bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal degradation of polymethacrylonitrile. Part V. The mechanism of the initiation step in coloration reactions
Authors: Grassie N. , McNeill I. C.
Published: April 2003

The coloration reaction of polymethacrylonitrile, which involves linking up of adjacent nitrile units, has previously been shown to be initiated by traces of methacrylic acid present in the polymer chains. It also occurs when pure polymer is heated with small quantities of a wide variety of substances including carboxylic acids, phenols, imides, and aliphatic amines. The carboxylic acid initiated reaction exhibits first order kinetics. The rates of initiation by a number of aromatic acids have been measured and compared with the pKa values. The initiating power is strongly influenced by the nature of substituents in the acid molecule, weaker acids giving a higher rate of initiation. A semiquantitative treatment has been applied to phenols with similar results. A mechanism for the initiation step in the color reaction is presented involving nucleophilic attack on a nitrile group. This is consistent with the results obtained for acids and phenols, and the observations of other workers on the alkali‐induced coloration in solution are explained similarly. It is noted that all the substances capable of acting as initiators are Lewis bases.
The kinetics of polymerization of α‐vinylnaphthalene
Authors: Loshaek S. , Broderick Edward , Bernstein Philip
Published: April 2003

The kinetics of the 2,2′‐azobisisobutyronitrile (AIBN)‐initiated bulk polymerization of α‐vinylnaphthalene (AVN) at 50, 60, and 70°C. is reported. The polymerization rate is proportional to the 1/2 power of the initiator concentration and the first power of the monomer concentration, and the ratio of the termination rate constant to the square of the propagation rate constant is slightly less than for styrene. Unlike styrene, however, very low molecular weight polymers (ca. 2000–6000) are obtained throughout the entire conversion of monomer to polymer. The molecular weight is shown to be controlled by a chain transfer reaction with the monomer, the value of the transfer constant being about 0.03 at 50, 60, and 70°C., about 300 times that of the monomer transfer constant for styrene. The transfer reaction is attributed to an attack of a growing polymer radical on the naphthalene ring of the AVN. In support of this, the transfer constant of the polystyryl radical with naphthalene was also found to be large (1.1 × 10−3), about 600 times that of the transfer constant (1.86 × 10−6 at 60°C.) of the same radical with benzene. A transfer constant of similar magnitude was obtained for the polynaphthalyl radical with naphthalene. This greater polystyryl radical affinity for naphthalene over benzene is in excellent agreement with expectations based on methyl radical affinities for these same substrates. The greater value of the monomer transfer constant of AVN over that of the polynaphthalyl or polystyryl radicals with naphthalene suggests an activation of the naphthalene ring in AVN. The differences in the polymerization kinetics of AVN and vinyl benzoate are discussed. The overall second‐order thermal rate constant for AVN is found to be about eight times that for styrene at the same temperature. Overall activation energies of 21.5 and 17.4 kcal./mole are obtained for the initiated and purely thermal polymerizations, respectively. An empirical intrinsic viscosity‐molecular weight relation for AVN polymer is given.
Reactivity ratios and rates in the copolymerization of α‐vinylnaphthalene and styrene
Authors: Loshaek S. , Broderick Edward
Published: April 2003

Copolymerization reactivity ratios at 60°C. for α‐vinylnaphthalene (AVN) and styrene are found to be r1 = 1.35 and r2 = 0.67, respectively, from which Price Q and e values for AVN of 1.15 and 0.49 are calculated. From these Q and e values and those published previously for 4‐chloro‐1‐vinylnaphthalene, styrene, and p‐chlorostyrene it is shown that the chlorine atom has a very similar electronegative effect in both the styrene and AVN rings. Initial rates of copolymerization at 60°C. with 2,2′‐azobisisobutyronitrile as initiator were determined over the entire composition range from pure AVN to pure styrene. The rate data are shown to be consistent with a value of 3 for ϕ, the cross‐termination rate constant.
Stereoregulated polymerization in the free propagating species. II. Effect of monomer structure on the polymerization of vinyl esters
Authors: Fordham J. W. L. , McCain G. H. , Alexander L. E.
Published: April 2003

The first paper of the series contained the theoretical prediction that syndiotactic propagation could be favored over isotactic propagation in free radical polymerization by the nature of the monomer substituent group. To check this hypothesis the steric structure of polymers of vinyl acetate and certain haloacetates was investigated. X‐ray examination of the polyvinyl esters and the solubility of derived alcohol polymers indicate that the degree of regularity increases in the order: acetate < monochloroacetate < polychloroacetates < trifluoroacetate. The influence of the substituent group is limited in the polyvinyl esters because only the trifluoroacetate shows true crystallinity, and, even in this polymer, the average length of the regular sequences appears to be small. The above order of regularity suggests that the electrostatic factor is more important than the steric factor in the stereoregulated polymerization of vinyl esters. The regular sequences of the trifluoroacetate are indicated to have a syndiotactic configuration from the chain repeat distance. The polymerization of the ester is believed to involve predominantly syndiotactic propagation, with relatively frequent interruptions of isotactic propagation. The generalizations agree with results reported for other stereoregular radical polymerizations. Conceivably, syndiotactic propagation may be preferred for free radical polymerization in general, and polymers produced under radical conditions may be more regular than has been realized.
Studies on the low pressure polymerization of ethylene by use of catalysts containing potassium alkyls
Authors: Zilkha Albert , Ottolenghi Ariel , Frankel Max
Published: April 2003

