title: Pressure-enhanced dynamic heterogeneity in block copolymers of poly(methyl vinyl ether) and poly(isobutyl vinyl ether).
abstract: The static structure factor and associated dynamics have been investigated in a series of block copolymers of poly(methyl vinyl ether) (PMVE) and poly(isobutyl vinyl ether) (PiBVE) using x-ray scattering and dielectric spectroscopy (DS). The origin of the dynamic arrest at the glass temperature (T(g)) of PiBVE has been explored by temperature- and pressure-dependent DS and pressure-volume-temperature measurements. Both temperature and volume are responsible for the segmental dynamics but temperature has a stronger effect. The copolymers display a minimal dynamic asymmetry (Delta T(g) approximately 7 K), nevertheless, are spatially and dynamically heterogeneous. Increasing pressure, unlike temperature, enhances the dynamic heterogeneity. This effect originates from the distinctly different pressure sensitivities of the homopolymers and can be traced back to differences in local packing.
authors.affiliation: University of Ioannina, Department of Physics, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Mpoukouvalas
authors.forename: G
authors.initials: G
authors.lastname: Floudas
authors.forename: B
authors.initials: B
authors.lastname: Verdonck
authors.forename: F E
authors.initials: FE
authors.lastname: Du Prez