bluuebunny/crossref_metadata_2025 huggingface dataset:
Products of initiation, retardation, and inhibition of peroxide‐induced polymerization of styrene
Authors: Cohen Saul G.
Published: April 2003

The inhibition by quinone and the retardation by hydroquinone derivatives of the peroxide‐induced polymerization of styrene have been studied. We have examined the end products of benzoyl peroxide at 74°C. in benzene, alone and in the presence of quinone and hydroquinone ethers, and in styrene in benzene, both with and without quinone. Absorption spectra have been obtained after several time intervals for some of these systems and for the benzoyl peroxide‐styrene‐benzene system, alone and in the presence of alkyl substituted hydroquinones. Consideration of the end products indicates that quinone interferes but little with the normal initiation process, particularly at low (0.0045 M) concentrations. Inhibition appears to result largely from reaction between the inhibitor and newly initiated chains. Quinone is converted to products—some of which are phenolic—which do not absorb in the visible. The phenolic products may react with the peroxide or radicals from it, interfering with the normal initiation reaction. The hydroquinone derivatives, which are retarders for the polymerization, appear to be converted initially to quinonoid products. The reactions in inhibition and retardation are discussed.
Preparation and properties of rubberlike high polymers. IV. Correlation between structure and properties of elastomers derived from dienes
Authors: Salomon G. , Koningsberger C.
Published: April 2003

The correlation between structure and properties of elastomers prepared from dienes, natural rubber, gutta‐percha, as well as those of some significant derivatives of natural rubber, are discussed. The similar influence exerted by methyl groups on the brittle point, elastic recovery, and permeability to gases is demonstrated and separated from the effect caused by insertion of —CH2—CHR— groups in straight‐chain polybutadiene, which takes place during copolymerization or 1,2 addition. The preponderant influence of an unbranched‐chain structure on tensile strength at elevated temperatures and in the swollen state is illustrated. Complex compounds with silver nitrate provide further evidence for the particular symmetry of the natural rubber chain: They are rein forcing agents for synthetic elastomers. The brittle points of hydrochlorides from natural rubber, gutta‐percha, and polyisoprene are compared with those of polyvinyl compounds. Correlation between the structure of molecular units in a polymeric paraffin derivative and its elasticity is pointed out.
Deformation mechanism of cellulose gels. III. Changes in orientation upon drying
Authors: Hermans P. H. , Hermans J. J. , Vermaas D. , Weidinger A.
Published: April 2003

The orientation of model filaments stretched to various extents in three different states of swelling was investigated by quantitative x‐ray analysis before and after drying. The change in orientation upon drying was found to be either very small or zero. This shows that the crystallites do not even approximately follow the rules of affined transformation which would require a very considerable increase in orientation on drying. There must be an entirely different mechanism which prevents the crystallites from being dragged along with the matrix in which they are embedded.
Deformation mechanism of cellulose gels. IV. General relationship between orientation of the crystalline and that of the amorphous portion
Authors: Hermans P. H. , Hermans J. J. , Vermaas D. , Weidinger A.
Published: April 2003

Ten series of model filaments with increasing orientation and swelling degrees ranging between 16 and 1.2 were prepared from three viscoses containing 4, 6, and 10.5% cellulose. Their birefringence was measured and their x‐ray diagrams taken and quantitatively evaluated in order to determine the over‐all orientation of the iiber substance and that of the crystalline portion. It is shown that a general relation exists between the orientation of the crystallites and that of the entire fiber substance which is the same in all fibers stretched in the swollen state. Once the birefringence of a filament is known, the orientation factor of its crystallitee can be computed without taking an x‐ray photograph. From the data further evidence can be derived to the effect that the orientation of the crystallitm cannot be accounted for by the theory of affined deformation.
Free energy, heat, and entropy changes accompanying the sorption of water vapor by proteins
Authors: Davis S. , McLaren A. D.
Published: April 2003

Recently published measurements of moisture sorption vs. relative humidity for a series of proteins have previously been analyzed in a way which permits calculation of the integral free energy of sorption for any final pressure of water vapor. The present paper is an extension of these calculations to additional proteins from the list reported by Bull; integral and differential free energies and integral and differential heats and entropies of sorption have been calculated as functions of the amounts of water sorbed onsilk, wool, egg albumin (unlyophilized and heat coagulated), salmine, collagen, gelatin and lactoglobulin (crystalline and lyophilized). All calculations are referred to saturated water vapor as the standard state. Some of the proteins show positive net differential entropies of sorption at low vapor pressures. It is postulated that the partial molal entropy of sorption is made up of two terms, a negative entropy of sorption proper and a positive entropy of solution. Partial rearrangements of the protein chains at the beginning of the sorption process would effectively be an incipient solution which would give rise to a positive partial molal entropy of sorption if the second term is greater than the first. This speculation has support in the fact that the differential entropy of salmine, which dissolves at a relative vapor pressure of about 0.7, begins to show positive values at a relative vapor pressure of 0.35.
Polymerization of styrene in soap solutions
Authors: Frilette V. J. , Hohenstein W. P.
Published: April 2003

