| Abstract
| - The thermodynamics and kinetics of adsorption of the redox-activedendrimers diaminobutane-dend-(NHCOFc)8, (dendrimer-Fc8),diaminobutane-dend-(NHCOFc)16,(dendrimer-Fc16),diaminobutane-dend-(NHCOFc)32,(dendrimer-Fc32), anddiaminobutane-dend-(NHCOFc)64,(dendrimer-Fc64) containing 8, 16, 32, and 64ferrocenylmoieties on the periphery, respectively, have been studied usingelectrochemical and electrochemical quartz crystalmicrobalance (EQCM) techniques. All of these materials adsorb ontoa Pt electrode surface. At an applied potentialof 0.0 V (vs SSCE), where the ferrocenyl sites are in the reduced formand the dendrimers are neutral, the adsorptionthermodynamics are well-characterized by the Langmuir adsorptionisotherm. The kinetics of adsorption wereactivation-controlled and the rate constant decreased with decreasingsize of the dendrimer. Potential scanning past+0.60 V, where the ferrocenyl sites are oxidized, gave rise to theelectrodeposition of multilayer equivalents of thedendrimers. The additional material gradually desorbed uponrereduction, so only a monolayer equivalent remainedon the electrode surface. Impedance analysis of the resonatorresponse suggests that at multilayer equivalent coverages,the adsorbed dendrimers do not behave as rigid films and thatincorporation of significant amounts of solvent and/orsalt accompany the adsorption of these materials at such highcoverages. On the other hand, at monolayer coverages,the adsorbed films appear to exhibit rigid film behavior. Usingtapping mode atomic force microscopy we havebeen able to image dendrimer-Fc64 adsorbed onto aPt(111) surface. The images reveal that the apparent size ofthedendrimer adsorbed on the surface is significantly larger thanestimated values based on calculations, which is ascribedto a flattening of the dendrimer upon adsorption.
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