Electrochemical stimuli

PEMs with electrochemical materials change color with an applied potential through a redox process. The LBL-based fabrication technique effectively immobi-hzes electrochromicaUy active polymers or nanoparticles on an electrode to achieve efficiency access of active materials for a maximum response. The first PEM electrochromism phenomenon was reported by Schlenoff and Laurent using PEM 

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Interlocked molecular compounds consisting of a Ti-electron-rich component and a 71-electron-deficient unit can be assembled to form nanoscale molecular switches influenced by external electrochemical stimuli. Materials composed of CyDs include polyrotaxanes [34-36]. 

A.R. Hillman, I. Efimov, and M. Skompska, Dynamics of regioregular conducting polymer electrodes in response to electrochemical stimuli. Faraday Discuss., 121, 423 (2002). 

Electrochemical stimulated systems have potential biomedical and micromechanical application. Electrochemical stimuli controlled loading/adsorption onto oppositely charged polyelectrolyte materials on porous microspheres that was previously reported by Malinova and Wandrey. ° Electrochemical stimuli cause an increase in osmotic pressure of the redox-active polyelectrolyte... 

Mazzoldi, A., F. Garpi, and D. DeRossi. 2004. Polymers responding to electrical or electrochemical stimuli for linear actuators. Ann Chim-Sci Mat 29 55. 

On the basis of the above studies, Stoddart etal. synthesized a [2]catenane (Figure 39) comprising a CBPQT + ring interlocked with a 1/5DN38C10 derivative with a TTF unit substituting one of the two naphthalene (NP) units. The [2]catenane could be switched by electrochemical stimuli, inducing a relative motion of the two macrocycles. 

Bistable [2]rotaxanes (Figure 40) that could be switched between the two binding states by electrochemical stimuli based on the oxidation and reduction of TTF unit were also developed by the same group. The cyclophane resides... 

Liu etal. reported a series of unsymmetrical donor-acceptor [2]catenanes (Figme 44), which could be switched by electrochemical stimuli. Such a feature makes these catenanes appealing candidates for the construction of molecular machines and rotary motors. It should also be noted that these interlocked molecules can be reversibly switched among several states, opening interesting routes for the development of molecular electronic devices that go beyond binary logic. 

Early in 1994, Kaifer, Stoddart, and coworkers reported the first bistable molecular shuttle (Figure 70) based on a [2]rotaxane driven by chemical and electrochemical stimuli. The [2]rotaxane comprised a CBPQ U+ ring threaded by an axle consisting of two binding sites, benzidine and biphenol units. Under redox reactions and the addition of acid or base, the CBPQT + ring moves back and forth along the axle. This molecnlar shuttle can be switched by two different mechanisms and is a good candidate for the construction of complex molecular machines. 

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