Regensburg 2016 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 35: Activated and Glassy Dynamics of Soft Matter (joint session CPP/DY, organized by CPP)
CPP 35.2: Talk
Wednesday, March 9, 2016, 09:45–10:00, H51
Transient Cooperative Process in Dewetting Polymer Melts — •Sivasurender Chandran and Günter Reiter — Institute of Physics, Albert–Ludwig University of Freiburg, Freiburg, Germany
Polymer melts exhibit a rich dynamic behavior when exposed to intense shear fields. For example, amorphous polymers display a shear thinning behavior, while crystallizable polymers form correlated segments within the flow induced oriented structures. However, the role of such correlations on the dynamic behavior of crystallizable polymer melts is highly unexplored.
To explore this crucial aspect, we have compared the high velocity dewetting (shearing) behavior of molten amorphous (atactic polystyrene, aPS) and crystallizable (isotactic polystyrene, iPS) polymer films, above the melting point. For aPS, the apparent viscosity of the films (ηf) derived from dewetting was less than zero shear bulk viscosity (ηbulk), displaying the expected shear thinning behavior. Surprisingly for iPS films, ηf was always larger than ηbulk, even at about 50 ∘C above the melting point, with ηf/ηbulk following an Arrhenius behavior. The corresponding activation energy of ∼160±10 kJ/mol for iPS films suggests a cooperative motion of segments which were aligned and agglomerated by fast dewetting. These observations were not anticipated by standard models and hence indicate to the need for a new concept in polymer physics.