Segmental Diffusion in Rubbers Studied by Neutron Quasielastic Incoherent Scattering

Neutron scattering experiments on polymethylphenylsiloxane, polypropylene oxide, polyiso butylene and polyethylene oxide show broadening in the quasi-elastic region similar to that previously reported from polydimethylsiloxane. Measurements on partially deuterated samples confirm that the effect arises from segmental diffusive motion, rather than rotations of pendant side groups. The temperature dependence of this motion gives activation energies which are smaller than the activation energies for self-diffusion obtained from experiments of longer time-scale such as nuclear spin-lattice relaxation measurements and viscometry.