TRANSIENT ENTANGLEMENT BEHAVIOR IN A POLY(PROPYLENE GLYCOLE) MELT - AFIELD GRADIENT NMR SELF-DIFFUSION STUDY

We report measurements of the temperature dependence of the self-diffu sion of a poly(propylene glycole) in the melt. Two kinds of magnetic h eld gradient NMR are used: pulsed held gradient NMR with large field g radients and static field gradient NMR in a specially designed cryomag net. The emphasis is put on large field gradients. The (true) longtime self-diffusion coefficients are compared with those calculated from n ormal-mode relaxation times in dielectric spectroscopy using the Rouse model. They agree very well. For temperature below about 270 K, a tim e-dependent self-diffusion coefficient appears which is an indication of anomalous diffusion. At 253 K we observe complete transient entangl ement behaviour of the PPG melt. These results are discussed in compar ison with dielectric and other experimental data.