COLL 452 |
| G. Julius Vancso1, Shan Zou2, Yujie Ma1, Mark A. Hempenius1, and Holger Schönherr2. (1) Science and Technology Department, MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE, Enschede, Netherlands, (2) Materials Science and Technology of Polymers, MESA+ Research Institute, University of Twente, P. O. Box 217, Enschede, 7500AE, Netherlands |
| Poly(ferrocenylsilanes) (PFS) belong to redox active polymers, which exhibit reversible conformational changes in response to electrochemical stimuli. For thin films these conformational changes cause reversible film thickness expansion and reduction during repeated electrochemical cycles. We have attached end-functionalized PFS chains to gold surfaces and performed single-molecule force spectroscopy experiments by AFM. For this purpose ethylene sulfide terminated PFS chains with different degrees of polymerization were inserted into pre-formed self-assembled monolayers of different OH terminated self-assembled thiol monolayers (SAM) on Au(111). The influence of the thiol chain length and of the molar mass of PFS on the macromolecular insertion process will be discussed. By combining AFM observations and electrochemistry we showed that single, isolated PFS molecules could be inserted into the SAM at controlled coverage. Single molecule force spectroscopy showed typical macromolecular extension curves, which could be fitted by a modified freely jointed chain model. The segment elasticity and Kuhn segment length obtained from these fits were found to depend on the redox state of the PFS macromolecules, i.e. the mechanical response of a single chain was reversibly different in the oxidized and reduced states. This hysteresis opens op the possibility of using PFS for constructing single-chain molecular thermodynamic machines. |
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“Smart” Polymers on Surfaces and Colloids
2:00 PM-4:40 PM, Wednesday, March 31, 2004 Marriott -- Grand Ballroom J, Oral
Division of Colloid and Surface Chemistry |