SURFACE ATTACHMENT OF WELL-DEFINED REDOX-ACTIVE POLYMERS AND BLOCK POLYMERS VIA TERMINAL FUNCTIONAL-GROUPS

Redox-active polymers and block polymers containing terminal groups for covalent attachment to surfaces have been prepared and characterized. Ferrocene- and phenothiazine-based redox-active polymers were prepared by ring-opening metathesis polymerization (ROMP) using Mo initiators of the type Mo(CHR)(NAr)(O-t-Bu)2 (R = tert-butyl or ferrocenyl, Ar = 2,6-diisopropylphenyl). The functional end groups introduced for surface attachment chemistry were Si(OEt)3, pyridyl, bromobenzyl, and pyrenyl derivatives. Polymers containing Si(OEt)3 were successfully used to derivatize Pt, In2(Sn)O3, and n-Si electrodes, whereas analogues of those same polymers lacking Si(OEt)3 groups do not bind to these surfaces. Polymers terminated with pyridyl or bromobenzyl groups, introduced in the capping reaction using the appropriate aldehydes, react with electrodes pretreated with benzyl chloride or pyridine groups, respectively, to give polymer-derivatized surfaces. Pyrene-capped polymers were made in an attempt to bind the polymers to carbon electrodes via selective pyrene adsorption. However, the polymer itself strongly adsorbs, precluding a specific role for the pyrene group. On the basis of the surface coverage found for the redox-active groups (approximately 1 X 10(-10) mol cm-2) and polymers (approximately 8 X 10(-12) mol cm-2) at the electrode surfaces, bound polymer chains hinder the access of unbound polymers to portions of the surface, thereby yielding a lower density of bound polymer than would be expected were the chain to extend away from the electrode surface.