SPIN-LATTICE RELAXATION OF POLYMERS - THE MEMORY-FUNCTION FORMALISM

An alternative and general formalism for the frequency dependence of t he spin-lattice relaxation time T1 of polymer liquids is derived on th e basis of memory functions of polymer theories. As examples the origi nal Rouse model [J. Chem. Phys. 21, 1272 (1953)] and the renormalized Rouse model by Schweizer [J. Chem. Phys. 91, 5802 (1989)] are consider ed. The results fit well the experimental data obtained for polydimeth ylsiloxane (PDMS) melts and solutions by the field-cycling technique. The Rouse model fits solutions and low-molecular-weight melts. The ren ormalized Rouse model explains the peculiar nu0.25 dispersion of the s pin-lattice relaxation time observed with PDMS melts at molecular weig hts M(w) >> M(c).