화학공학소재연구정보센터
Macromolecules, Vol.36, No.26, 10056-10062, 2003
Polyelectrolyte self-diffusion: Fluorescence recovery after photobleaching of sodium poly(styrenesulfonate) in N-methylformamide
The influence of added salt on the self-diffusion coefficients (D-self) of fluorescein-tagged sodium poly(styrenesulfonate) (SPS) chains in a high dielectric constant organic solvent was measured by fluorescence recovery after photobleaching (FRAP). N-Methylformamide (NMF) was chosen since it has a dielectric constant greater than that of water and it was hoped would better solvate the backbone. A new FRAP apparatus was built for the purpose that allowed for data collection of the entire modulated recovery profile of fluorescence intensity. The decay rates of the SPS were determined for multiple bleached grating periods and found to be diffusive in nature. D-self was measured for a broad range of added salt concentrations (0-0.1 M) for comparison to the diffusive dynamic modes seen by dynamic light scattering. The self-diffusion coefficients were distinct from both the "fast" and the "slow" modes observed in dynamic light scattering and persisted through the ordinary -extraordinary transition. The slight increase in D-self with C-s closely mirrored the "slow" mode diffusion. The slow mode has longer relaxation times as compared to the center-of-mass motion of a single chain, supporting the hypothesis that the slow mode arises from a collective dynamics of large multichain domains.