The low pressure polymerization of ethylene by use of catalysts prepared from either butyl or amyl potassium, or the reaction product of potassium with chlorobenzene and titanium tetrachloride was studied. The efficiency of the catalysts depended on the molar ratio of the potassium alkyl to titanium tetrachloride but was in every case considerably lower than that of the corresponding lithium or sodium alkyl containing catalysts. Optimum molar ratios of the butyl potassium–titanium tetrachloride catalysts were between 2.8 to 6.1 with sharp drops on both sides of the optimum; for the amyl potassium between 1.1 to 3.7. The reaction product of potassium with chlorobenzene yielded much weaker catalysts with titanium tetrachloride, and the properties of the polymers obtained were different. The physical properties of the polyethylenes obtained, as determined from x‐ray diffraction diagrams, infrared spectra, and from melting points, showed similarity to those obtained with the lower alkali metal catalysts. The lower activity of the potassium catalysts may be related to the large ionic radius of the potassium, which influences the properties of the catalyst complex formed with titanium tetrachloride. Propylene did not undergo polymerization with the potassium alkyl containing catalysts at low pressure.
Molecular weight dependence of intrinsic viscosity, diffusion constant, and second viral coefficient of polyacrylonitrile
Authors: Kobayashi Hidehiko
Published: April 2003

Careful intrinsic viscosity and diffusion constant measurements are reported for nine fractions of polyacrylonitrile prepared by repeated refractionation. For a molecular weight range of from 28,000 to 575,000, relationships are obtained between second virial coefficient, diffusion constant, or intrinsic viscosity in dimethylformamide at 35°C., and absolute molecular weight. These relationships are represented by the equations:

and

where the units of intrinsic viscosity are 100 ml./g. An explanation is offered for the difference between the viscosity equation and other similar equations in the literature, as well as for the discrepancies among the various equations in the literature. Empirical plots of kD vs. [η] are presented, giving lines which are straight within the limits of accuracy of the data. From these results, the following relation was obtained: c = 1 − α, where α is the exponent in [η] = KIMα, and c is the exponent in A2 = KIIIM−c.
Single‐point determination of viscosity
Authors: Poláček J.
Published: April 2003

Intrinsic viscosities of benzene solutions of fresh, naturally, and artificially aged Svitprene K polychloroprene and their fractions were calculated by using Hart's method for the single‐point determination of intrinsic viscosities. It was found that this quick method was sufficiently precise for Svitprene K. In most cases the deviations of the calculated values from those obtained by extrapolation according to the equation of Schulz and Blaschke were lower than 1% of intrinsic viscosity.
Theoretical considerations on the mechanism of stereospecific cationic polymerization in homogeneous systems
Authors: Higashimura T. , Yonezawa T. , Okamura S. , Fukui K.
Published: April 2003

A theoretical interpretation of the mechanism of stereospecific cationic polymerization in a homogeneous system at low temperature is given. The existance of a counterion in the vicinity of a charged carbon atom of a growing polymer ion is assumed and a repulsive interaction is considered to be between the substituent of the attacking monomer and that of the polymer. The most probable geometrical conformation of a monomer and a polymer ion in the transition state is determined by the magnitude of stabilization due to the overlap between atomic orbitals of ion and monomer. Our experimental results can be explained satisfactorily by this mechanism.
The oxidation of polyvinyl alcohol by ceric ion
Authors: Mino G. , Kaizerman S. , Rasmussen E.
Published: April 2003

The rate of reaction of ceric nitrate with the 1,2‐glycol units and the alcohol units of polyvinyl alcohol was determined at 20°C. It was found that the glycol units are oxidized much faster than the alcohol units even though they are outnumbered about one hundred to one in the polymer chain. Under the conditions studied, at least 83 glycol units reacted per 100 hours oxidized. Since the oxidation of the glycol units is accompanied by chain splitting, the free radicals are produced predominantly at the fragments end.
Transient catalysts for the polymerization of organosiloxanes
Authors: Gilbert Alfred R. , Kantor Simon W.
Published: April 2003

A study was made of the polymerization of siloxances with transient basic catalysts. These catalysts are active as polymerization catalysts for siloxanes and will decompose rapidly to inactive products at elevated temperatures with the formation of stable polymers. Several quaternary ammonium bases were studied as polymerization catalysts. It was found that bases such as tetramethylammonium hydroxide and benzyltrimethylammonium hydroxide were efficient catalysts. Similar bases having β‐hydrogen atoms decomposed too rapidly via an elimination reaction and were not good catalysts. The polymerizations of organosiloxanes with quanternary phosphonium hydroxides were also studied. The phosphonium bases decomposed thermally in a different manner than the ammonium bases to give phosphine oxides and hydrocarbones. The most efficient transient catalysts were found to be phosphonium silanolates. Tetrabutylphosphonium silanolate was conveniently prepared in an anhydrous form and it proved to be extremely efficient for the preparation of homopolymers and copolymers of organosiloxanes.
Isoprene polymerization by organometallic compounds. II
Authors: Tobolsky Arthur V. , Rogers Charles E.
Published: April 2003