A turbidimetric method has been developed for determining the styrene content in water and soap solution. The solubility of styrene in distilled water was 0.022% while in 2.0% potassium oleate solution it was 0.65 to 0.88%. The course of the polymerization of a saturated solution of styrene in 2% potassium oleate was followed by a colorimetric analysis based on reaction with dilute potassium permanganate. The rate of polymerization decreased rapidly after 50% conversion. The activation energy was estimated to be 17,000 kcal., somewhat less than in solution. The molecular weight of the polymer produced was 200,000. Occasional erratic results were ascribed to possible influence of various amounts of air sealed in the polymerization mixtures.
Aroyl disulfides as promoter‐modifiers for copolymerization of butadiene and styrene
Authors: Frank Robert L. , Blegen James R. , Deutschman Archie
Published: April 2003

Benzoyl, anisoyl, veratroyl, p‐bromobenzoyl, p‐phenylbenzoyl, p‐benzoylbenzoyl, p‐methylsulfonylbenzoyl, p(N,N‐dimethylsulfonamido)‐benzoyl and ‐naphthoyl disulfides are promoters of the emulsion copolymerization of butadiene and styrene, but exhibit little effect on the polymer properties. Furoyl, phenyl, p‐chlorophenyl and p‐bromophenyl disulfides are neither promoters nor modifiers.
Reduction activation of emulsion copolymerization of butadiene and styrene: The benzoyl peroxide‐ferrous pyrophosphate system
Authors: Marvel C. S. , Deanin Rudolph , Overberger C. G. , Kuhn Beryl M.
Published: April 2003

The German redox system of emulsion polymerization of butadiene and styrene has been found to be very sensitive to exact details of experimental procedure. Soap may be substituted for the alkanesulfonate used by the Germans; it is then unnecessary to add ferric laurate to the system.

Careful investigation of the soap‐emulsified mixture leads to the conclusion that 0.25 parts of benzoyl peroxide, 0.50 parts of ferrous sulfate heptahydrate, and 3.0 parts of sodium pyrophosphate decahydrate were the optimum concentrations of the essential ingredients for polymerization of an emulsion of 75 parts of butadiene and 25 parts of styrene in 200 parts of water and 5 parts of Procter and Gamble soap Flakes (S.F.) at 30°. At very low iron concentration the addition of a reducing agent as “booster” was beneficial; for this purpose sorbose can be replaced by fructose or, less satisfactorily, by a number of other reducing agents.
Photochemistry of proteins. III. Quantum yield for inactivation of soybean trypsin inhibitor by ultraviolet light
Authors: Katchman B. , McLaren A. D.
Published: April 2003

Crystalline soybean trypsin inhibitor has been inactivated by ultraviolet light (λ2537 Å.) with a quantum yield of 0.0088 based upton loss of ability to inhibit the action of trypsin on casein. Inactivation involves a “one‐hit” process.
Initial rate of polymerization of styrene
Authors: Goldfinger G. , Lauterbach K. E.
Published: April 2003

The initial rate of polymerization of highly purified styrene in bulk has been measured dilatometrically at 38.4, 56.4 and 70.1°C. For conversions up to one per cent a well‐reproducible rate was observed for samples handled in complete absence of atmospheric gases. For samples saturated with air an equally reproducible, though higher rate, was observed initially. The duration of this higher rate decreases with increasing length of storage between saturation and measurement. After polymerization at higher rate, the sample continues to polymerize at the rate observed for the air‐free samples.
Use of cobalt complexes as activators in emulsion copolymerization of butadiene and styrene
Authors: Marvel C. S. , Inskeep G. E. , Dearborn Robert J. , Saunders J. H. , Johnston H. W. , Shepherd Douglas A. , Deutschman A. J. , Damman Joseph A. , Oppegard A. L.
Published: April 2003

Cobalt complex compounds exhibited varying degrees of activation and retardation in butadiene‐styrene‐soap emulsion polymerization systems at 20–50°C. An accompanying effect was the wasting of modifier, particularly by large concentrations of activator. The most active complexes for use with dodecyl mercaptan were those in which the cobalt was coordinated with two or more negative groups other than thiocyanate, and in which the neutral coordinated groups were not ethylenediamine.
Low‐angle scattering in polymers
Authors: Kratky O.
Published: April 2003

The diffraction of x‐rays at small angles occurs in the form of sharp interferences (discontinuous) or as diffuse scattering (continuous). The first effect is observed mostly in crystallized proteins and in protein fibers. New measurements on collagen were obtained by the author in collaboration with Sekora, and independently by Bear. Using these data, an attempt has been made to establish a connection between the orders of the intense reflections belonging to the giant period of 642 Å. along the fiber axis and the frequency of the amino acid residues (frequency is defined as the number of amino acid residues of a particular kind among the total 220 residues which constitute the basic period of 642 Å. along the fiber axis). With the exception of the most abundant amino acids, glycine and proline, it is possible to assign to each frequency a corresponding reflection, and vice versa. This indicates a high degree of regularity in the arrangement of these amino acid residues. But the relationships are apparently more complex than would be expected from the Bergmann‐Niemann rule. For example, the frequencies of 11 and 20 (corresponding to an identical residue at each 220/11 or 20th location or at each 220/20 or 11th location, respectively) appear to play a role. Fundamentally, however, we arrive at a picture in accordance with the comprehensive investigations and results of Astbury. It has not yet been possible to arrive at a detailed structure.

