bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear magnetic resonance spectra of some fluorine‐containing polymers
Authors: Naylor R. E. , Lasoski S. W.
Published: April 2003

High resolution nuclear magnetic resonance spectra have been measured for the F19 resonance in some fluorine‐containing polymers. These data have shown that the F19 resonance frequency depends on the electronegativity of the other substituents on the carbon atom, in a manner similar to that found for small molecules. The resonance frequency also is dependent on substituents attached to adjacent carbons in a way not easily explained by inductive effects. It is hypothesized that these latter shifts may be due to direct potential interaction. The above generalizations, together with other supporting evidence, were utilized to assign a small peak in the spectrum of polyvinylidene fluoride to a head‐to‐head structure. This structure is present to the extent of 8–10%.
The effect of temperature on the equilibrium state of actin solutions
Authors: Asakura Sho , Kasai Michiki , Oosawa Fumio
Published: April 2003

The effect of temperature on the equilibrium level of the G–F transformation of actin was investigated in solutions containing very low concentrations of salts. It is shown by physical methods that the G–F transformation is favored by higher temperatures and the F–G transformation by lower temperatures within the range 0–20°. On the basis of the assumption that the transformation is a reversible condensation, the critical actin concentration was obtained was a function of temperature in a given solvent. Analysis of results by a conventional method gives a positive enthalpy change of the order of 10 kcal./mole actin for the GF transformation. The overall reaction of the GF transformation is postulated as a transition of hydrated G–actin into dehydrated F–actin plus free water, with net increases in enthalpy and entropy. A chemical method is employed for determining G–actin concentration in equilibrium solutions. Almost all actin other than F–actin filaments must be G–actin (ATP‐actin).
Structure of F–actin solutions
Authors: Kasai Michiki , Kawashima Hirotaka , Oosawa Fumio
Published: April 2003

For the purpose of investigating the structure of solutions of muscle protein F–actin and the effect of external force on this structure, simultaneous measurements of rigidity, viscosity, and birefringence were made under rotation and oscillation at very low rates of shear, and as a result a consistent picture of F–actin solutions has been obtained. The F–actin solutions of various concentrations are made by adding a small amount of magnesium ions to a salt‐free G–actin solution. Rigidity, viscosity, and degree of flow birefringence all increase in proportion to the F–actin concentration. Even at very low concentrations, F–actin solutions have a large rigidity. This rigidity is found to be due to a network structure of semiflexible F–actin filaments composed of very many G–actin molecules. The linkage‐to‐linkage length and the flexibility of filaments are estimated from experimental data. Rotation at very low rate of shear causes rigidity and viscosity to decrease rapidly. All results are reasonably explained by assuming that the filaments are elongated and then linkages are detached by shear of rotation. With a decrease in the number of linkages, F–actin filaments are completely oriented. Once attained as a result of shear, the orientation decreases very slowly on standing and gives an anomalous decay curve, probably as a result of setting of the network structure of oriented filaments. At high concentrations of F–actin, a spontaneous orientation occurs. Hysteresis phenomena of F–actin solutions observed under various mechanical treatments are all attributable to formation and detachment of linkages between semiflexible F–actin filaments.
Flow orientation and fracture strength of a model linear hard polymer solid
Authors: Hsiao C. C.
Published: April 2003

A mathematical analysis is given to describe the effect of prior large flow orientation on the variation of the fracture strength of a model linear hard polymer solid. For the simple state of uniaxial orientation, the fracture strengths in the direction of orientation and that perpendicular to the direction of orientation are evaluated as functions of the strain change and the strength of the unoriented material. The results indicate an increase of strength in the direction of orientation and a decrease of strength perpendicular to the direction of orientation as the degree of orientation increases.
Tables of light‐scattering functions for polymers
Authors: Beattie W. H. , Booth C.
Published: April 2003

Tables are presented for use in the determination of molecular weights and major dimensions of polydisperse polymers in solution from light scattering dissymmetry measurements. The calculations are based upon the Gaussian coil model of the polymer molecule.
Measurement of internal stresses by radiofrequency spectroscopy
Authors: Gutowsky H. S. , Bernheim Robert A. , Tarkow Harold
Published: April 2003

The shift with pressure of the Cu63 pure quadrupole resonance frequency in Cu2O has been used to measure the stress developed within a resin due to curing. The method has possibilities for general use in the measurement of internal pressure. It involves the incorporation within a sample of an inert, insulating powder containing nuclei from which a pressure‐sensitive pure quadrupole resonance frequency may be detected. For sample of Epon 828 cured at 80°C for 1½ hr., a stress corresponding to an internal pressure of 2300 ± 400 psi was detected. In addition to the frequency shift of the Cu63 resonance observed in the resin, the absorption was broadened, indicating that a distribution of internal pressures existed.
Polymer NSR spectroscopy. II. The high resolution spectra of methyl methacrylate polymers prepared with free radical and anionic initiators
Authors: Bovey F. A. , Tiers G. V. D.
Published: April 2003

