bluuebunny/crossref_metadata_2025 huggingface dataset:
The polymerization of acrylonitrile in aqueous solution. Part II. The reaction photosensitized by Fe3+, Fe3+OH−, Fe2+, and I− ions
Authors: Dainton F. S. , James D. G. L.
Published: April 2003

The polymerization of acrylonitrile in aqueous solution photosensitized by Fe2+, Fe3+OH−, and I− has been determined dilatometrically at 25°C. After an acceleratory phase caused partly by increasing intensity of absorbed light due to light‐scattering by the insoluble polymer particles, a steady rate Rp is established and continues up to ∼10% conversion. Rp is proportional to Iabs[m1]1.0, where x is slightly greater than 0.5 unless ferric ions are present which may oxidize and terminate polyacrylonitrile radicals and cause x to be greater than 0.5. In accordance with earlier measurements, ϕ for the reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Fe}^{3 +} {\rm OH}- {{{3130\ {\rm A}.} \atop {-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-4pt-\hskip-5pt\longrightarrow}}\atop{}}{\rm Fe}^{2 +} + {\rm OH}$$\end{document} is found to be 0.15. Propagation occurs by addition (a) of dissolved monomer molecules to polymer radicals S* (kp = 1.45 × 104 l. mole−1 sec.−1) and (b) of adsorbed monomer molecules to the radical in suspended polymer particles P* which contain several polymer molecules and one growing radical. S* radicals are subject to mutual termination (kt = 2 × 109 l. mole−1 sec.−1) and oxidative termination by ferric ion (k4 = 1.3 × 104 l. mole−1 sec.−1). As soon as the steady state is established [P*] is constant, but after stopping irradiation [P*] decays slowly and bimolecularly and therefore gives rise to a small aftereffect. Agitation causing the polymer suspension to coagulate (a) reduces Rp due to changes in Iabs and a decrease in the number of particles and (b) decreases the half‐life of the aftereffect by increasing the rate of mutual destruction of P* particles.
The polymerization of acrylonitrile in aqueous solution. Part III. The ferric ion‐photosensitized reaction at 15, 25, 30, and 50°C.
Authors: Dainton F. S. , Eaton R. S.
Published: April 2003

The Fe3+OH− photosensitized polymerization of acrylonitrile in aqueous solution at 15, 25, and 35°C. has been studied dilatometrically. Reproducible steady rates Rp, aftereffect rates Rpae, and stable fine polymer suspensions are observed. By the methods of kinetic analysis given in Part II, the following parameters of the reactions of S*‐type polyacrylonitrile radicals have been determined: propagation, Ap = 3 × 107 l. mole−1 sec.−1, Ep = 4.1 kcal. mole−1; mutual termination, At = 3.3 × 1013 l. mole−1 sec.−1, Et = 5.4 kcal. mole−1; termination by Fe3+OH−, Atf = 6.7 × 105 l. mole−1 sec.−1, Etf = 2.3 kcal. mole−1. Above 40°C. the polymer suspension precipitates more rapidly, Rp is less reproducible, and rate constants for the aqueous phase reaction cannot be determined. A system which has been photopolymerized at 25°C. when heated to 50°C. shows a short burst of reaction followed by an aftereffect which is smaller and decays more slowly than that which the system would have had at 25°C.
Stereoregulated polymerization in the free propagating species. I. Theory
Authors: Fordham J. W. L.
Published: April 2003

The theoretical aspects of a new method of regulating the steric structure in addition polymers are treated. The basic principle utilized is the directing force at the free end of the propagating species, as contrasted to the influence of a bound initiator. Only small differences in the free energies of activation of the isotactic and syndiotactic propagations are required for relatively significant changes in polymer structure, particularly at low polymerization temperatures. Both the relative amounts of the two configurations in the polymer and the distribution of individual sequence lengths bear a simple relationship to the two propagation constants. In the analogous rotational isomerism, the free energy difference between the gauche and trans conformations is known to be influenced by both steric and electrostatic factors. For molecules of the type ACH2CH2A, the difference in heat content is increased by an increase in the size or the polarity of the substituents and, for polar substituents, by a decrease in the dielectric constant of the medium. Steric and electrostatic factors at the free end of the growing polymer chain can, in theory, influence the structure in polymers. This conclusion is based on an estimate of steric and electrostatic energy components of the most probable conformational arrangements for the isotactic and syndiotactic configurations in representative polyvinyl chloride with theoretical structure. The refinement introduced by bond angle deformation can also be approximated for the two polymer configurations. With respect to each of the three energy components the syndiotactic configuration is the preferred structure, in agreement with known experimental results that polyvinyl chloride prepared under free radical conditions does contain syndiotactic sequences sufficiently long for x‐ray detection. The combined, alternate use of the directing force at the free end of the propagating species and that of a bound initiator to form syndiotactic–isotactic block copolymers is suggested.
Electrostatic interaction in dilute solutions of polyelectrolytes
Authors: Ise N. , Hosono M.
Published: April 2003

