ALBERT

Notes: A review of theoretical progress in copolymerization has shown that the results of previous authors are consistent and equivalent. A general scheme of copolymerization has been stated and its kinetic consequences worked out. The rate expressions have been derived for percentage polymerization against time, and initial rate against initial monomer concentration. Some experimental considerations have been given. The advantages of photochemical technique have been stressed, physical means of following the reaction outlined, and new methods of determining σ and μ described. Means of verifying the kinetics have been suggested, in particular the obtaining of the individual velocity constants. It is important to note in this connection, that further experiments to determine the lifetime of the growing polymer chain are not required.

Notes: Tetrachlorophthalic anhydride (TCPA) was reacted with cellulose diacetate and with cellulose diethyl ether in dioxane solution to produce esters with rather low tetrachlorophthalyl contents. Phthalic anhydride was found to be considerably more reactive than was TCPA with these cellulose derivatives, especially if pyridine was used as the reaction solvent. Acylations could not be executed with TCPA in the presence of pyridine as solvent, however, because this material decomposed the anhydride, removing chlorine from it. The TCPA derivatives were more limited in solubility than were the corresponding esters made from phthalic anhydride.

Notes: An attempt has been made in this communication to formulate explicitly the dependence of the frictional coefficients of threadlike molecules in solution upon the centrifugal field applied to them in the usual velocity ultracentrifuges. This quantitative treatment, using the Kuhn and Kuhn odel for randomly coiled free-draining thread molecules, verifies the assumption generally made that the effect considered is negligible. Since the molecular weight of the particles and the magnitude of the centrifugal field applied to them vary inversely with each other, the constant, \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\beta h_0^2 }$\end{document} rarely attains values which are significant, and the effect produced by orientation of the threads is balanced by the effect due to stretching them. Moreover, by a suitable change of parameters, this treatment could be extended to account for the action of other tensile forces acting on thread molecules in solution

Notes: The variation of the x-ray reflection to the interchain separation in sodium pectate has been determined as a function of moisture content. The crystalline regions in sodium pectate have been found to sorb about 24% water (dry basis) at a relative humidity of 95% at 25°C. The sample as a whole under these conditions has a water content of 64%. At high water contents, therefore, a large difference in water content must exist between the crystalline and amorphous regions of sodium pectate. A marked change in degree of crystallinity occurs, as determined by the number and sharpness of the x-ray reflections, at an average water content of about 6% on desorption and on sorption at an average water content of about 14%.

Notes: A description is given of the preparation, birefringence, and swelling capacity of a series of microscopically homogeneous, partially acetylated cellulose model filaments with an acetyl content varying from 0 to 2.3 acetyl groups per glucose residue, and obtained either by acetylation or by deacetylation. A higher degree of acetylation of these artificial fibers could not be attained without destruction of the fiber. The same holds true for native ramie fibers. The swelling was studied in water, acetone, and methanol. The degree of swelling of the filaments plotted against acetyl content yields entirely different curves for the acetylation and the deacetylation series. These curves can be readily explained by the hypothesis that the intercrystalline (so-called amorphous) portion of the fiber substance is more accessible to the esterification and saponification reactions and is affected earlier than the crystalline portion. The birefringence of the acetylation series shows but a small - although apparently real - difference from that of the saponification series.

Notes: The tensile properties of a range of pure gum natural rubbers has been reviewed, and it has been shown that their principal features can be understood on the assumption that the tensile strength measured in a given test depends directly on the amount of crystallization at break. The most important single factor in determining tensile strength is the degree of cross linking. Cross linking is only needed in order to prevent plastic flow, thus permitting the molecules to be aligned by stretching, and hence to crystallize. A very highly cross-linked rubber is weak because the load required to stretch it is so high, that the rubber is broken before the elongation becomes large enough to produce crystallization. In general, vulcanization also involves reactions, e.g., the combination of sulfur with the rubber, which inhibit crystallization by producing structural modifications of the rubber. These reduce the tensile strength, especially when the degree of cross linking is large. These ideas readily explain the effects of swelling and of the temperature of test. They are also used in a brief discussion of the phenomena of overcure, reversion, and aging.

Notes: The emulsion polymerizations of butadiene and styrene and of butadiene alone have been studied at temperature of 90-160°. The effects of changes in catalysts, modifiers, times of polymerization, and other variables have been investigated. The rate of polymerization at 110° is markedly increased over that at 50° and the final product is a less modified and less processable polymer. However, the standard evaluation and road tests indicate this polymer may be a useful one.

Notes: From the results of initial acid-catalyzed hydrolysis of cellulose, and from certain data in the literature it is concluded that (1) native cellulose possesses an indefinitely high molecular weight; (2) as a consequence of common procedure adhered to by most investigators, native cellulose is unintentionally degraded to about DP 3000; (3) mild, initial acidic degradation, intentional or accidental, causes further decrease in the DP values down to the probable limiting value of 128 or 256, with complete loss of the tensile strength of the cellulose fiber; and (4) the few covalent bonds (about 0.3%) which become cleaved during these mild reactions are equally spaced, acid-sensitive, and entirely different from the regular 1,4-glycosidic bonds which are responsible for the random hydrolysis of cellulose in strongly acidic media. It is suggested that these acid-sensitive linkages represent hemiacetal or acetal bonds which originate from openchain glucose anhydride residues of “limit hydrocellulose” units and connect the latter along the a and b axes of the fiber. The length of the “limit hydrocellulose” is supposed to correspond to that of 27 = 128 glucose anhydride residues - that is, 660 Å., or twice these figures. Extension of this concept to starch leads to the postulate of a three-dimensional network of glucose anhydride units of indefinite number. The latter are held together by regular 1,4-α-glucopyranosidic bonds and, at short intervals, probably by acetal bonds of open-chain glucose anhydride residues. On mild, acid-catalyzed hy-drolysis these acid-sensitive linkages rupture rapidly and completely, giving rise to a material which consists of linear molecules only, containing 1,4-, 1,6-, and possibly 1,3-, glycosidic bonds between two adjacent glucose anhydride residues.

