摘要:

AbstractAs an extension of our original program, one more polystyrene fraction was investigated in numerous laboratories by means of viscosimetry, osmometry, light scattering, and ultracentrifuge. The various results are compared and critically discussed. Possible explanations and suggestions for improvement are offered in those cases in which considerable discrepancies occur. The viscosity results show satisfactory agreement. The discrepancies among osmotic results are believed to be due largely to unsatisfactory performance of the so‐called semipermeable membranes. Discrepancies among light‐scattering results can mostly be traced back to the unsatisfactory state of the various calibration techniques. The results obtained with the ultracentrifuge agree quite satisfactor

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178301

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe measurement of the scattering of light by solid polymers is a means for studying their structure. Films are the most convenient form for working with highly scattering polymers, which are subjected to such treatment as temperature variation, mechanical deformation, and orientation. In measuring scattering from films, it is necessary to correct the observed scattered intensity for (a) refraction at film interfaces, (b) reflection, and (c) secondary scattering. The necessary correction factors are described in this paper. The application of these correction factors is illustrated in the case of scattering by a polyethylene film.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178302

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractDie Übertragungskonstante von Polymethylmethacrylat hei der Polymerisation von Methylmethacrylat hzw. Styrol wird dadurch bestimmt, dass man Polymeres von sehr kleiner Kettenlänge dem polymerisierenden Stoff zusetzt. Das zugesetzte α‐Polymere beeinflusst nicht die Bruttogeschwindigkeit, setzt aber den Polymerisationsgrad des entstehenden Polymeren herab. Für diesen Vorgang gelten dieselben Gleichungen wie für niedermolekulare Regler. Die Übertragungskonstante von Polymethacrylat setzt sich aus zwei Anteilen zusammen, welche den Mittelgruppen und einer Endgruppe entsprechen. Die wirksame Endgruppe ist hei der Disproportionierung entstanden. Polystyrol zeigt keinen Endgruppeneffekt, da das Kettenwachstum durch Kombination beendet wird. Aus den gemessenen Übertragungskonstanten kann der Grad der Verzweigung bei Polymethacrylaten und Polystyrolen abgeschät

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178303

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractBlock copolymers have been synthesized by heating a polymer, containing peroxidic linkages, in the presence of another monomer. The peroxide groups were introduced into the first polymer by initiating the controlled polymerization of its monomer with phthalyl peroxide. Separation of the block copolymers from the two parent homopolymers was made possible by their different solubilities in selected solvents or their mixtures. Polystyrene (Mn= 1.00 × 105), prepared at 75°C. in bulk with 0.5% phthalyl peroxide, initiated the polymerization of methyl methacrylate at 100°C. in benzene solution. The two block copolymer components isolated were found by infrared analysis to contain 22 and 30% polystyrene with number average molecular weights of 4.3×105and 3.0×105, respectively. Block copolymers were also obtained by heating styrene in benzene at 85°C. with polyvinyl acetate (Mn= 0.60 × 105), prepared in benzene solution at 70°C. with 0.5% peroxide. A 39% vinyl acetate‐61% styrene block copolymer was isolated and found to have a molecular weight of 1.65×105. Intrinsic viscosities, μ values, and κ′ values for the block copolymers and related homopolymers were determined and are discussed in terms of composition, molecular weight, and poly‐dispersity. Other experiments indicated that styrene‐phthalyl peroxide polymers were unable to initiate vinyl acetate or vinylpyrrolidone polymerizations at 100°C. in significant amounts; this behavior is interpreted in terms of the stability of

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178304

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe kinetic study of the polymerization of methyl methacrylate initiated by hydrogen peroxide in toluene, ethyl acetate, and methyl ethyl ketone as well as in bulk has been made. It has been established that the catalyst has no inhibition period and follows the square root relation. The initiation order is unimolecular with respect to the monomer in the fist two solvents and is half‐molecular with respect t o methyl ethyl ketone. The value of Δ (= κ 1/2t/κp) for methyl methacrylate a t 60°C. a t various concentrations in the three solvents has been measured and found to remain sensibly constant and its value is 8.43. From bulk polymerization data the value of Δ at temperatures of 50, 60, 80, and 115°C. has been determined and they are 11.62, 8.43, 5.26, and 2.48, respectively. The temperature variation of Δ, and hence the corresponding energy of activation (Ep− 1/2Et), has also been measured and its value is found to be 5.71 kcals. The initiation constant under a variety of conditions has been determined by two independent methods (kinetic and DP) which have been found to yield values in fairly good agreement with each other, leading to a strong support to the usually assumed mechanism of polymerization. However, the initiation constant is found to change considerably with monomer concentration and chang

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178305

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178306

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractIntrinsic viscosity measurements of polyacrylonitrile fractions in dimethyl formamide at 25°C. and molecular weight determinations by the sedimentation‐diffusion method led to the following relation :The data are consistent with the model of a coiled chain, impenetrable to the solvent, in agreement with the theories of Flory and co‐workers. The influence of the concentration upon the sedimentation constant was interpreted by an extension of the concept of the equivalent hydrodynamic sphere to the range of small finite concentrations. The following relation was thus obtained:Kshould be a universal constant and its value is about 1.6 for most flexible poly

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178307

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe rate of gelation of concentrated polyacrylonitrile solutions is measured by the increase of the elasticity modulus of the gels with time at constant temperature. The influence of the following factors has been determined : temperature, concentration, molecular weight of the polymer, and water content of the solutions. The rate of gelation increases when the temperature decreases and becomes rapid enough to be measured between 0 and −10°C. The rate of gelation increases further by a factor 150 when the concentration varies from 18 to 23% and by a factor of approximately 3, for a 20% solution, when the molecular weight changes from 100,000 to 150,000. The influence of the water content is such that gelation already takes place at room temperature when the solution contains more than 2% water. The gelation has been ascribed to the formation of crystalline nuclei in the supersaturated solutions and the influence of the factors mentioned above is in agreement with the prediction of the nucleation theo

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178308

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe relation between molecular size and weight for polystyrene in cyclohexane at 34, 43, and 57°C. and toluene at 20°C. has been determined by a light scattering method. For the molecular weight range, half‐million to five million, the data suggest a linear relationship:L2=κ(M−b) whereκandbare parameters which have their higher values in better s

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178309

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractA new combined viscometer‐dilatometer is described which requires only small quantities of liquid. The polymerization of unsaturated polyester “contact” resins has been studied, and the “Trommsdorf effect” is shown to be compressed into a sharp kink in the rate curve. This is compared with the form which the Trommsdorf effect takes in a simple methyl methacrylate polymerization, and an explanation for the difference is offered. The breakdown of polymers by mechanical means, and its effect on a system in the vicinity of its gel point, are

ISSN:0022-3832    

DOI:10.1002/pol.1955.120178310

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY