Neutron scattering investigation of a diluted blend of poly(ethylene oxide) in polyethersulfone.

By using quasielastic neutron scattering (QENS) with isotopic labeling we have investigated the component dynamics in a miscible blend of polyethersulfone (PES) and poly(ethylene oxide) (PEO) with 75% content in weight of PES. Due to the large difference in the glass-transition temperatures, T(g)'s, of the two polymers (T(g) (PEO) approximately equal to 220 K, T(g) (PES) approximately equal to 382 K) the dynamic asymmetry in the system dramatically increases when approaching the average T(g) of the blend, <T(g)(blend)>. For the fast (PEO) component, this leads to a behavior which hints a crossover from typical glass-forming liquidlike dynamics at high temperatures to confined dynamics close to <T(g)(blend)> induced by the freezing of the segmental motions of the slow PES. The features of the confined PEO motion observed by QENS are similar to those of the secondary gamma-relaxation detected for pure (semicrystalline) PEO. A neutron diffraction study of the short-range order of the homopolymers and the blend suggests that this coincidence could be due to similarities in the intermolecular packing of PEO and PES polymers.