Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 23: Poster: Polymer Dynamics
CPP 23.10: Poster
Mittwoch, 28. März 2012, 11:00–13:00, Poster A
Intimate coupling of heterogeneous dynamics and structural relaxation independent of molecular weight, temperature, and pressure. — •André Bormuth and Michael Vogel — Hochschulstraße 6, 64289 Darmstadt
Performing molecular dynamics simulations for an all-atom force field, we study the segmental or, equivalently, α relaxation of poly(propylene oxide) chains consisting of N=2−100 monomer units. In particular, we analyze the dependence of the α relaxation time τα on molecular weight, temperature, and pressure on the basis of incoherent intermediate scattering functions. Regarding dynamical heterogeneities, we monitor the non-Gaussian parameter and the weight-averaged mean cluster size. Both quantities exhibit a maximum for intermediate times, where the peak height and the peak time τp increase upon cooling and pressurizing. Interestingly, we find that data for different chain length, T, and p collapse onto a single Master curve τp = a * ταb, suggesting a close relation between structural relaxation and spatially heterogeneous dynamics. The exponent b turns out to be the same for the non-Gaussian parameter and the weight-averaged mean cluster size, indicating evidence for an underlying basic principle. Using the coupling model from Ngai et al. we discuss a way of tracing back the Parameters a and b to physical quantities.