Dispersions of metallic lithium, sodium, and potassium and some of their organoderivatives were used to initiate the polymerization of isoprene in several solvents. The propagating species in all cases were ion pairs of the type . The structure of the resultant polyisoprene depends on the character of the propagating pair. This in turn depends mainly on the counterion M+ and the solvent type. One quality of this ion pair which is of utmost importance is its ionic character (or degree of charge separation). In solvents such as diethyl ether and tetrahydrofuran, where we might expect large charge separation in the ion pair, all initiatiors produce similar, though not necessarily identical, polymer structures comprising 1,2 ‐3,4‐, and trans‐1,4‐adducts. With potassium‐dependent initiators, very nearly the same polymer structure is obtained in hydrocarbons as in the more basic ethers, attesting to the highly ionic character of the potassium‐carbon bond; this might perhaps be considered as the “limiting anionic behavior”. Sodium has smaller inherent ionic‐character and is more sensitive to changes in solvent basicity, but still it parallels the behavior of potassium. With lithium, the most covalent of the alkali metals, a dramatic change in behavior occurs when polymerization is conducted in hydrocarbon media; a 93% cis‐1,4‐,7% 3, 4‐polyisoprene structure is obtained. This may be merely a limiting structural from at the low end of the scale of ionic character of the propagating ion‐pair. The steric factors arising from complexes formed between the propagating ion‐pair. The steric factors arising from complexes may also have an important influence on the polymer structures product in the various solvents. A continuous seriese of polyisoprene structures intermediate between those formed in hydrocarbons with Li and the limiting “anionic structure” can be obtained by use of such solvents as phenyl ether or anisole, or by judicious choice of appropriate hydrocarbon–solvent ratios with a number of suitable cosolvents.
Relationship between the flow of polymeric substances in a parallel plate compression rheometer and in an extrusion rheometer
Authors: Ito Katsuhiko
Published: April 2003

The parallel plate compression rheometer is a typical measuring apparatus for the plastic flow of high polymers. In this rheometer, compressive creep curves of test specimens were studied at low rates of shear at constant temperature. Assuming Newtonian flow in the test specimen between the parallel plates, the coefficient of apparent viscosity was calculated from the lapsed viscous‐flow portion of these creep curves. The test specimen was a disk type with an initial‐diameter‐to‐initial‐height ratio of more than 30. Under low rates of shear, structural viscosity has little effect on the experimental results with cellulose acetate derivative plastics. At high rates of shear in the extrusion rheometer, however, the coefficient of apparent viscosity increases with a decrease of extrusion pressure. The experimental results in the parallel plate compression rheometer corresponds to those of zero extrusion pressure in the extrusion rheometer by the extrapolation method. The intrinsic flow energy, Uint., as a comparative value of the flow behavior of various kinds of linear polymers, is measured directly by the parallel plate compression rheometer.
Studies on the low pressure polymerization of propylene using catalysts containing alkali metal alkyls
Authors: Zilkha Albert , Calderon Nissim , Ottolenghi Ariel , Frankel Max
Published: April 2003

The low pressure polymerization of propylene was investigated using catalysts prepared from alkali metal alkyls and titanium tetrachloride. In all cases the efficiency of the catalysts depended on the molecular ratio of the metal alkyl to the titanium tetrachloride. In general the polymerization conditions were similar to those for ethylene although the propylene polymerized much more slowly. With n‐butyllithium–titanium tetrachloride, optimum molecular ratios were found between 1.8–2.5, with sharp drops on both sides. With amylsodium–titanium tetrachloride the optimum extended over a wide range (5.7–15), the activity decreasing sharply with lower molecular ratios. The catalysts prepared from sodium alkyls were more active than those prepared from lithium alkyls. Increasing yield was obtained on lowering the concentration of the catalyst. Up to a pressure of about 3 atmospheres, increase in the rate of polymerization was observed with increase in pressure; above this no influence of the pressure was observed. Isotactic polymers were isolated from the polymerization products by successive fractionation of the crude polymers in acetone, ether, and isooctane which dissolved the atactic polymers. With butyllithium–titanium tetrachloride catalysts, at and above optimum ratios, the isotactic fractions were about 60%. At lower ratios there was a great increase in atactic polymers. With amylsodium–titanium tetrachloride catalysts the isotactic fractions were about 70%. Phenylsodium–titanium tetrachloride catalysts were found to be very weak in the polymerization of propylene.
Polymers and group interaction. VIII. Synthesis of a styrene–amino acid copolymer
Authors: Goethals E. , Smets G.
Published: April 2003

A copolymer of styrene–maleimide has been obtained by reaction of a styrene–maleic anhydride copolymer with ammonia under pressure in acetone solution at 70–90°C. The co(styrene–maleimide) polymer was submitted to Hofmann degradation reaction in aqueous medium and in water–tert‐butyl alcohol solution. In aqueous solution the amine formation is accompanied by partial lactam formation resulting from interaction between acid and amine groups. In water–tert‐butanol this cyclization reaction did not take place, since there was formation of tert‐butyl carbamates. These carbamate groups may be hydrolyzed in acetic acid solution in the presence of hydrochloric acid, and afford free amino groups. In both media, appreciable hydrolysis proceeds simultaneously with the Hofmann reaction, so that the number of carboxyl groups exceeds by far the number of amino groups (75 vs. 20–25%).
The viscosities of concentrated polymer solutions. II. Extremely concentrated solutions
Authors: Hirai Nishio
Published: April 2003

