Study of translational dynamics in molten polymer by variation of gradient pulse-width of PGSE.
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.
University of Ljubljana, Faculty of Mathematics and Physics, Physics Department, Jadranska 19, 1000 Ljubljana, Slovenia; Institute Jožef Stefan, Jamova 39, 1000 Ljubljana, Slovenia. Electronic address: Janez.Stepisnik@fiz.uni-lj.si.
Janez
J
Stepišnik
Gojmir
G
Lahajnar
Ivan
I
Zupančič
Aleš
A
Mohorič
Diffusion; Gradient spin echo; Magnetic resonance; Molten polymers; Rouse model; Tube/reptation; Velocity correlation function