Notes: A substance may have a precipitating action on other dissolved substances. The concentration at which this action becomes apparent depends not only on the chemical nature of the constituents, but also on their molecular weights. In a homologous series the precipitating power increases with increasing molecular weight until it attains a very high value, as in macromolecules. The incompatibility of high polymers, which is manifested at very great dilutions, is due to this increase in the precipitating power with an increase of the molecular weight.

Notes: 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.

Notes: Part I traces fine structural features of polythene, beginning with the arrangement of carbon atoms disclosed by x-ray diffraction, and including the incorporation of crystalline segments into crystallites, and finally the combination of crystallites and amorphous regions to form spherulites-the largest structural elements of polythene. Attention is called to the frequent occurrence of side chains in the molecules. The structures of spherulitic and cold-drawn polythenes are compared. Part II describes an experimental study of the cold-drawing of polythene which discloses an interesting variant of this process, designated as “redrawing,” in which dimensional changes differ greatly from those of ordinary cold-drawing. On the basis of these observations and structural considerations presented in Part I, a mechanism of cold-drawing as a rheological process is outlined.

Notes: Experimental methods for measuring the mechanical properties of concentrated polymer solutions and other viscoelastic systems under periodically varying stresses are reviewed. These include direct measurements of stress and strain, measurements of response at resonance frequencies determined by the inertia of the apparatus, propagation of waves in extended media, and measurements of resonance vibrations. The conditions for the suitability of each method are discussed, and equations for the interrelation of the various quantities measured are given. Examples are shown to illustrate the fitting of experimental data to the calculated behavior of mechanical models, in order to obtain frequency-independent mechanical constants which can be interpreted in terms of molecular behavior.

Notes: The same point in the space cannot be occupied simultaneously by two molecules. In a solution of rigid rodlike macromolecules, each molecule prevents its neighbors from occupying certain positions, the whole of which form the forbidden angle. Calculation shows that in the case of rigid, filiform molecules, this angle is large even at very low concentrations. Isotropy is not possible at moderate concentrations. The consideration of the forbidden angle is necessary in the study of viscosity, osmotic pressure, flow birefringence, sedimentation, and molecular light scattering. In the solid state, the substance can be put under great tension, and the return to the normal state is extremely slow. This tension accounts for the abnormal solubility of disordered high polymers.

Notes: During recent years attempts have been made to formulate a viscosity-concentration relationship. The method of Huggins, in introducing a factor k′ as a hydrodynamic correction factor is examined, and in particular the attempts to draw conclusions relating k′ to the thermodynamic properties of the solution. An explanation is offered to correlate the experimental viscosity-concentration relationship and the change of solvent. A possible method for the actual calculation of concentration effects has been applied to the case of a suspension of spherical particles, for which, as a first approximation, a value of 10.6 for the coefficient of the c2 term has been obtained.

Notes: Tensile strengths of natural rubber samples quantitatively crosslinked with decamethylene dis-methyl azodicarboxylate have been determined. The proportion of the azo vulcanizing agent was varied 80-fold, the fraction p of cross-linked units in the products ranging from 0.10x 10-2 to 8.0 x 10-2. In spite of the small dimensions of the test specimen (cross section 0.10 in. by about 0.005 in.), the average error for a single observation is similar to that obtained in conventional testing procedures applied to specimens vulcanized with sulfur and accelerators. Deviations from the mean for 262 tests on 15 different cures are well represented by a Gaussian error function; a slight intimation of skewness is evident only at the extremities of the distribution of deviations. These results are incompatible with the commonly held view that rupture of the sample takes place at the “weakest link” in the series of flaws inevitably occurring along the specimen. It would appear that the ability to withstand tensile stress (applied in a specified manner) is an inherent characteristic of the bulk material. The rapid increase in tensile strength with the degree of crosslinking p for small values of this quantity is consistent with the conclusion, previously reached in the investigation of the physical properties of butyl rubber (6) that the tensile strength is directly related to the fraction of the structure which is permanently oriented by stretching. At higher degrees of cross-linking (at ρ x 100 = 1.0 to 1.5, depending on the molecular weight of the rubber) the tensile strength passes through a maximum and then declines steadily to quite low values for higher ρ's. This adverse effect of higher degrees of cross-linking is believed to result from the diminished elongation at which crystallization sets in and, hence, the smaller fraction of the network elements sufficiently oriented to participate in crystallite formation. Modification of up to 7% of the isoprene units of the rubber with the monofunctional compound, ethyl azodicarboxylate, depresses the tensile strength of the disazo vulcanized rubber relatively little. Evidently, the limited extent to which these modified (or copolymer) chains may enter into crystallization is adequate to bring about high tensile strength. Lack of direct correlation between modulus and tensile strength for rubbers vulcanized with various sulfur-accelerator combinations can only be explained by assuming that conventional vulcanization processes are accompanied to varying degrees by chain scission reactions. When vulcanized rubber is “over-cured,” or heat aged, chain scission becomes excessive.

Notes: The infrared and ultraviolet absorption spectra of Koresin are very similar to those of an acid-catalyzed p-tert-butylphenol-acetal- dehyde polymer. This is believed to be evidence that Koresin has Structure I. A variety of phenol-aldehyde resins have been prepared for comparison with Koresin. The ratings of some of these materials as tackifiers have been reported. These furnish further evidence that the molecular weight of a phenol-aldehyde resin is important in its tackifying action. An alkaline-catalyzed condensation product of acetylene and p-tert-butylphenol shows no tackifying action and has no free hydroxyl in the polymer as judged by its infrared pattern.

