is approached. This behavior is a direct consequence of the exponential dependence of diffusion on concentration.
Dipole moments and molecular structure of copolymers. I. Dipole moment of methyl methacrylate–styrene copolymers
Authors: Shima Mikiko
Published: April 2003

The dielectric properties of methyl methacrylate–styrene copolymers in benzene solution have been measured, and in a theoretical treatment it has been attempted to evaluate the effective dipole moment of the methyl methacrylate group in relation to the distribution of polar group sequences in the copolymer molecule. If it is assumed that the polar groups in a polar (A)–nonpolar (B) copolymer molecule can be classified into three types such that the nearest neighbors along the chain are (I) two polar groups A, (II) a polar group A and a nonpolar group B, and (III) two nonpolar groups B (the molecular polarizations of which are denoted by PAA, PAB, and PBB, respectively), then the average molecular polarization of polar group A in the copolymer molecule, Pav, can be written in the form

Here fAA and fAA2 are the probabilities of an AA sequence and a double AA sequence arising in the copolymer molecule, respectively. The values of fAA and fAA2 can be calculated from the reactivity ratios of the two monomers and the composition of the initial monomer mixture. The measurements were made on six samples of different compositions. It has been shown that the experimental values of Pav agreed satisfactorily with the values calculated from the above equation, over the whole range of copolymer composition. This seems to indicate that only the nearest neighbors in the polymer chain affect the effective dipole moment of the polar group in the copolymer molecule.
The calculation of the number‐average degree of polymerization starting from intrinsic viscosity and overall rate
Authors: Henrici‐Olivé G. , Olivé S. , Schulz G. V.
Published: April 2003

The relation between the intrinsic viscosity [η] and the number‐average degree of polymerization P̄n is a function of the molecular weight distribution of the polymer. In a polymer in which the termination of polymer radicals occurs partly by combination of two growing chains, this molecular weight distribution depends on number and extent of additional reactions such as chain transfer; i.e., it is variable. Therefore P̄n of such polymers cannot be obtained from intrinsic viscosity measurements by means of an equation of the type [η] = KP̄na.

A new method is proposed which allows the evaluation of P̄n in these cases, without necessity of osmotic (or related) measurements or fractionation. The viscosity‐average degree of polymerization P̄η, which can be obtained exactly by experiment, is related to the number average by P̄η = P̄n(1 + F). Here F is given as a function of experimental data: P̄η and the overall rate of polymerization. This function is represented in a graph which enables the exact determination of P̄n without knowledge of number and extent of additional reactions.

The P̄n values calculated according to the proposed method are compared with measured values (osmosis, endgroup analysis) for several polystyrene samples. The agreement is very satisfactory.
Dielectric dispersion of protein solutions in viscous solvent
Authors: Takashima Shiro
Published: April 2003

The dielectric dispersion of bovine hemoglobin, ovoalbumin, and bovine ferrimyoglobin was investigated in a glycerin‐water mixture. It was found that the dispersions, of these protein solutions were largely modified by the increase of the viscosity of the solvent and a linear relationship was obtained between the relaxation times and the viscosity of the solvent postulated by the Stokes law. On the contrary, the dispersion of catalase solution was not affected by the addition of the glycerin, which indicated that the dielectric polarization of this protein was due to the different polarization mechanism and the polarization by surface ion conduction was suggested.
Heats of polymeric reactions. Part I. Construction of the calorimeter and measurements on some new monomers
Authors: Joshi R. M.
Published: April 2003

A modified isothermal distillation calorimeter is described in which an electronic weight recording device has been incorporated. Heats of polymerization of four vinyl monomers have been verified and −ΔHp values at 74.5°C. for six new monomers are reported. The values for acrylamide and methacrylamide furnish some evidence of association in the monomeric state in nonpolar solvents.
Kinetics of block polymerizations
Authors: Brepoels J. , Smets G.
Published: April 2003

