The effect of carbon nanofillers on the performance of electromechanical polyaniline-based composite actuators

Different types of crystalline carbon nanomaterials were used to reinforce polyaniline for use in electromechanical bilayer bending actuators. The objective is to analyze how the different graphitic structures of the nanocarbons affect and improve the in situ polymerized polyaniline composites and their subsequent actuator behavior. The nanocarbons investigated were multiwalled carbon nanotubes, nitrogen-doped carbon nanotubes, helical-ribbon carbon nanofibers and graphene oxide, each one presenting different shape and structural characteristics. Films of nanocarbon-PAni composite were tested in a liquid electrolyte cell system. Experimental design was used to select the type of nanocarbon filler and composite loadings, and yielded a good balance of electromechanical properties. Raman spectroscopy suggests good interaction between PAni and the nanocarbon fillers. Electron microscopy showed that graphene oxide dispersed the best, followed by multiwall carbon nanotubes, while nitrogen-doped nanotube composites showed dispersion problems and thus poor performance. Multiwall carbon nanotube composite actuators showed the best performance based on the combination of bending angle, bending velocity and maximum working cycles, while graphene oxide attained similarly good performance due to its best dispersion. This parallel testing of a broad set of nanocarbon fillers on PAni-composite actuators is unprecedented to the best of our knowledge and shows that the type and properties of the carbon nanomaterial are critical to the performance of electromechanical devices with other conditions remaining equal.JCGG is grateful to CONACYT (2008-2010) and University of Alicante (2010-2012) for scholarship support. YIVC and FJRM thank CONACYT (Mexico) for grants SEP-CB-106942 and SEP-CB-2008-107082, respectively, for the parts of this work performed in Mexico, and the Rede NANOBIOTEC-Brasil (Edital 04/CII-2008 CAPES/MEC), as well as FACEPE and UFPE for additional support for a visiting professor stay at UFPE. IMG and JAC acknowledge support from the University of Alicante, MINECO (CTQ2013-44213-R) and GVA (PROMETEOII/2014/007 and ISIC/2012/008)