CLEAR EVIDENCE OF REPTATION IN POLYETHYLENE FROM NEUTRON SPIN-ECHO SPECTROSCOPY

The dynamic structure factor S(q, t) of polyethylene (PEB-2) was measu red by neutron spin echo in the Fourier time range of t = 0.3-175 nsec and for momentum transfers q between 0.05 and 0.145 Angstrom(-1) to t est the validity of competing phenomenological theories of relaxation in polymer melts. Previous spin-echo experiments limited to t < 25 nse c were equally well described by a variety of models. This ambiguity h as now been lifted, and the experiment clearly favors the reptation mo del, showing that the dominant relaxation mechanism in entangled linea r polymers is via reptation.