In the theory of diffuse low‐angle scattering, it is necessary to distinguish between densely packed systems and dilute systems. For the latter case, molecular scattering is computed in accordance with Debye's theory of scattering. It is shown how size factor and form factor may be separated. Both of these properties can be approximated without making previous assumptions, though the accuracy of the form factor determination can be improved appreciably if the particle weight is known. Preliminary trial measurements on solutions of edestin, tobacco mosaic virus, and hemocyanin are in agreement for the first two substances mentioned. The measurements on insulin indicate associated particles that deviate strongly from spherical shape (however, these measurements were made at an earlier date and require checking). Those on hemocyanin indicate an association similar to a string of pearls, a result which probably explains the contradiction of the substance appearing as spherical particles under the electron microscope, while exhibiting flow birefringence when in solution. When this method is developed further it will undoubtedly become a valuable tool for the determination of form and size of polymer molecules and other colloidal particles.
Polymerization of allyl compounds. IV. Emulsion polymerization of allyl acetate
Authors: Bartlett Paul D. , Nozaki Kenzie
Published: April 2003

The emulsion polymerization of allyl acetate yields a polymer of the same average molecular weight as is obtained in bulk polymerization. The decomposition of potassimn persulfate is of the first order but is greatly accelerated by the presence of allyl acetate or of ethyl acetate. Three independent methods of analysis agree in indicating the presence of sulfate groups in 75% of the polymer molecules. It is concluded that the mechanisms of chain initiation and termination are analogous to those in the peroxide‐induced bulk polymerization of allyl acetate. These facts do not serve to distinguish between different postulated loci reaction in emulsion polymerization.
Note on volume effect in coiling molecules
Authors: Simha Robert
Published: April 2003

An estimate of the magnitude of the interference effect in a coil‐like molecule is made by calculating the nearest neighbor density w around a given link as a function of the total number of contributing chain units. It is shown, for instance, that in a chain consisting of several hundred units, the first fifteen contribute about 75 % of the total nearest neighbor density at distances below the length of a link. The plots presented indicate that after about the first twenty links, the rate of increase of nearest neighbor density begins to flatten off. It is also possible to derive the modification of the distribution function of chain ends in real chains for a given form of w.
n‐Octyl mercaptan as modifier for emulsion polymerization at high temperature
Authors: Marvel C. S. , Lewis C. D.
Published: April 2003

n‐Octyl mercaptan has been found to be a better modifier for emulsion copolymerization of butadiene and styrene at 110° than is either n‐butyl mercaptan or n‐dodecyl mercaptan. Physical test data on vulcanized copolymers modified with n‐octyl mercaptan are presented.
Density of undrawn, drawn, and annealed nylon filaments
Authors: Black C. E. , Dole Malcolm
Published: April 2003

The densities of undrawn and drawn nylon filaments (6‐6 Nylon) are found to be 1.1339 and 1.1384, respectively, at 25°C. Annealing either the drawn or undrawn forms to the highest temperature possible short of melting increases the room temperature density to 1.1564, the most rapid increase in density with temperatures annealing coming at 210°C. The temperature coefficient of the density as measured at room temperature is greater for the drawn form of the nylon than the undrawn after annealing has taken place. The density of nylon calculated by Bunn and Garner from x‐ray diagram data is 1.24, considerably higher than the highest value obtained by us on annealing, namely 1.156.
Die kinetik des celluloseabbaus und die langperiodische struktur des cellulosemoleküls
Authors: Schulz G. V.
Published: April 2003

Eine Übersicht wird gegeben für die Argumente, die für das Vorhandensein eines regelmässigen, langperiodischen Aufbaus von Einheiten von 500 Glukoseresten in Fasercellulosen sprechen. Die Uneinheitlichkeit des Gewichtsdurchschnittes kann in ihrer Abhängigkeit vom Abbaugrad gemessen werden und nimmt viel langsamer ab als unter der Annahme von statistischer Spaltung. Die Interpretierung der kinetischen Studien mit Hilfe der Gleichung von Ekenstam führt zu zwei verschiedenen Geschwindigkeitskonstanten und Aktivierungsenergien für die Zerfallsreaktion. Schliesslich zeigen elektronenmikroskopische Aufnahmen charakteristische Unterschiede zwischen Fasern die durch Nassmahlung und durch Hydrolyse gewonnen wurden.
Calcul de l'écart quadratique moyen entre les extrémités de diverses chaînes moléculaires de type usuel
Authors: Benoit H.
Published: April 2003

Le calcul de l'écart quadratique moyen entre les extrémités d'une chaîne moléculaire a été fait de façon complète dans le cas de la chaîne aliphatique à rotations libres. Des solutions partielles ont été proposées dans le cas de la chaîne aliphatique avec empěchements stériques ou intéractions entre les chaînons. Le but du présent travail est de donner une méthode de calcul général que l'on applique aux exemples particuliers les plus usuels. (Chaînes aliphatiques, cellulosiques, polypeptidiques ainsi qu'aux substances type caoutchouc naturel.)
Anionic redox activation of butadiene‐styrene copolymerization
Authors: Johnson Paul H. , Bebb R. L.
Published: April 2003

A redox‐activated emulsion polymerization system has been developed in which benzoyl peroxide, sorbose and ferrous ammonium sulfate constitute the oxidation reduction system. Very rapid rates of reaction were obtained which permitted the use of lower polymerization temperatures. Redox polymers made at 10°C. had higher molecular weights and superior physical properties compared to standard GR‐S as well as to polymers prepared in the redox system at higher temperatures.
Combination of potassium ferricyanide, diazothio ether and mercaptan as “catalyst” for emulsion polymerizations of butadiene and styrene
Authors: Kolthoff I. M. , Dale W. J.
Published: April 2003