Interionic interaction in dilute solutions of polyelectrolytes (the polymer‐concentration effect) has been discussed using an ionic distribution formula which Wicke and Eigen had proposed, introducing volume exclusion effects of the ions. Thermodynamic quantities, e.g., the activity coefficients, osmotic coefficient, and electric mobility are found to have a tendency to decrease with polymer concentration and to increase after passing through a minimum. A formulation of the “activity coefficient of macroions” has been obtained and is known to give a reasonable expression for the rate of change of the activity coefficient with the polymer concentration. The heat of dilution of polyelectrolyte solutions is shown to be positive in dilute solutions. Moreover, the treatment is extended to the titration behavior, and an interpretation is given for the characteristic run of viscosity‐concentration curves.
Formation of graft polymers by γ‐irradiation of natural rubber latex and methyl methacrylate
Authors: Cockbain E. G. , Pendle T. D. , Turner D. T.
Published: April 2003

Exposure of mixtures of natural rubber latex and methyl methacrylate to γ‐radiation from a Co‐60 source results in polymerization of the methyl methacrylate to give a mixture of the homopolymer and grafted polymer. The ratio of grafted polymer to homopolymer and the molecular weight of the homopolymer are both considerably higher than in similar systems where polymerization was initiated by a redox catalyst. The ability of the irradiated to form continuous films on drying is much greater than that of corresponding redox‐polymerized systems. This difference is attributed primarily to the location of the polymerized methyl methacrylate throughout the individual latex particles, the polymerized methacrylate being more uniformly distributed in the case of the irradiated latex. Use of polymerization retarders which are soluble in methyl methacrylate swollen rubber supplies evidence that an increased proportion of the polymerized methacrylate is located in the surface regions of the latex particles. Conversely, a more uniform distribution of the polymer is obtained by the use of water‐soluble retarders. The probable significance of these results in relation to emulsion copolymer systems is pointed out.
Orientation of isotactic polypropylene filament and its new crystalline structure produced by high stretching
Authors: Sobue Hiroshi , Tabata Yoneho
Published: April 2003

Orientation of crystallites in stretched isotactic polypropylene filaments was examined by x‐ray diffraction. It was found that complete overall orientation parallel to the direction of stretching is obtained at a stretching ratio of 4 to 5. Preferential orientation was observed in the stretching process, that is, the orientation of the 010 plane along the fiber axis was predominant in the initial step of orientation and was complete by 100% stretching. It was found that a new crystal structure was formed on further stretching of completely oriented filaments at or slightly above room temperature. The crystal structure can be transformed to an ordinary stable crystal structure by treating the filaments at 100 to 150°C. for comparatively short time. The crystal structure may be a kind of metastable crystal, with nearly hexagonal projection in the plane perpendicular to the fiber axis.
The viscosities of concentrated polymer solutions. I. Moderately concentrated solutions
Authors: Hirai Nishio
Published: April 2003

The enormous increases of the viscosity, η, and the associated activation heat, Qη, in concentrated polymer solutions are attributed to the formation of intermolecular linkages between high polymer molecules and to the increase of glass transition temperature with increasing concentration of the solution. In this paper, the effects of the intermolecular linkages on the viscosity of moderately concentrated solutions were discussed. In this concentration range, η and Qη are represented by unique functions of reduced concentration, vR = BMv2, and the following equation was derived for Qη;

Here M is the molecular weight of the polymer, v2 is the volume fraction of the polymer, ΔE is the energy to form an intermolecular linkage, B is a constant for the solution, and Qη0 is the activation heat of viscosity for the solvent. The dependency of η on vR shifts from a first power proportionality to a third power at vR = 1/2. The theory was compared with experiments for solutions of cellulose tributyrate in trichloropropane, polyvinyl alcohol in water, polyvinyl acetate in acetone, and polyisobutylene in xylene.
The decomposition of benzoyl peroxide in polystyrene
Authors: Haas Howard C.
Published: April 2003

The rate of decomposition of benzoyl peroxide in polystyrene has been measured at 70.9, 80.1, and 89.5°C. The kinetics are strictly first order. There is no dependence of rate on concentration, which indicates that radical‐induced decomposition is absent. At 70–80°C., the Arrhenius relationship is k = 1.39 × 1017e−35,700/RT and at 80–90°C., k = 2.67 × 1013e−29700/RT. Above 80°C., the apparent second‐order transition temperature of polystyrene, the rates of decomposition correspond fairly closely to the rates of spontaneous decomposition of benzoyl peroxide in benzene. Below 80°C., the rates of decomposition of benzoyl peroxide in polystyrene are considerably smaller than those in benzene. Two possible explanations of this behavior are presented.
Stereospecific polymerization of isobutyl vinyl ether in homogeneous cationic systems
Authors: Okamura Seizo , Higashimura Toshinobu , Sakurada Ichiro
Published: April 2003