Notes: The paper deals with a tentative plan to extend quantitative x-ray measurements for determining the degree of crystallinity of polymers (as used earlier in cellulose determinations), to the investigation of rubber, polythene, and a polyamide. Strictly monochromatized copper radiation was used. The results show that further work along these lines may be promising. The raw rubber sample used was identical with one of those investigated by Goppel and by Arlman. It yielded a crystallinity figure higher than that reported by Goppel, but conformed with that found by Arlman. The figures obtained for polythene at different temperatures are compared with those derived from density and heat capacity measurements by other workers. The degree of crystallinity of polythene at room temperature is found to be ∼ 55%, and in samples of polyhexamethylene sebacamide, previously treated in different ways, figures between ∼50 and 70% are obtained. It is shown that the possibility of using the background intensity as a measure of the disordered fraction is confined to not too high angles of diffraction. A method is described (and experimentally checked) allowing for reducing the curves of intensity distribution as a function of 2θ as observed in various polymers to a comparable scale. It is further emphasized that, in polymers where hydrogen bonds play a decisive role in intermolecular cohesion, the x-ray results suggest that the “crystalline” or ordered fraction may to a considerable extent involve states of two-dimensional order.

Notes: 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.

Notes: During a definite polymerization time the rate of uncatalyzed polymerization of styrene may be decreased by the use of activated carbon. The intrinsic viscosities of the polymers formed may be either increased or decreased by the addition of active carbon, depending upon the activity of the carbon sample used.

Notes: The elastic and plastic properties of high polymeric materials are functions of the forces holding the molecules together and the ability of small segments of the chains to move about, relative to other segments. Internal plasticization is accomplished by introducing structural features which reduce intermolecular and intramolecular forces and which, in general, decrease the order of the polymer. Physical techniques used to determine the effect of such structural features have been discussed. The results of numerous investigations into the relations between structure and properties have been considered in an attempt to present a simple and consistent physical picture of these relations.

Notes: 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.

Notes: 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.

Notes: Cellobiose wird als Glykolsäure-glykosid nach der Azid-methode mit Protein kondensiert. Ferner werden aus Lacto-bionsäure und Proteinen nach der Azid-methode Lacto-bionyl-proteine synthetisiert.

Notes: 2-Chlorbutadien-1,3 (Chloropren) bildet schon bei niedrigen Temperaturen mit molekularem Sauerstoff ein Peroxyd. Die Bildungsgeschwindigkeit dieses Peroxyds ist so groß, daß es schwierig ist, peroxydfreies Chloropren herzustellen. Dies gelingt durch sorgfältige Destillation unter reinstem Stickstoff.Die Versuche zur Isolierung des Chloroprenperoxyds ergaben wegen seiner leichten Zersetzlichkeit keine befriedigenden Ergebnisse. Die quantitative Bestimmung des Peroxyds in Chloropren gelingt nach den üblichen Methoden nicht oder nur sehr schwierig. Chloroprenperoxyd oxydiert Antioxydantien, wie z. B. Phenyl-β-naphthylamin, zu gefärbten Produkten. Da Phenyl-β-naphthylamin die weitere Autoxydation des Chloroprens unterbindet, kann auf dieser Grundlage eine photometrische Bestimmung des Peroxyds durchgeführt werden.Die Geschwindigkeit der Sauerstoffaufnahme von Chloropren bei 0°C wurde volumetrisch gemessen. Die Sauerstoffaufnahme ist ein autokatalytischer, gleichförmig beschleunigter Vorgang. Er wird von Tetralinperoxyd stark beschleunigt, nicht aber von Benzoylperoxyde. Es wurden andere katalytisch wirkende Stoffe und der Einfluß des Lichtes untersucht.Da Chloroprenperoxyd die Polymerisation des Chloroprens auslöst und stark beschleunigt, ist es zweckmäßig, für die Stabilisierung dieser ungesättigten Verbindung solche Stoffe anzuwenden, die nicht nur die Polymerisation, sondern auch die Autoxydation hemmen. Die stabilisierende Wirkung der Antioxydantien wird bei Anwesenheit von Chloroprenperoxyd und Chlorwasserstoff nach einer Induktionsperiode durchbrochen. Dies kann dadurch erklärt werden, daß Phenyl-β-naphthylamin im Falle des Chloroprenperoxyds durch Oxydation, im Falle des Chlorwasserstoffs als Salz unwirksam gemacht wird.

Notes: Es wird ein einfaches Verfahren angegeben, den Transport von Wasser durch Textilfaserschichten zu messen, die einerseits in Wasser tauchen und andererseits an Luft mittlerer relativer Feuchtigkeit grenzen. Proteinfasern transportieren das Wasser langsam, Baumwolle rascher und Viskosekunstfasern sehr rasch.

Notes: Es wird der Einfluß von Seitenketten auf die Höhe der Viskositätszahl Zη von niedermolekularen Estern untersucht. Bei Dicetylmalonestern und Dicetylessigestern hat die Länge der Estergruppe keinen Einfluß auf die Höhe der Viskositätszahl. Bei substituierten Malonsäuredicetylestern resp. Disterylestern ändert sich dagegen die Viskositätszahl mit der Länge der in die CH2-Gruppe substituierten Alkylreste, und zwar ist sie bei kurzkettigen Substituenten kleiner, bei langgliedrigen größer als bei den unsubstituierten Verbindungen gleicher Kettenlänge. Das gleiche Verhalten zeigen β-alkylsubstituierte Stearinsäureester. Es wird weiter versucht, inwieweit das Einsteinsche Viskositätsgesetz in veränderter Fassung zur Klärung dieses Viskositätsverhaltens herangezogen werden kann.

