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Separation of polyelectrolyte chain dynamics and dynamics of counterion attachment by EPR spectroscopy
Author(s) -
Hinderberger Dariush,
Spiess Hans Wolfgang,
Jeschke Gunnar
Publication year - 2004
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200450705
Subject(s) - counterion , polyelectrolyte , chemistry , electron paramagnetic resonance , chemical physics , viscosity , spin probe , nitroxide mediated radical polymerization , molecular dynamics , spectroscopy , ion , analytical chemistry (journal) , materials science , nuclear magnetic resonance , computational chemistry , organic chemistry , polymer , copolymer , radical polymerization , quantum mechanics , composite material , physics
Rotational dynamics and local enrichment of counterions close to polyelectrolyte chains were studied by EPR spectroscopy in solvents of different viscosity. The results confirm previous findings (D. Hinderberger, G. Jeschke, and H. W. Spiess, Macromolecules 2002, 35, 9698) that electrostatic attachment of counterions to the chains is dynamic with lifetimes of contact ion pairs shorter than 1 ns. While in low‐viscosity solvents linewidths for a dianionic nitroxide probe and their dependence on polyelectrolyte concentration are dominated by the gradient of local concentration in the vicinity of the chain, they are more strongly influenced by changes in rotational dynamics in a glycerol/water mixture. The slowdown of dynamics at higher viscosity strongly depends on polyelectrolyte concentration, suggesting that the lifetime of the attached state increases. The linewidths of trianionic triarylmethyl probes and of the center line of the nitroxide probes are dominated by local counterion enrichment both at low and high viscosity. Comparison of these linewidths and of the extent to which the lineshapes are non‐Lorentzian indicates build‐up of larger concentration gradients at higher viscosity.