Isotactic polyisobutyl vinyl ether is generally less soluble in methyl ethyl ketone than is amorphous polymer, but the solubility of solid polymer in methyl ethyl ketone at room temperature is not always proportional to the crystallinity of polymer molecules. In this report it is made clear that the precipitation temperature can be utilized for the discrimination of the steric structure of polymer through comparative reference to x‐ray diagrams. Judging from the precipitation temperature, in the polymerization of vinyl isobutyl ether catalyzed by BF3·OEt2 at −78°C., the polyvinyl ethers obtained from a homogeneous polymerization system are of a more isotactic structure than those obtained from a related heterogeneous system, at low monomer concentration. In addition, the relative amounts of isotactic molecules are decreased in the cases of high monomer concentration and polar reaction systems. However, the wide differences in chain length of the polymers compared introduced doubt. These results do not indicate that stereospecific polymerization may proceed more easily in a heterogeneous system, as was considered to be the case.
Polysoaps. III. Polysoaps and related materials prepared by chemical modification of polystyrene
Authors: Medalia A. I. , Freedman H. H. , Sinha Sisir
Published: April 2003

A detailed description is given of the preparation of an anionic polysoap, poly[styrene co potassium styrylundecanoate], or poly‐K‐SSU, by the following route. Polystyrene is alkylated with methyl undercylenate in the presence of aluminum chloride; the polyester is then saponsified. Only about 50% of the phenyl groups are alkylated; thus, the structure may be written:
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Products of molecular weight from 60,000 to 1,760,000 have been prepared. Another anionic polysoap has been made by alkylation with methyl oleate; here, only about 35–39% of the phenyl groups are alkylated, apparently due to steric hindrance. Nonionic polysoaps have been prepared by ester interchange of the unsaponfied methyl esters with methoxy polyethylene glycol. A sulfate ester polysoaps has also been prepared. The properties of poly‐K‐SSU have been studied in some detail. The solubilizing power, and the viscosity of the aqueous solutions, are comparable to ordinary soaps; but the surface tension of the aqueous solution is very close to that of pure water. The nonionic polysoaps are also good solubilizing agents, e.g., for cholesterol; possible medical applications are considered.
A theory of the thermodynamic behavior of nonelectrolyte solutions. II. Application to the system rubber‐benzene
Authors: Maron Samuel H. , Nakajima Nobuyuki
Published: April 2003

The thermodynamic theory of nonelectrolyte solutions proposed by Maron has been applied to the experimental data of Gee and Treloar on solutions of rubber in benzene at 25°C. The theory was found to be capable of representing these thermodynamic data very satisfactorily on the basis of a constant interaction parameter μ, and on the basis of the dependence of the heat of mixing on the derivative of μ with respect to temperature rather than μ itself. Further, by assuming the heat of mixing to be temperature independent, an expression was set up for μ as a function of the volume fraction, v2, and the temperature. This equation reproduces \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\Delta F} _1 $\end{document} values measured at 100°C. with an accuracy of better than 4%, and shows that at temperatures above and below 25°C. μ is concentration‐ as well as temperature‐dependent.
The sulfinic acid‐initiated polymerization of methyl methacrylate
Authors: Overberger C. G. , Godfrey J. J.
Published: April 2003

The rate of polymerization of methyl methacrylate initiated by p‐methoxybenzenesulfinic acid, benzenesulfinic acid, and p‐trifluoromethylbenzenesulfinic acid in the absence of oxygen was studied. The p‐methoxy substituent accelerated the rate while the p‐trifluoromethyl substituent acted as a retarder. The order of the rate with respect to sulfinic acid concentration varied between 1 and 3/2; this is consistent with an initiation process of kinetic order between 2 and 3. Dilution of the monomer with benzene in an attempt to determine the order of the rate of polymerization with respect to monomer unexpectedly resulted in an increase in rate. Mixtures of p‐methoxybenzenesulfinic acid and p‐trifluoromethylbenzenesulfinic acid did not give an acceleration in rate. The rate of polymerization was accelerated by sulfonic acid, benzoyl peroxide, dicumyl peroxide, and di‐n‐butylamine hydrochloride. Decomposition of the very unstable 2,2′‐biphenyldisulfinic acid by disproportionation to the intramolecular sulfonic acid‐sulfenic acid was shown to be incompatible with the yield and rate of formation of the thiolsulfonate. The gross features of a mechanism consistent with the polymerization data is proposed.
Hydrolysis of methacrylic acid–methyl methacrylate copolymers
Authors: Loecker W. De , Smets G.
Published: April 2003

