Carbon Nanotube Enhanced Gripping in Polymer-Based Actuators

Ionic polymer membrane cast from the mixture of poly(sodium 4-styrenesulfonate-co-acrylic acid) (PSA) and polyvinyl alcohol (PVA) was used as an electromechanical actuator. Surface modified multiwalled carbon nanotubes (MWNTs) were used as an efficient element to enhance the gripping of this actuator. In particular, a thin layer of PSA with a thickness of 12 nm is uniformly grafted on the surfaces of MWNTs. The water-soluble PSA-g-MWNTs can be homogeneously dispersed in the PSA/PVA membrane with a loading ratio of up to 20 wt %. Such a uniform dispersion generated many unique properties in this composite membrane, including enhanced toughness, relatively constant ionic-exchange capacity, and prominent structure integrity after water uptake. We argue that all these novel material properties are due to a removal of the interface mismatch between the MWNTs and the polymer membrane. As a result, a much-enhanced gripping is resulted from electrical stimuli, an indication of a promoted electromechanical coupling. When the loading of PSA-g-MWNTs reaches more than 10 wt %, the small oscillation in the mechanical output of the actuator vanishes.