The enormous increases in the viscosity, η, and the associated activation heat, Qη, in concentrated polymer solutions are attributed to two different factors. One is the formation of intermolecular linkages between high polymer molecules, and the other is the increase of glass transition temperature, Tg, with increasing concentration of the solution. In this paper, the effect of the increase of Tg in solutions of extremely high concentration is discussed. The apparent activation heat of viscosity, Qη, in this concentration range is represented by the equation, Qη = 2ΔE + Qη0. The first term is the increase of Qη due to the intermolecular linkages, and ΔE is the energy to form a linkage. The second term is the activation energy for the vitrified solution where intermolecular linkages do not exist, and it is represented by the equations, (Qηs/Qη2)1/2 = 1 − Aw2 and A = 1 − (Qηs/Qη0)1/2, where A is a constant for the solution and Qη2 and Qηs are the activation heats of viscosity for the polymer and the solution, respectively. The value of A remains constant up to 100% for polystyrene in dibenzyl ether, polymethyl methacrylate in diethyl phthalate, and polyvinyl chloride in tricresyl phosphate. The constant A is always very close to unity for polymeric solutions. The general tendency of concentration dependence of Qη in the whole range of concentration is discussed.
Interfacial polycondensation. I.
Authors: Wittbecker Emerson L. , Morgan Paul W.
Published: April 2003

Interfacial polycondensation is a rapid, irreversible polymerization at the interface between water containing one difunctional intermediate and an inert immiscible organic solvent containing a complementary difunctional reactant. It is based on the Schotten‐Baumann reaction in which acid chlorides are reacted with compounds containing active hydrogen atoms (OH, NH and SH). A large number of polymers (heat‐sensitive and infusible as well as stable and meltable) can be prepared. The method has been applied to the preparation of polyurethanes, polyamides, polyureas, polysulfonamides, and polyphenyl esters. Interfacial polycondensations are run in simple, open laboratory equipment with or without stirring. With suitable agitation granular or powdered polymers with high molecular weight are prepared at room temperature and isolated within a few minutes. The intermediates need not be absolutely pure or in balance nor is a quantitative yield needed in order to obtain high polymer. The major variables in the interfacial polycondensation process are discussed and the laboratory techniques and principles are contrasted with melt polycondensation.
Interfacial polycondensation. VII. Polyurethanes
Authors: Wittbecker Emerson L. , Katz Manfred
Published: April 2003

Interfacial polycondensation of diamines and bischloroformates has been used to prepare a wide variety of high molecular weight polyurethanes, many of which cannot be synthesized by means of the diisocyanate‐glycol addition process. Almost every type of diamine normally used in condensation polymerization, i.e., aliphatic, alicyclic, cyclic secondary, and aromatic diamines, has been found suitable. Aliphatic, alicyclic, and aromatic bischloroformates have been prepared and utilized as coreactants. Of particular interest are the polymers melting above 200°C. which have been obtained from such intermediates as piperazine, ethylenediamine, and the bischloroformates of ethylene glycol, 2,2‐dimethyl‐1,3‐propanediol, hydroquinone, and the cis and trans isomers of 1,4‐cyclohexanediol. The purity of the reactants and the type of organic solvent, acid acceptor, and dispersing agent were found to be important variables which influenced the molecular weight of the polyurethanes.
Interfacial polycondensation. VIII. Application to AB‐type monomers
Authors: Schaefgen J. R. , Koontz F. H. , Tietz R. F.
Published: April 2003

The application of interfacial polycondensation to the preparation of several polyurethanes and polyamides from AB type monomers is described. The monomers are salts of aminoalkyl chloroformates and aminoacid chlorides, respectively. Differences in method and mechanism from the AA plus BB type interfacial polycondensation are discussed. Several new ring‐containing polymers were synthesized.
Interfacial polycondensation. XI. Ordered copolymers
Authors: Lyman Donald J. , Lup Jung S.
Published: April 2003

An alternating copolyurea was prepared by the interfacial polycondensation of 1,4‐piperazinedicarbonyl chloride with hexamethylenediamine. Comparison of this alternating copolyurea with the corresponding copolyurea having a random distribution showed that the alternating copolymer had a higher melting point, greater crystallinity, and was somewhat less soluble than the random copolymer. A series of copolyamideurethanes was prepared by the interfacial polycondensation of 2,5‐dimethylpiperazine with terephthaloyl chloride and ethylene bis(chloroformate), various modes of addition of the two diacid chlorides being used. The degree of order developed in these copolyamide–urethanes was postulated from the probable mechanism of the reaction. The directional “crystallinity” or lattice order of the copolymers, as determined from x‐ray diffraction patterns, was cited to support these postulated structures.
Electron exchange polymers. XII. Potentiometric titration of dicyclopentadienyliron (“ferrocene”) and some derivatives
Authors: Chen Yueh‐Hua , Fernandez‐Refojo Miguel , Cassidy Harold G.
Published: April 2003

