Single molecule force spectroscopy of smart poly(ferrocenylsilane) macromolecules: Towards highly controlled redox-driven single chain motors |
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Authors: | Shan Zou |
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Affiliation: | Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands |
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Abstract: | We investigated various stimuli-responsive poly(ferrocenylsilane) (PFS) polymers as model systems for the realization of molecular motors powered by a redox process. Covalently end-grafted PFS on gold, as well as PFS homopolymers and block copolymers in ultrathin films, were studied by AFM-based single molecule force spectroscopy (SMFS). Surface confined PFS macromolecules were chemically oxidized by addition of tetracyanoethylene or were completely and reversibly oxidized (and reduced) in situ by applying an electrochemical potential. Chemical oxidation was successful only for the block copolymers. The entropic elasticity of neutral PFS chains (Kuhn length IK∼0.40 nm) was found to be larger than that of oxidized PFS chains (IK∼0.65 nm) in the lower force regime. The elasticities could be reversibly controlled in situ by adjusting the applied potential in electrochemical SMFS experiments. For a single PFS macromolecule (DP=80) operating cycle, a work output and an efficiency of 3.4×10−19 J and ∼5%, respectively, were estimated based on the single chain experimental data. |
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Keywords: | Atomic force microscopy Electrochemistry Stimuli-responsive polymer |
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