Spectra of methyl methacrylate polymers in chloroform solution at 90° show three α‐methyl proton peaks. Measurements of their areas in spectra of polymers prepared with free radical and anionic initiators indicate that these may be attributed to (1) isotactic sequences (ddd or lll), (2) syndiotactic sequences (ldl or dld), and (3) heterotactic sequences (ldd, dll, ddl, or lld). The conformation and stereochemical configuration of the chains may thus be examined with considerable discrimination; degrees of regularity, block sizes, etc. appear to be determinable. Free radical polymers of methyl methacrylate are found to be predominantly syndiotactic, whereas those produced with anionic initiators. such as n‐butyllithium, are shown to be predominantly isotactic, in agreement with the findings of others. The backbone methylene resonance also shows striking changes with chain stereochemical configuration, such as to provide absolute, independent confirmation of the assigned structures.
Thermodiffusion distribution curve of polychloroprene
Authors: Kössler Ivo , Štolka Milan
Published: April 2003

Thermodiffusion distribution curves of polychloroprene have a characteristic course with two inflection points and are similar to distribution curves obtained by fractional precipitation. By use of an apparatus with a series of sampling holes along a continuous diffusion chamber, more homogeneous fractions were obtained rapidly than by use of the cascade method in a five‐reservoir apparatus. In the fractionation of polychloroprene, a vertical temperature gradient in the apparatus and an additional separation of the fractions of higher molecular weight which is based on the “extraction” of the polymer into the pure solvent aided separations and yielded a better distribution curve. Additional separation can be carried out in the apparatus without taking out the sample if the part the apparatus filled with the solvent has no horizontal temperature gradient in the first hours of the separation process.
Infrared spectra and crystal structures of polyamides
Authors: Miyake Akihisa
Published: April 2003

Infrared spectra and x‐ray diffractions of 24 nylons were investigated. The positions of the NH stretching and the amide I bands indicate that the amide groups form hydrogen bonds almost completely, irrespective of the number of CH2 groups. The position of the amide V band has been correlated with the crystal structure. Nylons characterized by a predominant peak at 725 cm.−1 show only one reflection in the x‐ray photograph. Odd‐odd nylons belong to this type (γ form). Even‐odd and odd‐even nylons also take this γ form when prepared from the melt through quenching. When cast from solution, they seem to take a new form. Amino acid nylons with an odd number of CH2 groups have a tendency to take the γ form. Three bands closely related with the position of the amide V band are found.
Stepwise and catalytic polymerization of butadiene by organosodium reagents
Authors: Morton Avery A. , Lanpher Edward J.
Published: April 2003

A comparison of the addition of organosodium reagents to 1,1‐diphenylethylene with their polymerization of butadiene helps to distinguish between stepwise and catalytic polymerization. In the best example of the latter, the failure to isolate intermediate steps and the high proportion of 1,4‐unions, (as much as is found in free radical polymerizations) are contrary to the established reaction as described in the literature on the behavior of these reagents. The process is reexamined in the light of present information and ideas. Initiation is the result of bond stretching, which can be far enough to produce radicals. Adsorption on solid surfaces seems to control polymer growth. Details are suggested for all operations in the alfin catalytic process, and a connection with stepwise polymerization is shown.
Polymerization reactions of the acrylate and methacrylate esters of alcohols from jojoba oil
Authors: Marvel C. S. , Paisley David M. , Khattab Ghazi M. A. , Bickford W. G. , Fore Sara P.
Published: April 2003

The acrylic and methacrylic acid esters of the mixed alcohols of jojoba oil have been prepared. These esters polymerize and copolymerize in the pattern of other acrylate and methacrylate esters. All are somewhat soft and show some promise as adhesives. The polymers crosslink and become insoluble on exposure to air.
The polymerization of propylene oxide
Authors: Simons Donald M. , Verbanc John J.
Published: April 2003

Polypropylene ether glycol synthesized by the base‐catalyzed polymerization of propylene oxide contains two monofunctional species: one is acetoxyl‐terminated, the other allyl or propenyl ether‐terminated. The presence of ester function is indicated by a sharp absorption peak at 5.75 μ, characteristic of ester carbonyl, in the infrared spectra of the glycols. The ester is readily removed by alkaline hydrolysis. It was identified as an acetoxyl endgroup, arising from anionic attack on vinylidene chloride, a minor impurity in the propylene oxide from which the glycols were prepared. The unsaturated ether functions result from two base‐catalyzed rearrangements. Propylene oxide is converted to allyl alcohol which, in the polymerization system, initiates polyether chains bearing allyl ether groups on one end. Some of these are subsequently rearranged to propenyl ethers in the basic medium. This latter reaction is an equilibrium in which the propenyl ether is the favored specie.
Halobenzenes as sensitizers for the radiation‐induced polymerization of styrene
Authors: Brown Daniel W. , Wall Leo A.
Published: April 2003

Halogenated benzenes, carbon tetrachloride, and other compounds have been used to sensitize the gamma‐ray‐induced polymerization of styrene. Benzene and fluorobenzenes are about equally effective, while the data from solutions of mono‐ and dihalogenated benzenes indicate that the order of increasing sensitivity to radiation is: fluorobenzenes < chlorobenzenes < bromobenzenes < iodobenzenes. One halogen is less effective than two, and the ortho isomers are more effective than the meta and para. The relations between the G values for radical production in the solutions and the electron fractions of solvent are linear only for benzene and the monohalogenated aromatics. With very highly halogenated benzenes and carbon tetrachloride, the departure from linearity is very marked. Significant sensitization is observed at very low electron fractions with the highly halogenated materials, except with hexafluorobenzene, which appears to be very stable to radiation. The generalizations concerning the effects of the kind and number of substituents in mono‐ and dihalogenated benzenes are not valid for more highly halogenated benzenes. Much of the curvature observed at high concentrations of carbon tetrachloride is apparently due to changes in the rate constants as the monomer concentration is changed. At low concentrations this is not the case with carbon tetrachloride and presumably also with the other highly halogenated materials. Various reaction mechanisms are considered, and one is advanced that reproduces many of the important features of the observed data.
Nonterminated polymeric anions: The initiation of polymerization of certain polar monomers
Authors: Graham Roger K. , Panchak John R. , Kampf Mary J.
Published: April 2003

