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

Abstract

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, Tg's, of the two polymers (Tg_PEO ~ 220 K, Tg_PES ~ 382 K) the dynamic asymmetry in the system dramatically increases when approaching the average Tg of the blend, <Tg_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 <Tg_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 γ-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.