摘要:

AbstractAs an alternative method to fractionating the polymer into portions of different molecular weight, in order to obtain the distribution of molecular weights, the method of fitting by statistical moments is proposed. It is shown how from a knowledge of differen order, utilising the inequalities between such averages and their relation to the dispersion of molecular weight, estimates of the distribution function can be obtained: (A) under the assumption of a standard form for the distribution function; (B) without such an assumption, but building up the approximation from a standard form as the norm function and its derivatives; (C) without using any standard form of distribution at all. Numerical examples of the fitting procedures accompany the exposition.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100101

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe various stages employed in the production of a phenolformaldehyde cast resin are discussed. It is assumed that the chains formed during the condensation stage undergo a rearrangement upon acidification to yield roughly spherical, stabilized micelles. These micelles are concentrated by dehydration until coalescence begins. At this point the chains again rearrange and the resin becomes the continuous phase. Pronounced changes in the properties of the system are observed at this critical point. The effects produced by undercondensation, overcondensation, overdehydration, etc. are mentioned briefly. The ionizable components, by determining the interfacialpH during the curing stage, are shown to be directly related to the rate of cure, stability, color, light transmissibility, etc. of the cured casting. Transparent castings are expected only when an ionizable component of the proper refractive powers is oriented at the interface. An examination of the immediately available data provides a lead to the future changes that can be expected as aging progresses.

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100102

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractNous avons appliaué à l'étude de suspensions de virus de la mosaïque du tabac les résultats de la théorie de la diffusion par des bâtonnets anisotropes. Dans ce but on détermine d'abord l'anisotropie δ du bâtonnet en extrapolant à angle de diffusion nul le facteur de dépolarisation ρv. On trouve ainsi δ = 0,3, valeur un peu forte comparée à celle déduite des expériences de biréfringence d'écoulement (δ = +0,1). Enfin comparant les répartitions angulaires des différentes composantes avec la courbe théorique, on obtient un accord trés satisfaisant en prenant pour longueur des bâtonnetsL= 2300 Å, ce qui constitue un bonne vérification de la théorie précitée.La même analyse appliquée à l'acide thymonucleique S VIII préparé par Schwander en solution NaCl 1Mneutre conduit aux valeurs:\documentclass{article}\pagestyle{empty}\begin{document}${\rm \delta } = - 0,15{\rm et}L = 2000\mathop {

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100103

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractCopolymers of vinylsulfonic acid derivatives with butadiene, isoprene, and styrene have been prepared. The evaluation of butadiene‐vinylsulfonic acid ester copolymers indicates that these rubbers have good low‐temperature characteristics and that the stress‐strain properties of then‐butyl vinylsulfonate copolymer approach those of the standard GR‐S rubber; however the oil resistance properties are poor. The stress‐strain properties of the butadiene‐n‐hexyl vinylsulfonate copolymer are inferior to those of th

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100104

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe rate of reaction of sulfur dioxide in styrene solutions at 60°C., with azodiisobutyronitrile as thermal catalyst, has been measured: (1) by gravimetric determination of the total rate of polymerization and analysis of the polymer formed and (2) volumetrically. An experimental arrangement for the latter method, which can be used when the partial pressure of the solvent (styrene solution) is appreciable compared to that of the solute (sulfur dioxide) is described. The kinetics of reaction conform to the mechanism previously proposed, according to which sulfur dioxide reacts in the form of a 1/1 styrene/sulfur dioxide complexC. It is shown that certain features attributable to depropagation reactions, such as theincreasein the styrene content of the copolymer withdecreasingstyrene concentration in the reaction mixture, are much more marked at 60°C than at 20°C. By combining the rate measurements with new data on the temperature dependence of copolymer composition at elevated temperatures, it is possible to assign an approximate value to the velocity constant of a depropagation reaction involving breakage of a carbon‐sulfur bond. The activation energy is estimated at 50 to 62 kJ. (12 to 15 kcals.), which is much lower than that for depropagation of a vinyl polymer; the frequency factor is about 4 X 1010to 3 X 1012sec.−1. Some data on the composition of polymers prepared at 0° and −20°C. are appended. It is shown that theC· +Cpropagation step, which seems negligible at 20°C. or above, becomes of some significance at lower temperatures. Under these conditions polymers containing less than two styrene units per sulfur dioxide can

