Investigations of self- and tracer diffusion in poly(ethylene oxides) and in blends of poly(dimethyl/ethylmethyl siloxanes) with the pulsed field gradient NMR
The pulsed field gradient NMR was used to measure the self-diffusion coefficients of poly(ethylene oxides) in solution and melt and the tracer-diffusion coefficients of both components in the blend of poly(ethylmethylsiloxane)/poly(dimethylsiloxane). In the melts of lower molecular weight poly(ethylene oxide) aggregation behaviour as reported in literature (VA Sevreugin et al. (1986) Polym 27:290) within the time scale of the experiment could be excluded. For high molecular weight solutions diffusion within the tube was detected and 〈z 2〉 ∼ t k with k=0.3 ... 0.4 was found. In polysiloxane blends the tracer diffusion has no discontinuity at the temperature of spinodal decomposition. The tracer-diffusion coefficients are to some extent averaged in the blend in comparison with the self-diffusion coefficients in the pure polymers.
Key wordsSelf-diffusion tracer diffusion PFG-NMR poly(ethylene oxide) poly(siloxanes)
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