Composition-dependent dynamics in miscible polymer blends: influence of intermolecular hydrogen bonding

Dynamics of the miscible blend of poly(vinyl methyl ether) and poly(4-vinylphenol) [PVME/PVPh] have been studied using broadband dielectric relaxation spectroscopy (DRS). The results are compared with those reported for PVME/polystyrene [PS] and PVME/poly(2-chlorostyrene) [P2CS] blends to examine the effect of intermolecular hydrogen bonding. These blends have similar chemical structures, with the exception that strong intermolecular hydrogen bonds are formed between PVME and PVPh. Whereas PVME and P2CS (or PS) relax individually in their blends due to intrinsic mobility differences and the absence of strong intermolecular interactions, the segmental relaxations of PVPh and PVME are coupled in the blends controlled by intermolecular hydrogen bonding. Dynamic heterogeneity was observed in PVPh/PVME blends with PVPh concentration higher than 50%. This is due to the decoupling arising from the strong intramolecular hydrogen bonding between PVPh segments. Finally, in the blend, the secondary relaxation processes of both components occur at approximately the same temperature-frequency location as those in corresponding neat polymers, but with much lower intensity, suggesting suppression by the intermolecular hydrogen bonding. Our results suggest that the composition-dependent dynamics in PVPh/PVME are even more complicated than that observed in blends without strong intermolecular interactions.