The combination of a diazothio ether and a mercaptan in an emulsion copolymerization recipe of butadiene and styrene containing potassium ferricyanide as a “catalyst” has a very strong activating effect on the polymerization. p‐Methoxyphenyl diazothio‐(2‐naphthyl) ether, designated as MDN, was found to be particularly suitable. In the present paper, ordinary household soap (S.F. flakes) and dehydrogenated rosin soaps of varying degrees of purity have been used as emulsifiers. By using various tertiary or primary mercaptans, polymers of any degree of modification were obtained. The recommended recipe at 40°C. gives about 80% conversion in 10 hours. The rate of conversion is greatly increased by adding to the recipe substances which have a strongly alkaline reaction in water, as sodium carbonate, trisodium phosphate, or sodium hydroxide. With such “alkaline” recipes attractive rates of conversion are obtained at around 0°C.
Carbonatotetramminocobaltic nitrate activation of butadiene‐styrene emulsion copolymerization
Authors: Deanin Rudolph , Lindsay Rex D. , Leventer Seymour E.
Published: April 2003

Rapid low‐temperature butadiene‐styrene emulsion copolymerization may be effected by a redox‐activated system composed of carbonatotetramminocobaltic nitrate and dodecyl mercaptan. This system reaches 75% conversion of monomer to polymer in 0.8 hour at 50°C., 2.8 hours at 30°C., or 27 hours at 0°C., and is thus about fifteen times as fast as standard recipes now in use. The modifying effect of dodecyl mercaptan improves as the polymerization temperature is lowered, producing loosely cross‐linked polymers at 30°C. and well‐modified polymers at 0°C.
Nitrostyrenes. I. Polymerization of m‐nitrostyrene
Authors: Wiley Richard H. , Smith Newton R.
Published: April 2003

m‐Nitrostyrene, prepared from m‐nitrocinnamic acid in 60% yields, has been converted to polymers of low molecular weight in bulk and in solution with benzoyl peroxide, boron fluoride, and aluminum chloride initiators, and in aqueous emulsion with persulfate initiator.
X‐ray studies of low‐temperature polybutadiene and butadiene‐styrene copolymers
Authors: Beu Karl E. , Reynolds W. B. , Fryling C. F. , McMurry H. L.
Published: April 2003

The fine structures of emulsion polybutadiene prepared at temperatures ranging from 55°C. to −20°C. and of various butadiene‐styrene copolymers prepared at −20°C. have been studied by x‐ray methods. The ability of emulsion‐polymerized butadiene to crystallize was found to depend to a large extent on the temperature of polymerization. Butadiene polymerized at 30°C. and above showed no evidences of crystallization when cooled unstretched to −70°C. as observed by x‐ray diffraction methods; however, butadiene polymerized at 20°C. and below showed crystallization effects when cooled unstretched to −70°C. These crystallization effects became more pronounced for samples polymerized at lower temperatures. Layer‐line diffraction patterns of butadiene polymerized at 30°C. and below were obtained by stretching the polymer at about 0°C. From these patterns the geometrical repeat distance along the polymer chains was found to be 5.1 ± 0.1 Å. This corresponds to a fully extended butadiene unit in the trans configuration. An anomaly was observed in the diffraction patterns of crystallizable polybutadiene stretched at 0°C. Some of the layer‐line spots varied in position with per cent elongation of the sample. This suggests that the molecules in crystallites of the polymer are inclined to the stretch axis at low elongations and that they become more nearly parallel to the stretch axis at higher elongations. A small addition of styrene as comonomer at −20°C. polymerization temperature did not prevent crystallization and preferred orientation effects in the polymer, since these effects could still be found in a 90/10 charge copolymer. Larger amounts of styrene did prevent crystallinity and preferred orientation as shown by the amorphous nature of an 80/20 charge copolymer. The ability of a compounded vulcanizate of a given polymer to crystallize is less than that of the purified polymer under the same conditions. This may be due to the combined effects of milling, vulcanization, and the presence of carbon black particles in the polymer. A description of the apparatus and techniques used for cooling and stretching these polymers is given.
Potentiometric titration of viscose
Authors: Herrent P. , Jnoff G.
Published: April 2003

A new method is investigated to determine by means of potentiometric titration the degree of ripening of viscose. It is found that when the e.m.f. of a characteristic inflection in the potentiometric titration curve is plotted against a measure of the degree of viscose ripening a sharp minimum occurs at a point corresponding to the optimal degree of ripening. Moreover, evidence is offered to indicate the formation of sodium dithiocarbonate in viscose during ripening. This last fact leads to a reasonable postulation of the complete scheme of reactions taking place in a ripening viscose.
Beiträge zur kinetik der indenpolymerisation. V. Reaktionskinetik der indenvulkanisation
Authors: Halla F. , Schützner W.
Published: April 2003

Es wird gezeigt, dass die Reaktion von Indol mit Schwefel zu einem Polymer führt, das ein Schwefelatom pro Indoleinheit enthält. Der Brechungsindex und das Absorptionsspektrum des Polymers werden mitgeteilt. Die Kinetik der Schwefelreaktion, mit und ohne Zusatz von Beschleunigern, wird untersucht um den Einfluss der Beschleuniger auf die Reaktiongeschwindigkeit und die Temperaturabhängigkeit der Reaktion festzustellen.
Refractometric determination of second‐order transition temperatures in polymers. III. Acrylates and methacrylates
Authors: Wiley Richard H. , Brauer G. M.
Published: April 2003

