Study of translational dynamics in molten polymer by variation of gradient pulse-width of PGSE

- Segmental dynamics in molten polymers was studied by the PGSE method.
- PGSE attenuation dependence on the gradient pulse width reduces artifacts.
- Spectral analysis gives the effect of motion on spin dephasing.
- Model of tube Rouse motion explains the measurements on the polyethylene.

Pulsed gradient spin echo is a method of measuring molecular translation. Changing Δ makes it sensitive to diffusion spectrum. Spin translation effects the buildup of phase structure during the application of gradient pulses as well. The time scale of the self-diffusion measurement shortens if this is taken into account. The method of diffusion spectrometry with variable δ is also less sensitive to artifacts caused by spin relaxation and internal gradient fields. Here the method is demonstrated in the case of diffusion spectrometry of molten polyethylene. The results confirm a model of constraint release in a system of entangled polymer chains as a sort of tube Rouse motion.

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