Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 57: Polymer Dynamics and Rheology (joint session CPP/DY, organized by CPP)
CPP 57.9: Vortrag
Donnerstag, 10. März 2016, 17:15–17:30, H40
Packing Length Dependence of Chain Dynamics in Polymer Melts near the Unentangled-Entangled Crossover — •Herwin Jerome Unidad1, Michaela Zamponi1, Oxana Ivanova1, Lutz Willner2, Wim Pyckhout-Hintzen2, Andreas Wischnewski2, Dieter Richter2, and Lewis J Fetters3 — 1JCNS, Outstation at MLZ, Forschungszentrum Juelich, Garching, Germany — 2JCNS-1/ICS-1, Forschungszentrum Juelich, Juelich, Germany — 3Department of Chemical and Biological Engineering, Cornell University, Ithaca, New York
Recently, we showed that the ratio between the critical molecular weight (Mc) and the entanglement molecular weight (Me) does not have the universal value of 2 for all polymer melts but rather shows a subtle dependence on the so-called packing length (p). All three parameters are important in describing the rheology and chain dynamics of polymer melts. With this, the packing length seems to be an important length scale for describing the non-universality of chain dynamics. To clarify this role, we performed neutron spin echo experiments on two polymer series with various molecular weights and different packing lengths. We obtained a good description of the measured intermediate scattering function using the Rouse model by suppressing long-wavelength internal modes. We then examine how this mode suppression could proceed as a function of both the chain length and the packing length. These findings are explained in the framework of earlier ideas on entanglement formation.