NMR self-diffusion study of polyethylene and paraffin melts

Autor:	G. Lahajnar, D. H. Reneker, I. Zupančič, David L. VanderHart, Robert Blinc
Rok vydání:	1985
Předmět:	Alkane chemistry.chemical_classification Self-diffusion chemistry.chemical_compound Monomer chemistry Attenuation Autocorrelation General Engineering Analytical chemistry Nuclear magnetic resonance spectroscopy Polyethylene Impulse (physics)
Zdroj:	Journal of Polymer Science: Polymer Physics Edition. 23:387-404
ISSN:	1542-9385 0098-1273
DOI:	10.1002/pol.1985.180230212
Popis:	The self-diffusion coefficient D of paraffin and polyethylene melts—covering the range between N = 19 and 103 where N is the number of monomeric units—was measured by the pulsed-magnetic-field-gradient NMR method for diffusion times between 3 ms and 1 s. For the paraffins, D is proportional to N−2 though the molecular weights are smaller than the critical molecular weight for entanglement. In polyethylene, melts a strong dependence of the diffusion coefficient on the diffusion time is observed, whereas no such dependence is found in paraffin melts. A mathematical formalism for describing spin-echo attenuation in terms of a velocity autocorrelation function is shown to yield qualitative agreement with the experimental results.
Databáze:	OpenAIRE
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