Fully conducting hydro-sponges with electro-swelling properties tuned by synthetic parameters

The present work details the synthesis and electrochemical characterization of four types of compacted polymeric 3D hydro-sponges prepared only from polypyrrole (PPy). During the synthesis, particles with cylindrical geometry were used as sacrificial templates, which promoted the growth of polypyrrole on their surfaces to form tubular structures. Hydro-sponges were then obtained under static conditions through the assembly of synthesized PPy microtubules into networks. Although these hydro-sponges were formed only by a conducting polymer, they showed good characteristics for their application in controlled-release systems because of their ability to swell in both deionized water and in electrolytic solutions, similar to the behavior exhibited for hydrogels. The well-known artificial-muscle properties associated with an electrically induced volume change of PPy were enhanced in these hydrogels because of their 3D structure, which led to volumes changes of up to 40% of their initial size. Both behaviors were extremely affected by the morphology of the four obtained PPy hydro-sponges. Our study shows that the morphology and, consequently, the hydro-sponges properties can be tuned as a function of the conditions employed during synthesis, which opens the possibility of preparing materials with potential applications in different types of controlled-release devices and smart membranes. (C) 2012 Elsevier Ltd. All rights reserved.