A refractometric technique for determination of second‐order transition temperatures (Tm) of polymers has been extended to include a series of alkyl acrylate and methacrylate polymers with transitions at temperatures down to −50°C. A convenient technique for determining refractive index down to −75°C. is described. Certain long‐chain alkyl polymers are birefringent below Tm. Correlations of brittle point with Tm and relations between viscosity and Tm are reported.
Elastoviscous properties of polyisobutylene. I. Relaxation of stress in whole polymer of different molecular weights at elevated temperatures
Authors: Andrews R. D. , Hofman‐Bang N. , Tobolsky A. V.
Published: April 2003

The relaxation of stress in polyisobutylene whole polymer of different average molecular weights has been investigated over the temperature range 30–100°C., and at different elongations. The shape of the relaxation curve is independent of elongation in a range of low elongations; above this range there is a gradual change in curve shape with increasing elongation. The shape of the relaxation curve for a given molecular weight is the same at different temperatures, when plotted as reduced stress vs. logarithmic time; a change in temperature essentially shifts the position of the curve along the logarithmic time scale. The activation energy for relaxation, calculated by use of the Arrhenius equation, is found to be independent of molecular weight in the molecular weight range investigated (M̄v = 665,00.0 to 1,420,000), the average value being 15.4 kcal. Straight lines are obtained when reciprocal viscosity‐average molecular weight is plotted against log time required for the reduced stress to reach a certain arbitrary value, at a fixed temperature and elongation. Relaxation rate depends on molecular weight with sufficient sensitivity so that relaxation measurements may be a practical method of measuring molecular weight directly in the solid state.
Action of regulators in polymerization of monomers containing allyl and methacrylate groups
Authors: Cohen Saul G. , Sparrow Donald B.
Published: April 2003

The peroxide‐initiated polymerization of allyl methacrylate has been examined in the presence of certain additives. By the use of mercaptans and diisopropyl dixanthogen the extent of polymerization at the point where gelation occurs may be extended from about 6% to 20–30% polymerization. Examination of samples of polyallyl methacrylate, polymethyl methacrylate, and the copolymer of methyl methacrylate and allyl chloroacetate indicates that the postponement of gelation results largely from diminution of the molecular weight by the regulators. The effects of regulators on the composition of copolymers and the molecular weight of polymers, and the relation between molecular weight and extent of reaction at the gel point are discussed.
Some relative monomer reactivity factors
Authors: Price Charles C.
Published: April 2003

Recently published data on copolymerization has been shown to correlate satisfactorily with the scheme of Q and e factors proposed by Alfrey and Price, thus lending further support to the utility and to the theoretical interpretation on which it was based.
Cross linking of nitrocellulose studied with the ultracentrifuge and consistometer
Authors: Jullander Ingvar , Blom‐Sallin Brita‐Stina
Published: April 2003

Experiments with cross linking of nitrocellulose in butyl acetate solution by means of titanium tetrachloride are described. The gels have been examined by means of sedimentation in the ultracentrifuge and measurements with a consistometer. The yield value of the flow curves and the extent of cross linking were studied as functions of nitrocellulose concentration, amount of cross‐linking substance, and time of reaction.
Occurrence of head‐to‐head arrangements of structural units in polyvinyl alcohol
Authors: Flory Paul J. , Leutner Fred S.
Published: April 2003

Polyvinyl alcohol prepared by hydrolyzing polymerized vinyl acetate is partially degraded within a few minutes by reagents known to attack 1,2‐glycol structures. The degree of degradation is limited, however, the final molecular weights of the degraded products being in the range of 3700 to 6500 (viscosity averages). The extent of degradation seems to depend solely on the temperature at which the vinyl acetate was polymerized. Mole percentages (based on the structural unit CH2CHOH) of 1,2‐glycol structures, corresponding to head‐to‐head unit arrangements, have been computed from the degree of degradation with periodic acid. They increase from about 1.23% for polymerization at 25°C. to 1.95% at 110°C. The occurrence of head‐to‐head structures is attributed to occasional “abnormal” addition of monomer in the chain‐growth phase of the polymerization. The activation energy for the abnormal addition reaction is 1250 calories higher than for the normal (preferred) addition; the steric factor for the abnormal addition is about one‐tenth that for the normal addition.
Copolymerization. VI. Mechanism of emulsion polymerization
Authors: Fordyce R. G. , Ham G. E.
Published: April 2003

Additional data relating to the mechanism of the emulsion copolymerization of styrene and copolymerization of styrene and acrylonitrile are presented. These results show the influence of varying the emulsifier and of varying the water–monomer ratio upon the relationship between monomer composition and the composition of the initial copolymer molecules formed. The composition of the initial copolymer produced in emulsion is the same as that which would be predicted if polymerization occurred in the oil droplet.
Application of infrared analysis to elucidate the mechanism of the boron trifluoride catalyzed vapor phase polymerization of isobutene at room temperature
Authors: Dainton F. S. , Sutherland G. B. B. M.
Published: April 2003

Measurement of the infrared absorption spectrum of the lowmolecular liquid polymer formed at room temperature from gaseous isobutene using BF3 as a catalyst and D2O as a cocatalyst indicates that the dominant end groups in the final polymer are (CH3)3C and , and that the cocatalyst D2O undergoes partial conversation to H2O during reaction. These results substantiate the mechanism advanced by Polanyi and others, namely: (a) initiation through formation of the trimethyl carbonium ion by acceptance by isobutene of a proton (or deuteron) from the catalyst‐cocatalyst complex, and (b) termination by explusion of a proton from a methyl group to the anionic complex fragment, with corresponding catalyst regeneration, i.e.:

