摘要:

AbstractThe molecular weight distribution of an anionically polymerized polystyrene sample was evaluated from sedimentation velocity measurements in two non‐theta solvents, ethyl acetate at 25°C. and methyl ethyl ketone at 25°C. The results were compared with that previously obtained by the same method in a theta solvent, cyclohexane at 35°C., and with that derived from precipitation fractionation. These molecular weight distribution curves agree fairly well with one another, and the method of sedimentation analysis employed is proved useful for the evaluation of the mass distribution in a given polymer sample when the data are taken at least in an appropriate poor solvent for the pol

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730101

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe molecular weight of bovine serum albumin (BSA) was obtained from sedimentation equilibrium in trichloroacetic acid and hydrochloric acid atpH3.8, in 0.0005Msalt (sodium chloride, sodium trichloroacetate and sodium thiocyanate) plus sulfuric acid atpH3.2 and in 0.1Msodium chloride plus hydrochloric acid atpH1.8. The extrapolated weight‐average molecular weights of BSA were within the range of light‐scattering values reported in the literature. The binding coefficient Γ is approximately equal to the electrostatic charge Z at allpHvalues studied. The constant value of Γ with a change in Z can be explained by assuming that about 50 carboxylate groups have abnormally low pK values and are paired with the cationic groups of BSA. Binding of salt by the cationic groups occurs only after titration of the carboxylate ions. The extrapolated molecular weight in the absence of salt is not equal to the polymer molecular weight divided by (1 + Z). In addition, it was concluded that the reciprocal of the apparent molecular weight may be plotted against (Ca+ Cb)/2 instead of (hCa+ Cb)/2 (where h = (BM̄w)a/(BM̄w)b) if haC does not influence Cbappreciably,i.e., when comparatively high rotational speeds are used. The experimental data obtained from the cell bottom indicate that the concentration coefficient obtained from the apparent Z‐average molecular weight is 2(M̄w/M̄z) times as large as that obtained from the apparent weight‐average mol

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730102

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractAn approximate form can be assumed for the concentration coefficient B in ultracentrifugal molecular weight determinations. By employing the electrostatic charge obtained from titration studies, this approximate form of the B coefficient predicts a value which is considerably higher than the experimental value for bovine serum albumin (BSA). This discrepancy suggests that the electrical potential term cannot be zero and, hence, that BSA must possess permanent or induced polarization or both. A dipole moment of approximately 1400 DEBYEunits was calculated for BSA by employing into the B coefficient a simplified model given by EDSALLand WYMAN. This compares favorably with a dipole moment of 760 units obtained from the dielectric constant of BSA. The (dCr/rdr)vs.Crcurves for BSA were examined for solutions containing a small amount of salt plus acid or for solutions containing the acid alone. When only the acid is present (hydrochloric or trichloroacetic), the concentration coefficient Brappears to decrease as the cell radius r increases. Thisdecreasein Brwith r is accompanied by anincreasein the total coefficient B which is a function of the initial polymer concentration. The most plausible explanation for this decrease in Brwith r is that the hydronium ion concentration decreases with r due to greater binding of the acid anion at the meniscus. This change inpHwith r decreases the value of BSA's electrostatic charge Z with cell radius. Thus the value of Brdecreases with r because of a corresponding decrease in the positive term — (Z/M)(d ln CB/d CP) and an increase in the absolute value of the negative dipole moment term. The latter term decreases with an increase in r because of a corresponding increase in the number of zwitterions on BSA. Calculations show that the total coefficient B will beincreasedthree‐ or fourfold for a difference in charge of (Zb−Za) = −0.04, because the coefficient of d(Z′/M′)/dCPis also negative. A small amount of salt (0.0005 molar) eliminates this decrease in Brand in

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730103

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

Abstract9‐Allylcarbazole, 9‐Δ3‐butenylcarbazole, 9‐Δ4‐pentenylcarbazole and 9‐Δ5−hexenylcarbazole were synthesized and their polymerization with ZIEGLER‐NATTAcatalyst systems studied. 9‐Allylcarbazole could not be polymerized and 9‐Δ3‐butenylcarbazole could only be polymerized with extreme difficulty. However, 9‐Δ4‐pentylcarbazole and 9‐Δ5‐hexenylcarbazole could be polymerized at conversions of about 55%. These results are interpreted in terms of steric hindrance about the vinyl group. No evidence of complexing due to the basic nitrogen atom was noted. Of the catalyst systems used only Et2AlClγTiCl3was found to be effective in the polymerization. As judged by X‐ray diffraction and insolubil

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730104

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractKinetic equations are developed for the bifunctional initiation of free radical polymerization using a system such as a ferrous compound and a dihydroperoxide. Whenever the concentration of hydroperoxide groups attached to polymer chains reaches a stationary state concentration, the system exhibits the kinetic behaviour predicted [but never yet observed] for diradical propagation.