Notes: Da nach den üblichen technischen Verfahren die Isolierung von Pektinen unvermeidlich mit einem gewissen Abbau verbunden ist, wurden die schonendsten Bedingungen festgestellt, unter denen es noch möglich ist, Pektin aus dem Fruchtfleisch von Äpfeln in ausreichender Menge zu gewinnen. Durch Wahl des günstigsten Reifezustandes, Ausschaltung einer Enzymtätigkeit, Einhaltung möglichst neidriger Extraktionstemperaturen und eines geeigneten pH konnte ein wenig abgebautes Pektin crhalten werden, dessen Methoxylgehalt dem für eine vollständig veresterte Polygalakturonsäure berechneten sehr nahe kommt. Die Molekulargröße wurde viskosimetrisch an einem aus diesem Material gewonnenen Pektinnitrat bestimmt, das nach einer schonenderen Nitrierungsmethode als der bisher üblichen hergestellt war. Die erhaltenen Werte liegen über den bisher beobachteten. Das im Apfelsaft vorhandene „freie Pektin“ wurde als niedriger molekular befunden.

Notes: Aus einer Zusammenstellung von Viskositätsmessungen an niedermolekularen Kettenmolekülen mit Doppelbindungen geht hervor, daß die trans-Formen eine höhere und die cis-Formen eine niedrigere Viskosität haben als die analogen gesättigten Verbindungen. Die verschiedene Viskosität von trans-, cis- und gesättigten Verbindungen kann mit der verschiedenen Form und Elastizität der Kettenmoleküle erklärt werden. Maleinsäureester und Maleinsäurepolyester lassen sich mit Brom als Katalysator in die entsprechenden Fumarester umlagern.

Notes: Es wurde die Polymerisationsgeschwindigkeit des Vinylchlorids bei 50° unter Zusatz verschiedener Mengen Benzoylperoxyd als Katalysator untersucht, indem der Umsatz das Molekulargewicht und die Zeitdauer beginnender Trübung durch Ausfallen des Polymerisats bestimmt wurde.Der Umsatz steigt zunächst langsam, dann schneller mit der Zeit an; über 80 - 90% nimmt er nur noch sehr langsam zu, so daß die letzten 1 - 2% praktisch nicht mehr polymerisieren. Mit sinkender Katalysatorkonzentration wird die Reaktion langsamer, derart, daß sich die Umsatzzeitkurven durch Dehnung der Zeitachse proportional der Wurzel aus der ursprünglichen Katalysatorkonzentration zur Deckung bringen lassen. Bis zu 70 - 80% läßt sich der Umsatz durch die Gl. u = (eat  -  1)b gut darstellen, wobei b = 0,1 und a = 0,240 · √c20 zu setzen ist.  -  Gegen Ende der Reaktion ließ sich im restlichen Monomeren Salzsäure nachweisen.Das Molekulargewicht nimmt mit steigender Menge Benzoylperoxyd und Sauerstoff deutlich ab; bei mäßigen Peroxydkonzentrationen wird dieser Effekt in der Streuung der Versuchswerte nicht sichtbar.  -  Die Zeit bis zur beginnenden Trübung ändert sich umgekehrt proportional der Wurzel aus der Katalysatorkonzentration und ist ferner unter reinem Sauerstoff größer, unter Stickstoff kleiner als unter Luft.Der Katalysator verschwindet während der Polymerisation, und zwar in um so stärkerem Maße, je höher seine ursprüngliche Konzentration, und um so weniger, je größer die Menge an Sauerstoff ist.  -  Mit Kaliumpersulfat erfolgt die Polymerisation nur in der wäßrigen Phase.Mit den Beobachtungen im Einklang steht das folgende Reaktionsschema (B = Benzoylperoxyd, M = monomeres Vinylchlorid). Die Hemmung der Polymerisation durch eine Anzahl von dritten Stoffen wurde orientierend, etwas eingehender die durch Styrol untersucht. Schwache Reduktionsmittel, Vinylderivate und einige anorganische Stoffe hemmen die Polymerisation, während chemisch indifferente Stoff sie nicht beeinflussen. Die Hemmung beruht vermutlich auf vorzeitigem Kettenabbruch.

Notes: Der bei Pektinpräparaten festzustellende P2O5-Gehalt in der Asche stammt teils von anorganischen und organischen Begleitstoffen (Phosphatiden), teils aber auch von Veresterungen der Pektinketten durch H3PO4; im Protopektin der Pflanzen hat man Vernetzungen der Pektinketten durch H3PO4-Brücken zu „Übermolekülen“ anzunehmen, die zahlenmäßig jedoch gegenüber den Vernetzungen durch mehrwertige Metallionen über die Karboxylgruppen zurücktreten.

Notes: 1Die Untersuchungen von Ohara (1933) über das polarisationsoptische Verhalten des Seidenfibroins wurden einer kritischen Betrachtung unterzogen und dabei Abweichungen von der Wienerschen Theorie festgestellt.2Die Hauptbrechungsindizes von Fibroinfäden, die 40 Stunden bei 100°C über P2O5 getrocknet worden waren, wurden nach der Immersionsmethode von Becke gemessen und zu für eine Wellenlänge von 589 mμ gefunden. Daraus resultiert eine Doppelbrechung von 0,0506 und für den Schwerpunkt des weißen Lichtes bei 550 mμ eine solche von 0,0514.3Imbibitionsversuche an trockenem und feuchtem Fibroin ergeben eindeutig das Fehlen eines Stäbchendoppelbrechungseffektes. Dies steht im Gegensatz zu den Untersuchungen von Ohara. Der mit Hilfe der Imbibitionsmethode gefundene Wert der Doppelbrechung stimmt mit dem der Immersionsmethode gut überein.4Die Abweichungen von diesem Wert in Wasser und wäßrigen Gemischen als Imbibitionsmedien lassen sich weitgehend mit Hilfe der Quellung erklären.5Durch Quellung und nachfolgende Imbibition kann keine Verstärkung eines etwa nur schwach entwickelten Stäbchendoppelbrechungseffektes erreicht werden.6Elektronenoptische Aufnahmen vermitteln Einblick in den Feinbau des Fibroins, welches aus feinen Fibrillen mit ganz verschiedenen Durchmessern besteht, die sehr fest und dicht gepackt sind.

Notes: Die molekulare Ultraschallgeschwindigkeit ist eine additive Eigenschaft für substanzen mit niedrigem Molekulargewicht und ergibt sich mit großer Annäherung aus der Summe der Geschwindigkeiten der verschiedenen Radikale, die das Molekül bilden.Die Übereinstimmung zwischen der experimentell festgestellten Geschwindigkeit und der auf Grund der Geschwindigkeiten der Radikale berechneten scheint besser zu sein als die auf Grund der Bindungsgeschwindigkeiten nach Lagemann und Corry berechneten. Wie schon von diesen Forschern angegeben, liefern die Bindungsgeschwindigkeiten zufriedenstellende Ergebnisse nur für unverzweigte Verbindungen.In den Verbindungen mit niedrigen Molekulargewichten führt die Gegenwart von Verzweigungen in den Molekülen zu einer Erniedrigung der molekularen Ultraschallgeschwindigkeit, die jedoch sehr geringfügig ist (12 Einheiten für die Methyl- und 20 für die Äthylgruppe in anderen Stellungen als  - 1 und  - 2).Für Verbindungen mit hohem Molekulargewicht und unverzweigter Kette stimmt der Wert der grundmolekularen Ultraschallgeschwindigkeit, d. h. bezogen auf die Grundgruppe, mit den auf Grund der Bindungsgeschwindigkeiten und auch mit den auf Grund der Radikalgeschwindigkeiten berechneten überein. Für verzweigte Moleküle ist die Übereinstimmung für die Radikalgeschwindigkeit besser, wobei die Erniedrigung der grundmolekularen Geschwindigkeit infolge der Verzweigungen höher ist im Falle von Verbindungen mit hohem als mit niedrigem Molekulargewicht.Die Bestimmung des Verhältnisses zwischen der experimentellen und berechneten Geschwindigkeit kann ein Mittel darstellen, um Anzahl und Größe der Verzweigungen zu bestimmen. Diesem Verhältnis ist die Bezeichnung „Formfaktor“ gegeben worden.Der Formfaktor ist gleich 1 oder etwas höher für die unverzweigten oder wenig verzweigten Verbindungen mit hohem Molekulargewicht (Paraffine, Polyäthylene, Polyäthylenoxyd, Nylon), niedriger als 1 für die verzweigten Verbindungen: 0,90 im Naturgummi, der eine Methylverzweigung an jedem vierten Kohlenstoffatom in den langen Ketten trägt, und 0,79-0,80 in den Polyisobutylenen mit zwei Methylverzweigungen an jedem zweiten Kohlenstoffatom in der Kette.Niedrigere Werte als der Naturgummi und unwesentlich höhere als die Polyisobutylene weisen die Formfaktoren des Polyalfabutylens und des Polystyrols auf (0,82), die eine äthylische, bzw, eine phenylische Gruppe auf jedes zweite Kohlenstoffatom in der langen Kette besitzen; dies beweist auch einen Einfluß der Länge der Verzweigungen auf den Formfaktor in dem Sinne, daß letzterer um so mehr erniedrigt wird, je größer die Verzweigung ist.Der Einfluß der Häufigkeit der Verzweigungen und ihrer Länge auf den Formfaktor wird beim Polymethylmetakrylat bestätigt, da diese Verbindung den niedrigsten von uns festgestellten Formfaktor aufweist; diese Verbindung besitzt nämlich zwei Verzweigungen an jedem zweiten Kohlenstoffatom der Kette, und zwar eine Methylgruppe und eine methylierte Karboxylgruppe.Die Übereinstimmung der Formfaktoren des Buna und des hydrierten Buna mit dem des Polyalfabutylens ist ein weiterer Beweis, daß die nicht bei niedriger Temperatur ausgeführte Polymerisierung des Butadiens in den Stellungen 1 - 2 oder 2 - 3 und nicht in der Stellung 1 - 4 stattfindet. Dies steht im Einklang mit den kürzlich mitgeteilten Versuchsergebnissen von Hanson und Halverson bei gestrecktem Buna.Der niedrige Formfaktor des Polyvinylisobutyläthers (0,79) kann ein Zeichen für den Einfluß der sekundären Verzweigungen auf den Formfaktor sein.Schließlich bestätigt die Unveränderlichkeit des Formfaktors für alle untersuchten Polyisobutylene mit verschiedenen Molekulargewichten, daß für hochmolekulare Verbindungen die grundmolekulare Ultraschallgeschwindigkeit und demzufolge der Formfaktor vom Molekulargewicht unabhängig ist.

Notes: Durch Untersuchung der Kettenlängenverteilung von oxydative in Kupferoxydammoniaklösung abgebauten Buchen- und Fichtencellulosen wird gezeigt, daß ebenso wie bei Baumwoll- und Ramiecellulosen eine Vereinheitlichung bei Polymerisationsgraden zwischen 400 und 500 eintritt. Auch bei hydrolytisch abgebauten Produkten ist dieser Effekt zu bemerken, läßt sich jedoch wegen der Viskositätsanomalien nicht quantitativ auswerten. Aus den Befunden wird geschlossen, daß auch in Holzcellulosen im Abstand von ca. 500 Glucoseresten Lockerstellen vorhanden sind, die durch Oxydationsmittel und Säuren erheblich schneller gespalten werden als die β-glucosidischen Bindungen. Diese periodische Struktur ist für alle bisher untersuchten Cellulosearten im Abstand der Lockerstellen identisch, jedoch unterschieden durch das Verhältnis der Spaltungsgeschwindigkeiten. Aus elektronenmikroskopischen Aufnahmen wird geschlossen, daß die Lockerstellen in Ebenen senkrecht zur Faserrichtung angeordnet sind.

Notes: The conductance in diphenyl ether at 35°C. and 60 cycles of the picrate of a 4-vinylpyridine-styrene copolymer (10:90) has been measured. The equivalent conductance, based on the nitrogen content, is of the same order as that of picoline picrate, and varies with concentration in accordance with the law of ion association.