The chain decomposition of tert‐butyl hydroperoxide in the presence of copperoctoate producestert‐butoxide and tert‐butyl peroxy radicals which are both able to initiate the polymerization of styrene. Consequently, half the number of the endgroups of the polymer molecules will be present, as peroxybutyl group, which can initiate a second‐step polymerization. In the first part of this paper, the kinetics of polymerization of styrene with t‐butyl hydroperoxide (t‐BHP) and copper octoate have been studied. In the absence of monomer, the chain decomposition is relatively short on account of the reaction of the Cu1+ ion with tert‐butyloxide radical and the precipitation of the copper salt; contrarily, in the presence of styrene the primary radicals add preferentially monomer, and no copper salt precipitation occurs. In both cases the overall energy of activation of decomposition t‐BHP/Cu2+ octoate is equal to above 21 kcal/mole. At constant Cu(oct)2 concentrations the square root law relationship between the rate of polymerization and t‐BHP concentration is only valid for the low concentrations; at higher values, it increases much slower up to an asymptotic value. Similar conclusions arise from the rate dependence on the copper octoate concentrations at constant t‐BHP and monomer concentrations.

In the second part of this paper, the polystyrene carrying peroxy‐t‐butyl end‐groups has been used as initiator of the polymerization of a second monomer (methyl methacrylate and vinyl acetate) for the synthesis of block polymers at 97°C. This second step polymerization is a first order reaction with respect to the monomer concentration, and 0.5 order with respect to the initiator. Some thermal polymerization of methyl methacrylate must be taken into account for the evaluation of the amounts of second homopolymer. The relative reactivity of both radicals has been evaluated from their ability of further monomer addition; by measuring the amounts of homopolymer RH and block polymer RB by fractional precipitation and determination of their styrene content, it was possible to determine the efficiency of block polymerization.

In the case of methyl methacrylate the ratio RB/RH is equal to 1.2 in agreement with the chain termination reaction; therefore the efficiency of both radicals is admitted to be equal, and consequently independent of their size.

In the case of vinyl acetate the much lower value of RB/RH (0.26) is not a measure of the relative efficiency but a consequence of chain transfer reactions on monomer and solvent, which increase the amount of homopolymer.
On the characterization of stereoregular polymers. III. Polymethyl methacrylate
Authors: Miller Robert L.
Published: April 2003

The tacticity theory previously reported was generalized so it could be applied to the proton magnetic resonance data obtained for a variety of methyl methacrylate polymers. This system is the only one known for which sufficient data exist or may be obtained to provide a test of the theory. From the data available, parameters characterizing the distribution of iso‐ and syndiotactic sequence lengths in each sample were obtained These parameters, in turn, were used to predict melting behavior for each sample capable of crystallization. The tacticity theory not only is consistent with the data on free radical‐initiated (syndiotactic) polymers, about which there was no question of interpretation, it also provides an explanation for an uncertainty in the interpretation of the data on anionic‐initiated (isotactic) polymers. Thus, in this case at least, the theory appears to provide a connection between experimentation and polymer configuration.
The thermal degradation of some epoxy resins
Authors: Neǐman M. B. , Kovarskaya B. M. , Golubenkova L. I. , Strizhkova A. S. , Levantovskaya I. I. , Akutin M. S.
Published: April 2003

The thermal degradation of epoxy resins was studied in a static system over the temperature range 300–450°C. The reaction proceeds without an induction period, the initial rate being maximum. The rate W increases with temperature according to the law W = Ae–E/RT. The effective activation energy was 35 kcal./mole. The reaction products consist of gases, a resinous liquid, and a solid residue. The liquid has practically the same spectral characteristics in the infrared as the initial epoxy compound. In the infrared spectrum of the residue the bands characteristic of the epoxy group are absent. Water and formaldehyde were found among the liquid products. Methane and carbon monoxide were found in large amounts by means of a chromatographic method. In the thermal degradation of the unhardened epoxy resin the low molecular fraction volatilizes, and the high molecular fraction degrades liberating the radical which isomerizes and decomposes to CO and ĊH3. The methyl radical abstracts a hydrogen atom from the polymer and is converted to methane. The ROĊH2 radical formed on liberation of the epoxy group yields formaldehyde. Among the gaseous products formed in the thermal degradation of the epoxy resin hardened by polyethylene polyamine (PEPA) were found H2, CO, CH4, C2H6, C2H4, C3H6, and C3H8. Ethane, ethylene, propylene, and propane are possibly produced by decomposition of the PEPA radical. The thermooxidative degradation of epoxy resins was investigated in a static system. The reaction was shown to be of the degenerate branching chain type. The dependence of the induction period on the oxygen pressure and on the temperature was determined.
Copolymerization with Ziegler‐Natta catalysts. Part I. Monomer reactivity ratios for two α‐olefin pairs
Authors: Anderson I. H. , Burnett G. M. , Tait P. J. T.
Published: April 2003

