Effect of Blending with Poly(ethylene oxide) on the Dynamics of Poly(methyl methacrylate):  A Quasi-Elastic Neutron Scattering Approach

The mobility of poly(methyl methacrylate) [PMMA] in a blend with 20 wt % poly(ethylene oxide) [PEO] is assessed using quasi-elastic neutron scattering (QENS) and compared to pure PMMA. The primary conclusion is that the change in dynamics of PMMA, upon blending with PEO, is solely a result of the shift in T_g. Although relaxation times of PMMA are smaller in the blend than in pure PMMA at a given temperature, they collapse onto a single curve when the difference in T_gs is taken into account. Relaxation times are Arrhenius in temperature throughout most of the data, with an activation energy consistent with that observed in dielectric spectroscopy for the merged αβ process. At temperatures less than ∼1.2T_g, the data suggest that at large spatial scales relaxation times grow in excess of Arrhenius temperature dependence, whereas at small spatial scales Arrhenius behavior continues. The approximate dividing point for this behavior is the static structure peak of PMMA.