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

The self-diffusion coefficient D s of dye-labeled polystyrene chains having M w = 3.90 × 10 5 g/mol and M w / M n < 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, D s 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 D s decreases strongly with rising concentration. This decrease is well represented by a power law, D s ∼ 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, D s = D 0 exp(−15 c 0.65 ), with D 0 = 2 × 10 -7 cm 2 /s and c given in g/mL.