Electrochemically Controlled Adsorption of Fc-Functionalized Polymers on β-CD-Modified Self-Assembled Monolayers

This work presents an in situ study of the adsorption/desorption behavior of ferrocene(Fc)-functionalized linear polymers on a gold surface covered with β-cyclodextrin(β-CD)-modified self-assembled monolayers (SAMs). The characterization of binary SAMs obtained with HS-(CH2)11-EG6-N3 and HS-(CH2)11-EG4-OH (EG, ethylene glycol) was performed using a quartz crystal microbalance with dissipation monitoring (QCM-D), cyclic voltammetry, and contact angle measurements. The functionalization of SAMs with β-CD was made via the "click" reaction between the β-CD monoalkyne derivative and azide groups exhibited by SAMs. The formation of the host−guest complex between SAM-β-CD and Fc-derivatized polymers (chitosan (CHI) and poly(allylamine hydrochloride) (PAH)) was studied by QCM-D. The viscoelastic model of Voinova was used to fit QCM-D curves recorded during the adsorption and electrochemically controlled desorption of CHI-Fc and PAH-Fc on SAM-β-CD. Using QCM-D coupled to cyclic voltammetry, we demonstrated that CHI-Fc and PAH-Fc can be successfully deposited on a SAM-β-CD-coated gold surface forming a stable multivalent inclusion complex between Fc moieties of polymer and β-CD cavities of SAM. We also showed that all specifically attached polymer chains can be detached from the SAM-β-CD-coated gold surface by applying an electric field.