摘要:

AbstractAn investigation of small‐angle scattering produced by polarized light from stretched and annealed polymer systems containing spherulites yields information on the supermolecular transitions that occur during such treatment. A series of semicrystalline polymer systems (films, fibers) show that stretching leads to deformation of spherulites and subsequent transformation to an orientational supermolecular order. The size of the single elementC2of the supermolecular order in the direction of stretching, determined from the distance between the layer lines of the scattering pattern, is related to the diameterD0of the initial spherulites by the relationC2=KD0λs, where λ, is the draw ratio of the macrosystem andKis a parameter determining the deformability of the spherulites. For polyethylene at room temperatureKis unity and for polychloroprene it is 1.2. Changes ofC2after annealing and restretching of the systems also obey this ra

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080701

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractPoly‐2,5‐distyrylpyrazine (poly‐DSP) was investigated by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and measurements of dynamic viscoelastic and electrical properties. From DTA and TGA studies it was confirmed that poly‐DSP melts at 321°C and depolymerizes rapidly to the monomer at temperatures between 335°C and 345°C in helium. The polymer is affected by oxygen above 200°C. TheE′ value from dynamic viscoelasticity measurements on amorphous film is 2 × 1011dyne/cm2at room temperature. It decrease abruptly in the temperature range 140–150°C; but the net decrease ofE′ within this temperature range is relatively small. The electrical properties of amorphous poly‐DSP are characterized by a small temperature dependence of the dielectric constant between room temperature and 100°C. The dielectric loss tangent was observed to be small, and the dc conductivity was extremely small. It is concluded that rotation of the phenyl branches in the polymer occurs above −30°C and the glass transition occurs at about 150°C. These properties are discussed in some detail in relatio

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080702

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe problem of inferring molecular weight distributions from concentration gradient data taken at sedimentation‐diffusion equilibrium for a single rotor speed is ill posed: significantly different distributions correspond to concentration gradients which differ so slightly that they cannot be distinguished by the experiment. It is this intrinsic property of the problem which accounts for the lack of success of the several schemes proposed for its solution. Integral equation theory is applied to show explicitly just what can be inferred with bounded error. Several methods for recovering this information are discussed and applied to example problem

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080703

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe dielectric properties of poly(vinylidene fluoride) have been studied in the frequency range 10 Hz to 100 kHz at temperatures between −196 and 150°C. Three dielectric relaxations were observed: the α relaxation occurred near 130°C, the β near 0°C, and the γ near −30°C at 100 kHz. In the α relaxation the magnitude of loss peak and the relaxation times increased not only with increasing lamellar thickness, but also with decrease of crystal defects in the crystalline regions. In the light of the above results, the α relaxation was attributed to the molecular motion in the crystalline regions which was related to the lamellar thickness and crystal defects in the crystalline phase. In the β relaxation, the magnitude of the loss peak increased with the amount of amorphous material. The relaxation times were independent of the crystal structure and the degree of crystallinity, but increased slightly with orientation of the molecular chains by drawing. The β relaxation was ascribed to the micro‐Brownian motions of main chains in the amorphous regions. The Arrhenius plots were of the so‐called WLF type, and the “freezing point” of the molecular motion was about −80°C. The Cole‐Cole distribution parameter of the relaxation time α increased almost linearly with decreasing temperature in the temperature range of the experiment. The γ relaxation was attributed to local molecular mot

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080704

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractA convenient pressure apparatus was designed for crystallization of high polymers under hydrostatic pressure up to 5000 atm. Melt crystallization as well as heat treatment under various temperatures and pressures was carried out on several polymers, and the effects of pressure on the molecular and crystal structures of the samples are discussed. Heat treatment of syndiotactic polypropylene under high pressure yields a new crystal modification rather than the previously known helix and planar zigzag modifications. Of the three modifications of poly(vinylidene fluoride), modification III was found as a high‐pressure phase for specimens in the unoriented state, while modification I was obtained as the most stable one on heat treatment of oriented specimens under high pressure. Heat treatment under high pressure converts ordinary isotactic poly‐4‐methylpentene‐1 with a lower density than the noncrystalline value, to a new crystal modification with higher density. As is reasonable, the dense modification is stable in a high‐pressure range. For these three cases, the orientation of specimens was found to remain unchanged during the transitions, which must therefore occur in the so

