Dielectric Studies of Blends of Poly(ethylene oxide) and Poly(styrene-co-p-hydroxystyrene). Semicrystalline Blends

Abstract

The segmental and local dynamics of semicrystalline, melt-miscible blends of poly(ethylene oxide) [PEO] and a poly(styrene-co-p-hydroxystyrene) copolymer [SHS] were investigated using dielectric relaxation spectroscopy (DRS). A broad, yet well-defined, DRS segmental process is observed for the 5 wt % SHS blend, and it gradually shifts to higher temperature and broadens further with increasing SHS content. It can be distinguished in the 3D spectrum of the 10 wt % SHS blend, but it is only barely discernible in the spectrum of the 15 wt % SHS blend, as it is masked by large low frequency losses likely arising from electrode polarization. On the basis of current and previous findings, we propose that the observed segmental process is comprised of a slower cooperative segmental relaxation involving both components, as well as a faster process due to less associated PEO segments. Furthermore, heterogeneous spatial distribution of the SHS segments also promotes broadening of the segmental process in these blends, particularly at higher SHS contents. Hydrogen-bonded hydroxystyrene units produce a βS1 process, which is more cooperative than typical local relaxations, in light of its activation energy and the temperature insensitivity of its relaxation strength. All blends exhibit a high-frequency γb relaxation, near the γPEO and SHS βS2 processes of the neat components. The f−T locations of the γb relaxation in the various blends are the same within experimental error, and they are closer to the γPEO than to SHS βS2 process.