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Photochemistry of proteins. V. Effect of pH and urea on ultraviolet light inactivation of crystalline pepsin
Authors: McLaren A. D. , Pearson Sidney
Published: April 2003

Quantum yields for the inactivation of crystalline swine pepsin have been determined as a function of pH at 2537 A. The quantum yield is near a minimum at pH 4.08, at which point a value of 0.0019 was found, rises rapidly above pH 6, and shows a slight maximum near pH 2.7. The maximum is more pronounced with polychromatic light. The quantum yield (at pH 2.01) was found to be the same with either hemoglobin or casein as a substrate. Urea had no effect on the quantum yield although urea alone, 7 M, inactivates pepsin at an appreciable rate. Urea and light denaturation do not modify the absorption spectrum of pepsin in the same way. The data of Gates has been recalculated; it shows an increase of quantum yields with decreasing wave length. It has been concluded, from experiments with model substances, that inactivation can occur by the absorption of a quantum by any aromatic group in pepsin.
Methods for estimating intrinsic viscosity
Authors: Billmeyer Fred W.
Published: April 2003

A number of equations are suggested for estimating intrinsic viscosity from one measurement of relative viscosity at a convenient concentration. Experimental data illustrate the validity of the equations.
Degree of lateral order in various rayons as deduced from x‐ray measurements
Authors: Hermans P. H.
Published: April 2003

X‐ray measurements on 16 different specimens of regenerated cellulose reveals that there exists a pronounced negative correlation between the integrated intensity of the 101 interference and its halfwidth. The 101 plane is a preferred cleavage plane and represents the lamellar plane of the ribbon‐shaped crystallites. Variations in the intensity of the other interferences are much less or nonexistent. These results show that the degree and the perfection of lateral order according to the 101 and 002 planes is little at variance, but that order according to the 101 plane is extremely variable in such a way that if the average thickness and (or) perfection of the lamellae increases, the total number of well‐ordered 101 plane contacts diminishes. As a possible explanation of this phenomenon it is suggested that various degrees of recrystallization with reference to this particular plane (i.e., various degrees of lateral order) may be associated with the various rayon specimens. This, however, does not necessarily imply differences in the total amount of ordered substance. This explanation is corroborated by the fact that cellulose acetate fibers which were previously allowed to “recrystallize” by heating in methanol, after saponification yield a rayon with a particularly sharp, but also particularly weak, 101 interference, without exhibiting a higher total percentage of ordered substance than the saponification products of acetate treated in this manner.
Preparation and properties of rubberlike high polymers. VI. Polymerization and dimerization of isoprene
Authors: Salomon G. , Boonstra B. B. S. T. , van der Meer S. , Ultée A. J.
Published: April 2003

The inhibitor and initiator action of 33 compounds on the bulk polymerization of pure isoprene has been studied. Picric acid was found to be the most powerful inhibitor at 100°C. The conclusion reached in Part I, that the initiator activity of diazoaminobenzene is superior to all other compounds has been found to be valid also between 100–150°C. The heat polymerization of isoprene between 100–150°C. in the presence of picric acid leads only to the formation of dimers. Three of the four possible isomers have been separated. The solid complex compound of diprene (I) with silver nitrate has been used to separate it from dipentene (II) and the hydrocarbon of Lebedew (III, IV) has been identified as a monochloride. The relative yields (I): (II): (III+IV) = 16:1:2 are in agreement with the relative availability and localization of π‐electrons in isoprene. Observations on the properties of polyisoprene are in agreement with the more extensive work by d'Ianni. Some remarks on polymers from bulk polymerization are added. Isoprene acts as a powerful inhibitor on the polymerization of vinylidene chloride. This effect is independent of the method of polymerization.
Investigations on cellulose nitrate. II. Liquid and vapor phase adsorption of acetone
Authors: Campbell H. , Johnson P.
Published: April 2003

The discrepancies in the published work on the interaction of acetone and cellulose nitrate are discussed and explained. Vapor phase adsorption isotherms for the adsorption of acetone by cellulose nitrate have been determined with an adsorption balance. They have been shown to be independent of the crystalline‐amorphous ratio of the polymer but dependent upon its nitrogen content. In cellulose nitrates which are completely soluble in acetone, no limiting adsorption has been found. Adsorption analysis (a modification of chromatography) has been applied to the determination of the liquid phase adsorption by cellulose nitrate of acetone from mixtures with petroleum ether. In terms of the liquid mixture concentrations, there appears to be limited adsorption, but this is shown to be due to the nonideal nature of the solutions of acetone and petroleum ether. When allowance is made for this, the liquid and vapor phase isotherms are the same within experimental error and do not support the existence of compounds of acetone and cellulose nitrate.
Polymerization in a system of discrete particles
Authors: Haward R. N.
Published: April 2003

