Experimental Test of Heterogeneous Rouse Model for the Origin of Time-Temperature Superposition Breakdown near the glass transition*

Time-Temperature Superposition (TTS) has been widely employed in analyzing dynamic and mechanical data. However, beginning with Plazek in the 1960's, data has been reported showing a breakdown of TTS near the glass transition. For example, rheological data on polystyrene show clear evidence of TTS breakdown between 105? and 130 ?. This breakdown takes the form of a decoupling of polymer chain and segmental dynamics. Our group recently proposed a Heterogeneous Rouse Model (HRM) that explains this effect based on the presence of a distribution of relaxation times. Here, we report on extensions of this model to predict multiple linear-regime rheological properties such as complex modulus and creep, and we compare these predictions to new experimental data combining dielectric spectroscopy and rheological measurements.