摘要:

AbstractThe results of an x‐ray and polarimetric study of a crystalline modification (form I) of isotactic poly‐(S)‐4‐methyl‐1‐hexene are reported and discussed. The x‐ray fiber spectra of this polymer are practically indistinguishable from those of isotactic poly‐(R)‐(S)‐4‐methyl‐1‐hexene. Although the crystal structure of the latter can be described on the basis of helices of different screw sense packed in aP4space group, the crystal structure of poly‐(S)‐4‐methyl‐1‐hexene is better described on the basis of aP1space group. The conclusion of the x‐ray investigation, that in the crystals of the optically active polymer an equal number of right‐handed and left‐handed helices must be present, is supported by the polarimetric measurements, which have shown that the polymer in the crystalline for

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090201

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe shear creep and creep recovery behavior of narrow molecular weight distribution polystyrene samples of low molecular weight, 1.1 × 103, 3.4 × 103, and 1.57 × 104are reported as a function of temperature, near and above the glass temperature. Time‐temperature equivalence for the total creep compliance is found to be nonapplicable, and in fact the steady‐state recoverable compliance,Je, is a strong function of temperature. The time‐scale shift factors for the recoverable compliance are analyzed in the light of free volume theory. Viscosity data are presented for samples with molecular weights between 1.1 × 103and 6.0 × 105. The temperature dependence of the characteristic time constant ηJecan be explained in terms of free volume concepts whereas that of viscosity η cannot. Effects of residual molecular weight heterogeneity are

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090202

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe two essential aspects of axial dispersion in gel permeation chromatography have been studied: (1) the relationship of axial dispersion to the continuity equations of chromatographic transport, and (2) the relationship to molecular size and the system parameters of an individual column. Theoretical analyses are presented for both of these problems and are applied to an experimental study of axial dispersion by both zonal (small‐zone) and frontal (large‐zone) experiments with a series of macromolecular species having discrete, precisely known molecular weights. Theoretically predicted non‐Gaussian elution profiles were observed for the small‐zone experiments, and axial dispersion coefficients for each molecular species were determined as a function of flow rate. Resulting values were found to be in good agreement with the theoretical equation relating axial dispersion to molecular size, flow rate, and two “calibration constants” of the column. These results provide a rational basis for axial dispersion effects in terms of the fundamental processes and system parameters of gel columns. Extension of the analysis to multicomponent systems i

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090203

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractOscillatory shear measurements have been made on a range of anionic polystyrene melts of molecular weights 1000‐‐500,000. ForM<5000 the polymer chain is too short to act as a Gaussian coil and hence the compliance of the melt is very low. For 10,000

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090204

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractMeasurements have been made of the tensile force required to pull a disk of a model viscoelastic adhesive away from an inert rigid substrate. Over a wide range of temperature and rate of deformation of the adhesive the results were found to yield a single master relation in terms of deformation rate by means of the Williams, Landel and Ferry rate—temperature equivalence for viscous materials. Thus, the strength of adhesion is due mainly to dynamic effects in the adhesive of a viscous nature, in a similar way to the cohesive strength of viscoelastic materials. This similarity is attributed to a common failure mechanism: initial failure at a highly stressed point, followed by spreading of the failure zone under local stresses which are governed by the dynamic response of a compliant material. An increase in the strength of adhesion is observed with decreasing thickness of the adhesive layer. This is also explained by the proposed failure mechanism if failure starts at a critical amount of local deformation energy, a form of Griffith's fracture criterio

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090205

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractA theoretical calculation of theHvlight‐scattering patterns for deformed three‐dimensional spherulites is presented. Affine deformation is assumed. The optic axis of the scattering element is allowed to lie at an arbitrary angle ß to the radius which is permitted to change in the course of the deformation in a manner that may depend upon the angular location in the spherulite. The consequences of twisting of the optic axis about the spherulite radius are also expl

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090206

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractRadial, tangential and cross cuts of Eastern spruce are examined by a solid‐state light‐scattering method which allows study of light scattering due to fluctuations in density and fluctuations in anisotropy. All of the samples investigated show well‐defined scattering maxima which are related to their anisotropic texture with limited contributions from random density fluctuations. The radial cuts give rise to scattering similar to that by a grating with orthogonal characteristic spacings. The gratinglike character is due mainly to the pit structure and their periodic spacings, which can be deduced from the “unit‐cell” dimensions of the scattering pattern. The scattered intensity is maximum when the fiber direction is at 45° to the polarization direction; when it is either horizontal or vertical, a distinct “spherulitic” scattering is observed from which size and asymmetry of the pit

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090207

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractThe adsorption of polydimethylsiloxane polymers from solution on glass has been studied. The amount of polymer adsorbed depends markedly on the solvent because of specific solvent—surface interactions. The presence of silanol groups in the polymer, particularly as endgroups, markedly increases the amount of polymer adsorbed. Large differences are shown between the adsorption of the commercially available, and fully trimethylsilylated polydimethylsiloxanes of narrow molecular weight distribut on. Possible adsorption mechanisms are discusse

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090208

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractUnder steady shear flow, the normal stress and the shear stress in both dilute and concentrated solutions of monodisperse poly‐α‐methylstyrenes and their blends were measured. It was confirmed that the molecular theories of Rouse and Zimm extended to concentrated solutions can explain the relation between the zero‐shear normal stress coefficient and the zero‐shear steady‐flow viscosity for both monodisperse and polydisperse systems. Shear‐rate dependence of steady‐flow viscosity can be understood fairly well by the molecular entanglement concept proposed by Graessley so long as the polymer is monodisperse or the amount of the higher molecular weight component is high. However, zero‐shear viscosity of blended systems cannot be explained quantitatively by the theory of Graessley. The shear‐rate dependence of steady‐state compliance of blended systems was also observed, and it can well be explained by the theory of Tanaka, Yamamoto, and Takano which interpreted the shear rate‐dependent steady‐state compliance in terms of the relaxation time spectrum and its v

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090209

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY

摘要:

AbstractAverage values for dispersion γsdand polar γsdcontributions of the solid surface tension γsγsd+ γspfor poly(methylene oxide) (PMO) and Na‐treated polytetrafluoroethylene (PTFE) are determined by a new computational analysis of wettability data. PMO displays γsdequals; 21.8 ± 0.9 and γsp= 11.5 ± 1.5 dyn/cm while Na‐treated PTFE displays γsd= 36.1 ± 3.0 and γsp= 14.5 ± 2.9 dyne/cm. These surfaces present the highest fractional surface polarityps= γsp/γs= 0.29‐0.35 yet encountered for organic polymers or oriented monolayers. These unusual surface tension properties are correlated with surface chemistry an

ISSN:0449-2978    

DOI:10.1002/pol.1971.160090210

出版商:John Wiley&Sons, Inc.    

年代:1971

数据来源: WILEY