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100105

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractDie Untersuchungen ergaben, dass beim Fibrin‐Molekül von einer kontinuierlichen Verteilung der aromatischen Aminosäuren im allgemeinen nicht gesprochen werden kann. Die Einwirkung von Cupriäthylendiamin auf Fibrin führt zu einem Zerfall des Teilchens in zwei Fraktionen “I” und “II”. Fraktion I macht etwa 75% des Moleküls aus, ist stabil, unlöslich in NaCl‐Lösung, enthält dasgesamte Tyrosin des Fibrinmolekülssowie 3% Tryptophan. Obwohl diese Fraktion noch deutlich die Eigenschaften eines hochpolymeren Eiweisskörpers zeigt, kann sie durch Thrombin nicht mehr fibrillär polymerisieren. Fraktion II dagegen macht rund 15% des Fibrins aus, ist labil, löslich in NaCl‐Lösung, enthältkein Tyrosin, jedoch ebenfalls 3% Tryptophan, wahrscheinlich viel mehr Arginin als Fraktion I und trägt

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100106

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractEs wird ein Differentialrefraktometer beschrieben das gegenüber den bisherigen Instrumenten eine um eine Zehnerpotenz gesteigerte Genauigkeit dadurch erreicht, dass es den Abstand der durch Beugung unscharfen Spaltabbildungen photometrisch aus markanten Kurvenpunkten bestimmen lässt. Das Gerät ist experimentell wie rechnerisch exakt kalibrierbar. Es erlaubt die Bestimmung der Dispersion von Brechungsindexdifferenzen. Kontrollmessungen an wässrigen Rohrzuckerlösungen ergeben gute Uebereinstimmung mit den Werten des National Bureau of Stand

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100107

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractSur une serie de palyméthacrylates de méthyl fractionnés des mesures de la diffusion lumineuse (en fonction de I'angle et de la longeur d'onde) on été faites, puis la constante de diffusion, la constante de sédimentation dans I'ultrazentrifugeuse et la viscosité intrinshque [η] ont été déterminés. Les poids moléculaires et les diamètres des chaînes souples sont en concordance d'après ces méthodes. La dépendance des diametres des chaines sonples d,l du poids molkculaire est un peu plus forte que d'aprh la loi de Kuhn (dst≃M0.6). L'influence de cette decouverte sur la fonction de la diffusion lumineuse de mihe que sur l'equation de la viscosite de Kirkwood et

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100108

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractThe extreme ultraviolet absorption spectra between 1700–3000 A of a series of monomers and polymers show that, in addition to absorption due to the presence of chromophores such as phenyl rings and residual double bonds, other factors such as light scattering, orientation or polarization effects, and interaction, both intermolecular and intramolecular, are important in the observed spectra. In polymers such as polystyrene and polybutadiene, the effect due to scattering becomes appreciable (about 20–30%) at about 1700 A but the other factors do not appear to be important. In proteins, the absorption at short wavelengths is seen to be a function of absorbing chromophores as well as of residual double bond character of the polypeptide chain, of light scattering, and orientation or polarization and intramolecular effects. In other polyelectrolytes, such as polyvinylpyridinium chloride, changes in the 2000 A transition indicate that there is a degree of orientation and/or molecular interaction of the aromatic groups in these polym

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100109

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY

摘要:

AbstractLight scattering and viscosity studies have been made on solutions of sodium desoxyribonucleate in 0.2MNaCl adjusted topH values of 6.5, 3.0, and 2.6 by dialysis in order to prevent contact with more concentrated acid. It is found that the molecular weight (7,700,000) is the same under these three conditions and remains so when the acid solutions are adjusted topH 6.5. Upon lowering thepH the molecular size decreases due to increased coiling, but returns to its original value upon reneutralization. AtpH 2.6 the mean radius of the molecule is less than half thepH 6.5 value. It is argued that these observations invalidate the existing evidence for degradation or disaggregation accompanying the appearance of new titratable groups. However, it is likely that most of the amino groups have not been titrated atpH 2.6 at the ionic strength employed here. Consequently the possibility remains that the stability atpH 2.6 is a consequence of a hydrogen‐bonded structure that is still largely intac

ISSN:0022-3832    

DOI:10.1002/pol.1953.120100110

出版商:Interscience Publishers, Inc.    

年代:1953

数据来源: WILEY