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730105

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe polymerization of styrene has been initiated by the reaction between ferrous acetylacetonate and an organic hydroperoxide in monomer as solvent. Kinetic evidence is presented which suggests that the two reagents rapidly form a 1:1 complex which can either decompose [yielding free radicals] or dimerize. The binuclear dimer is also capable of slow decomposition yielding free radicals.

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730106

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe molecular weights of polystyrenes, prepared using ferrous acetylacetonate and either cumene hydroperoxide orm‐diisopropylbenzene αα′‐dihydroperoxide, have been compared with the rates of polymerization. When the ferrous to dihydroperoxide ratio is unity, there is negligible reinitiation of polymeric hydroperoxide groups, and the system exhibits monoradical kinetics. In the presence of excess ferrous complex, the molecular weight is independent of the rate of polymerization. This indicates that termination occurs almost exclusively by combination and that the system exhibits “bifunctional

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730107

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractEs werden zwei neue Wege zur Synthese von 1,2‐Siloxacycloalkanverbindungen beschrieben. Von besonderem Interesse sind die hierdurch leicht zugänglich gewordenen 1,2‐Siloxacyclopentan‐Derivate, die sich durch ein außergewöhnliches Polymerisationsverhalten auszeichnen. Die reversible Polymerisation der ringförmigen Verbindungen läßt sich durch Basen und LEWIS‐Säuren leicht auslösen, erfolgt aber auch in Abwesenheit von Katalysatoren und führt zu einem Gleichgewicht zwischen monomeren, polymeren und wahrscheinlich auch oligomeren Molekülen, das infrarotspektroskopisch bestimmt werden kann. Näher untersucht wird die Polymerisation des 1‐äthoxy‐1‐methyl‐1,2‐siloxacyclopentans. Die Polymerisationsenthalpie wird zu −4,5 ± 0,4 kcal/Mol, die freie Enthalpie zu —1,05 kcal/Mol und die Entropie zu −11,7 ± 1,0 Clausius bestimmt. Beim Auflösen des Polymeren in Tetrachlorkohlenstoff depolymerisiert die Verbindung, wobei bis zu einem gewissen verdünnungsgrad die Konzentration des cyclischen Monomeren mit 24 g/l konstant bleibt. Es werden Mechanismen diskutiert, die dem Erscheinungsbild der katalysatorfre

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730108

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractThe molecular structure of polyethylene oxide (PEO), (—CH2CH2O‐)n, was studied by the X‐ray diffraction and infrared absorption spectroscopic methods. The X‐ray diffraction data were observed for the highly oriented PEO samples and were analyzed by use of the method of FOURIER transform of the helix proposed by COCHRANet al.Fully deuterated PEO was synthesized, and the polarized infrared spectra of PEO and PEO‐d4were measured in the 4000–80 cm−1region. The factor group analysis and the normal coordinate treatments were carried out. From the results of these studies, it was concluded as follows.1The PEO molecule in the crystalline state has a helical structure which contains seven chemical units and two turns in the fiber identity period 19.3 Å.2The internal rotation angles of this molecule are τ(OCCO) = 64°58′ and τ(CCOC) = 188°15′, and this corresponds to the succession of nearlytrans, trans,

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730109

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY

摘要:

AbstractPolyacrylnitril, das bei tiefen Temperaturen strahlenchemisch in Substanz dargestellt wird, zeigt in seinem Infrarotspektrum eine Absorptionsbande bei 2030 cm−1, die übereinstimmend der Anwesenheit von Ketenimingruppen zugeschrieben wird. Dagegen gehen die Ansichten darüber, ob sich diese Gruppen im Verlauf der Polymerisation — speziell beim Terminationsschritt — bilden oder ob sie durch Strahleneinwirkung auf das bereits gebildete Polymere zustandekommen, auseinander.Es wurde Acrylnitril bei −78 und −196°C in Substanz sowie bei −78°C in Lösungsmitteln polymerisiert und insbesondere die Abhängigkeit der relativen Konzentration an Ketenimingruppen von der Dosisleistung und der Dosis untersucht. Ferner wurde Polyacrylnitril i. Vak. und bei Anwesenheit von Luft bestrahlt. Es zeigte sich, daß die Konzentration an Ketenimingruppen, die sich bei der Polymerisation bilden, von der Wurzel der Dosisleistung abhängt, aber unabhängig von der Gesamtdosis ist. Wir folgern aus unseren Versuchen, daß die Polymerisation des Acrylnitrils in Substanz bei −78°C vorwiegend radikalisch verläuft und die Ketenimingruppen beim Kett

ISSN:0025-116X    

DOI:10.1002/macp.1964.020730110

出版商:Hüthig&Wepf Verlag    

年代:1964

数据来源: WILEY