Dielectric Studies of Poly(ethylene oxide)/Poly(styrene-co-p-hydroxystyrene) Blends: Influence of Hydrogen Bonding on the Dynamics of Amorphous Blends

The segmental dynamics of a poly(styrene-co-p-hydroxystyrene) random copolymer [SHS, 50 wt % HS] and its amorphous, melt-miscible blends with poly(ethylene oxide) were investigated using broadband dielectric relaxation spectroscopy. The fragility of the neat copolymer was found to be close to that of polystyrene with comparable molecular weight, consistent with the idea that intramolecular hydrogen bonding primarily enhances the monomer friction coefficient and T_g, while having little effect on fragility. Despite the large mobility difference between the component polymers, a single cooperative segmental relaxation is observed for the blends (SHS concentration ≥ 60%), demonstrating the coupling ability of intermolecular hydrogen bonds. Blend fragility increased significantly with SHS content, reflecting the combined contribution of the two components. The most intriguing finding was a fast process in blends containing ≥80 wt % SHS. The available evidence supports its assignment to noncooperative segmental relaxation of PEO repeat units, having some similarities to the modified segmental dynamics of nanoconfined polymers.