Self-diffusion and Cooperative Diffusion in Semidilute Polymer Solutions as measured by Fluorescence Correlation Spectroscopy

摘要

We present a comprehensive investigation of polymer diffusion in thesemidilute regime by fluorescence correlation spectroscopy (FCS) and dynamiclight scattering (DLS). Using single-labeled polystyrene chains, FCS leads tothe self-diffusion coefficient while DLS gives the cooperative diffusioncoefficient for exactly the same molecular weights and concentrations. UsingFCS we observe a new fast mode in the semidilute entangled concentration regimebeyond the slower mode which is due to self-diffusion. Comparison of FCS datawith data obtained by DLS on the same polymers shows that the second modeobserved in FCS is identical to the cooperative diffusion coefficient measuredwith DLS. An in-depth analysis and a comparison with current theoretical modelsdemonstrates that the new cooperative mode observed in FCS is due to theeffective long-range interaction of the chains through the transiententanglement network.