CHAIN DYNAMICS IN ENTANGLED POLYMERS - POWER LAWS OF THE PROTON AND DEUTERON SPIN-LATTICE RELAXATION DISPERSIONS

Chain modes of entangled polymer melts can directly be probed in a fre quency range 10(2) Hz <v<10(8) Hz with the aid of field-cycling proton or deuteron relaxometry. The frequency dispersion of proton spin-latt ice relaxation universally shows crossovers between the power laws T-1 alpha(v)(05+/-0.05) (region I), T-1 alpha v(0.25+/-0.05) (region II), and T-1 alpha v(0.45+/-0.05) (region III) from high to low frequencie s. Regions I and II are identified as limits of a theory based on the renormalized Rouse model assuming intrasegment dipolar interactions. R egion III does not appear in distinct form in the deuteron T-1 dispers ion of perdeuterated chains. It is inferred that proton relaxation in region III is influenced by intersegment interactions which are neglig ible with deuterons. A corresponding formalism is given. The compariso n with the experimental data suggests some multi-chain correlation of the displacement dynamics. (C) 1998 American Institute of Physics.