Several copolymers of methacrylic acid and methyl methacrylate have been prepared with acid contents of 28.8, 50, 60, 66, 72, 83, and 86.5%; they have been hydrolyzed in acidic medium at 110°C. at different neutralization ratios r = [HA]/[A‐]. Except for those with the highest acid content, all the copolymers show a two‐step hydrolysis, in which the second step is about 1/6−1/7 slower than the first. The order of reaction is one with respect to the acid concentration and one with respect to the ester concentration. On the basis of general catalysis, as suggested by Brønsted, two hydrolysis rate constants kHA and kA‐ may be evaluated; they correspond to the hydrolysis catalyzed by undissociated carboxyl groups and by carboxylate groups. At 110°C., kHA and kA‐ are equal, respectively, to 1.5 × 105 and 1.0 × 105; consequently, the rates of hydrolysis are practically insensitive to the ratios of neutralization r, except when r = 3. From comparison of the behavior of these acid‐ester copolymers with that of a methyl methacrylic‐N‐vinylpyrrolidone copolymer in the presence of an acid‐buffered solution (acetic tic or polymethacrylic acid), it becomes evident that the hydrolysis reaction consists essentially of a functional interaction between an ester function on one side, and a carboxyl and/or a carboxylate directly neighboring function on the other side. Moreover, on the basis of structural probability calculations, the immediate vicinality effect is insufficient to explain the rates and limited degree of conversion of the hydrolysis reaction. For the copolymers with high acid content (C72, C83, and C86.6) at r = 3, the rate of reaction is triple that at the other r‐values. This strong increase of the reaction velocity is, as expected, characterized by an appreciable decrease in the energy of activation (16 kcal. instead of 23 kcal.) This behavior is attributed to a “concerted” mechanism which should be particularly enhanced at r = 3. It has been demonstrated that the stereochemical composition of these copolymers exerts a deep influence on the rate of hydrolysis as well as on the degree of conversion in these reactions.
Catalytic reactivity of organometallic compounds for olefin polymerization. II. Vinyl chloride polymerization catalyzed by binary systems involving organometallic compounds
Authors: Furukawa Junji , Tsuruta Teiji , Shiotani Shigeo
Published: April 2003

The behavior of vinyl chloride toward various binary systems involving organometallic compounds was studied. Molecular oxygen, peroxides, quinone, and salts of silver or copper were used as the second component. Of the ethyl derivatives of boron, aluminium, zinc, and cadmium, the first exhibited the largest activity for the polymerization with the exception of benzoquinone as cocatalyst. Organic hydroperoxide seemed to be the most prominent cocatalyst. Thus, it was possible, by the use of the system of triethylboron and cumene hydroperoxide, to obtain polyvinyl chloride in fair yield at temperature as low as −65°C. Triethylaluminum was the sole compound which was able to induce vinyl chloride polymerization in cooperation with benzoquinone. The polymerization described in the present paper is considered to be a new type of the redox polymerization.
The additivity of some energy factors in normal alkyl compounds
Authors: Davies Mansel
Published: April 2003

Data for the heats of evaporation (of liquids), heats of sublimation, and heats of solution for a number of homologous families of simple alkyl derivatives are presented. These show a linear dependence upon chain length which allows the group contributions to be evaluated. Much of the quantitative analysis of polymer behavior is dependent upon these factors and the need for further more precise data and the advantage of direct determinations are emphasized.
Interfacial polycondensation. III. Polyamides
Authors: Beaman R. G. , Morgan Paul W. , Koller C. R. , Wittbecker Emerson L. , Magat E. E.
Published: April 2003

Experimental details are given for the interfacial polycondensation of thirteen polyamides having widely different structures. The method involves the fast, room‐temperature reaction in a two‐phase system between diamines and diacid chlorides. Aliphatic, alicyclic, and aromatic reactants, primary and secondary diamines, and many reactants containing other functional groups are all operable. The preparations illustrate a variety of procedural modifications and point up the simplicity, rapidity, and broad applicability of the method.
Interfacial polycondensation. IV. Polyphthalamides
Authors: Katz Manfred
Published: April 2003

High molecular weight polyphthalamides melting above 325°C. were prepared from piperazine, 2‐methylpiperazine, and 2,5‐dimethylpiperazine by interfacial polycondensation. The melt temperatures and decomposition points of the polyphthalamides, polyisophthalamides, and polyterephthalamides of the above diamines were determined. Only low molecular weight polyphthalamides were obtained from primary diamines. Copolymers of high molecular weight were prepared from piperazine and 2,5‐dimethylpiperazine with phthaloyl chloride containing various proportions of terephthaloyl chloride, isophthaloyl chloride, adipoyl chloride, or ethylene bis(chloroformate).
Interfacial polycondensation. IX. Polysulfonamides
Authors: Sundet S. A. , Murphey W. A. , Speck S. B.
Published: April 2003

Polysulfonamides may be prepared readily in high molecular weight by interfacial polycondensation. They are formed rapidly at room temperature when a disulfonyl chloride in an organic solvent is emulsified with a diamine in water containing an acid acceptor. The highest polymers have been obtained from aliphatic diamines and aromatic disulfonyl chlorides. Aromatic diamines have given only low molecular weight materials. Reaction conditions for preparing poly(hexamethylene‐1,3‐benzenedisulfonamide) are briefly described. Reactants must be very pure. Dichloromethane and chloroform have been the most useful organic solvents and must be pure and dry. The best concentrations are about 0.1M. The pH and the ionic strength of the aqueous phase exert a power ful effect on the desired partition of diamines between the two phases and the undesired hydrolysis of the sulfonyl chloride. Thus, sodium carbonate works better than sodium hydroxide as an acid acceptor and, in some cases, bicarbonate has been used to avoid imide formation and consequent branching.
Interfacial polycondensation. X. Polyphenyl esters
Authors: Eareckson William M.
Published: April 2003