Notes: A polyvinyl acetate polymer of medium viscosity was fractionated into sixteen fractions (first series) and three of the larger of these further separated into twenty subfractions (second series). The intrinsic viscosities and the osmotic pressure molecular weights were determined at 25°C. and the relation between them was found to be expressed by the equations: first series: [η] = (1.88 × 10-4) M0.69; second series: [η] = (1.76 × 10-4) M0.68. The data indicate that little, if any, increase in homogeneity is to be expected by further successive fractionations and that the equations applicable to the second fractionation series are representative of essentially homogeneous polyvinyl acetates in acetone. An equation applicable to fractionated and unfractionated vinyl acetate polymers is described that is useful in obtaining the intrinsic viscosity from a single viscosity measurement. Several unfractionated materials from different sources were also studied and the calculated ratios of the viscosity-average to the number-average molecular weight indicate that the degree of heterogeneity of chain-length distribution increases with increasing average molecular weight.

Notes: The rate of emulsion copolymerization of butadiene and styrene, with soap as emulsifier and potassium persulfate as catalyst, is extremely small at 50°C. The presence of very small amounts of high-molecular mercaptans promotes the copolymerization reaction. The promoting effect is at a maximum for primary, secondary, and tertiary dodecyl mercaptans and decreases for mercaptans of either higher or lower molecular weight. The promoting effect is independent within wide limits of the amount of mercaptan added after the minimum quantity has been exceeded. Mercaptans which are poor promoters may be so because they fail to bring about chain initiation or because they aid in chain termination. The low-molecular mercaptans which are poor promoters prevent the high-molecular mercaptans from exerting their good promoting effect when a mixture of both types of mercaptans is used. The mechanism of the promoting effect of mercaptans upon the emulsion copolymerization of butadiene (75 parts) and styrene (25 parts) or upon the polymerization of butadiene alone is not yet clear.

Notes: An empirical equation is described which predicts the intrinsic viscosities of 75:25 butadiene-styrene emulsion copolymers from data on mercaptan consumption. The form of the equation is as follows: \documentclass{article}\pagestyle{empty}\begin{document}$$\left[ \eta \right] = \left[ {\frac{{aP}}{{R_0 R}} + \frac{b}{{R_0 }}\int_0^P {\frac{{dP}}{{dR}}dP} } \right]^c $$\end{document} where [η] is the intrinsic viscosity, P is the conversion, R is the fraction of mercaptan consumed, R0 is the mercaptan charged, and a, b, and c are constants equal to 0.22, 1.12, and 0.66, respectively. Evidence is given that the intrinsic viscosity of mutual-recipe polymers can be described satisfactorily in terms of mercaptan consumption.

Notes: The calculation of the “theoretical” minimum modifier requirement, TMMR, for butadiene-styrene (75:25) copolymers of given intrinsic viscosities at various conversions is described. The TMMR of 75% conversion polymer of intrinsic viscosity 2.0 is R0 = 0.28, which is only about 60% of the value of R0 for commercial primary dodecyl mercaptan (C.M.) in large-size reactors. The efficiency, E, of a modifier for 75:25 butadiene-styrene copolymerization using soap as emulsifier and persulfate as catalyst has been defined by and calculated from the equation: \documentclass{article}\pagestyle{empty}\begin{document}$$E = \frac{{P\left( {0.2 + P} \right)}}{{R_0 \left( {M_v \times 10^{ - 5} } \right)}}$$\end{document} where Mv is the intrinsic viscosity molecular weight of the polymer at conversion, P, with an amount of mercaptan, R0, charged with the monomers. For all modifiers the efficiency is low at low conversions and gradually increases to a maximum with increasing conversion. For different modifiers this maximum may be as at low as 10% conversion or at higher than 80% conversion. After the maximum the efficiency decreases with further increase of conversion. The most efficient modifier for the production of polymers of intrinsic viscosity, [η], at conversion, P, will meet the following conditions, R = 1 at conversion, P, and dP/dR is constant. Inefficient modifiers may be made more efficient by changing the conditions or procedure of polymerization in such a way that the modifier more nearly complies with the above conditions.

Notes: The swelling of vulcanized natural rubber, Buna S, neoprene, Perbunan, and Perbunan Extra was measured in various organic liquids. The essential influence of polarizability and polarity on the swelling equilibrium is illustrated by comparing series of solvents and polymers with gradually changing geometrical and chemical structure. Experiments on the influence of temperature and of strain on the swelling equilibrium are reported. The swelling properties of ebonites and similar derivatives allow some conclusions on the amount of cross linking in these polymers.

Notes: The chemical reactivity of vinyl and diene polymers manifested during aging and degradation is similar to the reactivity manifested during polymerization; namely, the activated intermediates are radicals and the reaction proceeds by a chain mechanism. A discussion of the possible types of aggregative and disaggregative processes involved in aging is presented. On the basis that polymerization and degradation occur by means of the same radical mechanism, experimental evidence is given to indicate that under certain conditions both reactions may occur simultaneously. Viscosity changes of solutions of mono- and polystyrene and methyl methacrylate were studied under varying conditions of heat, oxygen, catalysts, light, and photosensitizers. An analysis of the concurrent aggregative and disaggregative reactions involved in aging may be obtained by isolating one reaction from the other, either by various physical methods, such as intermittent and continuous stress relaxation, or by such classical methods as sol-gel determinations and aging in solution. A comparative study of the rate of oxygen absorption of a large number of polymer types was undertaken to evaluate the factors affecting oxidation. Evidence is presented to show that these factors may be specified by the following: (1) chemical structure of the polymeric material, (2) presence of antioxidants, and (3) compounding and vulcanization. The oxidizability of polymeric materials was also studied in a circulating oxygen absorption apparatus in order to determine the effect of evolved, gaseous oxidation products. A preliminary study of the effect of light on the aging of butyl and GR-S rubber as measured by oxygen absorption and stress relaxation is presented.