Polymers bearing the dicyclopentadienyliron (“ferrocene”) functional group fall into the class of electron exchange polymers. Polyvinyl dicyclopentadienyliron is insoluble in common polar solvents suitable for use in electrometric titration. When sulfonated in the ferrocene rings, the material becomes more unstable toward oxidation than alkylsubstituted dicyclopentadienyliron, and upon oxidation readily loses iron. The midpoint potential for dicyclopentadienyliron (in acid alcohol) is −0.5369 ± 0.0005 v.; for cyclopentadienyl(ethylcyclopentadienyl)iron (in acid alcohol) it is −0.5081 ± 0.0005 v.; for the ammonium salt of monosulfonated dicyclopentadienyliron (in 0.5N aqueous sulfuric acid) it is −0.6143 ± 0.0007 v. on oxidation, and −0.6141 ± 0.0008 v. on reduction. The diammonium salts of disulfonated dicyclopentadienyliron and of cyclopentadienyl(ethylcyclopentadienyl)iron could not be titrated successfully. Sulfonated polyvinyldicyclopentadienyliron could not be titrated because of its easy decomposition at potentials in the neighborhood of −0.6 to −0.7 v.
Molecular weight distributions of polystyrene samples by turbidimetric titration
Authors: Gooberman G.
Published: April 2003

An analysis of the light scattered from suspended polymer aggregates formed during turbidimetric titration of the system polystyrene–benzene–methanol has been made. It has been shown that a knowledge of the precipitate composition and total number of aggregates is required before the precipitate mass can be calculated from turbidity measurements. Satisfactory results are obtained if the total number of aggregates is assumed to be proportional to the precipitate mass, provided the initial polymer concentration does not exceed 0.002% (w/v). On the basis of an empirical saturation law, two methods have been used to derive satisfactory molecular weight distributions for two polystyrene samples of known distribution. The better method is based on a Claesson grid. The other method is based on that given originally by Morey and Tamblyn. Turbidimetric titration tends to discriminate against the low‐molecular‐weight end of a distribution.
Molecular orbital considerations on the reactivities of vinyl compounds. I. Radical reactivity
Authors: Fueno Takayuki , Tsuruta Teiji , Furukawa Junji
Published: April 2003

According to the simple LCAO MO method, the π‐electron localization energies on the β‐carbon of several vinyl monomers (Lβ) and on the α‐carbon of monomer radicals (Lα′) were calculated. Comparison of the calculated values of Lβ and Lα′ with the experimental results so far reported for radical reactivity of vinyl compounds showed (1) that a linear relationship holds between Lβ and the logarithm of methyl affinity, (2) that the smaller the value of Lα′ the larger is the chain termination constant, and (3) that Lβ and Lα′ are parallel, respectively, to the values of Q and P in Price‐Alfrey's notation. These points imply that Lβ and Lα′ would be satisfactory indices for the radical reactivities of vinyl monomers and monomer radicals, respectively. It was also suggested that, in radical copolymerization, the localization energy difference between two monomers, as well as the difference in the π‐conjugation energies with attacking radicals in the transition state of the propagation step, would contribute to the determination of the monomer reactivity ratios.
A description of the rate of contraction‐relaxation of rat tail tendons
Authors: Elden Harry R. , Boucek Robert J.
Published: April 2003

Aging alters the contraction‐relaxation of rat tail tendons; this has been attributed to an increase in the degree of crosslinking of collagen and its surrounding mucopoly‐saccharides. An analysis was made of tendon mechanics after acetic acid exposure in the untreated and formaldehyde treated state as well as the properties of acetic acid–water solutions. Tendons were treated with formaldehyde solutions (pH 7–8) over a wide range of dilution (100,000: 1 to 1: 1, pF = 5 to 0) of a stock 37% formalin. The contraction‐relaxation and extractability were followed after exposure to 0.5M acetic acid. An empirical analysis of the length vs. time curves yielded the initial rate of contraction, dL/dtC, the rate of relaxation, dL/dtR, and a specifie rate constant for the process, KCR. There was a parallent dependence of formaldehyde concentration on the effect of incurbes as well as the exteractability of tendons. On the length‐vs.‐time curves as well as the extractability of tendons. This was interpreted as evidence of the effect of induced crosslinking on the properties of the macromolecule collagen. Since similar effects are observed as a function of natural aging the role of added crosslinking as the mechanism for this change is suggested again. Contimuous variation analyses of spectroscopic and viscometric data of the acetic spectroscopic and viscometric data of the acetic acid–water system demonstrated extensive molecular interaction. The hydrogen bond‐forming tendencies of the carboxyl CO and HO may be as the basis for the action of the solvent in the contraction‐relaxation process.
The influence of temperature on the viscosity of polystyrene solutions
Authors: Bianchi Umberto , Magnasco Valerio
Published: April 2003

Thermodynamical parameters for the system polystyrene–toluene at 25°C. have been calculated on the basis of the Flory theory from results of viscosity measurements in toluene and in ideal solvents at 25, 34, and 45°C. for 11 fractions of polystyrene. The results obtained are compared with those given in the literature. The values obtained for thermodynamical parameters permit calculation of intrinsic viscosities at different temperatures; these values are accurate to within ±2%.
A revised Q–e diagram
Authors: Thompson B. R. , Raines R. H.
Published: April 2003

New data are presented to establish the Q and e values of vinylidene chloride, acrylonitrile, and vinyl chloride relative to styrene as the reference monomer. Within the experimental error these values are shown to be entirely consistent with the observed copolymer compositions. Only the values for vinyl chloride are appreciably different from those published in the original paper of Alfrey and Price in 1947. With these better data it is hoped that renewed efforts will be made to place this empirical device on a sound theoretical basis.
Column fractionation of polymers
Authors: Krigbaum W. R. , Kurz J. E.
Published: April 2003