The use of nonterminated polymeric anions in tetrahydrofuran solution at low temperatures to initiate the polymerization of a second monomer to form block copolymer has been extended to several polar monomers. Anions of polystyrene and of poly‐(methyl methacrylate) have been shown to initiate the polymerization of alkyl methacrylates, isopropyl acrylate, methacrylonitrile, and acrylonitrile. Isopropyl acrylate when initiated with sodium naphthalene under similar conditions gives some nonterminated polymeric anions, but nonpolymeric or low‐polymeric initiator is also present. The criteria for order of addition of monomers and proof of block copolymer formation are discussed.
Isophasic transitions in polytrifluorochloroethylene
Authors: Baccaredda M. , Butta E.
Published: April 2003

Through determination of dynamic mechanical properties (sound velocity and damping factor) over the temperature range from −160 to 200°C. and frequency range from 4 to 16 kcycles/sec. evidence is found for the existence of two isophasic transition temperatures in polytrifluorochloroethylene: one at −58°C. and the other at 50°C. Both transitions are associated with motion in the main chain of the polymer, which is first excited at −58°C. for the molecular segments which are more freely rotating (because they are located near network defects) and at 50°C. for the majority of the chain elements in the amorphous regions. The transition point at −58°C. is regarded as the glass transition temperature for polytrifluorochloroethylene. The experimental results are discussed on the basis of the structure of the polymer examined, and a comparison is made between dynamic mechanical data and data obtained by measurements of specific volume, nuclear magnetic resonance, and dielectric losses.
Nylon single crystals
Authors: Geil P. H.
Published: April 2003

Several polyamides crystallize from dilute glycerin solution as single crystals and spherulites possessing a lamellar structure. The crystal of nylon 6 are rhombohedral and thicken by spiral growth of lamellae from screw dislocations. Electron diffraction patterns indicate that the molecules are folded within the lamellae, which are 50–100 A. thick. The single‐crystal electron diffraction spacings correspond to those of the high‐temperature crystalline modification as determined by x‐ray diffraction. The unit cell, however, does not show the hexagonal symmetry generally ascribed to the high‐temperature lattice. Spherulites of nylon 6 are composed of fragmented lamellae in which the molecules are folded and are in the low temperature crystalline lattice. Preparations of nylon 66 and 610 contain structures consisting of single‐crystal lamallae rolled or folded together. These structures also thicken by spiral growth of the lamallae from screw dislocations. The molecules are folded and are in the low‐temperature lattice, although there is some evidence of the high‐temperature modification with nylon 610.
The concentration dependence of the self‐diffusion coefficients of strontium ion in aqueous polystyrenesulfonic acid solutions
Authors: Hardy E. P. , Steigman J.
Published: April 2003

The diffusion coefficients of strontium in 10−4M aqueous solutions of polystyrenesulfonic acid were measured at 26°C. The coefficients were low, about 0.15 X 10−5 cm.2/sec., until strontium equivalent to one‐fifth of the sulfonates had been added. They then increased relatively rapidly, to about 0.7 X 10−5 cm.2/sec., as the concentration of strontium was increased to 10−4M. These results are interpreted to mean either that the binding of counterions to a polyelectrolyte is limited to parts of a chain and is not related to the chain as a whole, or else that there is a recurring regularity of structure in the atactic polystyrene sulfonic acid which limits binding of counterions to a fraction of the total charged sites.
The use of infrared spectra in the preparation and characterization of vinylcycloalkanes
Authors: Borchert A. E. , Overberger C. G.
Published: April 2003

The purpose of this paper is to report the application of infrared spectroscopy to the preparation and polymerization of vinylcyclopropane, vinylcyclopentane and vinylcyclohexane. Carbon‐hydrogen stretching frequencies in the 3005 and 3080‐cm. −1 regions were utilized in the evaluation of products and reactions. Precursors to vinylcyclopropane and these bands afforded independent evidence for the retention of the three‐membered ring in crystalline polyvinylcyclopropane. Absorptions characteristic of the cyclopentyl and the cyclohexyl groups were found to be of less utility in the analysis of processes leading to crystalline polyvinylcyclopentane and crystalline polyvinylcyclohexane, while bands in the 3020–3081‐cm. −1 region aided the establishment of type and location of unsaturation in several monomers.
Effect of type of catalyst on structure of poly(β‐vinyloxyethyl methacrylate)
Authors: Lal Joginder , Devlin E. F. , Trick G. S.
Published: April 2003

