Dynamical Heterogeneity in the Thermodynamically Miscible Polymer Blend of Poly(vinyl ethyl ether) and Styrene-co-p-hydroxystyrene Copolymer

Abstract

The dynamic heterogeneity of the thermodynamically miscible blend of poly(vinyl ethyl ether) and styrene-co-p-hydroxystyrene (PVEE/SHS) has been investigated using broadband dielectric spectroscopy (DRS) and other experimental probes. In our previous study of PVEE/poly(p-hydroxystyrene) blends, we found that the segmental relaxations of the component polymers can be coupled if there is sufficient intermolecular hydrogen bonding. For SHS/PVEE blends, however, two segmental relaxations are observed in the DRS spectra, even for blends with a fraction of intermolecular hydrogen bonds as large as that in the PVPh/PVEE blend, in which a single segmental relaxation was found as a result of the coupling effect from the hydrogen bonds. This behavior is explained by the existence of unfavorable interactions between PVEE and the styrene units in SHS, which is supported by the immiscibility between PS and PVEE. The repulsive force endows the non-hydrogen-bonded PVEE segments with more freedom to relax, so that they can be distinguished from the relaxation of intermolecularly hydrogen-bonded PVEE−SHS segments. This indicates more significant dynamic heterogeneity in SHS/PVEE than in PVEE/poly(p-hydroxystyrene) blends.

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

“…Note that if one repeat unit of the relaxing segment is hydrogenbonded, the entire segment will likely be coupled with the relaxation of PVPh to some degree. Similar behavior has also been observed in our DRS studies of PVEE/PVPh and PVEE/SHS blends and explained by the same stoichiometric model for intermolecular hydrogen bonding [19,20].…”

“…Strong intermolecular interactions are believed to be able to damp CF, thus this will not be considered further here. Because the primary difference between the present blend and P2CS/PVME (and PS/PVME) lies in the existence of strong intermolecular hydrogen bonding in PVPh/PVME, the different segmental relaxation behaviors can be rationalized by invoking the coupling effect of the intermolecular hydrogen bonding, as proposed in our previous studies on blends of poly(vinyl ethyl ether) [PVEE] with PVPh [19] and a styrene-co-p-hydroxystyrene random copolymer [SHS] [20]. Strong intermolecular associations like hydrogen bonding are capable of coupling components' segmental relaxations in polymer blends with large mobility difference.…”

“…A fast process was also observed in PVEE/SHS blends, but it is more apparent than in PVME/ PVPh, even in the blend with 40% SHS, in which the SHS concentration is too low to invoke domination by intramolecular hydrogen bonding or confinement. We interpreted this latter dynamic heterogeneity by considering the repulsion between the styrene repeating units and PVEE [20]. Strong intramolecular interactions between PVPh, along with confinement, undoubtedly contribute to the fast process in blends with higher SHS contents.…”

Composition depth profiling of polystyrene/poly(vinyl ethyl ether) blend thin films by angle resolved XPS

“…The -parameter, along with the MWs of the chains is all that is needed to define the miscibility of a polymer blend at a given composition using the regular solution theory of polymer mixtures [40].) This has been attributed to greater shielding of the interaction between the ether oxygen atom and the aromatic ring by the ethyl group of PVEE compared with the methyl group of PVME [41]. The less favourable interaction causes PST / PVEE blends to change from miscible to phase separated as the PST MW increases.…”

Dynamics of Poly(vinylmethyl ether) Blends with a Strongly Interassociating Copolymer

“…PVME is selected as the second component in the blend to facilitate comparison with the dynamics of similar blends reported in the literature. [2,16] The ether groups in PVME form relatively strong intermolecular hydrogen bonds with the phenolic -OH of polymers such as PVPh and poly(HFS). [2] The addition of a relatively small number of HFS hydrogen bonding sites ($14 mole % of the repeat units) renders the otherwise immiscible poly(DMB) and PVME miscible over the entire composition range, as predicted by the Painter and Coleman association model.…”