Relaxation study of Poly(methylmethacrylate) in miscible blends with poly(ethylene oxide) by low-frequency anelastic spectroscopy

Low-frequency anelastic spectroscopy is used to detect the relaxation of polymer blends. The temperature-dependence energy dissipation (tan Φ) is measured over several frequencies for poly(methylmethacrylate) (PMMA, M=34,000) and the PEO/PMMA blends with 15, 20 and 25 wt% PEO. Three peaks (α1, α2, α3) occur on each curve of blends, corresponding to the glass transition relaxation of PMMA (α1), the liquid–liquid transition of PMMA (α2) and the sec-liquid–liquid transition of PMMA (α3). Both α1 and α2 peaks move to low temperature, while the α3 peak tries to move to high temperature with addition of PEO. A mechanism of competition between the effects of free volume and steric hindrance from PEO chains is advanced to explain the phenomena. It is suggested that the increase in free volume controls the segmental dynamics at low temperature, and the steric hindrance is more and more obvious with the increase in temperature; when the temperature is far above the glass transition of blends, the large-scale coupling movement of PMMA and PEO chains play an important role in the dynamics of the blends.