It has been shown that subdivision of certain homogeneous polymerizing systems into droplets of diameter 10−4 to 10−5 cm. will entail a probability of finding only one active chain in each particle if the kinetics of the reaction remained otherwise unaffected. Some cases of polymerization in compartmentalized systems have been considered, and it has been shown that, where active centers are generated singly within completely isolated drops, the effect of increasing subdivision would be to increase the rate of reaction and chain length. On the other hand, with the formation of active chains in pairs, the opposite effect is to be anticipated, namely a decreasing rate of reaction with increasing subdivision. These conclusions are briefly considered in relation to the problem of dispersion polymerization, and it is shown that the theory of compartmentalization could account for the occurrence of high rates of reaction and chain lengths in the emulsion process, as compared with a bulk system. On the other hand, there is no evidence showing that the reaction rate is ever reduced in finely dispersed systems.
Polydispersité de la cellulose de la pâte de bois
Authors: Herrent P. , Govaerts R.
Published: April 2003

Nous avons étudié une méthode pratique et simple, dont les résultats soient parfaitement reproductibles, de détermination de la répartition des longueurs de chaînes de la cellulose provenant de pâtes de bois différentes. Cette méthode nous permettra de mieux comprendre l'influence des différents facteurs de fabrication sur les qualités mécaniques de nos produits finis.
Change in crystallinity upon heterogeneous acid hydrolysis of cellulose fibers
Authors: Hermans P. H. , Weidinger A.
Published: April 2003

The recently developed x‐ray method of crystallinity determination is applied to products of heterogeneous acid hydrolysis of cellulose fibers. Upon treatment of viscose rayon fibers with boiling 2.5 N sulfuric acid, the crystalline fraction is increased from 39 to 49% within half an hour, and remains constant upon prolonged treatment. Ramie does not show any change in percentage crystallinity when subjected to the same treatment. Its crystalline fraction is, however, transformed into cellulose IV. The observed changes in moisture regain of the hydrolyzed products are in line with the x‐ray results.
Specific refractivity‐temperature data for polyvinyl acetate and polybutyl acrylate
Authors: Wiley Richard H. , Brauer G. M.
Published: April 2003

Refractive index‐temperature and volume‐temperature data for polyvinyl acetate and polybutyl acrylate have been determined and used to calculate the specific refractivity as a function of temperature by the Lorentz‐Lorentz and the Eyckman equations. The results show a variation of specific refractivity with temperature which exceeds experimental error. The variation is evident as an increase of specific refractivity with temperature above Tm and suggests experiments which will show the increase more clearly. A theoretical justification for the increase of specific refractivity with temperature in polymers is discussed.
Redox recipes. I. Reaction between ferrous iron and peroxides. General considerations
Authors: Medalia A. I. , Kolthoff I. M.
Published: April 2003

Various mechanisms which have been proposed for the reaction between ferrous iron and hydrogen peroxide are reviewed. Two of these mechanisms appear equally satisfactory on the basis of present evidence: that of Bray and Gorin, involving formation of tetravalent (ferryl) iron, and that of Haber and Weiss, involving formation ofhydroxyl and perhydroxyl radicals. Mechanisms involving these intermediates have been developed for the ferric iron‐catalyzed decomposition of hydrogen peroxide; the mechanism of Bray and Gorin appears satisfactory, while that of Haber and Weiss leads to certain inconsistencies. A mechanism with ferrous iron and hydroxyl and perhydroxyl radicals as intermediates is presented, which accounts for the experimental observations in the ferric iron‐catalyzed decomposition of hydrogen peroxide. The reaction between hydrogen peroxide and ferrous iron induces the reaction between hydrogen peroxide and various organic compounds; this induced reaction (termed a Fenton reaction) is a chain reaction which is initiated by the active intermediates (ferryl iron or hydroxyl radical) formed in the primary reaction. The determination of hydrogen peroxide by reaction with ferrous iron, if carried out in the presence of various organic compounds (termed promoters), gives incorrect results, due to induced oxidation of the promoters; other compounds, termed suppressors, reduce the extent of this induced oxidation of promoters. It appears that both types of compounds react with ferryl iron or hydroxyl radical to form radicals, which if formed from promoters, reduce ferric iron or hydrogen peroxide, while the radicals formed from suppressors oxidize ferrous iron. These considerations are of particular importance in the determination of organic hydroperoxides. The reaction between hydrogen peroxide or organic peroxides and ferrous iron can induce, or initiate, the polymerization of vinyl monomers; this is an example of redox polymerization, which is of considerable practical importance at present.
Polyelectrolytes. V. Osmotic pressures of poly‐4‐vinyl‐N‐n‐butylpyridonium bromide in ethanol at 25°
Authors: Strauss Ulrich P. , Fuoss Raymond M.
Published: April 2003

The osmotic pressures of two samples of poly‐4‐vinyl‐N‐n‐butylpyridonium bromide (average D. P. 730 and 1900) were measured in 93% ethanol in the concentration range 0.02‐0.20 g./100 cc. The osmotic pressures were higher than those of the corresponding parent polymers, due to partial dissociation of bromide ions. Because of the low dielectric constant ( ε′ = 28) of the solvent and the high concentration of positive charge in the polycations, however, a large fraction of the bromide ions (≥ 95%) were bound by electrostatic attraction to the cations and contributed neither to osmotic pressure nor to conductance. Unlike neutral polymers, the ratio (osmotic pressure over concentration) increases with dilution, due to increasing dissociation with dilution. Addition of an excess of a simple one‐one electrolyte (lithium bromide) almost completely suppressed the dissociation of the polysalt and gave osmotic pressures of the same order of magnitude as those of the neutral polymers. The resulting curves were linear, with a considerably smaller slope than for the parent polymer. Combining the results on osmotic pressure with conductance data, the transference numbers of the polycations were estimated to be 0.28 and 0.52 for degrees of polymerization 730 and 1900 respectively. The conductance of lithium bromide is decreased by the addition of these polyelectrolytes, possible due to the association of an excess of anions to the polycations under the influence of their electrostatic fields.
Compléments à l'étude de la statistique des chaînes moléculaires en solution diluée
Authors: Benoit H. , Sadron C.
Published: April 2003

