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Digitale Medien

Nuclear magnetic relaxation in polymer melts and solutions (1962)

McCall, David W. ; Douglass, Dean C. ; Anderson, Ernest W.

Hoboken, NJ : Wiley-Blackwell

Journal of Polymer Science 59 (1962), S. 301-316

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ISSN: 0022-3832

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Nuclear magnetic relaxation times have been studied in some polymer liquids and solutions. The nonexponential decay of the transverse magnetization has been ascribed to the distribution of molecular weights. The use of such measurements as a means of determining average molecular weights and distributions is discussed. A preliminary application of this use is made for polyethylene. The implications of nuclear magnetic relaxation measurements are discussed in terms of molecular motional processes of the polymer chains.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1962.1205916808

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Digitale Medien

Molecular motion in polyethylene. III (1963)

McCall, David W. ; Anderson, Ernest W.

New York : Wiley-Blackwell

Journal of Polymer Science Part A: General Papers 1 (1963), S. 1175-1184

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ISSN: 0449-2951

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Proton magnetic resonance studies of polyethylene have been extended. The relationship of the rigid fraction (NMR) to the crystalline fraction is discussed, and a case is presented for the relative importance of the rigid fraction (or its complement, the mobile fraction). When the polymer has been swollen by low molecular weight solvents, the NMR spectra yield rather direct evidence that the rigid, and presumably crystalline, regions are unaffected. The nature of the molecular motion is discussed in terms of a model, and it is shown that NMR data imply a rather general type motion.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1963.100010409

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Digitale Medien

Self-diffusion and nuclear relaxation in polyisobutylene (1963)

McCall, David W. ; Douglass, Dean C. ; Anderson, Ernest W.

New York : Wiley-Blackwell

Journal of Polymer Science Part A: General Papers 1 (1963), S. 1709-1720

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ISSN: 0449-2951

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Various self-diffusion and nuclear relaxation experiments are reported for a polyisobutylene of rather low molecular weight, in bulk and in solution. In the bulk, the self-diffusion coefficient obeys the Arrhenius relation, yielding an activation energy of 5.5 kcal./mole. In solution the activation energies are lower, approaching the value for the solvent at low concentration. The self-diffusion coefficient of the polymer at infinite dilution is 1.2 × 10-5 cm.2/sec. in CS2 and 0.44 × 10-5 cm.2/sec. in CCl4. The ratio is close to the inverse ratio of the solvent viscosities. Measurements of self-diffusion of the solvent have been made for cyclohexane in polyisobutylene. A simple interpretation of the data in terms of Stokes-Einstein models yields molecular dimensions which are too small by a factor of two or three.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1963.100010523

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