Proceedings of the XIVth International Congress on Rheology pages:PS22-1-3
XIVth International Congress on Rheology edition:XIV location:Seoul, Korea date:22-27 August 2004
The coil-stretch transition of polymers in transient extensional flow fields gives a unique possibility to observe the stress distribution between polymer and solvent even for very dilute solutions in sub-ppm regions. In this paper we will present recent investigations on the capillary break-up behavior of dilution series of narrow distributed polystyrene in solvents with different viscosities and report on the existence of a critical dilution concentration below which the stress is solely carried by the solvent. A simulated evolution of the stress contribution of single polymer coils in different states of the coil-stretch transition, using a multimode FENE-P mode algorithm based on the one-dimensional analysis of Entov and Hinch for transient extensional flows, is compared to the experimental results and the general visco-elastic properties of the solution. The influence of the molar mass as well as a molar mass distribution and therefore the relaxation spectrum on the stress evolution and the critical dilution concentration is discussed as well as the influence of the chemical structure of more complex single polymer coils on the transient extensional flow.