摘要:

AbstractThe anionic preparation of monodisperse polymers of predictable molecular weight, by simple techniques involving conveniently purified starting materials, has been investigated using styrene as a model. Active impurities, predominantly water, oxygen and carbon dioxide present in the solvent, the monomer and in the reaction system which would cause deactivation of propagation centers, are rendered inactive prior to polymerization by gradual addition of (colored) initiator at a temperature low enough to suppress chain growth. Upon completion of the purging step, indicated by the persistence of colored propagation centers, additional initiator appropriate for the molecular weight of the sample desired\documentclass{article}\pagestyle{empty}\begin{document}$${\rm \bar M}_{{\rm nk}} = \frac{{ {\rm monomer} \left( {\rm g.} \right) }} {{ {\rm initiator} \left( {\rm moles} \right) }}$$\end{document}is added. The system is then warmed to the polymerization temperature at which the reaction is allowed to go to completion. The predictability of the molecular weights was found to be within 10% for two polymers prepared. The M̄w/M̄nratio, calculated from fractionation data, was 1.06 in both case

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430101

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThe molecular weight distribution curves of six samples of polyvinyl chloride taken during a suspension polymerization were determined. The degrees of conversion of the samples varied from 4% up to 94%. Fractionations of the samples were carried out in the system tetrahydrofuran‐water by fractional precipitation. It appears that the molecular weight distribution does not substantially vary in the course of the polymerization. The experimental results are discusse

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430102

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractIt has been demonstrated that the molecular weight distribution of some isotactic polypropylene samples can be described by a modified ROSIN‐RAMMLERdistribution equation:\documentclass{article}\pagestyle{empty}\begin{document}$${\rm I }\left( {\rm M} \right){\rm = 1 - exp.}\left( { - \frac{{\rm M}^{\rm b}}{{\rm M}_{\rm e}^{\rm b}}} \right)$$\end{document}in which I (M) is the cumulative weight fraction of molecules having a molecular weight less than or equal to M and Meand b are constants for a particular sample. The width of the molecular‐weight distribution is represented by the value of b. The quantity\documentclass{article}\pagestyle{empty}\begin{document}${\rm Q = }\frac{{ {\rm M}_{\rm w} }} {{{\rm M}_{\rm n} }}$\end{document}which is the more conventional measure for this width, can be expressed as a function of b for b>1. It is shown that for a detailed comparison of polymer samples knowledge of Q has to be supplemented with information on the type of distribut

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430103

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractAs the third stage of the block copolymer synthesis, hydroperoxide‐ended polystyrenes have been treated with ferrous ions and methyl methacrylate in aqueous emulsion at temperatures between 0 and 25°C.; the products of the reactions were shown, by the weight increases and by infrared analyses, to contain polymethyl methacrylate in amounts of the same or twice the weight of the starting polystyrenes.Turbidimetric titrations on these products indicated that they consisted largely of a mixture of the two homopolymers, with only small amounts (about 10%) of a third component, precipitating between the homopolymers and suggested to be the block copolymer; this ascription was confirmed by extraction experiments, which gave partial separations of the copolymer.Suggestions are made to explain the low yield of block copolym

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430104

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThe effects ofp‐benzoquinone upon the sensitized copolymerization of styrene and methyl methacrylate at 60°C. have been examined. Rates of polymerization were measured and the resulting copolymers were analyzed for combined quinone, by a tracer method involving14C‐labelled material, and for styrene by spectrophotometry. In its early stages, the copolymerization is quite strongly retarded but the rate gradually builds up as the quinone is consumed. The copolymer first formed is of low molecular weight and contains combined quinone, but as the reaction proceeds the average molecular weight of the polymer rises and the proportion of combined quinone falls. It is possible to account qualitatively for the differences between the effects of the quinone upon the copolymerization and the polymerizations of the separate mono

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430105

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractA new asymmetric synthesis of polymers is described; it was obtained from monomers which do not contain asymmetric carbon atoms.The polymerization, in the presence of asymmetric cationic catalysts, of an unsaturated cyclic compound, benzofuran, by opening of the double bond of the furan ring, led to polymers having high optical activity.The rotation dispersion curve, which shows a maximum at 303 mμ ([M] = –800) is here shown. Each monomeric unit of these polymers contains two carbon atoms in the chain, which are asymmetric, even if considered in their immediate surrounding.Optically active polybenzofurans do not remarkably contain asymmetric end‐groups deriving from the catalyst. The asymmetric synthesis may therefore be related to the orienting effect of the negative asymmetric counter

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430106

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThis paper deals with the stereospecific polymerization of alkyl thiolacrylates (alkyl group: ethyl,n‐propyl, isopropyl,n‐butyl, isobutyl,sec‐ andtert‐butyl). These esters have been found to be polymerized by some anionic catalysts to give crystalline polymers, with the exception of the ethyl ester

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430107

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractBy binary catalysts consisting of diethylzinc and various metal oxides (Bi2O3, MgO, CaO, BaO, etc.) or fluorides (CaF2, KF), propylene oxide was polymerized. These binary catalysts were found to give polymers of much higher molecular weights in higher yields than metal oxides or fluorides alone.It was found that the product of the intrinsic viscosity and the yield(%) of the produced polymers increased as PAULING's ionic character of the bond of metal oxide or fluoride increased.By the X‐ray diffraction spectrum and the polarization micro‐photograph the polypropylene oxide thus obtained was proved to be crystall

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430108

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractMehrere Cyclodiurethane wurden unter Anwendung des RUGGLI‐ZIEGLERschen Verdünnungsprinzips nach zwei verschiedenen Verfahren synthetisiert. Bei der Darstellung aus Diaminen und Diol‐bis‐chlorkohlensäureestern konnten die Verbindungen in guten Ausbeuten gewonnen werden. Dagegen werden bei Anwendung von Diolen und Diisocyanaten als Ausgangsmaterialien im wesentlichen lineare Polyurethane e

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430109

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractZwei polymerhomologe Reihen von Diol‐oligo‐urethanen wurden röntgenographisch untersucht. Die vor allem im Kleinwinkelbereich durchgeführten Messungen führten zu dem Ergebnis, daß die gefundenen Langperioden bis zum Diol‐okta‐urethan eine Funktion des Molekulargewichtes sind und dann über einen weiten Molekülgrößenbereich bis zum Polymeren einschließlich

ISSN:0025-116X    

DOI:10.1002/macp.1961.020430110

出版商:Hüthig&Wepf Verlag    

年代:1961

数据来源: WILEY