Crystalline copolymers of styrene and 4‐methylpent‐1‐ene and styrene and 5‐methylhex‐1‐ene have been prepared with the catalytic system α‐TiCl3–AlEt3 in toluene. The polymerizations were carried out in dilatometers with the use of a special stirring apparatus which is described. The copolymers produced were shown to be heterogeneous in composition. Fractions soluble in cold pentane are enriched in 5‐methylhex‐1‐ene and have x‐ray diffraction patterns similar to those of crystalline isotactic poly(5‐methylhex‐1‐ene). The fractions insoluble in cold pentane are enriched in styrene and on crystallization have x‐ray diffraction patterns similar to those of crystalline isotactic polystyrene. Infrared spectra were also examined. Determination of reactivity ratios gave the values: styrene (M)‐4‐methylpent‐1‐ene, r1 = 0.89 ± 0.05, r2 = 3.67 ± 0.22; styrene (M)‐5‐methylhex‐1‐ene, r1 = 0.59 ± 0.057, r2 = 4.00 ± 0.28. Statistical analysis shows that the copolymer is probably a mixture of block macromolecules, the chain backbones consisting mainly of one monomer type with short blocks of the other.
Synthesis of new monomers and polymers. II. 3‐methyl‐5‐isopropenylpyrazoles and derivatives
Authors: Dufonteny L. , Mifuna E. , Neirynck G. , Teyssié Ph.
Published: April 2003

The synthesis of 3‐methyl‐5‐isopropenylpyrazole and 1‐phenyl‐3‐methyl‐5‐isopropenylpyrazole is described, as well as the isolation of an addition compound with vinyl isocyanate, namely the N‐vinyl‐1‐(3‐methyl‐5‐isopropenylpyrazolyl)carboxamide. The 3‐methyl‐5‐isopropenylpyrazole only is able to homopolymerize, giving a characteristic polyelectrolyte, but both pyrazoles copolymerize readily with acrylic acid to yield polyampholytes. The addition compound, whose structure is proved by several methods, polymerizes readily; the soluble product obtained may undergo a grafting reaction with other monomers, but the polymer obtained is highly crosslinked.
Anionic polymerization of acrylonitrile by cyclopentadienyl sodium
Authors: Zilkha Albert , Ottolenghi Ariel
Published: April 2003

The anionic polymerization of acrylonitrile by cyclopentadienyl sodium in tetrahydrofuran was studied. The effects of the concentration of monomer, catalyst, temperature, and added cyclopentadiene on the polymerization were investigated. Contrary to previously studied anionic polymerizations, the molecular weight was found to increase with monomer concentration as a result of the cyclopentadiene radical acting as a polyfunctional catalyst due to the following equilibrium:
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The cyclopentadienyl polymer anions thus formed (which have 5 resonance structures) initiate polymerization especially at high monomer concentration leading to increase in molecular weight as a result of the formation of several polymeric chains attached to the same cyclopentadienyl radical. Proof for the existence of such polymers was obtained on treatment of the polymers with ozone which caused considerable lowering of the molecular weight due to scission of polymer side chains as a result of the opening of the cyclopentadiene rings. X‐ray diffraction diagrams of the branched polymers showed no strong reflection band at 5.3 A. which is associated with hydrogen bonding between chains of polyacrylonitrile. The molecular weight was independent of catalyst concentration and increased with lowering in temperature. Polymerization in the presence of free cyclopentadiene led to lowering in molecular weight due to termination by the acidic hydrogen of cyclopentadiene; plot of molecular weight against the reciprocal of the cyclopentadiene concentration gave a straight line. The polyacrylonitriles, having cyclopentadiene end groups, were utilized to introduce different end groups by the Diels Alder Reaction with dienophiles. Thus the adduct of the polymer with maleic anhydride gave an amide on reaction with amine.
Polymer–diluent interactions. III. Polyethylene—diluent interactions
Authors: Coran A. Y. , Anagnostopoulos C. E.
Published: April 2003

The interactions between polyethylene and a number of hydrocarbon diluents were characterized on the basis of the Flory‐Huggins interaction parameter χ and the closely related heat of mixing parameter B. The evaluations of these parameters were based on Flory's statistical‐thermodynamic treatment of the effect of diluents on the melting points of crystalline polymers. Necessary for each evaluation was a single microscopic determination of the depressed melting point of polyethylene in its mixture with a given diluent as indicated by the disappearance of the last visible traces of crystallinity upon slow heating. Each mixture was diluted to an extent that the volume fraction of diluent approximated unity. This permitted the use of a simplified form of the Flory equation. The data obtained from the study of thirty diluents were utilized in an attempt to correlate diluent structure with solvency. Generally, the various types of hydrocarbon diluents can be rated in the following order of increasing solvency: aromatic, alkylaromatic, aliphatic, alicyclic. In addition, it was demonstrated that the value of B for a given diluent can be reliably estimated as a function of a new parameter which is calculated from the diluent structure, density, and an estimated value of the ionization energy. This new parameter also correlates well with the solubility parameter δT.
The use of high pressure to study polymer—solvent interaction
Authors: Ham Joe S. , Bolen Max C. , Hughes James K.
Published: April 2003

The behavior of polymer—solvent systems has been studied as a function of hydrostatic pressure to 3000 atm. The swelling of crosslinked neoprene and crosslinked Hevea has been studied in several solvents, and the temperature of phase separation of polystyrene in cyclohexane has been determined. These measurements permit an indirect evaluation of the volume of mixing that is felt to have advantages over the direct method due to the small magnitude of the effect in polymer systems. In all of the cases studied by the swelling technique, the volume of mixing is negative and tends to be greater in magnitude the better the solvent. For the very poor solvent—polymer system studied by the precipitation technique, a small positive value is obtained. In addition, the compressibility of swollen polymers is compared with that expected from an assumption of additivity and found to be much smaller. These phenomena are presumably the result of a more tightly packed liquid structure within the polymer network. This explanation suggests that the descriptions of the volume of mixing in terms of the apparent specific volume, while certainly formally correct, may be misleading physically. An attempt to relate the observations on these systems to a theory involving a power series expansion in terms of the solvent fugacity was unsuccessful due to the slow convergence of the series.
Light scattering by poly‐L‐xbenzyl glutamate solutions subjected to an electrical field
Authors: Wallach Morton L. , Benoit Henri
Published: April 2003

A study has been made of the light scattering of poly‐L‐benzyl glutamate solutions subjected to orientation by an electrical field. Measurements were taken of the effect as a function of the field strength, the angle of observation, the direction of the field, and the frequency of the field. The principal results obtained were the following. (a) The helical molecules are not deformed by the electrical field. (b) The molecular orientation is due primarily to a permanent electric moment whose axial component per monomer unit is of the order of 3 Debye. (c) As predicted by the theory of Burgers, the rotatory diffusion constant was found to vary inversely as the cube of the rod length.
Molecular motion in polystyrene and some substituted polystyrenes
Authors: Odajima A. , Sauer J. A. , Woodward A. E.
Published: April 2003

Proton magnetic resonance spectra of nine substituted polystyrenes: polymers of o‐methyl, m‐methyl, p‐methyl, p‐chloro‐, 2,4‐dimethyl‐, α,β,β′‐trideutero‐, β‐ deutero‐, 2,6‐dimethyl‐4‐tert‐butyl‐, and p‐tert‐butylstyrene, in addition to five polystyrene samples differing in molecular weight (M̄n's from 1.25 × 105 to ∼35 × 105) or tacticity have been obtained at temperatures from 77 to above 400°Kg. Measurements have also been made on p‐tert‐butyltoluene, 2,4‐dimethylstyrene, and 2,6‐dimethyl‐4‐tert‐butylstyrene. All polymers studied were found to exhibit single‐component derivative line shapes and to undergo rapid motional narrowing with increasing temperature in the region of the glass transition; in this region the line width for atactic polystyrene was found to be essentially independent of molecular weight. At lower temperatures a gradual line narrowing effect was also observed for some of the polymers, even near 77°K., and is attributed to limited phenyl or substituted phenyl group oscillation. This effect was apparent for polystyrene, poly‐α,β,β′‐trideutero‐, poly‐β‐deutero‐ poly‐p‐chloro, and poly‐p‐methylstyrene, less apparent for the o‐ and m‐methyl compounds and the p‐tert‐butyl‐substituted polymer, and absent for the 2,4‐dimethyl and the 2,6‐dimethyl‐4‐tert‐butyl polymers. By a comparison of experimental second moments with approximate ones obtained from theory, it is concluded that rotation of all methyl groups attached directly to benzene ring for all polymers studied is taking place at 77°K. For both p‐tert‐butylsubstituted polymers and the low molecular weight analogs, a motional narrowing process occurs in the ≤77° to 150°K. region, and for all but 2,6‐dimethyl‐4‐tert‐butylstyrene this is attributed to rotation of the methyl groups in the tert‐butyl part of the molecule; for the latter compound, onset of rotation of one of the methyl groups attached directly to the ring in addition to the methyl in the tert‐butyl part is responsible for the line narrowing. The contributions of various proton interactions to the total second moment of polystyrene and its derivatives are discussed.
Synthesis of new monomers and polymers. III. Preparation of poly‐N‐salicylidenevinylamine and derivatives
Authors: Decoene C. , Teyssié Ph.
Published: April 2003

By condensation of polyvinylamine with several aromatic aldehydes, poly‐Schiff bases were obtained, which were practically 100% pure. The polysalicylidenevinylamine and its 5‐chloro‐, 5‐nitro, 4‐hydroxy, and 3‐methoxy derivatives, as well as the poly‐2‐hydroxynaphthylidenevinylamine and the polyfurfurylidenevinylamine were isolated. Their structure was checked by elementary analyses as well as by qualitative and quantitative infrared spectrophotometry. These compounds from interesting polychelates with transition metals.
Diffusion, thermodiffusion, and thermal diffusion of polystyrene in solution
Authors: Meyerhoff G. , Nachtigall K.
Published: April 2003

Diffusion coefficients D and Ludwig‐Soret coefficients D′/D of polystyrene in toluene were determined in a convection‐free thermodiffusion cell of 1 to 4 mm. height, 100 mm. length, and at a temperature differences of 0.1 to 0.3°C. The cell had two chambers, thus allowing observation of the concentration gradient alone by optical elimination of the temperature gradient. Philpot‐Svensson and Gouy optical methods were used. Both equilibration from homogeneous concentration to Ludwig‐Soret equilibrium and from this back to homogeneous concentration lead to D and D′/D. The last method, operating with ΔT = 0 gave more exact results. It was possible to measure very low diffusion coefficients (below 10−7 cm.2sec.−1). For sharp fractions the agreement with the free diffusion is good. For broader samples the thermodiffusional D is smaller than D of free diffusion. This difference is in accordance with the different averaging of the two methods. Up to ΔT = 0.3°C. no variation of D′/D with temperature was found. The Ludwig‐Soret coefficients increase with increasing molecular weight M and decreasing concentration. The thermal diffusion coefficient D′ is nearly independent of M and shows only a very slight decline with concentration. The results of our experiments are discussed together with the work of other authors using different techniques.
Determination of the dependence of the ultracentrifugal sedimentation coefficient on concentration by a single experiment
Authors: Gehatia Matatiahu
Published: April 2003

The dependence of the ultracentrifugal sedimentation coefficient s on the concentration has been derived directly from the theory of hydrodynamics for the case of very dilute solutions. The following general expression has been obtained: s = s0(1 − k1c1/3 − k2c), where s0 is the zero value of s and k1 and k2 are constants. If compact and not extremely big molecules are investigated under the usual experimental conditions k1c1/3 ≪ k2c. In such a case the term k1c1/3 can be neglected, and the general expression leads to the well‐known equation: s = s0(1 − k2c). As s depends linearly on c, the constant s0 can be estimated with help of the straight line obtained if s is plotted against c. For very big and elongated particles, however, measured at very high dilutions k1c1/3 ≫ k2c. In this case the approximate equation s = s0(1 − k1c1/3) holds, and for the purposes of extrapolation s must be plotted against c1/3. A method has been developed which enables to decide from one experiment which of the two given equations may be preferred, or if s can be seen as a constant.
Crosslinking of single linear macromolecules
Authors: Kuhn Werner , Balmer G.
Published: April 2003