The interfacial polycondensation method has been used for the preparation of polyphenyl esters. Polyphenyl esters can be prepared easily and reproducibly in high molecular weight by mixing in a home blender an aqueous solution of the sodium salt of the bisphenol and a dispersing agent with a solution of the diacid chloride in a water immiscible organic solvent. The organic solvent should be a solvent or swelling agent for the polymer being prepared. Polyphenyl esters with inherent viscosities as high as 2.3 have been prepared by this method. This system is widely applicable to a large number of bisphenols and dibasic acid chlorides, although aromatic acid chlorides, in general, give higher molecular weight polymer than aliphatic acid chlorides. Bisphenols containing negative substituents do not readily give high molecular weight, tough polymers because of the reduced basicity of the phenoxide ion. A series of copolymers of 2,2‐bis(4‐hydroxyphenyl)propane with isophthaloyl and terephthaloyl chlorides has been prepared and the physical properties, such as melting point, glass transition temperature, solubility, and inherent viscosity, have been measured. All of the polymers melt above 225°C. and have glass transition temperatures above 180°C. Polymers with inherent viscosities greater than 0.4 form tough films.
A further interpretation of resonance and electrical factors affecting copolymerization
Authors: Schwan T. C. , Price C. C.
Published: April 2003

New equations for evaluation of resonance (q) and electrical (ϵ) factors affecting copolymerization have been derived:

The new equations will apply over any temperature range, and will express ϵ in terms of e.s.u. and q in kcal./mole. These factors were determined for an extensive list of monomers and were tabulated. Agreement with Hammett σ values and other kinetic and theoretical considerations were found.
Crystallization behavior and melting properties of m‐phenylene group containing polyesters
Authors: Conix A. , Van Kerpel R.
Published: April 2003

Contrary to what has been thought before, polyesters containing meta phenylene groups can be crystallized. The entropies and enthalpies of melting of isomeric poly‐isophthalates and polyterephthalates have been determined. It is shown that the lower crystal melting points of the polyisophthalates are due mainly to a greater entropy of melting.
Polymerization of β‐pinene with ziegler‐type catalysts
Authors: Marvel C. S. , Hanley James R. , Longone Daniel T.
Published: April 2003

The effect of Ziegler‐type catalysts on β‐pinene and camphene was investigated. The use of the cocatalyst system aluminumtriisobutyl–titanium tetrachloride proved to give a higher yield of polymeric material having a higher inherent viscosity than did the use of an equivalent amount of titanium tetrachloride alone. The polymers prepared by Ziegler‐type catalysts appear to be identical with those of the commercial type resin prepared by Friedel‐Crafts catalysis. The use of aluminumtriisobutyl with titanium trichloride gave only a very low yield of methanol insoluble resin. Ziegler‐type catalysts did not initiate polymerization of camphene.
Dead‐end polymerization with redox initiators
Authors: O'Driscoll K. F. , McArdle S. A.
Published: April 2003

A general method has been developed to describe the course of a free radical polymerization initiated by a redox system which produces free radicals via a second‐order rate process. The method is verified experimentally, the system dimethylaniline–benzoyl peroxide being used to initiate styrene polymerization.
Sorption and flow of gases in polyethylene
Authors: Michaels A. S. , Parker R. B.
Published: April 2003

Solubilities and diffusivities of N2, O2, CO2, and He in a variety of polyethylenes were measured in the temperature range 0–50°C. Polyethylene films studied covered a range of crystallinities (43–82%) and branching indices, and were prepared under a variety of known thermal histories. Diffusivities were determined by the time‐lag method; solubilities, by time‐lag, and also by a newly developed and more accurate static method. Solubilities were found to obey Henry's Law; the solubility constants determined by both methods were found to agree within the limits of accuracy, confirming the applicability of the unsteady‐state diffusion equation to essentially isotropic crystalline polymers. For a given gas at constant temperature, the solubility constant is directly proportional to the volume fraction of amorphous material in a polyethylene sample (as determined by density), irrespective of its origin or thermal history; the concept of the crystallites as an impermeable, dispersed phase thus appears justified. Diffusivities were found to vary widely (nearly fivefold) depending on polymer crystallinity and thermal history and were as much as tenfold lower than the values estimated for completely amorphous polyethylene. Application of principles of flow through porous media to this system leads to a conclusion that abnormally low diffusivities arise predominantly from the impedance to gas flow offered by the dispersed crystalline phase. Variations in diffusivity with branching index and thermal history correlate qualitatively with expected corresponding variations in crystallite growth kinetics and shape; the existence of highly anisometric, laminar crystallites in annealed linear polyethylene is indicated from these studies. The combined influence of crystallinity on solubility and diffusivity permits as much as a tenfold variation in gas permeability of polyethylene depending on polymerization method or fabrication process.
Stereoregulated polymerization in the free propagating species. III. Effect of temperature on the polymerization of vinyl chloride
Authors: Fordham J. W. L. , Burleigh P. H. , Sturm C. L.
Published: April 2003

