NMR FIELD GRADIENT DIFFUSOMETRY OF SEGMENT DISPLACEMENTS IN MELTS OF ENTANGLED POLYMERS

Segment diffusion in a polyethyleneoxide melt (M(w)=5 000 000) was stu died with the aid of the supercon fringe field version of field-gradie nt NMR diffusometry. The evaluation based on the second moment of the probability density function, i.e., the mean squared displacement, sho ws reasonable agreement with the predictions of the tube/reptation mod el. However, taking into account the whole probability density functio n, leads to substantial discrepancies. (C) 1996 American Institute of Physics.