摘要:

AbstractAnalysis is made of the system of parallel chain molecules which has a long‐range order in the arrangement of the structural units along the chains, and a short‐range order in the packing of molecules. A solution has been obtained of the problem of scattering x‐rays on such a system. Analysis of the correspodence between theoretical results and the results for certain fibrous proteins and polymers has been made. This analysis shows that in some parts of these substances there are regions where the parallel chains are arranged without any correlation to the packing of the units of neighboring c

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112301

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe stability of complexes and associates formed in compound molten electrolytes can be quantitatively estimated from the excess thermodynamic functions (free enthalpy, entropy, enthalpy). These functions can be most conveniently determined by measuring the electromotive force of chemical cells of the type\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Me}_{\rm I} [{\rm Me}_{\rm I} {\rm X}_m,{\rm Me}_{{\rm II}} {\rm X}_n ]{\rm X}_2 $\end{document}where × is halogen. In this way the following systems were experimentally investigated: BeCl2–NaCl; MgCl2–LiCl; MgCl2–NaCl; MgCl2–KCl; MgCl2–RbCl; PbCl2–LiCl; PbCl2–NaCl; PbCl2–KCl; PbCl2–RbCl. The dependence of the excess partial free enthalpy on the mole fraction can be expressed by the equation\documentclass{article}\pagestyle{empty}\begin{document}$ Z_1^E = \alpha (1 - {\rm X}_1 )\beta $\end{document}where α and β are constants (for example β = 2.4 for PbCl2). In logarithmic coordinates, (ZE; (1—X1)), the experimentally determined data show a linear dependence. A curve‐linear dependence in these coordinates indicates a deviation from an ideal system. According to the magnitude of these deviations, it is possible to judge the stability of the complexes in the melts. The stability of the complexes in the melts regularly increases in the or

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112302

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA study has been made of the photochemical behavior at 2537 A. of the following substances: 2′‐, 3′‐, 5′‐, and cyclic 2′:3′‐cytidylic acids and various preparations of apurinic, ribonucleic, and deaminated ribonucleic acids. The behavior of all the cytidylic acids is qualitatively similar, the photoproduct exhibiting a new maximum at 2360 A. The reaction can be reversed completely in the dark by heating, acidification, or addition of alkai. The 5′‐cytidylic acid differs quanlitatively from the other cytidylic acids in that the quantum yield is lower, as is also the extinction of the new maximum. These results are in agreement with previous findings and support the suggestion that there is hydrogen bonding in cytosine nucleosides and nucleotides between the pyrimidine 2‐carbonyl and the 5′‐sugar hydroxyl which influences the photochemical reaction. The results indicate also the possible existence of weaker bonds involving the 2′‐ and 3′‐hydroxyls. The irradiation of apurinic and ribonucleic acids is accompanied by a decrease in extinction of the principal absorption maximum and very little change below 2400 A. If the decrease of the principal absorption maximum does not exceed 50% as a result of photolysis, then it is subsequently possible to restore about 50% of this decrease by heating a few minutes at 70–90°C. The quantum yield for photolysis of apurinic acid is of the same order of magnitude as for 2′‐ and 3′‐cytidine nucleotides; for ribonucleic acid it is lower. For deaminated ribonucleic acid, the reaction is not reversible. The photochemical behavior of nucleic acids is discussed from the point of view of the photochemistry of uracil and cytosine nucleotides, as well as the relation of the

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112303

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA study has been made of the kinetics of heat inactivation in light and heavy water, of lysozyme, ribonuclease, and desoxyribonuclease. In all instances, the isotope effect for inactivation (kH/kD) is found to be related to the activation energy and to decrease to approximately unity for low activation energies. For lysozyme at acid and neutral pH and for ribonuclease at acid, neutral, and slightly alkaline pH, the results indicate that hydrogen bonding is not of great importance for enzymatic activity, in agreement with the results of previous studies in ordinary water. For desoxyribonuclease at neutral and alkaline pH, the isotope effect varies from 1.5–5.0 which, in agreement with the high values of the thermodynamic constants for heat inactivation of this enzyme, suggests that the rupture of a considerable number of hydrogen bonds is involved in this process. Although the heat inactivation of this enzyme in the pH range 2.4–3.2 in H2O is partially reversible on cooling (if 50% inactivation is not exceeded), no such reversibility was found in D2O; it is believed that this may be due to a decrease in the pK of the protein carboxyl groups in heavy water. It was also found that the isotope effect decreases with temperature, as is to be expected, the result being a small increase in the activation energy and entropy change for the inactivation process in heavy water. The results are discussed, and it is shown that no general conclusion may be drawn from studies on a single enzyme (or protein), but that the findings must be considered individually in relation to structure, deuterium exchange in solution, titration curve in heavy water, etc. Suggestions for further studies are advan