Mixtures of fractions of atactic polystyrene dissolved in cyclohexane were resolved by elution from a column at different temperatures. A coarse‐grained Ottawa sand was used to minimize the surface area of the support. Comparison with the critical miscibility temperature data of Schultz and Flory shows that the lower molecular weights are eluted from the column at a temperature somewhat below the critical miscibility temperature, as expected, but for molecular weights above 3 × 105 the elution temperature increases abruptly, and even exceeds the critical miscibility temperature. This rapid rise occurred at 1.5 × 105 when the surface area of the support was increased by use of a very fine Celite. We conclude that for the higher molecular weights additional thermal energy is required to desorb the polymer, and hence the partitioning of these species is not determined solely by solubility considerations. Concerning the efficiency of the column extraction, considerable resolution of each component was obtained, and attempts to determine the M̄w/M̄n ratios of the individual components were at least partially successful. As predicted by theory, for a given molecular weight interval the range of elution temperature was increased fivefold by the use of a mixed solvent, benzene–ethanol, in place of the single poor solvent, cyclohexane. Customary fractionation procedures are very inefficient when applied to high‐melting crystalline polymers. For these polymers we investigated selective precipitation upon a column having a temperature gradient, rather than elution from the column. For dilute solutions, amorphous phase separation may precede crystallization, particularly in the case of polymers whose rates of crystallization are low, owing to the presence of bulky side groups. The column precipitation method failed to give improved fractionation of polyacrylonitrile, owing to phase separation of the dimethylformamide–heptane mixture part way down the column. On the other hand, good resolution was obtained for an unfractionated sample of isotactic polystyrene up to 1.5 × 106. Molecular weights above this level were compressed into a narrow band at the top of the column. Thus, if the distribution is extremely broad, a second fractionation with a different solvent:‐ precipitant ratio may be required. Even so, a single pass through the column resulted in a better resolution than that obtained by a large‐scale, two‐stage extraction‐precipitation procedure, indicating that the column precipitation method does posses an advantage for the fractionation of crystalline polymers.
Soluble homopolymers and copolymers from 2,6‐disubstituted‐1,6‐heptadienes
Authors: Milford G. N.
Published: April 2003

A method is described for the preparation of high molecular weight, soluble homopolymers from 2,6‐disubstituted‐1,6‐heptadienes. Contrary to expectation, the disubstituted heptadienes readily form soluble, high molecular weight copolymers with vinyl‐ and acrylate‐type monomers if dilute solutions are employed and polymerization is not too rapid. The absence of unsaturation in copolymers and their excellent solubility indicates that the disubstituted heptadienes polymerize by an intramolecular‐intermolecular mechanism even in the presence of reactive monomers.
Molecular weight distribution of anionically polymerized α‐methylstyrene
Authors: McCormick Herbert W.
Published: April 2003

The molecular weight distribution of anionically polymerized α‐methylstyrene has been measured by sedimentation velocity analysis. Molecular weight dependence of sedimentation constants and solution viscosities are reported. It is shown that the molecular weight distribution of poly‐α‐methylstyrene made by sodium complex is very narrow. Formation of a two‐peaked distribution polymer is reported; the data give support to the mechanism of double‐ended polymer propagation.
Ch2‐rocking vibrations and structural correlations of poly(ethylene glycols)
Authors: White Horace F. , Lovell Channing M.
Published: April 2003

Infrared absorption spectra of ethylene glycol and various higher molecular weight poly(ethylene oxides) have been obtained both in the liquid and solid phases. The similarity of the solid and liquid phase spectra for the poly(ethylene oxides) suggest that these materials exist in essentially the same conformation (gauche) in both phases. The disappearance of a band similar to one in liquid ethylene glycol with increasing molecular weight suggests a molecular weight dependence of a trans conformation. Oriented high molecular weight poly(ethylene oxide) spectra are consistent with recent x‐ray diffraction studies.
Alkaline hydrolysis of methacrylic acid–ester copolymers
Authors: Smets G. , de Loecker W.
Published: April 2003

The alkaline hydrolysis of six different copolymers of methacrylic acid and methyl methacrylate having acid contents of 28.9, 49.5, 58.5, 66, 72, and 83 mole‐% was studied. At pH values smaller than 12.5 the reaction mechanism is principally intramolecular, as a result of neighboring acid‐ester group interactions. Both the chemical composition and the stereochemical configuration of the polymers exert a strong influence on the course of the reaction. In strongly alkaline medium, the hydrolysis results primarily from the external action of hydroxyl ions, except in the case of a copolymer containing 83 mole‐% acid, in which the reaction again results essentially from an intramolecular mechanism.
The copolymerization characteristics of vinylene carbonate, γ‐crotonolactone and methyl bicyclo(2,2,1)‐2‐heptene‐5‐carboxylate
Authors: Judge Joseph M. , Price Charles C.
Published: April 2003

The copolymerization of three cyclic vinylene monomers has been investigated. For vinylene carbonate, we found Q = 0.005, e = −0.8, and for methyl bicyclo(2,2,1)‐2‐heptene‐5‐carboxylate, Q = 0.02, e = 0.0. A convenient preparation of γ‐crotonolactone is reported, but no satisfactory copolymerization for this material was found.
Allyl polymerization. V. Effective chain transfer in the polymerization of 3‐buten‐2‐‐yl acetate. Polymerization of 3‐buten‐2‐‐ol
Authors: Gaylord Norman G. , Kujawa Francis M.
Published: April 2003

The bulk polymerization of 3‐buten‐2‐yl acetate with benzoyl peroxide as catalyst at 80°C. is characterized by degradative and effective chain transfer. Effective chain transfer constitutes 86% of the total transfer reactions. The polymerization results in a polymer with a DP of 2.8, independent of initial catalyst concentration, and in any given polymerization the disappearance of monomer is a linear function of the disapperance of peroxide, i.e., dM/dC is constant, and decreases linearly with increasing catalyst concentration, extrapolating to 38.1 at zero catalyst concentration. The values of dM/dC and conversion to polymer are higher with 3‐buten‐2‐yl acetate than with allyl acetate. The polymer from the α‐methylallyl ester contains approximately one double bond for every three monomer units at 2% peroxide concentration. The decomposition of benzoyl peroxide in 3‐buten‐2‐yl acetate is more rapid than in the allyl ester and is characterized by considerable induced decomposition. The decomposition of peroxide in methyl vinyl carbinol is extremely rapid and the conversion of monomer to polymer is very low.
Nuclear magnetic resonance and molecular motion in polymethyl acrylate, polymethyl methacrylate, and polyethyl methacrylate
Authors: Sinnott K. M.
Published: April 2003

The proton magnetic resonance in polymethyl acrylate, polymethyl methacrylate, and polyethyl methacrylate has been studied between 77 and 400°K. The second moments of the absorption lines are compared with the values calculated for some of the modes of molecular motion possible in these polymers. This comparison leads to the conclusion that motion of the ester methyl and ethyl groups in the respective polymers occurs below 77°K. and that motion of the main chain methyl groups in polymethyl methacrylate and polyethyl methacrylate occurs above 130°K. This interpretation of the results is shown to be in agreement with previous measurements of the mechanical and dielectric properties of these polymers. The shape of the absorption line observed in polymethyl methacrylate at 77°K. was reproduced by a suitably weighted superposition of the absorption lines of rigid and rotating methyl groups and a rigid methylene group confirming that motion of one methyl group occurs below 77°K. in polymethyl methacrylate.
Ultrasonic degradation of polystyrene. Part 1. A proposed mechanism for degradation
Authors: Gooberman G.
Published: April 2003

The ultrasonic degradation of macromolecules can be considered to be caused by the rapid pressure changes accompanying the shock wave radiated from a collapsed cavity. Assuming that all the cavities are identical and that the shock wave is similar to that generated by an underwater explosion of TNT, rate constants for the degradation of polystyrene in benzene have been found as a function of molecular weight. The variation in the limiting molecular weight with ultrasonic intensity has been calculated and shown to agree with that obtained experimentally. The theory indicates that the maximum pressure reached during the collapse of a cavity is about 1600 atm.
The ferrous chelates of polyaminocarboxylic acids as initiators in the emulsion polymerization of styrene. I
Authors: Bond Joan , Jones T. I.
Published: April 2003

The ferrous iron–ethylenediaminetetraacetic acid–hydrogen peroxide‐initiated emulsion polymerization of styrene has been investigated, potassium palmitate being used as emulsifying agent. It was found that there was acritical concentration of iron, 0.01 part of ferrous iron per 100 parts of monomer, above which the zero‐order rate of polymerization was not appreciably increased. The rate is also proportional to the square root of the hydrogen peroxide concentration and to the soap concentration to the 0.6 power.
The ferrous chelates of polyaminocarboxylic acids as initiators in the emulsion polymerization of styrene. II
Authors: Bond Joan , Jones T. I.
Published: April 2003

The polyaminocarboxylic acids, ethylenediaminetetraacetic acid (EDTA), methylethylenediaminetetraacetic acid (MeEDTA), diethylenetriaminepentaacetic acid (DTPA), and cyclohexanediaminetetraacetic acid (CDTA) have been used to chelate the iron in the system ferrous iron–hydrogen peroxide when it is used as an initiator for the emulsion polymerization of styrene. In each case, the zero‐order rate of polymerization decreased from pH 0.5, when it was identical to that in the absence of any chelating agent, to a minimum value in the pH region 3.5–6.5, after which it rose again. In acid solution the results are not the same as those anticipated from the redox potentials of the ferrous–ferric–chelating agent system at various pH values, and this has been found to be due to the dissociation of the iron chelate at a low pH.
The statistical analysis of polymer fractionation data. Part I
Authors: Booth C. , Beason L. R.
Published: April 2003

The analysis of simple successive polymer fractionation data by conventional and statistical methods is discussed. The fractionation model originating in the Flory‐Huggins theory of polymer solutions is used to test the alternative methods. The direct statistical methods are shown to be superior to alternative procedures. Such methods approximate the individual fraction distributions by simple statistical distributions (binomial or generalized exponential), the parameters of which are calculated directly from a knowledge of two average molecular weights (M̄n and M̄w).
Stereospecificity and electric polarization in high polymers
Authors: Bacskai R. , Pohl H. A.
Published: April 2003

