LOCAL RELAXATION BEHAVIOR AND DYNAMIC FRAGILITY IN HYDROGEN BONDING POLYMER BLENDS

Kevin A. Masser1, Hanqing Zhao2, Paul Painter2, James Runt2

1National Institute of Standards and Technology 2Department of Materials Science and Engineering, Penn State University

 

The dynamics of intermolecularly hydrogen-bonded polymer blends of poly(p-(hexafluoro-2-hydroxyl-2-propyl)styrene) with poly(vinyl acetate), poly(ethylene[30]-co-vinyl acetate[70]) and poly(ethylene[55]-co-vinyl acetate[45]) are investigated by broadband dielectric relaxation spectroscopy and Fourier transform infrared spectroscopy.  Each blend component exhibits a glassy state (β) relaxation, and these relaxations are affected by the formation of intermolecular associations.  The glassy state behavior of the blends can be modeled using the Painter-Coleman association model.  All blends exhibit a single Tg and a single dielectric segmental (α) relaxation, indicative of dynamic homogeneity.  The fragility of the glass-formers depends on the volume fraction of intermolecularly associated segments, and the association model predicts which compositions have the highest fragilities.  A relaxation related to the breaking and reforming of hydrogen bonds is observed at temperatures above the α process, and its temperature dependence varies systematically with ethylene content.