Direct Measurement of Mass Transport in Actuation of Conducting Polymers Nanotubes.

Nanostructured Conducting polymer (CP) actuators are promising materials for biomedical applications such as drug release systems. However, understanding the actuation behavior at the nano-scale has not yet been explored. In this work, poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(pyrrole) (PPy) nanotubes doped with a large counter ion (i.e. poly(styrene sodium sulfonate) (PSS)) were fabricated using electrochemical deposition of PEDOT and PPy around poly(L-lactide) (PLLA) nanofiber templates, followed by template removal in chloroform. The actuation and mass transport behavior of PPy and PEDOT nanotubes were investigated and compared. The nanotubes were subjected to a redox process using cyclic voltammetry in 0.1M NaPSS electrolyte solution as the potential swept between -0.8 V and +0.4 V for 20 cycles at 10, 50, 100, and 200 mV/s scan rates. The mass transport behavior of these nanotubes was characterized via electrochemical quartz crystal microbalance (EQCM) technique. The EQCM results showed that PEDOT nanotubes had a higher mass exchange capability than their PPy counterparts, especially at higher scan rates. Also, it was revealed that PPy nanotubes were more sensitive to the scan rate than the PEDOT nanotubes, and the maximum mass exchange capability of the PPy nanotubes was noticeably reduced by increasing the scan rate.