Le cas le plus simple pour calculer l'écart quadratique moyen entre les extrémités d'une chaǐne macromoléculaire est celui oùtoutes les rotations sont libres. Mais cette condition n'est généralement pas réalisée, aussi avons nous examiné dans cet article les résultats obtenus en introduisant une fonction de répartition symétrique pour les positions de chaque atome de la chaîne sur le cercle de base du cǒne de valence. Nous comparons les formules proposées jusqu'ici en représentant graphiquement leurs résultats (figs. 2 et 3). Cette comparaison montre que la formule de Kuhn et Taylor (8,9) est une approximation de celle que nous avons établié dans un article précédent (7) et a, de ce fait, un domaine de validité plus restreint. Ce domaine augmente avec le nombre des chaǐnons de la chaîne. En utilisant les fonctions de répartition proposées par Taylor nous représentons les valeurs de l'écart quadratique moyen en fonction de l'énergie d'interaction (figs. 6 et 7). Nous montrons ensuite que cette énergie d'interaction ne peut avoir la valeur calculée pour les vapeurs de carbures aliphatiques normaux mais est la somme de plusieurs termes et doit varier avec la nombre de chaǐnons et la température. Les formules établies permettent de prévoir deux aspects différents de la précipitation suivant qu'elle est effectuée par abaissement de la température ou adjonction d'un précipitant. Enfin, lorsque dans leurs rotations les atomes de la chaîne doivent passer par dessus des barrières de potentiel on peut prévoir des anomalies dans son comportement.
Thermodynamics of high‐polymer solutions. III. Swelling of cross‐linked rubber
Authors: Scott Robert L. , Magat Michael
Published: April 2003

The equilibrium swelling of the gum stocks of twelve different rubber vulcanizates has been measured in thirteen organic solvents. The results are in good agreement with the theory of Flory and Rehner. Values of the internal pressure (cohesive energy density) and the average molal volume between cross‐linkages Vc have been determined for the rubbers. The molal volume Vc is shown to agree closely with that obtained from measurement of the elastic modulus. An analysis of earlier data on the swelling of polybutadiene shows the number of cross‐linkages to be directly proportional to the sulfur content.
Photochemistry of proteins. VI. pH dependence of quantum yield and ultraviolet absorption spectrum of chymotrypsin
Authors: Finkelstein Paul , McLaren A. Douglas
Published: April 2003

The quantum yield of inactivation of chymotrypsin was found to be independent of variations in conditions of irradiation including light intensity, concentration of the irradiated solution, rate of stirring and the presence or absence of oxygen. The quantum yield for inactivation is at a minimum at the isoelectric point (pH 5.4). An explanation is offered for the variation of the quantum yield with pH in terms of an internal Franck‐Rabinowitch mechanism. The absorption spectra of the enzyme was also studied as a function of pH, as was that of an amino acid mixture whose composition corresponded to that of chymotrypsin. Evidence is presented for the existence of bound, un‐ionizing tyrosine in the native enzyme and of unbound tyrosine in alkali‐denatured enzyme. The significance of changes in the absorption spectra accompanying irradiation is discussed.
Pyrolysis of polyisobutene (vistanex), polyisoprene, polybutadiene, GR‐S, and polyethylene in a high vacuum
Authors: Madorsky Samuel L. , Straus Sidney , Thompson Dorothy , Williamson Laura
Published: April 2003

Samples of polyisobutene, polyisoprene, polybutadiene, GR‐S, and polyethylene, weighing about 25 to 50 mg., were pyrolyzed in a vacuum of about 10−6mm. of mercury in a specially designed apparatus at temperatures ranging between 300 to 475°C. The volatile products of pyrolysis were separated into four fractions: (IV) gaseous, volatile at ‐196°; (IIIA) liquid, at ‐75°, (IIIB) liquid, at 25°; and (II) waxlike fraction, volatile at the temperature of pyrolysis. The gaseous fraction was analyzed in the mass spectrometer and was found to consist in all cases of CH4. The liquid fraction, IIIA, was analyzed similarly and was found to give a mass spectrum characteristic for any given polymer. A molecular weight determination of the waxlike fraction by the micro freezing point‐lowering method, showed it to vary from 543 to 739, depending on the polymer from which the fraction was obtained. It is shown that the method of pyrolytic fractionation of high molecular weight polymers, in conjunction with mass spectrometer analysis of the more volatile fractions, can serve as a means of identifying the polymers.
Polymers and copolymers of o‐acetoxystyrene and o‐hydroxystyrene
Authors: Marvel C. S. , Rao N. Shanmukha
Published: April 2003

o‐Hydroxystyrene did not copolymerize with styrene and butadiene in GR‐S‐type systems. A terpolymer of these three monomers was obtained by copolymerizing o‐acetoxystyrene, styrene and butadiene in carbon tetrachloride solution by the action of stannic chloride followed by hydrolysis of the acetate groups in the polymer with dilute hydrochloric acid in dioxane solution. The polymer thus obtained did not improve the tack of GR‐S.