Notes: 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.

Notes: Various problems related to the determination with x-rays of the atomic configuration of organic fibers are discussed. Because of the approximate nature of the underlying theory, too far-reaching conclusions should be avoided, especially since, in the case of organic fibers, the situation is much less simple than in the case of sodium chloride powder or metallic wires, for example. Because of these facts, and because of the relative poorness of fiber patterns, the atomic coordinates as well as the space group of the structure can be found only within certain limits. Though the use of macroscopic models is very helpful in visualizing the spatial arrangement, no conclusions of a quantitative nature can be reached with their aid because the assumptions embodied in these models are too numerous and too inexact to justify speculations on details of the structure. In the case of cellulose fibers, it is shown that the problem cannot yet be solved completely; the outlook for a really unique solution is not hopeful. The structure proposed by Meyer and Misch is still the best approximation available. More recent propositions are shown to be less well founded; the atomic configuration introduced by Peirce, being at variance with chemical, crystallographic and x-ray evidence, is to be discarded.

Notes: Intrinsic viscosity, calculated in accordance with the empirical relation established by Schulz and Huggins, deviates considerably from its true value in the case of increasing viscosities. The introduction of a simple corrective, second degree term η2sp/150, applicable to most of the polymers, permits the direct computation of intrinsic viscosity based upon polymer solutions of various concentrations. Specific viscosities may vary to a great extent and reach a value as high as 15; the use of high concentrations permits the reduction of experimental errors and the determination, to within an average of one per cent, of the intrinsic viscosity of the polymer sample, and thus of its molecular weight.

Notes: A solvent prepared by mixing 70 parts by volume of ethanol, 30 parts of toluene, and 10 parts of water is found to be a suitable solvent for the extraction of organic nonrubber material from GR-S. The presence of the water has no effect on the rate of extraction of the nonrubber, while it reduces the extractibility of low molecular polymer to one-tenth of that found in the absence of water in the solvent. A procedure is described for the determination of small amounts of GR-S in the extracts. This procedure is based on the quantitative precipitation of the ICl addition product of the rubber from a chloroform solution by addition of ethanol. A routine procedure for the determination of the amount of rubber in GR-S is given.

Notes: The refractive index-temperature data for polyvinyl acetate show a second-order phase transition temperature of 24°C.

Notes: Rubber hydrocarbon irradiated in vacuo is decomposed by ultraviolet light of wave length less than 4000 Å. The rubber very rapidly becomes insoluble, and liberates a gaseous mixture which consists mainly of hydrogen when the irradiation temperature is less than 150°C. The reaction characteristics have been investigated and point to the occurrence of dissociation processes similar to those deduced for comparable simple olefins. When irradiated above 150°C., small but significant amounts of isoprene appear in the volatile product, thereby providing an experimental means of determining the activation energy for the separation of isoprene from a polyisoprene chain terminated by an allyl radical.

Notes: The addition of silver nitrate to polymerizable systems containing butadiene can result in increased over-all rates of conversion. When butadiene is the only monomer and a cationic soap is used the addition of silver nitrate causes* a significant decrease in rate. The most active system studied was one which contained butadiene, styrene, a cationic soap, a peroxide, and silver nitrate. Comparison runs in a GR-S type formulation with silver nitrate and potassium ferricyanide indicate that the silver salt is the more effective in producing higher over-all rates of conversion.

Notes: The viscoelastic properties of plasticized Vinylite VYNW were studied over a wide range of time scale by means of the tensile creep test. A number of different plasticizers were compared as to their plasticizing effectiveness. It was found that different plasticizers imparted distinctly different shapes to the creep curve of the plasticized ferent plasticized resin. The flat creep curve, characteristic of trioctyl phosphate, is considered to be superior to the steep creep curve of tricresyl phosphate. Mixtures of plasticizers were also studied. A number of conjectures are advanced concerning the molecular mechanism of plasticizer action. One important characteristic of a plasticized formulation of the polyvinyl chloride types of resin is the existence of a three-dimensional gel structure of great permanence which prevents the occurrence of irrecoverable viscous flow.

Notes: The preparation of perbenzoic acid has been investigated in a n attempt to obtain standard solutions of perbenzoic acid suitable for the amlyszk of unsaturated compounds. Some modifiations of the procedure given by Braun for the preparation of a solution of perbenzoic acid in a n organic solvent are recommended. A study has been made of the stability of solutions of perbenzoic acid in chloroform and in benzene. Benzene or benzene-chloroform mixtures are recommended as solvents for perbenzoic acid. Chloroform solutions of perbenzoic acid which do not contain inhibitors for decomposition have been found to be definitely undesirable in analytical work because perbenzoic acid catalyzes the decomposition of chloroform by oxygen. construction Finance Corporation, in connection with the Government Synthetic Rubber Program.

Notes: The conductance of a series of salts made by the addition of n-butyl bromide to 4-vinylpyridine-styrene copolymers (1.5 to 90 mole per cent vinylpyridine) has been measured in dioxane (∊′ = 2.2), ethylene dichloride (∊′ = 10.2), and a series of nitromethane-dioxane mixtures (16.0 ≤ ∊′ ≤ 39.4). Three independent arguments deduced from the data show that ionic association under the influence of interionic electrostatic forces must occur in solutions of polyelectrolytes in such a way that a certain average fraction of the counter ions accompany the large polycation and contribute nothing to conductance. First, the conductance at fixed copolymer composition and fixed salt concentration decreases with decreasing dielectric constant of the solvent medium. Second, at a given counter ion concentration in a given solvent, the conductance decreases with increasing pyridonium content of the chain. Third, for a given salt and solvent, the conductance decreases with increasing salt concentration at a rate much slower than that characteristic of simple electrolytes.