Theoretical treatment had shown that syndiotactic propagation should be slightly favored energetically over isotactic propagation in free radical vinyl chloride polymerization. This prediction has been confirmed experimentally by x‐ray and infrared investigations of vinyl chloride polymers prepared at various temperatures. The initiator was a peroxide, azodiisobutyronitrile, or tri‐n‐butylboron, and had no detectable influence on the x‐ray and infrared results. As the polymerization temperature is lowered, the number of lines or arcs in the x‐ray diffraction pattern and their sharpness gradually increase as a result of the increased crystallinity arising from improved regularity. The regular sequences are indicated to have the syndiotactic configuration from the chain repeat distance. The change in the infrared absorbance ratio of two carbon‐chlorine stretching bands with polymerization temperature can be interpreted in agreement with increasing syndiotacticity at decreasing temperature. With the use of simplifying assumptions, the activation energy difference between isotactic and syndiotactic propagation is estimated to be of the order of one‐half kcal/mole. The stereoregulated free radical polymerization of vinyl chloride is thus qualitatively similar to that disclosed for other monomers.
The critical factors involved in fractionating cellulose acetate by selective adsorption onto carbon
Authors: Miller Bernard , Pacsu Eugene
Published: April 2003

Cellulose acetate can be fractionated by allowing it to be adsorbed from acetone solution onto activated carbon. Sharpest fractions are obtained when small amounts of adsorbent are used successively to take up increments of the total polymer in solution. Each adsorbate is refractionated during elution with a good solvent, and in one adsorption‐desorption cycle the polymer can be divided into a large number of fractions, suitable with certain limitations, for molecular weight distribution analysis. Smaller molecules are both preferentially adsorbed and are the first eluted. Temperature and concentration have some influence on the sharpness of fractionation, but the most critical factor is the ratio of adsorbent to polymer.
Polymer texture: The arrangement of crystallites
Authors: Statton W. O.
Published: April 2003

This is a study of the structural arrangement in a polymer which is on a size level larger than the crystallite but smaller than the spherulite. It is based on the data from x‐ray diagrams at small angles, combined with crystallite dimensions measured from wide‐angle x‐ray patterns. The earlier interpretations of polymer texture by Hess and Kiessig which describe alternating regions of order and disorder appear to be most probable. However, those earlier interpretations are extended by showing that oriented crystalline polymers can be thought of as having aligned elementary fibrils which consist along their length of a regular alternation of bulky and condensed regions. The width of these elementary fibrils is proportional to the width of the crystallites. The amount of regularity of crystallite positions along an elementary fibril and the length of the repeat period are both variable; they depend on the manner of original nucleation and the thermal treatment after nucleation. The length of the long period is a function of the length of the crystallites. These elementary fibrils can pack closely to form a higher state of ordered texture. The amount of close packing is variable; it is optimal after a relaxation treatment. Elongated voids exist between the elementary fibrils. The difference between the effects of original nucleation and thermal after‐treatment is emphasized. Elementary fibrils are proposed as a basic unit of aggregation in polymer melts, solutions, and fibers.
Diffusion measurements on low molecular weight polystyrenes
Authors: Rossi Corrado , Bianchi Estella
Published: April 2003

Measurements of diffusion, viscosity, and cryoscopic determinations of molecular weight were carried out in benzene on eight fractions of polystyrene with low molecular weight (up to about 3,000). These indicate that there is a linear relation between MD and M1/2. This relationship corresponds to the Einstein‐Stokes equation in which the equivalent radius is replaced by the gyration radius. The value of the rotation hindrance factor A calculated from the results of diffusion measurements on polystyrenes with low molecular weights was found to be equal to that calculated from the viscosity data on polymers of high molecular weight in θ solvents, where the swelling effect is nil. This confirms, therefore, that this factor is constant over a wide range of molecular weights. The viscosity data on low molecular weight polystyrene in benzene at 20°C. are very similar to those for samples of high molecular weight in θ solvents. The molecular dimensions of polystyrenes with low molecular weight are therefore unaffected by the swelling effect. The Flory constant Φ, deduced from cryoscopic, diffusion, and viscosity measurements, for the values of M, (h̄2)1/2, and [η], respectively, assumes a value of 3 × 1021. The results have been briefly discussed, from the point of view of the Kirkwood‐Riseman and Debye‐Bueche theories.
The crystallization of modified cis‐polybutadiene
Authors: Trick G. S.
Published: April 2003

From a sample of polybutadiene of high cis‐1,4 content, the microstructure is modified by cis‐trans isomerization or by crosslinking. Measurements of rates of crystallization and melting point are made on the modified samples. An increase in trans content or crosslink density markedly decreases the rate of crystallization at a fixed temperature. It is found, however, that this retardation in rate may usually be accounted for by the depressed melting point of the modified samples.
Diffusion of small molecules in semicrystalline polymers. II. The permeability of unoriented polymer films
Authors: Klute C. H.
Published: April 2003

In a previous publication, the diffusion of small molecules through semicrystalline polymers was compared with the flow of electrical current through a heterogeneous conductor. In this way it was possible to solve the diffusion equations numerically, and to apply the results successfully to the description of the permeability of some polyethylene films as a function of their density. In the present paper, the electrical model has been investigated further and in particular, the effect of blind alleys in the diffusion path has been described. The theory has then been applied to the permeability data published recently by Lasoski and Cobbs for three series of unoriented polymer films differing primarily in crystalline content. Although the experimental data do not conform perfectly to the theory, a large area of agreement has been established, and in view of the complexity of the problem this agreement appears to be satisfactory. The theory developed here requires that the activation energy for permeation be substantially independent of the degree of crystallinity. This has been shown to be in harmony with activation energy data determined on polyethylene specimens of different densities, both by permeability measurements and by nuclear magnetic resonance measurements. The abrupt increase in the apparent activation energy for the permeation of natural rubber films by small molecules below the temperature of crystallization has been shown to be due, most probably, to the reduction of the amorphous volume fraction as the temperature is decreased.
Phase separation in mixed polymer solutions
Authors: Sieglaff Charles L.
Published: April 2003

