ISSN:
0098-1273
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
We have measured 1H and 19F NMR relaxation times T1, T1ρ, and T2, and diffusion constants, in trace penetrants hexafluorobenzene and n-hexadecane dissolved in stretched cis-polyisoprene, as function of temperature, rubber elongation, and angle with respect to the stretch direction. Values of T1 and T2 in the rubber were also measured. At all temperatures ( - 40 ≤ T ≤ 85°C), T1 in rubber and penetrants is isotropic and independent of elongation; the differences between rubber and penetrants are related to penetrant diffusion. All T2 above - 15°C are anisotropic and elongation dependent, and follow a motional narrowing model. For the penetrants, averaging the dipolar interactions implies averaging over a diffusion path; this correctly reproduces the observed much higher T2 anisotropy in the penetrants. Penetrant diffusion rates, however, are essentially isotropic and elongation independent. These effects depend only weakly on the shape of the penetrant molecules.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1981.180190107
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