Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 20: POSTER A

CPP 20.18: Poster

Montag, 24. März 2003, 19:00–21:00, ZEU/250

Diffusion controlled polymeric reactions in concentrated polymer solutions — •Katrin Wondraczek, Joerg Adams, and Juergen Fuhrmann — Institute of Physical Chemistry, TU Clausthal, Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld

In polymer solutions having a polymer concentration above the critical entanglement concentration, diffusion processes such as the diffusion of polymer chains and solvent molecules are mainly controlled by the hindred segmental motion. The segmental motion can be monitored via fluorescence spectroscopy by studying the lifetime of well chosen exciplexes. In our experiments, we used a labelled oligostyrene and a labelled polystyrene chain, both immersed in a highly concentrated solution of a matrix polymer dissolved in cyclohexane close to the theta-temperature. The fluorescence life time of the exciplex formed in such a solution is proportional to the inverse diffusion coefficient of the oligomeric species. We found a strong dependency of this diffusion coefficient on the concentration. Variation of the temperature revealed discontinuities near the theta-temperature of the system. Different models describing diffusibility in terms of either mobility or thermodynamical factors are compared. For our results, a separation in both factors is proposed.