EVIDENCE FOR REPTATIONAL MOTION AND THE ENTANGLEMENT TUBE IN SEMIDILUTE POLYMER-SOLUTIONS

The internal dynamics of high molar mass polystyrene in semidilute solution have been examined using pulsed gradient spin echo NMR. We find evidence for reptationlike motion characterized by mean-square displacement phi(t) is similar to t1/4, t1/2, and t regimes. We observe clear transitions between phi(t) is similar to t1/2 and phi(t) is similar to t regimes and the data are broadly consistent with the quantitative predictions of Doi-Edwards theory. In an experiment akin to dynamic neutron scattering, we obtain a structure factor from which some information about entanglement tube dimensions can be deduced.