Notes: The method for the evaluation of the percentage crystallinity in cellulose preparations from x-ray intensity measurements, previously described in detail (J. Appl. Phys., in press) is reviewed briefly and new material presented consisting of crystallinity percentages between 8% and 70%. Cotton, flax, and ramie possess equal crystallinity (70%) and so do the majority of rayons, independent of their degree of orientation and including cuprammonium and Lilienfeld rayons. Cellulose acetates saponified under varying conditions also yield almost the same value as rayon (40%). The New product Fiber G (du Pont) holds an exceptional position with 53% crystalline substance. In the series of native celluloses, wood pulp has about 65%, Valonia 65-70%, and bacterial cellulose about 40%. By dry grinding of rayon, a powder was obtained containing only slightly less than 10% crystalline substance, which on recrystallization in water, yields 2 product having the same crystallinity as rayon. The difference between the heats of wetting of the criginal and the recrystallized powder affords additional support of the results obtained.

Notes: 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.

Notes: By means of chain transfer agents such as dodecyl mercaptan, polyisoprenes whose number-average molecular weights range between 300-1200 and which are liquid at room temperature have been prepared. The structure and physical properties of these substances have been investigated. Vulcanization of these liquids to rubberlike materials at room temperature and above is described.

Notes: The construction of a thermostated osmometer of the Fuoss-Mead pattern is described. The technique of preparation of bacterial cellulose membranes for osmotic measurements on high polymer systems is given. The permeability of such membranes may be controlled by growth to a thickness of 4-5 mm., drying in contact with a stainless steel surface, and reswelling in water or alcohol-water mixtures. The degree of reswelling required to give membranes suitable for use with polymers of a range of molecular weights is given. The factors affecting the behaviour of the membranes in the osmometer are discussed.

Notes: 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.

Notes: The strong ultraviolet absorption in the wave-length region 280-330 mμ shown by copolymers of acenaphthylene with styrene or methyl methacrylate is due to acenaphthylene residues. The spectra of samples of copolymer containing a small percentage of acenaphthylene are different from the spectrum of polyacenaphthylene. As a result of the comparison of the spectra of these copolymers with the spectra of acenaphthene and with the two forms of 1,1′-biacenaphthyl it is concluded that spectra of the copolymers can be explained as arising from the presence of pairs of acenaphthylene groups. Finally it is shown that the spectra can be used to estimate the acenaphthylene contents of the copolymers.

Notes: Es werdenn für cine Reihe von Erscheinungen bei Lösungen mit Fadenmolekülen, wie die künstliche Doppelbrechung, die Viskosität, den Depolarisationsgrad des molekularen Streulichtes, die Abhängigkeit vom Polymerisationsgrad und von der Form (Stäbchenform und statistische Grenzfälle) angegeben. Ferner werden Methoden zur Untersuchung von Verzweigungen und zur Betimmung der Mikroform mitgeteilt.

Notes: 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.

Notes: A close correlation exists between the modifying effect of mercaptans in emulsion copolymerization of butadiene (75 parts) and styrene (25 parts) and mercaptan consumption during the polymerization. A procedure is described for the rapid amperometric titration of mercaptans in latices. Mercaptan disappearance curves (i.e., mercaptan used at various conversions) are given for a series of primary and tertiary mercaptans of widely varying molecular weight and of two secondary mercaptans. The consumption of (and modification by) primary mercaptans is affected to a much greater extent by the molecular weight of the mercaptan than that of tertiary mercaptans. The consumption of pure and of commercial n-dodecyl mercaptan is greatly affected by the mode and rate of agitation during the polymerization, manner of preparation of the charge (preformed soap and soap “in situ,” separate emulsification of the modifier), dilution of the monomers with inert organic solvents, excess of free caustic in the charge, amount and kind of emulsifier, and the presence of substances which from complexes with the mercaptan. The consumption of tertiary dodecyl mercaptan is not affected by these variables. The difference in behavior between the two mercaptans is interpreted as a faster rate of solubilization into the locus of the reaction of tertiary mercaptans than of primary mercaptans of the same molecular weight. The disappearance curve of a mercaptan from a mixture of two mercaptans remains unaffected by the presence of the other mercaptan. At the same conversion the consumption of a mercaptan increases with decreasing temperature. Disappearance of mercaptan during the polymerization as a result of nonmodifying reactions is discussed.

Notes: The phase separation in solutions of high polymers in the same solvent (technically known as incompatibility) has been studied for fourteen high polymers (cellulose, vinyl, and acrylic derivatives) dissolved in thirteen solvents. The influence of solvent, concentration, molecular weight and constitution of the macromolecules has been studied for 78 mixtures: the results are represented in triangular diagrams. Incompatibility appears to be the normal situation, compatibility the exception. Moreover, in cetain cases the exception may be only apparent. Phase separation is discussed in its relation to osmotic pressure, solubility, and the isomorphism of the molecules. Phase separation furnishes new means - useful at leat for technical research - of measuring the molecular weight of macromolecules. It is a simple and rapid procedure.

Notes: From data in the literature on relative rates of copolymerization it has been possible to evaluate two constants, Q and e, characteristic of an individual monomer, which appear to account satisfactorily for its behavior in copolymerization. The constant Q describes the “general monomer reactivity” and is apparently related to possibilities for stabilization in a radical adduct. The constant e takes account of polar factors influencing copolymerization.

Notes: A procedure is given for the determination of the external double bonds in synthetic rubbers. The method is based on the difference in the rates of reaction of perbenzoic acid with internal and with external double bonds. The principles of the interpretation of the analytical data are discussed. Calibration curves for use in the analysis of butadiene and isoprene polymers are given. The procedure is also applicable to the analysis of a mixture of two compounds, one of which contains an external double bond and the other an internal double bond. Data are given for the analysis of mixtures of oleic acid and undecylenic acid.

Notes: A mechanism is presented which shows how terpenes and related compounds, some of which are found associated with trans - polyisoprene in nature, may be expected to be formed by a radical chain oxidative degradation of trans - polyisoprene.