Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: POSTERS Rheology
CPP 7.3: Poster
Montag, 25. Februar 2008, 16:45–19:00, Poster A
Uncommon rheological effects during melting of dibenzylidene sorbitol fiber networks in poly (propylene oxide) — •Martin Kühne and Christian Friedrich — Freiburger Materialforschungszentrum, Stefan-Meier-Str. 21, 79104 Freiburg
Dibenzylidene sorbitol (DBS) is known to gel organic liquids as well as polymers such as poly (propylene oxide) (PPO) due to its capability of forming semiflexible fibers and corresponding networks. These networks are thermoreversible, which means they are melted by temperature increase and rebuild again during temperature decrease.
We investigated the melting process and related rheological effects of DBS fiber networks in PPO with special regard to temperature rate and deformation. At certain temperature rates and deformations an uncommon rheological behavior was found: Both G’ and G” increase with increasing temperature. We found that this behavior is the result of a temperature gradient within the sample, which causes fragmentation of fibers. The temperature dependent balance between fragmentation and reorganization is responsible for the observed effects. As a consequence, at the lowest rates, the samples do not show such uncommon behavior and now G’ depends on temperature with T−1. This is in accordance to the predictions for the temperature dependence of plateau modulus of a network of semiflexible fibers.