Infrared analysis and glass transition temperature measurements on the polymers obtained from β‐vinyloxyethyl methacrylate with stannic chloride (cationic) and titanium tetrachloride–triisobutyl aluminum (Ziegler‐type) catalysts indicate that these polymers have essentially the same structure, comprising a polyvinyl ether backbone with pendant methacrylatoethyl groups. The polymer obtained with lithium–tributylamine (anionic) catalyst has a different structure involving a methacrylate backbone with vinyloxyethyl pendant groups. These data suggest that in the polymerization of this monomer with the Ziegler‐type catalyst the mechanism of polymerization is cationic. Polymerization with triethylboron gives a crosslinked material similar in structure to the peroxide‐catalyzed polymer.
Polymyrcene
Authors: Marvel C. S. , Hwa Charles C. L.
Published: April 2003

Myrcene has been polymerized by treatment with triisobutylaluminum and titanium tetrachloride, triisobutylaluminum and vanadium trichloride, and by free radical initiation in emulsion systems. The polymers thus obtained vary in molecular weight range but all have a predominantly 1,4‐arrangement of the diene unit in the polymer chain. It is not possible to say whether this is a cis or trans structure on the basis of present information. Different samples of the polymyrcene obtained by the action of triioso‐butylaluminum and vanadium trichloride have inherent viscosities of 2 to 5.5. Myrcene polymerized by boron trifluoride etherate appears to have a cyclic recurring unit and is probably identical in structure with polymers prepared from β‐pinene by cationic initiation.
Polyurethanes. I. The solution polymerization of diisocyanates with ethylene glycol
Authors: Lyman Donald J.
Published: April 2003

Contrary to statements in the literature, it was found that useful polyurethanes could be prepared by the reaction of a diisocyanate with ethylene glycol. In this investigation m‐phenylene diisocyanate, p‐phenylene diisocyanate, 2, 4‐toluene diisocyanate, methylene bis(4‐phenyl isocyanate), durene diisocyanate, biphenylene diisocyanate, bis(4‐isocyanatophenyl) sulfone, 4,4′‐diisocyanatodiphenyl ether, 3,3′‐dimethyl‐4,4′‐biphenylene diisocyanate, and 1,5‐naphthalene diisocyanate reacted with ethylene glycol in solution to give the corresponding polyurethanes. The reaction of methylene bis(4‐phenyl isocyanate) with ethylene glycol in dimethyl sulfoxide/4‐methylpentanone‐2 (50/50) gave a high molecular weight, linear polyurethane that could be solvent‐cast into films and dry‐spun into fibers. These films and fibers showed properties similar to those of existing commercial films and fibers.
The polymerization of allylbenzene with heterogeneous catalysts
Authors: D'Alelio G. F. , Finestone A. B. , Taft L. , Miranda T. J.
Published: April 2003

Data are presented for the preparation of high molecular weight and crystalline polymers of allylbenzene. With specific cationic catalysts, low molecular oligomers of β‐methylstyrene are produced. With anionic catalysts, such as sodium and cesium, nonpolymerizable metallates are obtained from which the monomer may be regenerated. Stereospecific catalysts, prepared from triethylaluminum and titanium halides have been investigated as catalysts for allylbenzene. Solid polymers of allylbenzene have been obtained only under very specific catalytic conditions.
Polyethylene crystallinity from x‐ray studies
Authors: Kakudo M. , Ullman R.
Published: April 2003

An x‐ray determination of crystallinity of polyethylene has been carried out. The emphasis in this investigation has been on setting up an experimental procedure which is both theoretically sound and experimentally feasible. It has been shown that the per cent crystallinity is best determined by determining the percentage of amorphous material and subtracting this from one hundred. The importance of monochromatization has been discussed, as well as the need for various corrections arising from incoherent scattering, absorption of x‐rays, and sample expansion. A few numerical results are reported.
Polymerization of methacrylonitrile with potassium in ammonia
Authors: Overberger C. G. , Yuki H. , Urakawa N.
Published: April 2003

The polymerization of methacrylonitrile with potassium and potassium amide in liquid ammonia has been investigated. The results indicated that the degree of polymerization was approximately independent of the monomer and the catalyst concentrations. Furthermore, unlike lithium amide catalysts, potassium amide in ammonia initiates the polymerization of methacrylonitrile as rapidly as potassium does. The results with potassium amide catalysis were similar to those in potassium catalysis. When methacrylonitrile was reacted with potassium in ammonia, small amounts of isobutyronitrile could be detected in the reaction product. On the basis of these results, it is suggested that part of the initiator system in the methacrylonitrile—potassium—ammonia system is potassium amide produced in situ. This is similar to the styrene—potassium—ammonia system studied by Wooding and Higginson. The major termination reaction proposed is a transfer to monomer and to a small extent to the solvent ammonia. Methacrylonitrile was polymerized rapidly to a colorless polymer by initiation by potassium hydroxide. The reaction appears to be slower than that with potassium and potassium amide as catalysts and is retarded by trace amounts of water.
Determination of polycaprolactam fiber crystallinity by x‐ray differential‐filtration method
Authors: Urbańczyk G. W.
Published: April 2003

An x‐ray method for determination of polycaprolactam fiber crystallinity is described. The basis of the method is the differential filtration of the radiation diffracted by the specimen. The use of method is illustrated by a determination of crystallinity of two fiber samples.
Application of an expanded copolymerization theory to systems involving α‐methylstyrene
Authors: Ham George E.
Published: April 2003