A phase separation occurs in the system microgel‐linear polymer‐solvent due to an attractive force between microgel molecules. A theory is proposed that attributes the attractive force to the fact that linear polymer is excluded from a shell surrounding the microgel particle and the overlapping of these shells gives rise to a net decrease in the free energy of the system. This decrease in free energy is a function of the free energy of dilution for the linear polymer and of the shape and size of the microgel and linear polymer. The system styrene‐divinylbenzene microgel‐polystyrene‐toluene has been studied. The findings of these studies substantiate the proposed theory.
Polymers of ketene dialkylacetals
Authors: Lal Joginder
Published: April 2003

The observed insolubility of poly(kentene diethylacetal) in chloroform, carbon tetrachloride, and other organic solvents has been found to be due to its crystallinity. Its solubility in hot o‐dichlorobenzene suggests that the polymer is linear and not crosslinked. Poly(ketene di‐n‐butylacetal), also crystalline, was readily soluble in chloroform and carbon tetrachloride, as were also the copolymers prepared from ketene diethylacetal and ketene dibutylacetal.
The effect of polymer density on the diffusion of ethane in polyethylene
Authors: Brandt W. Wilfried
Published: April 2003

Diffusion and solubility coefficient were determined by the time‐lag method for ethane and some other low hydrocarbons in various polyethylenes. The time‐lag method was modified to give significant savings in experimental time and increased precision. Diffusion and solubility coefficients both depend quite strongly on the density and hence on the crystallinity. There is no discernible effect of weight‐average molecular weight, and the effect of polymer chain side branches is found to be small or absent. The thermal and fabrication history of the samples has some effect on the diffusion coefficients. The character of the amorphous regions appears to be independent of the overall density as far as the diffusion process is concerned. The effect of the size of the penetrant molecule is analogous to that found by other authors for rubbers. The findings support the view that small molecule diffusion in polymers requires only short range motions, whereas other mechanisms, such as the dissolution of entanglements, are known to be of importance in melt flow and polymer self‐diffusion.
Small molecule diffusion in cold‐drawn or stretched polymer films
Authors: Brandt W. Wilfried
Published: April 2003

Diffusion and solubility coefficients for several gases in undrawn and drawn films of four high polymers (polyvinyl butyral, nylon 66, polyethylene, and polypropylene) are reported as functions of temperature. In general, the diffusion, solubility, and permeability coefficients of the semicrystalline polymers investigated changed on drawing. The magnitude and direction of such changes depended on the penetrant used and on the experimental temperature. The molecular orientation introduced by stretching in one direction had little or no effect on the diffusion properties of the amorphous polyvinyl butyral. With the other polymers, the changes in void content on cold drawing were usually found to be associated with changes of the opposite sign in the activation energy of diffusion, in consequence of the relatively weak temperature dependence of diffusion in the gas phase. The process of solution of low molecular weight gases in high polymers was found to be more exothermic for those samples which had a comparatively low void content (i.e., drawn polyethylene, undrawn nylon 66, and undrawn polypropylene, as compared, respectively, to undrawn polyethylene, drawn nylon 66, and drawn polypropylene). Possible explanations for this result are given.
The sorption and desorption kinetics of water in a regenerated cellulose
Authors: Newns A. C.
Published: April 2003

The sorption and desorption kinetics for different parts of the hysteresis loop of a water–cellulose system have been determined. Tentative explanations of these kinetics are advanced in terms of changes of polymer structure. It is proposed that during sorption the water first clusters in the more accessible regions of the polymer structure, and that this is followed by a dissolution of network bonds. During desorption the reformation of interchain bonds is hindered by the presence of water and the rigidity of the structure. The proposed structural changes which occur during sorption are somewhat similar to those advanced to explain the viscoelastic properties of the polymer.
Caprolactam polymerization
Authors: Reimschuessel Herbert K.
Published: April 2003

The equilibrium resulting from the water initiated polymerization of caprolactam has been investigated for initial water concentrations (w) in the range, 0.01 ≤ w ≤ 1 (moles H2O/mole caprolactam) at temperatures 220, 235, 250, and 265°C. Based upon the postulate that, at a given temperature, the degree of polymerization is directly proportional to that part of caprolactam converted to linear macromolecules and inversely proportional to the initial water concentration, the following formula, which is a combination of functions, has been derived:
Infrared study of oxygenated groups formed in polyethylene during oxidation
Authors: Luongo J. P.
Published: April 2003