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080705

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe gelation of poly(methacrylic acid) in water was studied as a function of degree of neutralization with NaOH. It was found that charging the molecular displaces the onset of gelation to higher concentrations but makes the transition occur over an even narrower concentration range. This extreme sensitivity of rheological properties to charge may play a role in biocolloidal systems. The phenomenon of reversible gelation is discussed in general and related to the properties of the particular system. The method of measurement, which involves the determination of the dynamic response in the 1 Hz region and the measurement of phase angle, is described in detail. A method of deriving the relaxation time spectrum from measurements of phase angle is given.

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080706

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractComonomer and stereosequence distributions in linear high polymers are considered from the point of view of the general theory of stationary random sequences. Although the discussion is centered about binary polymerizations which may be regarded as stationary Markov processes of low order, attention is paid to distinguish results valid for any stationary random process including stationary non‐Markov processes from those special to a particular Markov process. Alternative derivations of copolymer composition equations are given along with a corrected version of a previously suggested scheme of relating conditional probabilities of different orders. The nature and relative merits of the several measures proposed in the literature to characterize comonomer and stereosequence distributions are also discussed in some detai

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080707

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe theory for scattering of light from films in which the orientation correlation between two scattering elements depends upon the angle β between the optic axes and the vector connecting the two elements is extended. A delta‐function type dependence is assumed in which the correlation is strongest when β equals some preferred value β0. Calculated results of scattered intensities are shown to be similar to experimental observat

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080708

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractThe scattering of light by a two‐dimensional spherulite of radiusRis calculated when there is disorder of optic axis orientation with respect to the radius. Special cases are considered when (1) the disorder occurs in the radial direction only, (2) the disorder occurs in the angular direction only, (3) there is combined radial and angular disorder, and (4) the optic axis makes a constant angle with the radius but there is disorder in the twist angle about the axis. In all of these calculations, a correlation function for disorder is defined and the scattering pattern depends on the ratio of the associated correlation distance to the size of the spherulite. With decreasing correlation distance, the azimuthal dependence of the scattering becomes less and there is a change in the variation of scattered intensity with scattering angles in a manner dependent upon the type of disorde

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080709

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY

摘要:

AbstractESR and electrical conductivity measurements have been made on a recently prepared polymer, polypropiolamide. The polymer was obtained as a fine powder which exhibited a nearly Lorentzian line with a width between derivative maxima of 5.2 ± 0.1 gauss and agvalue of 2.0036 ± 0.0005. The signal intensity increased with increasing molecular weight. The signal was retained in a dilute solution in formic acid with a slight narrowing of the line. Permanent changes were produced in the spectra at room temperature by heat treatments of the polymer at temperatures up to 800°K. The changes were similar for samples sealed in tubes containing air, dry nitrogen gas and a vacuum of 3 × 10−5mm of Hg. Spectra obtained at temperatures up to 500°K showed no dependence on the presence or absence of oxygen in the ambient atmosphere. The deresistance of pressed pellets of the polymer was measured in the temperature range 450°K to 525°K, and the results were described by the relationR=R0cE/kT. The activation energyEhad a value of 1.2 ± 0.2 ev and the resistivity at 500°K was approximately 1013ohm‐em. The ESR signal is attributed to an intrinsic property of the polymer which is associated with a conjugated bond system along the polymer backbone. Neither the activation energy nor the magnitude of the resistivity suggest that the delocalized electrons associated with the conjugated bond system have produced unusual electrical characteristics in

ISSN:0449-2978    

DOI:10.1002/pol.1970.160080710

出版商:John Wiley&Sons, Inc.    

年代:1970

数据来源: WILEY