It was shown that the copolymer system α‐methylstyrene—acrylonitrile conforms to the equation:

where r1 = K—aaaa/K—aaab = 0, r1′ = K—baaa/K—baab = 0.05, r1″ = K—baa/K—bab = 0.13, and r2 = K—bb/K—ba = 0.06. The system α‐methylstyrene—fumaronitrile was found to obey the equation:

where r1 = K—aaaa/K—aaab = 0, r1′ = K—baaa/K—baab = 0.05, r1″ = K—baabaa/K—baabab = 0.12, and r1‴ = K—babaa/K—babab = 0.17. These results demonstrated the inability of α‐methylstyrene to add to a sequence of three α‐methylstyrene units.
Polycondensation of alkylene dichlorides with alkylene polyamines
Authors: Suen T. J. , Senior A. , Swanson D. L. , Jen Y.
Published: April 2003

Polycondensation of ethylene dichloride and 3,3′‐iminobis(propylamine) resulted in high molecular weight soluble polymers or insoluble gels, depending on the ratio of the reactants and the extent of reaction. It is shown that the functionality of a polyfunctional compound containing groups of unequal reactivities can be determined experimentally. The effective functionality of 3,3′‐iminobis(propylamine) was found to be 2.9 from gelation studies and 3.5 based on the relative reaction rates of the primary and secondary amino groups. By using the effective functionality value, the reaction kinetics can be treated in a simple manner. A typical soluble polymer formed has a low intrinsic viscosity and a very high M̄w/M̄n ratio. Condensations of other alkylene dichlorides and alkylene polyamines demonstrated the validity of Carothers' rule that high polymers will not result if formation of 5‐ or 6‐membered rings is possible.
A theory of gel formation with terfunctional interunit junction
Authors: Fukui Kenichi , Yamabe Tokio
Published: April 2003

A theory related to the molecular size distribution and gel point in the polymerization by successive formation of terfunctional interunit junctions is presented. This type of polymerization may be realized in three‐dimensional networks containing isocyanuric and s‐triazine rings from polyisocyanate and polynitrile compounds, respectively. The gel point is obtained as αcrit equals; 1/2(f − 1), while in the polymerization due to bifunctional interunit junction it had been given by Flory and Stockmayer as αcrit equals; 1/(f − 1), where αcrit is the fraction of reacted groups at the gel point and f is the number of functional groups borne by a monomeric unit.
Poly(4′‐vinyl‐cis‐benzalacetophenone)
Authors: Unruh C. C.
Published: April 2003

The trans isomers of both poly(4′‐vinylbenzalacetophenone) and a model compound, 4′‐ethylbenzalacetophenone, readily form the corresponding cis isomers on exposure of their solutions to ultraviolet radiation. The cis isomers can be isolated and, in the case of the nonpolymeric material, the cis form reverts readily to the trans form upon addition of a trace of hydrogen chloride. The polymer, however, only partially reverts to the trans form. An explanation is offered to account for this, namely, that, even in dilute solution, intramolecular dimerization occurs in the coiled polymer. These tie points in the polymer chain prevent complete reversion to the trans form.
Mechanism of amine crosslinking of fluoroelastomers. I. Solution studies
Authors: Paciorek K. L. , Mitchell L. C. , Lenk C. T.
Published: April 2003

Solution studies of Kel‐F elastomer and Viton A with various amines have shown that dehydrohalogenation is the primary step in crosslinking and usually proceeds at temperatures lower than those required for gelation. There is a difference in the reactivity between the two polymers; dehydrohalogenation and gelation occur more readily with Kel‐F elastomer than with Viton A. The rate of reaction and temperature at which gelation is observed depend upon the type of amine. Mechanisms of crosslinking are proposed and discussed.
On the mechanism of ozone degradation of SBR
Authors: Delman A. D. , Simms B. B. , Ruff A. E.
Published: April 2003

The reaction mechanism of the ozone attack of SBR copolymers was studied to obtain information for use in the development of elastomeric materials having improved resistance to deterioration in service. Techniques of ultracentrifugation and viscometry were utilized to follow molecular changes induced by ozone. Chemical changes were investigated by measuring variations in active oxygen group concentration. Results suggest that the autocatalytic degradation of uninhibited SBR was initiated by a random ozone attack at a double bond on the unozonized chain, producing an ozonide which decomposed spontaneously, forming small segments with activated chain‐ends. This primary reaction, in the presence of oxygen, activated an α‐methylenic chain cleavage process which was terminated when the molecules were degraded to a limiting size, where no more R. radicals were formed from α‐methylenic groups. The reaction was also terminated when oxygen was removed from the system.
Hydrogen and deuterium exchange of polypropylene
Authors: Case L. C. , Atlas J. D.
Published: April 2003

“Isotactic” and “atactic” polypropylenes in cyclohexane solution have been exchanged with hydrogen and deuterium in the presence of a large‐pore‐size nickel—kieselguhr catalyst. The resulting polymers were freed from catalyst, precipitated, pressed into films, and the density and stiffness determined. If the “isotactic” polymer were actually stereoregular, it would be expected from studies of model compounds that racemization of the tertiary carbon atoms in the chain would occur upon exchange. The racemization of the polymer would lead to a less “isotactic” polymer, and a drop in density and stiffness. The deuterium content of the polymer was determined by the refractive index of the water of combustion. The exchange values were as high as 3.0%. If all this deuterium were in the tertiary positions, about 18% of the tertiary carbons in the chain would be racemized. However, no detectable loss of stiffness or density occurred. This work failed to confirm the theory of isotacticity. The results, although no conclusive, seem to cast doubt on the theory.
Polymer fractionation. A comparison of successive precipitation fractionation and precipitation chromatography
Authors: Booth C.
Published: April 2003

