Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 26: POSTER Dynamics and Diffusion
CPP 26.8: Poster
Donnerstag, 30. März 2006, 17:00–19:00, P2
The retraction process captured by SANS : segmental fluctuations — •Ekkehard Straube1, Ariane Blanchard2, Wim Pyckhout-Hintzen2, and Dieter Richter2 — 1Uni Halle-Saale — 2Froschungszentrum Jülich
The retraction process of linear chains after a fast non-linear stretch was re-investigated in long polyisoprene chains, characterized by approximately 58 entanglements. For the first time, the non-linear process of retraction, along with measurable amounts of constraint-release events could be detected from time-resolved but quenched small angle neutron scattering experiments. This contrasts numerous attempts to proof already decades ago. The results are in fair agreement with a recent curvilinear description, which heavily relied on linear rheology concepts concerning path length fluctuations and constraint release mechanisms. In this work quantitative evaluations of the segmental fluctuation range are now enabled on the basis of a modified single chain approach to which dynamic parameters had been added in a defined way. Also extensive use is made in the experimental carry-through of the parameters of linear rheology. This experimental study covers various strains from linear to non-linear regime and is discussed within the framework of the original Doi-Edwards work. Inadequately described features of the scattering curves in the previous communication, mainly due to the straight comparison of theory with data without optimizing could be relieved. We conclude that segmental fluctuations are anisometric and comparison to rheology is critical.