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112304

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractOxidation reactions, as followed by infrared spectrometry, may serve as a measure for judging the relative extent of oxidative degradation and crosslinking of two independent parallel reactions subsequent upon the primary destruction. Such information can be derived from a kinetic analysis of the processes taking place in the rubber as a result of the absorption of energy, using the expressionw= (k/b) (1 −e−bη) (1 − η). Since in this equationkis proportional to the rate of chain branching (which leads predominantly to oxidation), andbis proportional to the rate of recombination of the radicals (leading to crosslinking), the total degree of crosslinking will increase with increasing values ofb/k. This assumption has been verified experimentally for the thermal and photochemical ageing of rubber, both in the absence of additives and in the presence of sulfur, of vulcanizing mixtures, and of copper as a catalyst of oxidation. At increased temperatures and pressures (130°C., 3 atm.) in the absence of vulcanizing additives and in a nitrogen atmosphere, radicals of long life are formed; this leads to an increased rate of the subsequent oxidative degradation. The number of active centers formed, and hence the final extent of oxidation, is a function of the time of exposure to the increased tem

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112305

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractAdsorption experiments were made to determine the time required for a complete adsorption of certain highly molecular substances from solutions. Aluminum oxide was preliminarily subjected to hydrophobization by caproic acid. Samples of polystyrene, polyisoprene, and polyethers of acrylic and methacrylic acids, ranging from methyl to heptyl inclusive, were taken as objects of the experiments. In all cases the time required for a complete extraction of the substances from solution was shown to be directly proportional to square of the characteristic viscosity. “Bad” solvents take a shorter time to effect a complete adsorption. The investigation of adsorption of polyethers of acrylic and methacrylic acids has shown that the increase in the alcohol radical influences the velocity of the adsorption process as a whole in different ways. While the increase in the alcohol radical of the polyacrylic ethers reduces the time required for a practically complete adsorption of the substance, in the case of polyethers of methacrylic acid the reverse relation was observed. Hydrophobic aluminium oxide is shown to adsorb polymethyl acrylate from solution reversi

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112306

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractEs wird versucht, den Mechanismus der Radikalbildung aus organischen Hydroperoxyden in homogener Lösung aufzuklären. Die scheinbare Diskrepanz, dass die bekannte thermische Zersetzung von Hydroperoxyden in Lösung kinetisch nach der 1. Ordnung verläuft, dagegen die Katalyse der Autoxydation ungesättigter Verbindungen durch Hydroperoxyde in einer Reaktion 2. Ordnung erfolgt, wird diskutiert und durch eine Arbeitshypothese überwunden. Ihre experimentelle Nachprüfung durch dilatometrische Verfolgung von Polymerisationen lieferte kinetische Ergebnisse, die sich durch folgende einfache Annahmen deuten lassen: (1) Hydroperoxyde bilden in Gegenwart von Styrol freie Radikale nach der Gleichung:Styrol greift also in die Startreaktion ein. (2) In Methylmethacrylat und Vinylazetat bilden Hydroperoxyde Radikale nach der Gleichung:(3) Alkylperoxy‐Radikale (ROO·) bewirken einen zusätzlichen Kettenabbruch durch Reaktion mit Makr

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112307

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractResults obtained in the investigation of polymers containing pentavalent phosphorus in the main polymer chain are presented. A number of polyamides and polyesters derived from phosphorus‐containing dicarboxylic acids have been synthesized. Two types of dicarboxylic acids were used: alkyl‐ or aryl‐phosphinic acids (I) and bis‐carboxyphenyl‐phosphine oxides (II):their chloroanhydrides or esters being used in the reaction. To obtain polyesters, various glycols or dihydric phenols were used as the second component. For preparing polyamides, aliphatic diamines were used as the second component. The nature of the starting materials has a very marked effect on the properties of the polymers obtained. Polyesters with an aliphatic chain are viscous, thick oils or low‐melting resins. Polyesters with aromatic unit are high‐melting, solid elastic substances. Comparison of the properties of the polymers synthesized by us with the properties of polymers of related composition not containing phosphorus, shows that the introduction of phosphorus into the chain leads to molecules of much greater flexibility. For this reason the softening points of the phosphorus‐containing polymers are much lower than those of their c

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112308

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA general method for describing the crystal orientation in a uniaxially oriented crystalline polymer is presented. It is shown that two orientation functions may be quantitatively evaluated from x‐ray diffraction data. The variation of these during mechanical and thermal treatment may be studied. These functions are sufficient to completely characterize the crystal contribution to birefringence and infrared dichrosim. By subtracting the crystal contribution from the total birefringence or dichroism, the amorphous orientation may be characterize

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112309

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA set of functions for characterizing the crystal orientation in a biaxially oriented crystalline polymer is proposed. The additional orientation functions may be determined from a measurement of the variation of x‐ray intensity with tilt angle of a film. From these functions and those described in Part II, the crystal contribution to the birefringence and the infrared dichroism of normal and tilted films may be calculate

ISSN:0022-3832    

DOI:10.1002/pol.1958.1203112310

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY