Viscoelastic study of conducting polymers using quartz crystal microbalance

Abstract

Application of conducting polymers has been growing widely in different fields such as batteries, solar cells, capacitors and actuators. Mechanical properties of conducting polymers like flexibility, high power to mass ratio and high active strain make them potentially applicable to robotic and automation industries. Obviously, a dynamic model of the actuation phenomenon in conducting polymers is needed to study its controllability and also to optimize the mechanical performance. De Rossi and colleagues suggest treating the mechanical behaviour of conducting polymers separately from the viscoelastic structural model and electrochemical actuation [1] . But it has been observed that the effects of electrochemical actuation and diffusion of ions on the viscoelastic coefficients cannot be neglected in some conducting polymer actuators, as shown in [1] . In this paper, we present the effects of cyclic voltammetry actuation on shear modulus of polypyrrole in propylene carbonate and EMI.TSFI as measured by an electrochemical Quartz Crystal Microbalance (eQCM). The QCM consists basically of an AT-cut piezoelectric quartz crystal disc with metallic electrode films deposited on its faces. One face is exposed to the active medium. A driver circuit applies an AC signal to the electrodes, causing the crystal to oscillate in a shear mode, at a given resonance frequency. QCM has been routinely used for the determination of mass changes. Measured resonance frequency shifts are converted into mass changes by the wellknown Sauerbrey's equation. In this paper, we correlate the admittance output of QCM to the real shear modulus of polypyrrole. Then the results of the correlation which contains mechanical data are presented during actuation using two different types of electrolyte.

Biofouling-Resistant Electroactive Polymer Composites for Protein-Triggered Counterion Delivery

“…Positive frequency shifts have been observed due to the dehydration of surface adlayers. 30,31 In these cases, positive frequency shifts are coupled with changes in adlayer viscoelasticity, measured as a reduction in the QCM-D dissipation factor, indicating a stiffening or rigidification of the layer as water is removed from the film. Here, the positive frequency shift commences on introduction of the protein solution and continues during the entire 60 min incubation with protein, until the positive shift levels off on rinsing with fresh PBS.…”

“…Exceptions include measurements taken during complex and dynamic adhesion processes of microbial and mammalian cell adhesion to QCM sensor surfaces. − In our system, the positive Δ f can only be attributable to protein–polymer interactions and/or the movement of water and ions between the film and the interacting solvent. Positive frequency shifts have been observed due to the dehydration of surface adlayers. , In these cases, positive frequency shifts are coupled with changes in adlayer viscoelasticity, measured as a reduction in the QCM-D dissipation factor, indicating a stiffening or rigidification of the layer as water is removed from the film. Here, the positive frequency shift commences on introduction of the protein solution and continues during the entire 60 min incubation with protein, until the positive shift levels off on rinsing with fresh PBS.…”