The electric polarization of a polymer is shown to depend upon the steric order along the chain. This is in accord with the previously observed electric polarization behavior of diastereomers. Solution measurements of the molar polarization of polymethyl methacrylates in benzene gave values of 32 ± 0.5 cc./mole for syndiotactic, and 41 ± 0.5 cc./mole for isotactic material, with atactic polymer showing intermediate values. It is believed therefore that the polarizability method can form a means of differentiating and interpreting the behavior of polar stereospecific polymers.
Molecular weight distribution in anionic polymerization involving a chain transfer to monomer
Authors: Litt M. , Szwarc M.
Published: April 2003

Polymerization involving a chain transfer to monomer but not involving a termination step was discussed. Such a polymerization produces a mixture of dead and living polymeric molecules, and the resulting molecular weight distribution was calculated both for polymers initiated on one end and those initiated on both ends. The results permit calculation of number and weight average degree of polymerization. Application of these results to polymerization of isoprene permits the approximate evaluation of the chain transfer to monomer constant for anionic polymerization of isoprene and estimation of the parameter α in the relation [η] = K · [DPn]α.
Crystalline modifications of cellulose. Part IV. Determination of x‐ray intensity data
Authors: Mann J. , Roldan‐Gonzalez L. , Wellard H. J.
Published: April 2003

The intensities of x‐ray reflections from ordered regions of Cellulose I (ramie) an Cellulose II (Fortisan) have been determined by photometering the x‐ray diagrams. The results are reported as intensities of resolvable reflections, to provide a basis for comparison with postulated crystal structures to be described in Part V of this series. In many cases reflections from several crystallographic planes could not be resolved and the total intensity for the group of reflections is given. This procedure does not make full use of the experimental results; the factors which would have to be taken into account in a more complete interpretation of the data are discussed.
Crystalline modifications of cellulose. Part V. A crystallographic study of ordered molecular arrangements
Authors: Jones D. W.
Published: April 2003

With the arrangements of molecular chains postulated in Part III as a basis, crystal structures for the ordered regions of ramie and regenerated celluloses have been set up. Comparison of the (hkl) x‐ray intensities calculated for cellulose I structures with the measurements reported in Part IV reveals serious discrepancies on the first layer‐line. From extensive calculations over a range of structures, it appears that no conventionally ordered structure built from a P21 unit cell of approximate dimensions 8.2 × 10.3 × 7.9 A., β = 84°, can be expected to yield as weak (h1l) planes as are observed. An element of randomness in the polarity of the chains would diminish the discrete intensities on the higher layers relative to the (h0l) reflections and so be more in accord with experiment. For cellulose II, attention was concentrated on antiparallel chain structures with the r shift near 0.29. Although the overall agreement was better than for cellulose I, such structures did not account for the very weak low‐order (h1l) reflections observed. The disparity was not reduced by types of disordering acceptable on stereochemical and spectroscopic grounds. The major part of the disagreement is tentatively attributed to regarding the observed coherent scattering as emanating from fully ordered unit cells of the accepted dimensions and symmetry, and to neglecting contributions from oriented amorphous regions.
Absolute rate theory for spherulite growth of polymeric substances
Authors: Hirai Nishio
Published: April 2003

The rate of spherulite growth has been measured for various polymers. Several authors have developed the theory for the rate with emphasis on its temperature dependence but without reference to its absolute value. In this paper, a theory of the absolute rate of growth is put forward on the basis of the perfect crystal growth mechanism of Volmer‐Frenkel and the absolute reaction rate theory of Eyring. The linear rate of growth, G is given by

For typical polymers, this equation is approximated by

where d1 is the diameter of the polymer molecular, d3 the length of the segment, ηL the local viscosity near the crystal surface, ΔHm the heat of fusion for a mole of segments, Tm° the equilibrium melting temperatures, and ΔT = Tm° – T. The glass temperature for the local viscosity is assumed to be lower by δTg than that for usual viscosity, and the equilibrium melting temperature Tm° is assumed to be 5° higher than the apparent melting point Tm. The values of G calculated by this theory show good agreement with observed values for polyethylene succinate and nylon 6.
A study of the deuterium isotope effect in antioxidant activity
Authors: Shelton J. Reid , McDonel E. T. , Crano John C.
Published: April 2003

In an attempt to correlate the conflicting reports in the literature with regard to the presence of a deuterium isotope effect in antioxidant activity, this study was undertaken to investigate the factors on which this effect depends. It was found that variations in the magnitude and direction of the isotope effect in a study of this type could be brought about by varying each of the following factors separately: (1) concentration of the antioxidant; (2) temperature of the oxidation run; (3) nature of the antioxidant. The reason for the dependence of the isotope effect on these factors is thought to be the possibility for direct oxygen attack on the antioxidant, yielding radicals capable of beginning a kinetic chain. This study also demonstrated the amazing ease of exchange of the labile hydrogen on the antioxidant for deuterium in the presence of the inert organic solvent and heavy water. This is the basis for a very simple new procedure which was developed for the preparation of deuterated antioxidants. It also emphasizes that in an attempt to discover an isotope effect in antioxidant activity all water must be continuously excluded from the system. The isotope effects demonstrated in this and a previous study support the hydrogen abstraction mechanism for antioxidant activity.