Successive precipitation fractionation data have been analyzed by the statistical method. The resulting molecular weight distribution is compared to the distribution obtained from precipitation chromatography data using the conventional analysis. The agreement between the two distributions is good.
The oxidative degradation of polyethylene. II
Authors: Beachell Harold C. , Tarbet G. Wilfrid
Published: April 2003

The nature and extent of the atmospheric oxidation at elevated temperatures of various polyethylenes in the form of thin films has been studied. A grating spectrophotometer covering the 5–7 μ region was used to follow the production of carbonyl groups during the oxidation. The use of deuterated polyethylenes supports the formation of aldehydes, in addition to ketones, in the primary oxidation step after the production of hydroperoxides. Normally the aldehydes and some of the ketones are oxidized to acids, which react with hydroxyl groups produced in other reactions to give esters. The branched polymers start to oxidize sooner than the linear ones, but when the latter do start to oxidize the rate and extent are greater. None of the accepted mechanisms suggest that linear chains should oxidize rapidly, so it is probable that the high crystallinity or degree of order provides the resistance to oxygen; when this order is lost, oxidation takes place and the fast reaction ensues. This also occurs in the branched materials, but since they have already partially oxidized and have a lower crystallinity, the effect is not so marked.
Polymerization of methacrylonitrile induced by ionizing radiation
Authors: Tabata Yoneho , Oda Eisuke , Sobue Hiroshi
Published: April 2003

The polymerization of methacrylonitrile induced by ionizing radiation was investigated in bulk in the temperature range of 40 to −196°C. It was found from this investigation that two different polymerization mechanisms can exist in the polymerization under the same conditions at different temperature regions. The two different polymerization phenomena at room and at low temperature regions proceed by two different mechanisms: ionic and radical. It was found that the apparent activation energy in bulk polymerization is 6.3 kcal./mole in the 40 to −10°C. range and ca. 0.3 kcal./mole for polymerization initiated by high energy radiation in the −40 to −196°C. range. The effects of additives in the polymerization at both temperature regions were investigated. The viscosity of the polymer was measured in acetone solution at 25°C. and the infrared spectrum of the polymer was also measured. The authors believe from these experiments that the polymerization at room temperature proceeds by a radical mechanism and that the polymerization in the solid state at low temperature proceeds by an ionic mechanism. An important possibility was emphasized that a stereoregular ionic polymerization would be possible even in solid state of monomer by ionizing radiation.
Ziegler polymerization of 4‐methyl‐1‐pentene
Authors: Watt William R.
Published: April 2003

Polymerization of 4‐methyl‐1‐pentene was carried out at 40°C. in n‐heptane with the use of catalysts prepared from TiCl4 and triethylaluminum or triisobutylaluminum. Yield of polymer at the end of a fixed time (4 hr.) was used as a measure of catalyst activity. Solubility of the polymer in boiling heptane was used as a measure of stereospecificity. Both activity and stereospecificity are strongly affected by the ratio of aluminum alkyl to titanium tetrachloride in the catalyst. Yield was greatest for catalysts in which Al/Ti was between 1.2 and 2.0. Highest percentage of heptane‐insoluble polymer was obtained at Al/Ti equals; 1. Stereospecificity was little affected by the monomer/catalyst ratio in the ranges studied. Catalysts prepared from triethylaluminum gave slightly higher percentages of heptane‐insoluble polymer than did triisobutylaluminum.
The glass temperature of semicrystalline polymers
Authors: Newman S. , Cox W. P.
Published: April 2003

This study focuses attention on the relation between the glass transition temperature, Tg, of the amorphous phase of semicrystalline polymers and the morphological state of the polymer. By use of dynamic mechanical and thermal distortion tests, the influence of stereospecificity; crystallinity; and, orientation in the absence and presence of crystallinity, has been assessed for crystallizable polystyrene (CPS). These results, together with some analogous data on crystallizable polypropylene (CPP), are compared to published information on other polymers. Studies of quenched, oriented CPS by thermal distortion tests under load indicate that the retractive stress and external load are the prime factors in determining the glass temperature as measured by this type of test. The influence of Tg of the configurational state, sorted out from the other two factors, is shown to be small. For CPS, an increase in Tg of 5–15°C., depending on the method of test, is observed to accompany crystallization. An increase of 15–25°C. in Tg, relative to amorphous CPS, is noted for samples annealed in the stretched condition. The combined effect of crystallinity and orientation is significantly greater than the sum of the individual effects; a mechanism is postulated for this synergistic behavior. The breadth of the transition of oriented, annealed samples appears to depend on the direction of test relative to the direction of stretch. Stereo‐specificity in polystyrene and polypropylene appears to have a negligible influence on Tg.
Degradation of poly(ethylene oxide)
Authors: McGary C. W.
Published: April 2003