When a crosslinking agent is added to a very dilute solution of a linear high polymer, there will be practically exclusively a self linking of the individual statistical coils, i.e., the molecules of the crosslinking agent will link different parts of the same macromolecule, transforming the original linear high polymer into a three‐dimensional network, practically without a change of its molecular weight. The process of self‐linking of a single coil is associated with a contraction of its average external dimensions and therefore with a decrease of the intrinsic viscosity. If the crosslinking produced by the action of v molecules of the crosslinking agent on one linear polymer molecules occurs statistically and if the original linear high polymer molecule is made of Nm statistical chain elements, a decrease of the intrinsic viscosity should occur from the value [η]open to [η]v crosslinks, statist, where \documentclass{article}\pagestyle{empty}\begin{document}$ [\eta ]_{\nu {\rm crosslinks, statist}} = [\eta ]_{{\rm open}} [1 - \nu (\sqrt 2 /\sqrt {N_m } )] $\end{document}. In order to test the validity of this formula a dilute, slightly acid solution of polyvinyl alcohol with M = 100,000 was crosslinked by means of terephthalaldehyde [CHOC6H4CHO]. The agreement of the values of [η] observed in very dilute solution with the theoretical value indicates the actual statistical formation of cycles through the reaction of terephthalaldehyde on dissolved solitary linear polyvinyl alcohol molecules.
Polymer solutions. VIII. A new absolute method of molecular weight determination of polymers from solution viscosities
Authors: Gundiah S. , Kapur S. L.
Published: April 2003

An empirical method for absolute molecular weight determination of polymers from viscosity measurements is described. The essential assumptions of the method are: (a) the Huggins' slope constant for any flexible polymer has a maximum value of 0.5 at the precipitation point; (b) the viscosity—concentration plots for a particular polymer in different solvents (when extrapolated) meet at a common point; (c) the ordinate at the common point of intersection [η]R (when the viscosity function is In ηr/c is identical with the limiting viscosity number for the polymer at the point of incipient precipitation); (d) the value of the ordinate at the common point of intersection [η]R is related to molecular weight by the relation [η]R = 9.0 × 10−4M0.5. The method gives satisfactory results in case of polymers like polystyrene and polymethyl acrylate.
Studies on the configuration and conformation of vinyl‐type polymers. II. Temperature dependence of the infrared spectrum of polyvinyl chloride in solution and stereoregularity
Authors: Takeda Masatami , Iimura Kazuyoshi
Published: April 2003

The temperature dependence of the infrared spectra of polyvinyl chlorides in concentrated cyclohexanone solution has been studied. It is found that the absorbance ratio of the band at 696 cm.−1 to the band at 616 cm.−1, D696/D616, decreased as the measuring temperature was raised. This experimental finding has been interpreted as due to the reversible conformational change of the chain in the syndiotactic sequences of PVC. The syndiotacticity α of PVC was estimated to be in the range of 0.86 to 0.52 with varying of the polymerization temperature from −60°C. to 50°C. The stable conformations of the polymer chain in solution were also discussed.
Molecular weight of polymers from electrical resistivity of solutions
Authors: Purdon J. R. , Morton M.
Published: April 2003

An investigation has been carried out to further establish the usefulness of electrical resistivity techniques for the study of polymerization kinetics, and to determine the extent of molecular weight dependence of electrical resistivity. The resistivity increment, (p − p0)/p0, which may be regarded as the fractional increase in resistivity of a system due to the presence of polymer, was found to be directly proportional to the concentration of polymer in solution. Based on the assumption that conductance in polymeric systems occurs by migration of ionic impurities, the resistivity increment was shown to be identical to the specific local viscosity. A marked dependence of (p − p0)/p0 upon molecular weight was found. The relationships observed provide expressions for determination of molecular weight from resistivity data in the systems: polystyrene‐styrene, polystyrene‐cyclohexane, and poly(methyl methacrylate)‐benzene. Furthermore, these relationships indicate the existence of a “critical packing volume” for the polymer chains in solution. This effect permits a determination of the unperturbed end‐to‐end chain dimension of the polymer (polystyrene) which agrees reasonably well with the published value.