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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