The changes in the molecular structure of polyethylene during oxidation are studied. The presently accepted theory involves a free‐radical process and is based largely on measurements of reaction kinetics with model compounds. Infrared spectroscopy afford an alternate method of following the course of the oxidation reaction. By recording the infrared spectra of polyethylene samples during oxidation, it was possible to follow continuously the formation of various oxygen‐containing groups. During the early stages of oxidation, the formation of hydroperoxides was noted, as was their subsequent decomposition into the predominant secondary oxidation products. The alpha carbon was found to be quite susceptible to oxygen attack after autocatalytic oxidation had begun, and a resulting decrease in methylene content was observed. The results provide a description of the oxygenated molecular groups that form during the initial stages of oxidation and support and broaden the presently accepted mechanism for the oxidative degradation in polyethylene.
Crystalline modifications of cellulose. Part VI. Unit cell and molecular symmetry of cellulose I
Authors: Fisher D. G. , Mann J.
Published: April 2003

A study of the electron diffraction diagram of Valonia ventricosa cellulose has confirmed the conclusions reached by Honjo and Watanabe concerning the size of its unit cell. The a and c axes of the cell are twice the length of those usually accepted for cellulose I. The symmetry of the cell is P1, but the evidence available at present does not allow a decision to be made concerning the symmetry of the molecular chains. Consideration of x‐ray diffraction and infrared spectroscopic data suggests that bacterial cellulose probably has the same unit cell as Valonia ventricosa, but that other native celluloses may have different cells.
The effect of polymer dilution on acid‐catalyzed gelation of partially N‐methylolcarbamoylethylated polyvinyl alcohol
Authors: Nakamura Y. , Koide T. , Negishi M.
Published: April 2003

The effect of polymer dilution on the acid‐catalyzed gelation of partially N‐methylolcarbamoylethylated polyvinyl alcohol has been studied viscometrically and chemically. The result that the higher the degree of dilution the greater the extent of reaction at gelation, especially in the polymer concentration below 15% by weight, indicates that a certain increase of intramolecular crosslinking with dilution occurs. However, sufficient agreement with Kilb's theory could not be found. Also, even when the extent of reaction at gelation was extrapolated to infinite concentration of polymer, it was far greater than that obtained from Flory's theory. The discrepancy may presumably be attributed to the fact that in addition to the intramolecular crosslinking, all the methylol groups on the polymer chains which are coiled, entangled, and strongly solvated prior to crosslinking are not equally reactive sterically.
Isomorphous replacement in copolyamide systems: Adipic and terephthalic acids
Authors: Yu Arthur J. , Evans Robert D.
Published: April 2003

Copolyamides with mixtures of adipic and terephthalic acids in various mole rations and three types of diamine were prepared, and a melting point vs. composition curve for each system was constructed. The three types of diamine were: (1) straight‐chain aliphatic diamines with six to twelve carbon atoms, (2) m‐xylylenediamine, and (3) 4,4‐dimethyl‐1,7‐heptanediamine. These curves for copolyamides containing straight chain aliphatic diamines had no minimum at the intermediate ranges of composition. The curve for m‐xylylene diamine had a minimum at a point corresponding to 77 mole‐% of adipic acid. The copolyamide containing 4,4‐dimethyl‐1,7‐heptanediamine was not crystalline. Evidence suggested that isomorphous replacement of adipic and terephthalic acids in copolyamide systems was greatly influenced by the structure of the diamine, possibly through the bulk effect of its substituents on chain‐packing.
Synthesis kinetics and sequence distribution in synthetic polynucleotides
Authors: Simha Robert , Zimmerman J. M.
Published: April 2003

A simple kinetic model for the formation of a nucleotide homopolymer is presented and evaluated. It consists of an initial dinucleotide formation followed by growth through further monomer addition and a competitive phosphorolysis. The molecular weight distribution is narrow up to the first 10–30% conversion and broadens on approach to equilibrium. From the equilibrium amounts of phosphate liberated, the final average molecular weight, and the time pattern of the synthesis, it is possible to obtain estimates of the rate constants. Turning to copolymers, the analysis of experimental data on sequence frequencies in an AU polymer in terms of addition probabilities indicates the existence of a penultimate effect, and a consistent set of four such probability parameters is derived. Finally, we consider a set of rate equations for binary copolymer formation suggested by these results. Their solution will permit a calculation of sequence distributions by utilizing kinetic experimental results exclusively.
Studies of the ethylenediamine‐cellulose complex. II. Stability of the complex
Authors: Segal Leon , Loeb Leopold
Published: April 2003

The ethylenediamine‐cellulose complex in the dry state has a sharp characteristic x‐ray diffraction pattern and usually contains from 17 to 26% diamine when freshly prepared. High vacuum and elevated temperature failed to reduce this below 17%. Rapid decomposition of the complex as evidenced by the x‐ray diffraction patterns was associated, however, with storage at room temperature in a paper envelope. A slow decrease in diamine content accompanied by shifts in the x‐ray pattern resulted from storage under controlled conditions of temperature and humidity. An especially dried sample rapidly gained weight at first when exposed to the open air, then very slowly lost weight. There is an indication from the data that a 2:1 complex is present with two anhydroglucose units per diamine molecule, strongly suggesting a hydrogen‐bonded crosslink. The increase in fiber cross‐sectional area and the distention of the crystal unit cell are of an order of magnitude to suggest that complex formation can account for most of the fiber swelling.