POLYMER SELF-DIFFUSION MEASUREMENTS BY SMALL-ANGLE NEUTRON-SCATTERING

The time dependence of small-angle neutron scattering is used to follow the interdiffusion of conventional and labeled polymers to obtain the self-diffusion coefficient, D, of chains in the melt. A number of experimental procedures and applications are reviewed. The most comprehensive results have been obtained for linear and three-arm star polymers of hydrogenated polybutadiene (HPB) and deuterated polybutadiene (DPB). The dependence of D on molecular weight, the effect of matrix dynamics on D, and the relation of D to zero shear viscosity are discussed in terms of the tube model for dynamics of entangled polymer chains.