A Fluorescence Correlation Spectroscopy Study on the Self-Diffusion of Polystyrene Chains in Dilute and Semidilute Solution

Abstract

The self-diffusion coefficient Ds of dye-labeled polystyrene chains having Mw = 3.90 × 105 g/mol and Mw/Mn < 1.10 was measured over almost 4 decades of polymer concentration in toluene solution, from 10-4 to 0.4 g/mL, by fluorescence correlation spectroscopy. In the dilute regime up to 5 × 10-3 g/mL, Ds remains practically constant. The transition to the semidilute regime is observed around 0.01 g/mL, and from 0.02 to 0.4 g/mL Ds decreases strongly with rising concentration. This decrease is well represented by a power law, Ds ∼ c-1.75, as predicted by scaling and reptation theory. As an alternative, a good fit over the whole concentration range can be obtained with a stretched exponential function, Ds = D0 exp(−15c0.65), with D0 = 2 × 10-7 cm2/s and c given in g/mL.