The degradation of high polymers of ethylene oxide in aqueous and organic solutions is accelerated by strong acids, certain oxidizing agents, ultraviolet light, and certain heavy metal ions. The effectiveness of the latter two components is related to the solution stability of various polymer samples upon long‐term, natural aging. These facts are interpreted by assuming that poly(ethylene oxide) degrades primarily by autoxidation, giving hydroperoxides which decompose by polymer chain cleavage. Certain oxidizable materials and compounds which form stable free radicals are effective in retarding the solution viscosity decrease. Aqueous polymer solutions containing alcohols, such as isopropyl alcohol, are very stable to all of the normally detrimental aging conditions. The effectiveness of the alcohol is related to the theoretical ease with which the α‐hydrogen atom is extracted, and, consequently, these effects are interpreted in view of the selective autoxidation of the alcohol present. Other types of stabilizers were investigated.
Isolation of high molecular weight amylose by dimethylsulfoxide dispersion
Authors: Killion Philip J. , Foster Joseph F.
Published: April 2003

The problem of the isolation of the amylose component of starch under conditions of minimal degradation has been re‐examined. It is confirmed that aqueous leaching of granules under anaerobic conditions as advocated by Gilbert and co‐workers leads to amylose of high intrinsic viscosity and very high molecular weight (M̄w > 1 × 106), and of high degree of digestion by crystalline β‐amylase (∼95%). However, yields are poor under practical conditions. An alternative procedure is described based on the fact that fresh undried potato starch can be quantitatively dispersed in dimethylsulfoxide by prolonged contact at room temperature. Addition of butanol to this solution results in precipitation of both amylose and amylopectin components. This precipitate can, however, be redissolved in water and the amylose component separated in the customary manner by butanol complexing (following a brief heating of the aqueous solution to 70°C). After one recrystallization a product has been attained which possesses an iodine binding capacity of 18.9 mg./100 mg., and intrinsic viscosity and M̄w even higher than in case of the material leached by water under anaerobic conditions. Further, the high degree of digestibility by crystalline β‐amylase (>95%) indicates negligible chemical alteration of the normal linkages under the preparative conditions.
Studies on polyoxypropylene glycols. Part III. Equilibrium swelling of crosslinked polyurethane elastomers
Authors: Conway B. E. , Tong S. C.
Published: April 2003

Swelling equilibrium measurements on three polyurethane elastomers prepared from a polyoxypropylene glycol are reported. Values of the equilibrium swelling volume v2 have been obtained by determinations of both weight and dimensional changes. The solvents used were methanol, 1,4‐dioxane, benzene, and water. In the case of methanol, the temperature coefficients of swelling volumes were derived. Values of the polymer‐solvent interaction constant χ are obtained from dv2/dT and v2 and also from v2 and measurements of elasticity described in Part IV. The relationship between the swelling volume and the elastic retractile force in extended samples of the elastomers is discussed.
Degradation and crosslinking in irradiated polyamides and the effect of oxygen diffusion
Authors: Zimmerman Joseph
Published: April 2003

The changes in relative viscosity which occur when nylon 66 is irradiated with 2 m.e.v. electrons under an oxygen‐free atmosphere under various conditions have been observed. A mechanism is proposed which reconciles all of these observations, and on the basis of this postulated mechanism yields of chain breaks and crosslinks are calculated. The effect of the presence of a small concentration of a vinyl monomer (acrylic acid) in the polymer during irradiation on degradation and crosslinking is also considered. The rate of penetration of oxygen into irradiated polyamides has been measured. There is a marked reduction in penetration rate which results from the presence of free radicals in the fiber and the irreversible reaction which results. The data are treated by an approximate diffusion equation and estimates of true diffusion coefficients are given. The effect of filament diameter on the extent of degradation which occurs when fibers of nylon 66 are irradiated and then exposed to air has been investigated. The marked dependence of degradation on fiber thickness is related qualitatively to the data on rate of oxygen penetration.
Local regularity of chain substances. III
Authors: Miyake Akira , Adachi Hatsuko
Published: April 2003

The statistics of polymer chain configuration is examined from the viewpoint of local regularity. The partition function of the chain composed of N linked bonds, internally rotating through the hindering potential, under the stretching force f is given, provided the bond length b and the bond angle γ are kept constant. The averages of the chain end separations R and the internal energy are calculated. When only three configurations, T (ϕ = π), G (ϕ = cos−1 c), and G′ (ϕ = −cos−1c), are possible for the internal rotation angle ϕ, we can have for the average numbers of T and G (including G′) bonds

and

where ε is the energy difference between G (or G′) and T; that of T or G parts is n = NTNG/N and those of bonds per T and per G part 〈t〉 = N/NG and 〈g〉 = N/NT, respectively. These results can be also deduced by the method of virtual boundary energy.
Temperature dependence of NMR absorption spectra of polyethylene
Authors: Peterlin Anton , Pirkmajer Edo
Published: April 2003

A single‐crystal preparation from solution, polycrystalline Marlex crystallized from the melt, and five branched Du Pont polyethylenes were investigated by NMR from −170°C. to the melting point in order to study chain mobility and relaxation phenomena. Line width, line shape, and second moment measurement can be easily interpreted by chain mobility in lattice defects of the paracrystal which rapidly increase in number and extent with rising temperature and branching. Irreversible mobility changes were found in the single‐crystal preparation which, with increasing temperature, approaches that in Marlex crystallized from the melt.
The use of permselective membranes to determine the activity of the counterion in some polyelectrolyte solutions
Authors: Hardisty D. R. , Neale S. M.
Published: April 2003

