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Photoinduced Shuttling Dynamics of Rotaxanes in Viscous Polymer Solutions
Author(s) -
Jagesar Dhiredj C.,
Fazio Sandro M.,
Taybi Jimmy,
Eiser Erika,
Gatti Francesco G.,
Leigh David A.,
Brouwer Albert M.
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200900668
Subject(s) - viscosity , materials science , polymer , rheology , chemical physics , scaling , kinetics , microviscosity , intrinsic viscosity , chemical engineering , thermodynamics , optics , composite material , chemistry , classical mechanics , fluorescence , physics , geometry , mathematics , engineering
The effect of external friction, caused by medium viscosity, on the photoinduced translational motion in a rotaxane‐based molecular shuttle 1 is investigated. The shuttle is successfully operated in solutions of poly(methacrylonitrile) (PMAN) of different molecular weights in MeCN and PrCN. The viscosity of the medium is tuned by changing the PMAN concentration. The rheological behavior of the polymer solution gives insight into the structure of the polymer solution on the microscopic scale. In PrCN, the entanglement regime is reached at lower concentration than in MeCN. This is also reflected by the effect on the shuttling: in the PrCN/PMAN system, a larger viscosity effect is observed compared to MeCN/PMAN. The shuttle is found to be slowed down in the polymer solutions but is still active at high viscosities. The observed retardation effect on the kinetics of shuttling in MeCN/PMAN and PrCN/PMAN can be correlated to the PMAN concentration through the hydrodynamic scaling model. The Stokes–Einstein relationship proves inadequate to correlate the shuttling rates to macroscopic viscosity, but the dependence of the shuttling rate on the bulk viscosity fits well to a commonly observed power‐law relationship. The viscosity effect on the shuttling is found to be weak in all cases.