Quartz crystal microbalance and electrochemical studies on the electrode modified by layer-by-layer multilayers of viologen polyelectrolytes

Abstract

Cationic poly(viologen) derivatives [(V 2+) m ] and anionic polymer [poly(styrenesulfonic acid- co-maleic acid), sodium salt] were assembled on electrode surfaces by layer-by-layer (LBL) and Langmuir–Blodgett (LB) methods. The assembling process was in situ investigated by quartz crystal microbalance (QCM) technique. Based on the frequency change, the average surface coverage of poly(butylviologen) in the LBL multilayers is in the range of 1.6∼3.3×10 −10 mol/cm 2. The mass change for one-layer LB film of poly(dodecylviologen)-anionic polymer is about 44, 96 and 263 ng/cm 2 for the films deposited at 5, 10 and 15 mN/m, respectively. The assembled LBL and LB multilayers show well reversible redox characteristics of the viologen. For poly(viologen) with short alkyl chains, the cyclic voltammograms (CVs) show two redox couples of (V 2+) m ↔ (V +) m and (V +) m ↔ (0.5(V +) 2) m when the last layer is poly(viologen), or one redox couple of (V 2+) m ↔ (V +) m when the last layer is anionic polymer. While for poly(viologen) with long alkyl chains, the CVs show only one couple of (V 2+) m ↔ (V +) m . The LBL multilayers show much higher stability than the self-assembled monolayers and LB films in electrolyte solution.