Various cation‐selective membranes have been examined for sodium ion response in dilute solutions. The oxidized nitrocellulose membranes of Sollner have been used to determine cationic activities in solutions of Sky Blue FF, of cellulosic polyelectrolytes and of sodium polymethacrylate. The dyestuff behaves as a normal electrolyte of between 1:2 and 1:4 valence type, whereas the polyelectrolytes show the usual pronounced sequestering of the cation.
Polymerization with redox initiators. III. Complex formation between benzoyl peroxide and dimethylaniline
Authors: O'Driscoll K. F. , Richezza E. N.
Published: April 2003

When a dilute solution of benzoyl peroxide is mixed with one of dimethylaniline, the resultant solution has an absorbance in the ultraviolet which is different from that which can be calculated assuming no interaction. The difference is temperature dependent and reversible. It is believed that the absorbance difference may be attributed to the rapid equilibrium formation of a complex between the amine and peroxide.
Polymerization of isobutene in homogeneous systems
Authors: Kennedy J. P. , Thomas R. M.
Published: April 2003

The homophase polymerization of isobutene in pentane solution with AlCl3 catalyst solutions has been studied at −78°C. The DP of isobutene increases with increasing amounts of pentane present. Below about 10% monomer content the polymerization is completely homogeneous. The reaction is extremely fast, and conversions and molecular weights do not change after the introduction of catalyst. Only when more catalyst is added can the reaction proceed to higher conversions. A linear relation exists between conversion and catalyst concentration. The dependence of DP or the conversion has been established. The differential DP's increase until a well defined maximum is reached at low conversions. At higher conversions the DP starts to decay sharply. A hypothetical termination mechanism has been proposed.
Sorption of water vapor by starch. Thermodynamics and structural changes for dextrin, amylose, and amylopectin
Authors: Volman D. H. , Simons J. W. , Seed J. R. , Sterling C.
Published: April 2003

Water vapor sorption isotherms of a commercial dextrin prepared by dry acid treatment, amylose recrystallized from n‐butanol, and amylopectin precipitated from methanol were determined at various temperatures in the range of 10–40°C. The differential thermodynamic functions for water vapor sorption on the various materials were calculated, and B.E.T. constants were determined. A striking characteristic of the thermodynamic functions is the strong similarity for amylopectin and amylose. A model for the sorption is proposed. X‐ray patterns for the starch samples equilibrated with water vapor at various relative pressures of water vapor were determined. The major changes are explicable on the basis of intramicellar swelling. As the relative pressures increase, the crystalline patterns gradually fade and disappear. However, some new spacings appear with increased sorption in amylose and amylopectin. These spacings are explained on the basis of the formation of transitory lattices during the swelling of the starch crystallites.
The electrochemistry of vinyl polymer membranes
Authors: Kumins Charles A. , London Arnold
Published: April 2003

The electrochemical properties of polyvinyl acetate, polyvinyl chloride, and a copolymer of vinyl acetate and polyvinyl chloride have been studied. By means of membrane and bi‐ionic potential measurements, it has been shown that films made from these polymers are cation‐selective with a very low ion‐exchange capacity. The variation of membrane potential with external salt solution concentration occurs in a manner which may be predicted by the Meyer, Teorell, Sievers equations for permselective membranes. These have been used to calculate the fixed ion concentration within the polymers. The results suggest a possible mechanism for the passage of ions through mechanically perfect films.
Tracer techniques for the determination of monomer reactivity ratios. III. Ionization chamber assay and the reactivity ratios for the styrene/p‐methylstyrene copolymerization
Authors: Wiley Richard H. , Davis Burns
Published: April 2003

Monomer reactivity ratios for the copolymerization of styrene (M1)with p‐methylstyrene (M2)using labeled styrene and an ionization chamber assay technique gave values of r1 = 0.83 and r2 = 0.96. These values are believed to be more reliable than those obtained by direct counting techniques (r1 = 0.99 and 0.94). There is a possibly significant difference between these values and those for this monomer pair in the aluminumtrialkyl–titanium chloride‐initiated copolymerization (r1 ∼ r2 ∼ 1.0), which requires further evaluation.
Heterophase polymerization of isobutene with aluminum chloride catalyst solutions
Authors: Kennedy J. P. , Thomas R. M.
Published: April 2003

The low temperature polymerization of isobutene with AlCl3 in methyl chloride solutions has been investigated. In a series of experiments the degree of polymerization of poly(isobutene)as a function of monomer concentration has been determined. It was found that increasing amounts of methyl chloride causes a marked increase in molecular weight until a sharp maximum is reached at about 0.10 mole fraction isobutene. Further dilution causes a precipitous drop in the molecular weights. It has been shown that increase in dielectric constant does not account for the rise in degree of polymerization. The log of degree of polymerization was found to be inversely proportional to the log of catalyst concentration between about 10−3–10−2 wt.‐% (7.53 × 10−5–10−4 mole liter−1)AlCl3 on monomer. At higher catalyst concentrations the degree of polymerization becomes concentration independent. This was true for methyl isobutene–chloride systems containing 1.0, 0.65, and 0.25 mole fraction of monomer. The product degree of polymerization times monomer concentration falls on the same curve.